A new study reveals a complex interplay between soil fungi and tree roots that could be the cause of rare-species advantage. The researchers found that the type of beneficial soil fungi living around tree roots in a subtropical forest in China determined how quickly the trees accumulated harmful, pathogenic fungi as they grew. The rate of accumulation of pathogenic fungi strongly influenced how well the trees survived when growing near trees of the same species.
Before Europeans arrived in America, longleaf pine savannas sprawled across 90 million acres from present-day Florida to Texas and Virginia. Today, thanks to human impacts, less than 3 percent of that acreage remains, and what’s left exists in fragmented patches largely isolated from one another.
Species of daisy that close their flowers at night, produce colour in their exposed lower petals that makes them harder to spot for herbivores, reducing herbivory rates of flowers. The findings are presented in the British Ecological Society journal Functional Ecology.
Researchers from Stellenbosch University, South Africa found that tortoises, one of the main herbivores of the daisies, were unable to distinguish the lower petal surfaces against a green leaf background. Tortoises prefer to eat protein-rich flowers over leaves, but when confronted with closed flowers, they showed no preference between them.
When the researchers modelled the colours of the lower petal surfaces in the vision of other herbivores, they also found these colours to be indistinguishable from leaves.
In contrast, species of daisy that do not close at night produced the same colouration on their lower petals as the upper petals exposed to pollinators.
Plants face an evolutionary conflict between having flowers that attract pollinators while avoiding herbivores. Often plants defend themselves chemically, but this can have adverse effects on pollination.
“When plants defend their flowers chemically, the pollination interactions can be negatively influenced. Our study shows a novel way in which flowers can avoid herbivores, without compromising pollination interactions.
– says Dr. Jurene Kemp, lead author of the study.
“These flowers can potentially circumvent the conflict of attracting both pollinators and herbivores by producing attractive colours on the surfaces that are exposed to pollinators (when flowers are open) and cryptic colours that are exposed when herbivores are active (when flowers are closed).”
In Namaqualand, South Africa, where the research took place, daises bloom annually in a spring flowering. This makes preserving flowers, responsible for reproduction, particularly important.
The researchers examined the colouration of 77 Asteraceae species, modelling how they appear in the visual systems of chameleons, horses and goats as proxies for tortoises and larger herbivores in the area, like springbok. They then tested the preferences of real tortoises with both open and closed flowers against leaf backgrounds.
Not all Asteraceae species that close their flowers had cryptically coloured lower petal surfaces, but in the experiments, the tortoises did not readily eat these flowers. Dr. Kemp said, “One interesting question would be to test whether non-cryptic flowers have chemical defences, and whether these chemical defences are absent in the cryptic flowers.”
On further research Dr. Kemp said “Unfortunately, we could only do this using one plant family in one botanical region, it would be great to see if other plant species also use colour to avoid herbivores.”
The researchers would also have liked to use larger herbivores such as springboks in their behavioural experiments, but Dr. Kemp adds that “this was practically not possible.”
Read the paper: Functional Ecology
Article source: British Ecological society Press Office
Image: Jurene Kemp
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.
Read the paper in Nature: The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea.
BLOG: You can find out more about the secrets of seagrass in our blog post.
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:
Read the paper in Current Biology: Rules and self-organizing properties of post-embryonic plant organ cell division patterns.
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”.
Read the paper in PNAS: Calcium-dependent oligomerization of CAR proteins at cell membrane modulates ABA signaling.
*If you’d like to read more about stress resilience in plants, check out the meeting report from the Stress Resilience Forum run by the GPC in coalition with the Society for Experimental Biology.*
This plant root is infected with arbuscular mycorrhizal fungi. Image credit: University of Zurich.
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 Wiemsken explains: “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”.
Read the paper in Ecology Letters: Options of partners improve carbon for phosphorus trade in the arbuscular mycorrhizal mutualism.
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 Stevenson explains: “What’s interesting is that aquatic algae can’t respond to ABA: the next challenge is to discover how this hormone signaling process arose.”
Read the paper in The Plant Cell: Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE, a regulator of ABA responses unique to basal land plants and required for desiccation tolerance.
Professor Michael Knoblauch shows off a microscope image of phloem tubes. Image credit: Washington State University.
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.
Read the paper in eLife: Testing the Münch hypothesis of long distance phloem transport in plants.
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 Schünemann predicts that “DNA-analysis of archaeological remains of prehistoric plants will provide us with novel insights into the origin, domestication and spread of crop plants”.
Read the paper in Nature Genetics: Genomic analysis of 6,000-year-old cultivated grain illuminates the domestication history of barley.
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 Henry suggested: “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.”
Read the paper in Scientific Reports: New evidence for grain specific C4 photosynthesis in wheat.
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.
Read more in the Umeå University press release: Umeå researcher served a world first (?) CRISPR meal.
BLOG: We interviewed Professor Stefan Jansson about his prominent role in the CRISPR/GM debate earlier in 2016 – check out his post here.
*You may also be interested in the upcoming meeting, ‘New Breeding Technologies in the Plant Sciences’, which will be held at the University of Gothenburg, Sweden, on 7-8 July 2017. The workshop has been organized by Professor Jansson, along with the GPC’s Executive Director Ruth Bastow and Professor Barry Pogson (Australian National University/GPC Chair). For more info, click here.*
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 Wigge explains: “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”.
Read the paper in Science: Phytochromes function as thermosensors in Arabidopsis.
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 Zhao said, “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”.
Read the paper in GigaScience: Draft genome of the living fossil Ginkgo biloba.
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.
Read the paper in Science: Characterization of a dynamic metabolon producing the defense compound dhurrin in sorghum.
Another amazing year of science! We’re looking forward to seeing what 2017 will bring!
P.S. Check out 2015 Plant Science Round Up to see last year’s top picks!
With another year nearly over we recently put out a call for nominations for the Most Influential Plant Science Research of 2015. Suggestions flooded in, and we also trawled through our social media feeds to see which stories inspired the most discussion and engagement. It was fantastic to read about so much amazing research from around the world. Below are our top five, selected based on impact for the plant science research community, engagement on social media, and importance for both policy and potential end product/application.
Choosing the most inspiring stories was not an easy job. If you think we’ve missed something, please let us know in the comments below, or via Twitter! In the coming weeks we’ll be posting a 2015 Plant Science Round Up, which will include other exciting research that didn’t quite make the top five, so watch this space!
Sweet potato contains genes from bacteria making it a naturally occurring GM crop. Image from Mike Licht used under creative commons license 2.0
Scientists at the International Potato Center in Lima, Peru, found that 291 varieties of sweet potato actually contain bacterial genes. This technically means that sweet potato is a naturally occurring genetically modified crop! Alongside all the general discussion about GM regulations, particularly in parts of Europe where regulations about growing GM crops have been decentralized from Brussels to individual EU Member States, this story caused much discussion on social media when it was published in March of this year.
It is thought that ancestors of the modern sweet potato were genetically modified by bacteria in the soil some 8000 years ago. Scientists hypothesize that it was this modification that made consumption and domestication of the crop possible. Unlike the potato, sweet potato is not a tuber but a mere root. The bacteria genes are thought to be responsible for root swelling, giving it the fleshy appearance we recognize today.
This story is incredibly important, firstly because sweet potato is the world’s seventh most important food crop, so knowledge of its genetics and development are essential for future food supply. Secondly, Agrobacterium is frequently used by scientists to artificially genetically modify plants. Evidence that this process occurs in nature opens up the conversation about GM, the methods used in this technology, and the safety of these products for human consumption.
Read the original paper in PNAS here.
Our number two on the list also relates to genetic modification, this time focusing on methods. Regardless of whether or not we want to have genetically modified crops in our food supply, GM is a valuable tool used by researchers to advance knowledge of gene function at the genetic and phenotypic level. Therefore, systems of modification that make the process faster, cheaper, and more accurate provide fantastic opportunities for the plant science community to progress its understanding.
The Cas9 system is a method of genome editing that can make precise changes at specific locations in the genome relatively cheaply. This novel system uses small non-coding RNA to direct Cas9 nuclease to the DNA target site. This type of RNA is small and easy to program, providing a flexible and easily accessible system for genome editing.
Barley in the field. Image by Moldova_field used under creative commons license 2.0
Inheritance of genome modifications using Cas9 has previously been shown in the model plants, Arabidopsis and rice. However, the efficiency of this inheritance, and therefore potential application in crop plants has been questionable.
The breakthrough study published in November by researchers at The Sainsbury Laboratory and John Innes Centre both in Norwich, UK, demonstrated the mutation of two commercial crop plants, Barley and Brassica oleracea, using the Cas9 system and subsequent inheritance mutations.
This is an incredibly exciting development in the plant sciences and opens up many options in the future in terms of genome editing and plant science research.
Read the full paper in Genome Biology here.
Striga is a parasitic plant that mainly affects parts of Africa. It is a major threat to food crops such as rice and corn, leading to yield losses worth over 10 billion US dollars, and affecting over 100 million people.
Striga infects the host crop plant through its roots, depriving them of their nutrients and water. The plant hormone strigolactone, which is released by host plants, is known to induce Striga germination when host plants are nearby.
In a study published in August of this year the Striga receptors for this hormone, and the proteins responsible for striga germination were identified.
Striga plants are known to wither and die if they cannot find a host plant upon germination. Induction of early germination using synthetic hormones could therefore remove Striga populations before crops are planted. This work is vital in terms of regulating Striga populations in areas where they are hugely damaging to crop plants and people’s livelihoods.
Read the full study in Science here.
Striga, a parasitic plant. Also known as Witchweed. Image from the International Institute of Tropical Agriculture used under creative commons license 2.0
Resurrection plants are a unique group of flora that can survive extreme water shortages for months or even years. There are more than 130 varieties in the world, and many researchers believe that unlocking the genetic codes of drought-tolerant plants could help farmers working in increasingly hot and dry conditions.
During a drought, the plant acts like a seed, becoming so dry that it appears dead. But as soon as the rains come, the shriveled plant bursts ‘back to life’, turning green and robust in just a few hours.
In November, researchers from the Donald Danforth Plant Science Centre in Missouri, US, published the complete draft genome of Oropetium thomaeum, a resurrection grass species.
O. thomaeum is a small C4 grass species found in Africa and India. It is closely related to major food feed and bioenergy crops. Therefore this work represents a significant step in terms of understanding novel drought tolerance mechanisms that could be used in agriculture.
Read the full paper in Nature here.
Currently, one of the greatest challenges for ecologists is to quantify plant diversity and understand how this affects plant survival. For the last 500 years independent research groups around the world have collected this diversity data, which has made organization and collaboration difficult in the past.
Over the last 500 years, independent research groups have collected a wealth of diversity data. The Botanical Information and Ecology Network (BIEN) are collecting and collating these data together for the Americas using high performance computing (HPC) and data resources, via the iPlant Collaborative and the Texas Advanced Computing Center (TACC). This will allow researchers to draw on data right from the earliest plant collections up to the modern day to understand plant diversity.
There are approximately 120,000 plant species in North and South America, but mapping and determining the hotspots of species richness requires computationally intensive geographic range estimates. With supercomputing the BIEN group could generate and store geographic range estimates for plant species in the Americas.
It also gives ecologists the ability to document continental scale patterns of species diversity, which show where any species of plant might be found. These novel maps could prove a fantastic resource for ecologists working on diversity and conservation.
Read more about this story on the TACC website, here.
Dr Peng Jiang, University of Georgia, USA
Peng Jiang and Hui Guo at the University of Georgia think you can! They are currently raising money via a crowdfunding approach to sequence the first cactus genome – but the question is: why would they want to? Peng explains all in this guest blog post.
A Prickly Proposal: Why Sequence the Cactus?
In these times of growing food insecurity due to climate change and population pressures, the prickly pear cactus (Opuntia ficus) has growing commercial and agricultural importance across much of the world – you will find it growing in Mexico and Brazil, Chile, large parts of India and South Africa, and in Spain and Morocco.
The goal of our proposal is to sequence the genome and transcriptome of the prickly pear cactus, a recognized food and forage crop in these challenging semiarid regions of the world.
With more than 130 genera and 1,500 species of Cactaceae, we will create a draft genomic and transcriptome database that would aid the understanding of this understudied plant family, and provide the research community with valuable resources for molecular breeding and genetic manipulation purposes. Here are some of the reasons why we think a first cactus genome would be so important:
The Prickly Pear Cactus
1. Ecological Improvement
The beauty of the drought-tolerance cactus is that it can grow on desert-like wastelands. Nowadays, more than 35% of the earth’s surface is arid or semiarid, making it inadequate for most agricultural uses. Without efforts to curb global warming, “Thermageddon” may hit in 30–40 years time, causing desertification of the US, such that it may become like the Sahara. Opuntia helps create a vegetative cover, which improves soil regeneration and rainfall infiltration into the soil. This cactus genome research may help us to adapt our food crops to a much hotter, drier climate.
2. Food Crops, Feed and Medicine
The fruits of prickly pear cactus are edible and sold in stores under the name “tuna”. Prickly pear nectar is made with the juice and pulp of the fruits. The pads of prickly pears (“Nopalito”) are also eaten as a vegetable. Both the fruits and pads of prickly pears can help keep blood sugar levels stable because they contain rich, soluble fibers. The fruit contains vitamin C and was used as an early cure for scurvy.
Furthermore, there has been much medical interest in the prickly pear plant. Studies [1, 2, 3] have shown that the pectin contained in prickly pear pulp lowers cholesterol levels. Another study [4] found that the fibrous pectin in the fruit may lower a diabetic’s need for insulin. The plant also contains the antioxidant flavonoids quercetin, (+)-dihydroquercetin (taxifolin), quercetin 3-methyl ether (isorhamnetin) and kaempferol, which have a protective function against the DNA damage that leads to cancer.
3. Biofuels in Semiarid Regions
Planting low water use, Crassulacean acid metabolism (CAM; a water saving mode of photosynthesis) biofuel feedstocks on arid and semiarid lands could offer immediate and sustained biogas advantages. Opuntiapads have 8–12% dry matter, which is ideal for anaerobic digestion. With an arid climate, this prevents the need for extra irrigation or water to facilitate the anaerobic digestion process. Requiring only 300 mm of precipitation per year, Opuntiacan produce a large amount of dry matter feedstock and still retain enough moisture to facilitate biogas production. It’s possible to get as much as 2.5 kWh of methane from 1 kg of dry Opuntia.
4. Phylogenetic Importance
Trained botanists and amateurs alike have held cacti in high regard for centuries. The copious production of spines, lack of leaves, bizarre architecture and impressive ability to persist in the harshest environments on Earth are all traits that have entitled this lineage to be named a true wonder of the plant world.
The cacti are one of the most celebrated radiations of succulent plants. There has been much speculation about their age, but progress in dating cactus origins has been hindered by the lack of fossil data for cacti or their close relatives. Through whole genome sequencing, we help will reveal the genomic evolution of Opuntia by comparing this genome with that of other sequenced plant species.
Cacti are typical CAM plants. We will analyse the evolution of CAM genes in the cactus to help reveal the secret of drought tolerance. Furthermore, plant architecture genes and MADS-box gene family members will be analysed to reveal the specific architecture and structure of cactus.
Crowdfunding the Cactus Genome Project
Cactus has several fascinating aspects that are worth exploring, not just for its biology, but also its relevance to humanity and the global environment. We plan to generate a draft genome for Opuntia, and have launched a crowdfunding campaign to help fund this project – we have already raised $2300 USD (46% of what we need), but we only have 15 days to raise the rest. If you would like to help fund this project, please visit our Experiment page at: https://experiment.com/projects/sequencing-the-cactus-genome-to-discover-the-secret-of-drought-resistance.
If we are successful in raising enough money to initiate the Cactus Genome Project, not only will this be the first plant genome to be sequenced in the Cactaceae family, we will be releasing the results to the plant science community through GeneGarden, an ornamental plant genome database. Our citizen science approach is also allowing us to reach out directly to members of the public, creating exciting opportunities for outreach and engagement with plant science.
If you have any further questions, please contact project leader Dr Peng Jiang at pjiang@uga.edu.
This blog post is slightly adapted from a post originally appearing on GigaScience Journal’s GigaBlog. Reproduced and adapted with permission, under a CC-BY license.
References
