As a reader of our blog, we know that you are passionate about the power of plant science to tackle global challenges, such as food security, climate change, and human health.
The Global Plant Council is dedicated to promoting plant science collaborations across borders to address global challenges in a sustainable way. We are a strong voice for science, but as a not-for-profit organization we need your support.
Help us to keep supporting researchers and plant science by making a single or monthly donation today, via our secure PayPal system.
Struggling East African dairy farmers could benefit from new varieties of high-quality, drought-resistant forage grass known as Brachiaria that boosts milk production by 40 per cent, a report says.
The forage grass could enable farmers to increase their incomes, according to experts at the Colombia-headquartered International Center for Tropical Agriculture (CIAT) – a CGIAR Research Center.
Steven Prager, a co-author of the report — which was published last month — and a senior scientist in integrated modelling at the CIAT, says the report was based on many years of forage research in Latin America and the Caribbean, and recent field trials in Kenya and Rwanda from 2011 to 2016.
According to Prager, the study demonstrates the high potential for improved forages in East Africa and high payoff for investment in improved forages.
“The results are based on multiple scenarios of an economic surplus model with inputs derived from a combination of databases, feedback from subject matter experts and a literature review,” he explains, adding that the economic analysis was carried out at CIAT headquarters with the support of tropical forage experts in East Africa.
“The objective of this study was to understand the potential payoff for investment in action to improve dissemination and use of improved forages,” Prager tells SciDev.Net.
“The objective of this study was to understand the potential payoff for investment in action to improve dissemination and use of improved forages.”
Steven Prager, International Center for Tropical Agriculture (CIAT)
One of the big unknowns in the development and implementation of agricultural technology, according to Prager, is how many potential users are required to make it worthwhile to invest in the development and designation of different technologies.
Solomon Mwendia, a co-author of the report and forage agronomist at CIAT, Kenya, says the Brachiaria grass is climate-friendly and has high crude protein and less fiber, which leads to better use and digestion by cattle, in turn leading to less methane gas produced for each unit of livestock product such as milk or meat. Methane is one of the gases associated with global warming.
“This grass is relatively drought-tolerant compared to the Napier or elephant grass commonly used in East Africa. In addition, the grass can easily be conserved as hay for utilisation during forages scarcity or for sale,” Mwendia adds.
Smallholder dairy farming is important in East Africa for household nutrition and income. In Kenya, for instance, Mwendia says that milk production increased by 150 per cent between 2004 and 2012, from 197.3 million litres to 497.9 million litres.
The grass is native to Africa, according to Mwendia. It can grow in areas with up to 3,000 millimetres of rainfall and also withstand dry seasons of three to six months during which the leaf may remain green while other tropical species die. These conditions exist in other regions outside eastern Africa such as in Democratic Republic of Congo, Malawi, Zambia and Zimbabwe.
Sita Ghimire, a senior scientist at the Biosciences eastern and central Africa (BecA) Hub, who leads a research programme that focuses on Brachiaria, says 40 per cent increase in milk production is achievable in East Africa after feeding livestock with Brachiaria.
“Forage has been always a major challenge in livestock production in East Africa. It is mainly because of declining pastureland, frequent and prolonged drought and not many farmers conserve forage for dry season,” Ghimire says.
The major challenges for adoption of Brachiaria technology in East Africa are limited availability of seeds or vegetative materials, lack of standardised agronomic practices for different production environments and lack of varieties that are well adapted to East African environment, Ghimire explains, citing other challenges such as pest and diseases, and low funding forage research and development.
Edith, you have put a huge amount of work into uncovering the history of plant physiology research in Argentina. Why did you decide to do it and how did you undertake this challenge?
The current president of the SAFV, Pedro Sansberro, asked Alberto Golberg and myself if we would be willing to document the history of the society. Unaware of the tremendous task ahead, we agreed.
The information was scattered, so the first thing we did was try to collect as many SAFV conference books as possible. Sending requests through the SAFV mailing did not work, so it was essentially through personal contacts that we were able to put together the whole collection of conference books. It is now deposited in the library of CIAP (Centro de Investigaciones Agropecuarias – contact: [email protected]). People also sent the minutes of past meetings and pictures.
Initially we were only going to analyze the conference books and interview some plant scientists that were among the first disciples of the “founding fathers” of Argentinian experimental plant biology, but as we worked, our book grew and diversified.
What was the most interesting thing you discovered while writing the book?
It’s hard to narrow down which discovery was most exciting!
Victorio Trippi, one of the disciples of the “founding fathers”, told us that many researchers initially published in the journal Phyton, which was founded in Argentina in 1951. Our inspection of the archives of this publication yielded a lot of valuable information, and was an enlightening experience. We traced great names in Argentine plant science to the very beginning of their careers, looking at their topics of interest, how they moved from one job to another, and who their co-authors were. Even earlier than this though, we managed to trace the first mention of plant hormones in Argentina to a paper written by Guillermo Covas in 1939.
Writing the book was rewarding too, because we realized that plant physiology research has steadily grown in Argentina, judging by the participation in the conferences and the amount of research groups all over the country. It was very good to reveal the significant contributions that Argentine experimental plant science has made to many topics, such as photobiology, crop ecophysiology, germination physiology, senescence, mineral nutrition and carbohydrate metabolism, among others.
Why did you decide to include essays from the many groups researching plant physiology in Argentina?
We included them to reflect how much plant physiology has grown and diversified in Argentina. In the book we also invite those that did not have a chance to join this edition to contribute to a future one.
What words of wisdom did the researchers who were interviewed want to share with early career researchers for the future?
Most of them emphasized the need for team work, with people from different background joining forces to tackle a specific problem. The SAFV, they point out, has provided a friendly environment that has promoted collaboration and exchange of ideas among its members, and they hope this spirit will persist. They are moderately optimistic about the future, underscoring the need for new research paradigms both in the public and private sectors.
Carlos Ballaré underscored the human aspect of the history of the SAFV in his description of your book, printed on the cover. Could you elaborate on this?
Carlos meant that the book includes personal accounts from the people that have devoted their professional lives to plant physiology and ecophysiology, anecdotes of how the research groups developed and grew, and tales of how researchers replaced the lack of equipment with clever ideas. He highlights that the book has an emphasis on human endeavor, rather than being just a review of numbers, places, and dates.
Beyond the analysis of numbers and growth, the book reveals how early researchers worked on problems that largely sprang from their environment, attempting to understand the causes of issues that had an impact on crop productivity. Thus, those in Tucumán initially worked on sugar cane, those in Mendoza researched grapevines, and the focus in Buenos Aires was potatoes. As groups grew and diversified, this initial link was often blurred; young researchers joining ongoing work never realized what the initial question had been.
In a country where agricultural products or their derivatives still make a significant contribution to GDP, it is sensible to resume the link to local agricultural problems. For this task, it will be essential to adopt a systemic collaborative approach.
The authors of the book, Edith Taleisnik and Alberto Golberg.
Food biodiversity needs both systems, just like pandas need zoos and bamboo forests, say Marie Haga and Ann Tutwiler.
The efforts of many organisations mean that most of us understand the importance of conserving the biodiversity of wild animals and their habitats. But few of us think about food in the same way we think about pandas, even though the issues are much the same.
And as with pandas and other wild animals, conservation of agricultural biodiversity can and must be done both in the laboratory and in the field.
From pandas to seeds
If you had a choice, would you rather see a panda in a zoo, or in the bamboo forests of southern China?
For most of us, seeing wild and endangered animals in their own habitat and watching how they behave, adapt and survive in their natural surroundings would be the preferred choice. But, the role of zoos in conserving wild and endangered animals is equally important.
Many zoos are home to breeding programmes. These can help re-introduce animals into wild areas from which they have disappeared, and maintain the genetic diversity of small populations of threatened species. Zoos that are well-run carry out vital conservation research and can increase public support for conservation. And the only chance that most of us (and our kids) will have to see a panda is in a zoo.
Much in the same way, and for several decades now, dedicated researchers around the world have invested a great deal of effort in collecting and storing the seeds of different varieties of crops in genebanks, for what’s called ex situ conservation. Their collective work has created a precious global collection of over seven million seed, tissue, and other samples in many global and national genebanks.
“The problem is that systems of in situ and ex situ conservation have been largely disconnected for some time. Some conservationists even see them as antagonistic.
And while devotees of one side argue with the other, the diversity that underpins the food we eat is lost both in genebanks and in farmers’ fields.”
Marie Haga and Ann Tutwiler
At the same time, some concerns that apply to zoos — that they cannot maintain the evolutionary dynamics which allow ‘wild’ animals to evolve and adapt, for example — also apply to seed banks.
Researchers are increasingly recognising that in situ conservation is also important: maintaining crop and livestock diversity in farmers’ fields and farms, gardens, orchards, and the natural landscapes in which these are embedded.
A call for collaboration
Ex situ and in situ conservation each has their benefits.
It is relatively cheap to maintain crop diversity in a genebank, where it is safe from the vagaries of changing climates, and is readily accessible for research and breeding. But crop diversity stored in genebank is less accessible to farmers, and is not exposed to changing environments — which means it does not evolve and adapt.
On the other hand, crop diversity in farmers’ fields and under other in situ conditions, continues to evolve and adapt as a result of natural and human selections. As it evolves and adapts, this genetic diversity contributes directly to the resilience and sustainability of agricultural systems, as well as to farmers’ livelihoods and to their empowerment. But there’s a downside: it is more difficult for breeders to use in their crop improvement programmes.
This shouldn’t be about choosing one over the other — the world needs both conservation systems, with good communication channels and knowledge transfer between them. This will help to properly conserve the genepools of crops and make them available for use into the future, for food and nutritional security.
The problem is that systems of in situ and ex situ conservation have been largely disconnected for some time. Some conservationists even see them as antagonistic.
And while devotees of one side argue with the other, the diversity that underpins the food we eat is lost both in genebanks and in farmers’ fields.
Crop diversity in farmer’s fields continues to decline in many parts of the world, often driven by market forces beyond the control of farmers’ themselves. Diversity is also lost from genebanks — a shortage of funding and staff means collections are often poorly maintained.
But if we stop looking at these two forms of conservation as antagonistic but rather as complementary, attention can be focused on what matters most: how best to safeguard this diversity for the future.
The First International Agrobiodiversity Conference is an opportunity to begin anew. That’s why practitioners in all these fields, from all over the world, both industrialized and developing, and from both the formal and informal sector, are coming together in New Delhi, India this week.
This congress gives conservation and agro-biodiversity experts and policy makers the opportunity to start mapping out a future that breaks down barriers between the two approaches, integrating them to ensure global food and nutritional security.
Most importantly, this means helping politicians and the public understand that conserving the diversity of our food is just as important as conserving the diversity of wild animals.
The congress is a first step in the right direction.
Marie Haga is executive director of The Crop Trust, and Ann Tutwiler is director general of Bioversity International. Haga can be contacted on Twitter at@CropTrust, and Tutwiler at @AnnTutwiler.
Another fantastic year of discovery is over – read on for our 2016 plant science top picks!
A Zostera marina meadow in the Archipelago Sea, southwest Finland. Image credit: Christoffer Boström (Olsen et al., 2016. Nature).
The year began with the publication of the fascinating eelgrass (Zostera marina) genome by an international team of researchers. This marine monocot descended from land-dwelling ancestors, but went through a dramatic adaptation to life in the ocean, in what the lead author Professor Jeanine Olsen described as, “arguably the most extreme adaptation a terrestrial… species can undergo”.
One of the most interesting revelations was that eelgrass cannot make stomatal pores because it has completely lost the genes responsible for regulating their development. It also ditched genes involved in perceiving UV light, which does not penetrate well through its deep water habitat.
Plants are known to form new organs throughout their lifecycle, but it was not previously clear how they organized their cell development to form the right shapes. In February, researchers in Germany used an exciting new type of high-resolution fluorescence microscope to observe every individual cell in a developing lateral root, following the complex arrangement of their cell division over time.
Using this new four-dimensional cell lineage map of lateral root development in combination with computer modelling, the team revealed that, while the contribution of each cell is not pre-determined, the cells self-organize to regulate the overall development of the root in a predictable manner.
Watch the mesmerizing cell division in lateral root development in the video below, which accompanied the paper:
In March, a Spanish team of researchers revealed how the anti-wilting molecular machinery involved in preserving cell turgor assembles in response to drought. They found that a family of small proteins, the CARs, act in clusters to guide proteins to the cell membrane, in what author Dr. Pedro Luis Rodriguez described as “a kind of landing strip, acting as molecular antennas that call out to other proteins as and when necessary to orchestrate the required cellular response”.
In April, we received an amazing insight into the ‘decision-making ability’ of plants when a Swiss team discovered that plants can punish mutualist fungi that try to cheat them. In a clever experiment, the researchers provided a plant with two mutualistic partners; a ‘generous’ fungus that provides the plant with a lot of phosphates in return for carbohydrates, and a ‘meaner’ fungus that attempts to reduce the amount of phosphate it ‘pays’. They revealed that the plants can starve the meaner fungus, providing fewer carbohydrates until it pays its phosphate bill.
Author Professor Andres Wiemskenexplains: “The plant exploits the competitive situation of the two fungi in a targeted manner, triggering what is essentially a market-based process determined by cost and performance”.
The transition of ancient plants from water onto land was one of the most important events in our planet’s evolution, but required a massive change in plant biology. Suddenly plants risked drying out, so had to develop new ways to survive drought.
In May, an international team discovered a key gene in moss (Physcomitrella patens) that allows it to tolerate dehydration. This gene, ANR, was an ancient adaptation of an algal gene that allowed the early plants to respond to the drought-signaling hormone ABA. Its evolution is still a mystery, though, as author Dr. Sean Stevensonexplains: “What’s interesting is that aquatic algae can’t respond to ABA: the next challenge is to discover how this hormone signaling process arose.”
Sometimes revisiting old ideas can pay off, as a US team revealed in June. In 1930, Ernst Münch hypothesized that transport through the phloem sieve tubes in the plant vascular tissue is driven by pressure gradients, but no-one really knew how this would account for the massive pressure required to move nutrients through something as large as a tree.
Professor Michael Knoblauch and colleagues spent decades devising new methods to investigate pressures and flow within phloem without disrupting the system. He eventually developed a suite of techniques, including a picogauge with the help of his son, Jan, to measure tiny pressure differences in the plants. They found that plants can alter the shape of their phloem vessels to change the pressure within them, allowing them to transport sugars over varying distances, which provided strong support for Münch flow.
BLOG: We featured similar work (including an amazing video of the wound response in sieve tubes) by Knoblauch’s collaborator, Dr. Winfried Peters, on the blog – read it here!
Preserved remains of rope, seeds, reeds and pellets (left), and a desiccated barley grain (right) found at Yoram Cave in the Judean Desert. Credit: Uri Davidovich and Ehud Weiss.
In July, an international and highly multidisciplinary team published the genome of 6,000-year-old barley grains excavated from a cave in Israel, the oldest plant genome reconstructed to date. The grains were visually and genetically very similar to modern barley, showing that this crop was domesticated very early on in our agricultural history. With more analysis ongoing, author Dr. Verena Schünemannpredicts that “DNA-analysis of archaeological remains of prehistoric plants will provide us with novel insights into the origin, domestication and spread of crop plants”.
BLOG: We interviewed Dr. Nils Stein about this fascinating work on the blog – click here to read more!
Another exciting cereal paper was published in August, when an Australian team revealed that C4 photosynthesis occurs in wheat seeds. Like many important crops, wheat leaves perform C3 photosynthesis, which is a less efficient process, so many researchers are attempting to engineer the complex C4 photosynthesis pathway into C3 crops.
This discovery was completely unexpected, as throughout its evolution wheat has been a C3 plant. Author Professor Robert Henrysuggested: “One theory is that as [atmospheric] carbon dioxide began to decline, [wheat’s] seeds evolved a C4 pathway to capture more sunlight to convert to energy.”
Professor Stefan Jansson cooks up “Tagliatelle with CRISPRy fried vegetables”. Image credit: Stefan Jansson.
September marked an historic event. Professor Stefan Jansson cooked up the world’s first CRISPR meal, tagliatelle with CRISPRy fried vegetables (genome-edited cabbage). Jansson has paved the way for CRISPR in Europe; while the EU is yet to make a decision about how CRISPR-edited plants will be regulated, Jansson successfully convinced the Swedish Board of Agriculture to rule that plants edited in a manner that could have been achieved by traditional breeding (i.e. the deletion or minor mutation of a gene, but not the insertion of a gene from another species) cannot be treated as a GMO.
Phytochromes help plants detect day length by sensing differences in red and far-red light, but a UK-Germany research collaboration revealed that these receptors switch roles at night to become thermometers, helping plants to respond to seasonal changes in temperature.
Dr Philip Wiggeexplains: “Just as mercury rises in a thermometer, the rate at which phytochromes revert to their inactive state during the night is a direct measure of temperature. The lower the temperature, the slower phytochromes revert to inactivity, so the molecules spend more time in their active, growth-suppressing state. This is why plants are slower to grow in winter”.
A fossil ginkgo (Ginkgo biloba) leaf with its modern counterpart. Image credit: Gigascience.
In November, a Chinese team published the genome of Ginkgo biloba¸ the oldest extant tree species. Its large (10.6 Gb) genome has previously impeded our understanding of this living fossil, but researchers will now be able to investigate its ~42,000 genes to understand its interesting characteristics, such as resistance to stress and dioecious reproduction, and how it remained almost unchanged in the 270 million years it has existed.
Author Professor Yunpeng Zhaosaid, “Such a genome fills a major phylogenetic gap of land plants, and provides key genetic resources to address evolutionary questions [such as the] phylogenetic relationships of gymnosperm lineages, [and the] evolution of genome and genes in land plants”.
The year ended with another fascinating discovery from a Danish team, who used fluorescent tags and microscopy to confirm the existence of metabolons, clusters of metabolic enzymes that have never been detected in cells before. These metabolons can assemble rapidly in response to a stimulus, working as a metabolic production line to efficiently produce the required compounds. Scientists have been looking for metabolons for 40 years, and this discovery could be crucial for improving our ability to harness the production power of plants.
Genome editing technologies comprise a diverse set of molecular tools that allow the targeted modification of a DNA sequence within a genome. Unlike “traditional” breeding, genome editing does not rely on random DNA recombination; instead it allows the precise targeting of specific DNA sequences of interest. Genome editing approaches induce a double strand break (DSB) of the DNA molecule at specific sites, activating the cell’s DNA repair system. This process could be either error-prone, thus used by scientists to deactivate “undesired” genes, or error-free, enabling target DNA sequences to be “re-written” or the insertion of DNA fragments in a specific genomic position.
The most promising among the genome editing technologies, CRISPR/Cas9, was chosen as Science’s 2015 Breakthrough of the Year. Cas9 is an enzyme able to target a specific position of a genome thanks to a small RNA molecule called guide RNA (gRNA). gRNAs are easy to design and can be delivered to cells along with the gene encoding Cas9, or as a pre-assembled Cas9-gRNA protein-RNA complex. Once inside the cell, Cas9 cuts the target DNA sequence homologous to the gRNAs, producing DSBs.
The guide RNA (sgRNA) directs Cas9 to a specific region of the genome, where it induces a double-strand break in the DNA. On the left, the break is repaired by non-homologous-end joining, which can result in insertion/deletion (indel) mutations. On the right, the homologous-directed recombination pathway creates precise changes using a supplied template DNA. Credit: Ran et al. (2013). Nature Protocols.
Genome editing in crops
Together with the increased data availability on crop genomes, genome editing techniques such as CRISPR are allowing scientists to carry out ambitious research on crop plants directly, building on the knowledge obtained during decades of investigation in model plants.
The concept of CRISPR was first tested in crops by generating cultivars that are resistant to herbicides, as this is an easy trait to screen for and identify. One of the first genome-edited crops, a herbicide-resistant oilseed rape produced by Cibus, has already been grown and harvested in the USA in 2015.
Researchers used CRISPR to engineer a wheat variety resistant to powdery mildew (shown here), a major disease of this crop. Image credit: NY State IPM Program. Used under license: CC BY 2.0.
Genome editing could also revolutionize the management of viral plant disease. The CRISPR/Cas9 system was originally discovered in bacteria, where it provided them with molecular immunity against viruses, but it can also be moved into plants. Scientists can transform plants to produce the Cas9 and gRNAs that target viral DNA, reducing virus accumulation; alternatively, they can suppress those plant genes that are hijacked by the virus to mediate its own diffusion in the plants. Since most plants are defenseless against viruses and there are no chemical controls available for plant viruses, the main method to stop the spread of these diseases is still the destruction of the infected plant. For the first time in history, scientists have an effective weapon to fight back against plant viruses.
The cassava brown streak disease virus can destroy cassava crops, threatening the food security of the 300 million people who rely on this crop in Africa. Image credit: Katie Tomlinson (for more on this topic, read her blog here).
Genome editing will be particularly useful in the genetic improvement of many crops that are propagated mainly by vegetative reproduction, and so very difficult to improve by traditional breeding methods involving crossing (e.g. cassava, banana, grape, potato). For example, using TALENs, scientists from Cellectisedited a potato line to minimize the accumulation of reducing sugars that may be converted into acrylamide (a possible carcinogen) during cooking.
Concerns about off-targets
One of the hypothesized risks of using CRISPR/Cas9 is the potential targeting of undesired DNA regions, called off-targets. It is possible to limit the potential for off-targets by designing very specific gRNAs, and all of the work published so far either did not detect any off-targets or, if detected, they occurred at a very low frequency. The number of off-target mutations produced by CRISPR/Cas9 is therefore minimal, especially if compared with the widely accepted random mutagenesis of crops used in plant breeding since the 1950s.
GM or not-GM
Genome editing is interesting from a regulatory point of view too. After obtaining the desired heritable mutation using CRISPR/Cas9, it is possible to remove the CRISPR/Cas9 integrated vectors from the genome using simple genetic segregation, leaving no trace of the genome modification other than the mutation itself. This means that some countries (including the USA, Canada, and Argentina) consider the products of genome editing on a case-by-case basis, ruling that a crop is non-GM when it contains gene combinations that could have been obtained through crossing or random mutation. Many other countries are yet to issue an official statement on CRISPR, however.
Recently, scientists showed that is possible to edit the genome of plants without adding any foreign DNA and without the need for bacteria- or virus-mediated plant transformation. Instead, a pre-assembled Cas9-gRNA ribonucleoprotein (RNP) is delivered to plant cells in vitro, which can edit the desired region of the genome before being rapidly degraded by the plant endogenous proteases and nucleases. This non-GM approach can also reduce the potential of off-target editing, because of the minimal time that the RNP is present inside the cell before being degraded. RNP-based genome editing has been already applied to tobacco plants, rice, and lettuce, as well as very recently to maize.
In conclusion, genome editing techniques, and CRISPR/Cas9 in particular, offers scientists and plant breeders a flexible and relatively easy approach to accelerate breeding practices in a wide variety of crop species, providing another tool that we can use to improve food security in the future.
For more on CRISPR, check out this recent TED Talk from Ellen Jorgensen:
About the author
Dr Damiano Martignago is a plant molecular biologist who graduated from Padua University, Italy, with a degree in Food Biotechnology in 2009. He obtained his PhD in Biology at Roma Tre University in 2014. His experience with CRISPR/Cas9 began in the lab of Prof. Fabio Fornara (University of Milan), where he used CRISPR/Cas9 to target photoperiod genes of interest in rice and generate mutants that were not previously available. He recently moved to Rothamsted Research, UK, where he works as Genome Editing Specialist, transferring CRISPR/Cas9 technology to hexaploid bread wheat with the aim of improving the efficiency of genome editing in this crop. He is actively involved with AIRIcerca (International Association of Italian Scientists), disseminating and promoting scientific news.
Aquaporins are water-channel proteins that move water molecules through cell membranes. They are found in every kingdom of life. Cell membranes are semi-permeable to water, but often require more rapid movements of water across membranes; cells achieve this using aquaporins.
Aquaporins play key roles in your kidneys, which typically filter each of the three liters of plasma in your body 60 times per day – that’s 180 liters of plasma each day! Around three times your body weight in water passes through your own aquaporins each day.
Around 50% of global rainfall passes through plants, and half of this moves through the aquaporins. Image credit: Dennis Seiffert. Used under license: CC BY-ND 2.0.
Have you got on the scales recently? Nearly 70% of your body weight is water. Water is the major component of cells in all of your tissues and this is the same for plants. Around 50% of global precipitation passes through plants, and half of this moves through aquaporins, so aquaporins account for the largest movement of mass for any protein on earth.
Often, in cell membranes, four aquaporin proteins will come together to form a tetramer to assist with the transportation of water across the cell membrane. There are types of aquaporins that only transport water, and others that transport glycerol, neutral acids or gasses. Historically, plant science literature has reported that the molecular structure of aquaporins prevents any charged particles, such as ions, from permeating. This is different in the animal world where there are reports of aquaporins that are permeable to ions. For example, in humans one of the most highly expressed aquaporins, AQP1, can function as a dual water and ion channel.
Testing plant aquaporins in frog cells
Recently, we observed that one of the most highly expressed plant aquaporins is permeable to ions when expressed in heterologous systems such as Xenopus laevis (frog) oocyte (egg) cells or yeast cells. This indicates that plants may also have types of aquaporins that can function as a dual water:ion channels.
The function of plant aquaporins can be studied by expressing them in different systems such as the Xenopus laevis oocyte cells pictured here. Photo credit: Dr Caitlin Byrt.
If you want to know if a particular plant aquaporin can function as a water channel you can test it by expressing the aquaporin in a laboratory oocyte expression system. We use a tiny needle to inject RNA coding for plant aquaporins of interest into the oocyte, and for control oocytes we inject the same amount of water. The oocytes are kept in a saline solution and we usually study them one or two days after injecting the RNA to allow time for them to synthesize the protein.
If you place oocytes expressing an aquaporin into water alongside control oocytes, then the aquaporin-expressing oocytes will burst much quicker than the controls because water rushes in through the aquaporin and causes the cell to swell rapidly. To explore whether a protein conducts ions, we use electrodes to measure the currents generated when charged ions pass across the oocyte membrane. We can also use ion-specific electrodes to explore which ions are transported.
AtPIP2;1 can transport water and ions
The plant aquaporin we studied is coded in the genome of the model plant Arabidopsis; it is a plasma membrane-located protein called AtPIP2;1. The AtPIP2;1 protein is known to be highly prevalent in root epidermal cell membranes, and it also functions in the guard cells of leaves, which act like tiny valves to regulate the uptake of carbon dioxide for photosynthesis and the release of water vapor.
The model plant Arabidopsis has an aquaporin, AtPIP2;1, that can function as a dual water:ion channel. Photo credit: Dr. Jiaen Qiu.
We observed that AtPIP2;1 expression induces both water and ion (salt) movement across the cell membrane of oocytes. We know that the ionic conductance can be carried in part by sodium ions and that it is inhibited by calcium, cadmium and protons. This means AtPIP2;1 is a candidate for a previously reported calcium-sensitive non-selective cation channel responsible for sodium ion entry into Arabidopsis roots in saline conditions.
We are investigating the physiological role of ion permeable aquaporins in plants, and exploring how plants regulate the coupling of ion and water flow across key membranes. The regulation of ion permeability through plant aquaporins could be important in the control of water flow and regulation of cell volume. There is increasing discussion around the hypothesis that plants could drive water transport in the absence of water potential differences using salt and water co-transport, and this makes us wonder whether ion-permeable aquaporins may be involved. Testing whether ion-permeable aquaporins can function as an ‘all-in-one’ osmotic system in plants is an exciting new direction for research in this field.
Dr. Caitlin Byrt, Professor Steve Tyerman and colleagues are investigating whether aquaporins permeable to ions are present in a range of different plant species. Photo credit: Wendy Sullivan
Dr. Mike Roberts, Lancaster University, UK, Mike with an experiment to test the effects of parental herbivory on defense priming in the next generation of Arabidopsis plants. (Photo credit: Lancaster University)
It is widely accepted that achieving agricultural sustainability means reducing our reliance on synthetic agrochemicals. One major group of agrochemicals is pesticides, which include the insecticides and fungicides that protect crop plants against pests and diseases. Pests and diseases aren’t going to go away, so reducing pesticide usage means that alternative crop protection approaches are needed. EU Directive 2009/128/EC (Sustainable Use of Pesticides) recommends the use of integrated pest and disease management (IPM) – the combined use of multiple approaches that together provide sufficient protection.
Our contribution to this challenge has been to identify ways in which we might enhance a plant’s own natural defense mechanisms. Plants have a wide array of structural and chemical defenses that they can employ to fight off enemies. Many of these are inducible, meaning that they are only activated in response to attack, which allows plants to balance the costs and benefits of defense. For crop plants, these costs can often translate into reduced yields. Spraying with compounds that switch on inducible defenses, such as the plant hormones jasmonic acid (JA) and salicylic acid (SA), can make plants more resistant, but this approach also risks unwanted growth reductions.
Fortunately, evolution has produced another way of regulating inducible defenses that we can take advantage of: the phenomenon we refer to as ‘priming’. When we ourselves get infected with something like a virus, our immune system generates antibodies to quickly fight it off, but it also produces memory cells that can respond to the same infection many months, or even years, in the future, with a more rapid and effective immune response. This is the basis of the familiar concept of vaccination. While plants don’t make antibodies, they are nevertheless able to alter future patterns of defense activation in response to previous infection by disease or feeding by herbivorous insects; thus, priming results in a faster and stronger activation of future inducible defense responses.
Transgenerational immune priming enhances disease resistance in Arabidopsis. All the plants in the photograph were inoculated by spraying the whole tray with a suspension of Pseudomonas syringae bacteria. The plants on the right side of the photo are from seed collected from parent plants that were infected with the same P. syringae bacteria, whilst those on the left come from healthy parents. (Photo credit: Belinda Ameyaw)
If we can find ways to prime defenses in crop plants, we might be able to improve pest and disease resistance with minimal impacts on yield. One way to do this is through seed treatments. We found that treating seeds with the defense hormone JA provides long-term enhanced resistance against herbivory and some fungal diseases, without affecting growth and development. We were able to patent this discovery, and the approach has since been successfully commercialized. The same approach can also be used to prime defenses against other forms of biotic and abiotic stress.
How and why seed treatments provide long-term defense priming can be explained by the phenomenon of transgenerational immune priming, which my lab has also been investigating. After our success with the seed treatment, we wondered, “What if seeds were exposed to hormones like JA during the course of their development on the parent plant?” We tested this by infecting plants with bacteria or exposing them to herbivores, and then examined defense in their offspring. Remarkably, we saw that priming responses established in the parent were passed on to the offspring; something we refer to as transgenerational immune priming.
The evidence we have at present suggests that the mechanism for this heritable stress memory is epigenetic, meaning the genes that control priming are chemically tagged to alter their activity. These epigenetic modifications don’t involve changes in the DNA sequence and are reversible, allowing rapid, flexible responses to environmental stress. Understanding the nature of these epigenetic changes may provide another way to exploit priming for crop protection. Introducing the right epigenetic marks onto genes in elite crop varieties may enable the priming of defense without altering their genetic make-up. Given the difficulty of introducing new chemical and biological methods of crop protection, which require time-consuming and costly regulatory approval before they can be brought to market, this could prove an especially attractive option in the future.
Plant samples in the genebank at the International Center for Tropical Agriculture’s Genetic Resources Unit, at the institution’s headquarters in Colombia. Credit: Neil Palmer / CIAT. Used under license: CC BY-SA 2.0.
It was too dry in the Australian region of Wimmera to produce crops last summer. This year, floods are set to wipe out yields again. Like a number of other regions across the planet, climate change is starting to be felt.
For Norton and many of her colleagues in agricultural genetics, the picture is increasingly clear: The variety of crops used today are not able to withstand the changing conditions and changes expected in the future.
Australia’s biodiversity may offer some help, according to discussions at the recent International Genebank Managers Annual General Meeting held in Horsham, Victoria. The gathering, which brings together 11 countries, focused on how to better conserve seeds, build databases to manage collections, boost capacity across the world and fill gaps in genebanks.
Researchers are particularly interested in crop wilds, “the ancestors of our domesticated crops,” Marie Haga, executive director of the The Crop Trust, explained to Devex. Australia is one of the richest sources of these seeds. “It’s like the wolf being the ancestor to our domesticated dogs. Crop wild relatives have traits that we have lost in the domestication process — they might need less water, might live in unfriendly conditions, may be resistant to pests and diseases.”
As climate change continues to batter agricultural yields, crop wild relatives could provide resilience. The seeds give breeders and farmers new options of plant varieties with traits to withstand a variety of conditions based on the harsh climates they are found — drought, fire, flood, poor soil, high salinity.
For Haga, crop wild relatives are a solution for food security. “The challenge is that many of the varieties widely used in modern agriculture are very vulnerable, because we have been breeding on the same line and they are adapted to very specific environment,” Haga said. Varieties that flourish today, she said, could wither as the climate fluctuates.
“Utilization of the natural diversity of crops is key to the future,” she said. “The climate is rapidly changing and we need to feed a growing population with more nutritious food. It is very hard to see how we can do this unless we go back to the building blocks of agriculture.”
Norton agreed: “Crop wild relatives have an amazing adaptability to changing conditions,” she told Devex. “When we talk about food security, we are talking about getting varieties in farm paddocks that have greater resilience to extreme conditions. It may not be the highest yield, but you are going to get something from this crop.”
Why have they been overlooked?
Crop wild relatives have so far been underutilized in the research and breeding process of crops.
“We have this fabulous natural diversity out there including 125,000 varieties of wheat and 200,000 varieties of rice.” Haga said. “We have not at all unlocked the potential of these crops.”
One reason is a dearth of research. “Adapting Agriculture to Climate Change: Collecting, Protecting and Preparing Crop Wild Relatives,” a 10-year project led by Haga to ensure long-term conservation of crop wild relatives, conducted a global survey of distribution and conservation and found that of 1,076 known wild relatives for 81 crops, more than 95 percent are insufficiently represented in genebanks and 29 percent are completely missing. They are missing purely due to the fact that they have yet to be collected.
“Genebank managers are generally open to include crop wild relatives in their collections.” Haga said. “It’s just quite simply that not enough work has been done in this area and the full potential is yet to be realized,” she said.
At the moment, seeds are being collected in 25 countries around the world as part of the crop wild relative project, but it is Australia that has been identified as one of the richest sources for crop wild relatives in the world. Because of the continent’s low population density and vast, undisturbed natural environment, a wide variety of species have been conserved, said Norton.
Australia holds significant diversity of wild relatives of rice, sorghum, pigeon pea, banana, sweet potato and eggplant currently missing from global collections, according to research by the Australian Seed Bank Partnership. Forty species have been prioritized for collection with high hopes that they will enable crops to withstand the harsh environmental conditions in which Australian species are found.
There are still many areas of Australia yet to be surveyed, and the full extent of its agricultural riches may yet to be tapped.
Australian researchers will play an important role in pre-breeding local species of wild relatives to improve their use in breeding programs. Crop wild relatives have historically been used in a variety of crops including synthetic wheat, but Australian native wild relatives have been harder to include in the breeding process.
“In the next 10 to 15 years it would be surprising if there is not something coming out that hasn’t got a component of Australian native wild relative in it,” Norton said who is currently involved in the collection of Australian crop wild relatives.
Collection of crop wild relatives is time sensitive
There is an urgency to collect crop wild relatives. Not only are wild species needed now to support changing environmental conditions affecting crops and farming, urbanization is putting crop wild relatives at risk of disappearing.
“We need to collect these sooner rather than later,” Norton told Devex. “Urbanization has a big impact on any native environment, let alone crop wild relatives. We know what species on our target list are more threatened than others — urbanization, flooding and fire are all risks to their security. We certainly have a priority list of species to collect and we need to make sure we target the ones that are under threat first.”
Once the varieties are conserved, breeders and farmers will need to be convinced to start using crop wild relatives. Many are already on board. “Most breeders understand these wild relatives have great potential,” Haga said.
Still, wild relatives can be difficult to work with and produce a lower yield. Haga expects there to be some reluctance, though limited.
“The understanding of the need is increasing and we feel very confident that this material will be used and some of them may be the game changer we are looking for,” she said.
The plans for crop wild relatives
Haga’s 10-year project on crop wild relatives is halfway complete. They are nearing the end of the collection phase and entering the pre-breeding process, before they are able to breed and deliver new species to farmers.
Australian support for the program includes an agreement for additional amount of $5 million. That comes on top of previous support of $21.2 million to the Crop Diversity Endowment Fund, which supports crop diversity globally and with a focus on the Indo-Pacific. Brazil, Chile, Germany, Japan, New Zealand, Norway, Switzerland and the United States are among other supporters of the endowment fund that hopes to reach $850 million. In Australia, further resources are still required to fund and support better seed collection at home.
Globally, plans for crop wild relatives includes raising greater awareness of their potential and importance.
“We have a big job to do to create awareness of the important of crop diversity generally and crop wild relatives specifically,” Haga said. “We have been speaking for years about biodiversity in birds and fish and a range of other animals, but we have talked very little about conserving the diversity of crops. I will fight for all types of diversity, but especially plants.”
Agricultural production in temperate regions is highly productive with a significant proportion of global output originating from temperate (i.e. non-tropical) countries – 21% of global meat production and 20% of global cereal production [link opens PDF] originate from Europe alone. This proportion is very likely to increase in light of climate change.
Little fluffy clouds: temperate zones are well suited to agricultural production. Image credit: connect11/Thinkstock
TempAg is an international research collaboration network that was established to increase the impact of agricultural research and inform policy making in the world’s temperate regions. Its work does not solely focus on research, but also provides insights into current thinking through mapping existing scientific findings and outstanding knowledge gaps. In this way, the network aspires to become a platform for the alignment of national agricultural research and food partnership programs (such as Global Food Security) that will enable the development of more effective agricultural policies with a long-term vision.
Since its official inauguration in Paris in April 2015, TempAg has been leading a series of on-going workstreams around:
Boosting resilience of agricultural production systems at multiple scales and levels
Optimising land management for ecosystem services and food production
Improving sustainability of food productivity in the farms & enterprise level
After 18 months of existence, TempAg held a foresight workshop in London on 5–7 October to determine its future priorities.
Forty delegates took part in the workshop, coming from the 14 different countries in the temperate region, and from academia, policy, industry, and professionals at the science–policy interface. Through a series of presentations and interactive sessions, participants were invited to consider what the current and future challenges are in temperate agriculture, taking into account the needs of policy makers and industry in helping them to improve sustainable agriculture practices.
To tackle sustainability in temperate agriculture, there is a need to better manage risks and stresses (both biotic and abiotic), as well as finding ways to manage the restoration of natural capital, ecosystem services, and soils. During the workshop, it was noted that utilizing the diversity within different agricultural systems, via identifying the best practice and using the appropriate technological mix, may be a way forward in making production systems more sustainable.
Participants stressed the importance of taking a holistic view of the sustainability agenda within agriculture, without just focusing on environmental aspects. This means also taking into consideration socioeconomic factors, such as making food value chains (like turning milk into cheese), more equitable by identifying who gets the equity from the food commodities’ prices, or identifying what the optimum legal framework for sharing data might be.
The group also considered sustainable agriculture issues from a policy and industry needs angle. It was interesting to see that dealing with shocks (environmental, socioeconomic, and technological) featured highly in this discussion as well. It was suggested that increasing resilience to these shocks could be facilitated via the widespread diffusion of existing technologies. Engaging with farmers during this time would be necessary to identify technology uptake barriers.
Future-proofing agricultural resilience and enhancing the capacity to respond to shocks was deemed an urgent priority, so the development of a comprehensive map identifying the multiple shocks that could impact on farm resilience in temperate zones might be a future workstream for TempAg. Work in this area could help develop models to assess the flexibility within agricultural production systems.
What we eat is largely based on the types of food we produce. Therefore, healthy diets are intrinsically linked with our production systems. Another area of interest for TempAg could be to explore what the nutritional value of crops should be for better health, and what a nutritional diet will look like for sustainable temperate agriculture. Developing frameworks in this area could further inform future farming practices in temperate areas.
Since TempAg’s initiation, two major global policy agendas have been adopted by the international community: the Sustainable Development Goals and the Paris COP21 agreement. Identifying what types of data and scientific evidence policy makers will need to achieve the agriculture-relevant targets was another area where TempAg could focus its activity moving forward.
Finally, delegates highlighted areas of work that could help to build more effective policies with a longer-term vision. These included developing economic tools for valuing natural capital and ecosystem services, as well as integrated assessment tools to monitor the performance and impact (environmental cost) of existing policies.
Evangelia is International Coordinator & Programme Manager for the Global Food Security program (GFS). Before joining GFS, Evangelia worked as an Innovation Manager for GFS partners BBSRC. She holds a PhD in plant development and genetics from the University of Oxford.