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The composition of regrowing wet and dry tropical forests follow opposite pathways while these forests are growing older. This has large consequences for forest restoration initiatives. The findings of a new study published in Nature Ecology and Evolution provide insights to select the best tree species for a forest area, thus enhancing and accelerating tropical forest restoration success.

Tropical forests can regrow naturally after agricultural fields are abandoned. During this regrowing process, called succession, the vegetation gradually builds up, leading to changes in environmental conditions at the forest floor. And because species differ in their growing strategies this leads to shifts in species composition over time. Understanding how succession works is crucial to improve forest restoration initiatives and to select the best species for planting.
Soft woods have a rock-and-roll life style

A large team of ecologists from Latin America, United States, Australia and Europe followed recovery of tropical forests in fifty locations across ten Latin American countries. This 2ndFOR research team found that wet and dry forests show actually opposite successional pathways. Species with different characteristics thrive under different environmental conditions, says Prof. Lourens Poorter from Wageningen University & Research and lead author of the study. “A key characteristic of tree species is their stem wood density. Species that produce soft, and cheap, wood have the ability to grow very fast when light and water are abundant. However, this soft wood comes at the expense of a reduced survival, especially under suboptimal conditions like shade and drought. As a result, soft-wooded species have a ‘rock-and-roll’ life style; they peak early in life, live fast and die young.”

On the other hand, species that produce durable, and expensive, wood can persist for a very long time, especially under adverse conditions, the research team describes in their paper. This strategy comes at the expense of a reduced and slow growth. These results provide an important step to understand the shift in species composition during forest succession. The successional theory predicts that early in succession light and water resources are in abundant supply, which leads to the dominance of ‘fast’ pioneer species with soft wood. Later in the succession resource availability declines, leading to the dominance of ‘slow’ late-successional species with hard wood, like Maçaranduba (Manilkara bidentata) a Neotropical timber species that produces such heavy wood that it sinks in water.

“In wet forest we see a shift from soft- to hard-wooded species over time. However, in dry forest we see an opposite shift from hard- to soft-wooded species” Danaë Rozendaal.

Shift from soft to hard wood species in wet forests

To evaluate successional changes in wood density, the research team analysed forest recovery at an unprecedented spatial scale, using original data from fifty sites, 1400 plots and more than 16,000 trees from tropical forests across Latin America. Co-author Dr. Danaë Rozendaal says: “Our results show that in wet forest we indeed see a shift from soft- to hard-wooded species over time. However, in dry forest we see an opposite shift from hard- to soft-wooded species.”
Opposite trend in dry forests

This opposite trend happens because in wet forests, resources (e.g. light) decline during succession, whereas in dry forests initial conditions are very harsh, dry and hot. Only hard-wooded species can tolerate these extreme conditions. When they grow they create a milder micro environment, which paves the way for the establishment of soft-wooded species. “Intriguingly”, Danaë Rozendaal adds, “the results show that wet and dry forests start out very differently, but become more similar over time in terms of microclimate and species wood density.”

Tree species selection for forest recovery

The new ecological insights can be used to improve species selection for restoration, Wageningen Professor Frans Bongers assures. “Where possible, forest restoration should rely on natural regeneration, as it is cheaper, and leads to a more diverse and resilient vegetation. However, in degraded areas, where natural regeneration is difficult, active planting provides a good alternative. Our findings suggest that forest restoration in areas with an intense dry season, covering 16% of the Neotropical forests, should prioritize planting species with high wood density. These have higher chances of surviving the dry period. In addition, well-adapted, native tree species are preferred rather than exotic species, because they support biodiversity. This selection can also lower mortality rates among planted trees, which often exceeds more than one third of the planted trees. In wet forests, though, a mix of local soft and hard wooded species can be successfully planted at the onset. The fast soft-wooded species rapidly establish a protecting vegetation, and shelter the slower growing hard-wooded species that will form the basis of a long-term stable forest.”

Read the paper: Nature Ecology and Evolution

Article source: WUR

Image: Frans Bongers

Nanyang Technological University, Singapore (NTU Singapore) scientists have developed a sustainable way to demonstrate a new genetic modification that can increase the yield of natural oil in seeds by up to 15 per cent in laboratory conditions.

The new method can be applied to crops such as canola, soybean and sunflower, which are in a multi-billion dollar industry that continues to see increasing global demand.

The research team led by Assistant Professor Wei Ma from NTU’s School of Biological Sciences genetically modified a key protein in plants which regulates the amount of oil they produce. This results in larger oil reserves in the seed that primarily serves as an energy source for germination.

The team’s patent-pending method involves modifying the key protein known as “Wrinkled1” or “WRI1”, which regulates plants’ oil production. After modification, the seeds have a wrinkled appearance, which is the basis for its scientific codename.

In the lab, these modified seeds have successfully displayed seed oil increase that is able to produce up to 15 per cent more natural oils. The research findings were published in the scientific journal Plant Signaling & Behavior.

“Plant seed oil is an essential component in our daily diet and the agricultural industry is seeking ways to maximise plants’ yield while reducing environmental effects of crop cultivation, especially land use. Our research helps to increase the production of seed oil in a sustainable and cost-effective way, and it also opens up new doors in agriculture research,” said Asst Prof Ma.

The ability to increase oil yield in a sustainable manner is expected to result in higher economic gain. Past research has shown that a small 1.5 per cent increase in oil yield (by dry weight) in soybean seeds equates to a jump of US$ 1.26 billion in the United States market.

Discovery a boost for biofuel production

The increased yield in seed oil would also benefit the production of biofuel, which is a form of clean fuel produced from organic sources, such as vegetable oils.

Biofuel is being used in various applications, including powering machines in protected forests to reduce fossil fuel contamination and fuelling long-distant transportation by automobiles, ships, and airplanes.

“Global demand for vegetable oil is increasing very rapidly, and it is estimated to double by 2030. In addition, research is also ramping up in the use of biofuels in various applications, which can provide a cleaner and more sustainable source of fuel than petroleum. Increasing oil production of key crops such as soybean, sunflower, and canola is thus essential for a more sustainable and greener future,” said Asst Prof Ma.

He is currently exploring industrial collaboration to commercialise and further develop the technology.

The NTU team is also studying other ways to maximise plants’ oil reserves, for example, using other plant parts such as stems, for oil production.

Sustainable way to increase oil yield

Previous research efforts to improve seed oil yield involved increasing the number of the WRI1 protein – known as overexpression – but this did not succeed in increasing the oil yield stably and consistently.

Asst Prof Ma used the Arabidopsis plant – a small flowering plant related to cabbage and mustard. It contains all the characteristics of crops such as sunflower, canola and soybean, which serves as an ideal model plant for research.

He and the NTU research team developed a patent-pending method that stabilises the key WRI1 protein which also improves its ability to interact with other proteins. This enhances its effectiveness in producing natural oils and the method can be easily done on other crops. This also encourages a more sustainable way for industries to produce natural oils instead of simply increasing the amount of land used for agriculture.

Dr. Bo Shen, a Senior Manager at DuPont Pioneer, a US-based international producer of hybrid seeds for agriculture who is not involved in the NTU team’s research said, “Vegetable oil is an important renewable resource for biodiesel production and for dietary consumption by humans and livestock. The total production of vegetable oil worldwide reached about 185 million tons in 2017. Wrinkled1 (WRI1) is a ubiquitous regulator controlling oil biosynthesis in maize, soybean, canola, and palm. With increasing demand for vegetable oil, Asst Prof Wei Ma’s research on WRI1 can have global importance. A better understanding of how WRI1 regulates oil biosynthesis could inform how we breed plants that produce more oil.”

Providing another independent view, Dr. Eric Moellering, a Senior Scientist from Synthetic Genomics, a California company focusing on synthetic biology, said, “Asst Prof Ma’s research on the plant transcriptional factor WRI1 has greatly advanced our understanding of how seed oil biosynthesis is regulated. While the WRI1 gene has been known for some time, Asst Prof Ma’s research has revealed key insight into the structural features of the WRI1 protein that are critical for its function, WRI1 interactions with other regulatory proteins, and the role of WRI1 in processes outside of seed oil regulation.

“These discoveries will undoubtedly contribute to the optimisation of seed oil yield in a variety of crops. As such, Asst Prof Ma’s research is helping to address some of the major 21st century challenges we face in feeding a growing global population and developing renewable transport energy.”

Read the paper: Plant Signaling & Behavior

Article source: Nanyang Technological University

Image: Manfred Richter / Pixabay

Scientists from 21 research institutes globally, have successfully completed sequencing of 429 chickpea lines from 45 countries to identify genes for tolerance to drought and heat.

The efforts equipped the team with key insights into the crop’s genetic diversity, domestication and agronomic traits. The study also mapped the origins of chickpea and its ascent in Asia and Africa.

The team led by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in close collaboration with the BGI-Shenzhen, China, involved 39 scientists from leading research institutes (listed below) world over. This is the largest-ever exercise of whole-genome resequencing of chickpea.

What this means to the agricultural community is potential development of newer varieties of chickpea with higher yields, which are disease-and-pest-resistant, and better able to withstand the vagaries of weather.

The results of the three-year-long efforts have been published in Nature Genetics online with the title, ‘Resequencing of 429 chickpea accessions from 45 countries provides insights into genome diversity, domestication and agronomic traits’.

More than 90% of chickpea cultivation area is in South Asia. Drought and increasing temperatures are said to cause more than 70% yield loss in chickpea globally. Chickpea being a cool season crop is likely to suffer further reduction in productivity due to rising temperatures.

“The genome-wide association studies identified several candidate genes for 13 agronomic traits. For example, we could identify genes (e.g. REN1, β-1, 3-glucanase, REF6) which can help the crop tolerate temperatures up to 38oC and provide higher productivity,” says Dr Rajeev Varshney, the project leader and Research Program Director, Genetic Gains, ICRISAT.

Dr Xu Xun, CEO and President, BGI Research, China, co-leader of the project said, “BGI is very excited to work with CGIAR institutes like ICRISAT in high-end science research which could enable development of drought and heat-tolerant chickpea varieties for India and Africa. BGI has been enjoying a collaboration with ICRISAT for the past decade and we look forward to work together on many exciting projects in the years to come”.

The study established a foundation for large-scale characterization of germplasm, population genetics and crop breeding. It also helped understand domestication and post-domestication divergence of chickpea.

“This new found knowledge will enable breeders to enhance the use of diverse germplasm and candidate genes in developing improved (Climate-change ready) varieties that will contribute significantly to the increased productivity and sustainability of agricultural development in developing countries,” said Dr Peter Carberry, Director General, ICRISAT.

Highlighting the importance of this study, Ms Marie Haga, Executive Director, Global Crop Diversity Trust based in Germany, said, “This is exciting work by ICRISAT and partners to unlock the genetic diversity of chickpea. This deeper understanding of the crop could enable scientists to breed new varieties that are both highly productive and resilient to climate change, benefitting farming communities in many developing countries”.

The study was done in close collaboration with partners from the National Agricultural Research Systems. India, for instance as the biggest consumer of pulses in the world, faces increasing production gap. This new research could take India closer towards attaining self-sufficiency in pulse production.

“This is a significant contribution to global agricultural research and these unique, scientific solutions will help mitigate issues the world is facing right now. Science is key to ongoing efforts within ICAR and ICRISAT and also the way forward for agriculture in the country,” said Dr Trilochan Mohapatra, Secretary, Department of Agricultural Research and Education & Director General, Indian Council of Agricultural Research (ICAR).

The study also confirms that chickpea came to India from Fertile Crescent/ Mediterranean via Afghanistan and may have been introduced back to the primary centers of origin after 200 years. The new study speculates about possible introduction of chickpea to the New World directly from Central Asia or East Africa rather than the Mediterranean.

“Our study indicates Ethiopia as secondary center of diversity and also maps a migration route from Mediterranean/ Fertile Crescent to Central Asia, and in parallel from Central Asia to East Africa (Ethiopia) and South Asia (India),” Dr Varshney added.

Read the paper: Nature Genetics

Article source: International Crops Research Institute for the Semi-Arid Tropics -ICRISAT

Image: Patricia Maine / Pixabay

Plants have developed a robust system that stops their cell cycle in hostile environments such as abnormally hot temperatures. In response, they direct their energy to survival rather than growth. A new study led by scientists at the Nara Institute of Science and Technology (NAIST) reports in eLife that two transcription factors, ANAC044 and ANAC085, are critical for this response in the flowering plant Arabidopsis. The findings give clues on ways to modulate the growth of crops and other agriculture products.

Upon DNA damage, plants and animals halt cell division and execute DNA repair. This response prevents the damaged cells from proliferating. NAIST Professor Masaaki Umeda has made a career studying the molecular biology behind this protective measure.

“We reported that SOG1 is activated by DNA damage and regulates almost all genes induced by the damage,” he says. Another study from the lab showed “Rep-MYBs are stabilized in DNA damage conditions to suppress cell division,” he adds.

In the laboratory’s newest study, Umeda’s research team shows that ANAC044 and ANAC085 act as a bridge between SOG1 and Rep-MYB.

The scientists disrupted DNA in Arabidopsis cells by treating the cells with bleomycin, a compound commonly used to halt the growth of human cancer cells. The Arabidopsis cells failed to proliferate as expected unless they possessed a mutation in ANAC044 or ANAC085. In the mutant cases, the cells proliferated as though they were never exposed to bleomycin.

“We found that ANAC044 and ANAC085 are essential for root growth retardation and stem cell death, but not for DNA repair,” says Umeda.

Specifically, ANAC044 and ANAC085 were responsible for preventing the cell cycle from proceeding from G2 phase to mitosis in response to the DNA damage.

Rep-MYBs cause the same arrest in the cell cycle. Consistently, in normal cells, bleomycin caused a rise in the accumulation of Rep-MYBs, but not in cells with ANAC044 and ANAC085 mutations. These findings suggest ANAC044 and ANAC085 act as a bridge between SOG1 and Rep-MYBs in the halting of the cell cycle upon DNA damage.

DNA damage is just one form of stress that can cause the cell cycle to pause. To investigate whether ANAC044 and ANAC085 act in response to other forms of external stress, the researchers exposed the cells to different temperatures and osmotic pressure which cause the retardation in G2 and G1 progression, respectively.

Growth arrest was observed in both mutant and normal cells at a high osmotic pressure, but higher temperatures only caused pauses in the cell cycle in normal cells, indicating that ANAC044 and ANAC085 act as gatekeepers in the progression from the G2 phase in the cell cycle under abiotic stress conditions.

The fact that ANAC044 and ANAC085 operate in response to different types of abiotic stress suggests to Umeda that they may be at the core of new technologies designed to modulate plant growth.

“The research illuminates a new mechanism that optimizes organ growth under stressful conditions. When trying to increase plant productivity, scientists should consider ANAC044 and ANAC085,” he says.

Read the paper: eLife

Article source: Nara Institute of Science and Technology (NAIST)

Image: Masaaki Umeda

Compounds produced by sorghum plants to defend against insect feeding could be isolated, synthesized and used as a targeted, nontoxic insect deterrent, according to researchers who studied plant-insect interactions that included field, greenhouse and laboratory components.

The researchers examined the role of sorghum chemicals called flavonoids –specifically 3-deoxyflavonoid and 3-deoxyanthocyanidins — in providing resistance against the corn leaf aphid, a tiny blue-green insect that sucks sap from plants. To defend against pests like the aphids, sorghum has evolved defenses that includes biosynthesis of secondary metabolites, including flavonoids to poison the pests.

A previous Penn State study showed that in sorghum, accumulation of these flavonoids is regulated by a gene called yellow seed1 that controls responses to stresses such as fungal pathogens, noted Surinder Chopra, professor of maize genetics, Penn State. His research group in the College of Agricultural Sciences led both studies.

In the current research carried out at the University’s Russell E. Larson Agricultural Research Center, researchers grew two nearly identical lines of sorghum — one with a functional _y1_ gene that produced flavonoids, and the other a mutant called null y1, which did not possess the functional yellow seed1 gene responsible for producing the flavonoids.

When they compared the two lines of plants, researchers found that a significantly higher number of adult corn-leaf aphids colonized null y1 plants compared to the plants with functional _y1_ gene that produced flavonoids. The aphids actively fed on the null y1 plants to where some of them showed signs of stress with yellowed leaves. The functional sorghum plants that produced the flavonoids had much lower aphid numbers and showed no ill effects from aphid feeding.

Greenhouse experiments with similar potted sorghum plants demonstrated that the aphids clearly preferred to feed and reproduce on null y1 plants, and the adults produced many more nymphs.

In a companion laboratory experiment, researchers fed two groups of adult aphids diets of sorghum leaf tissues — but to one they added an extract containing the flavonoids. After a few days, most of the aphids that fed on the flavonoid-enriched leaf tissue died and reproduction was curtailed — none of those aphids had nymphs before they succumbed.

Perhaps surprisingly, Chopra explained, the flavonoids are not present in the phloem — vascular tissue in plants that conducts the sugars aphids seek — but are in the epidermal cells that form the outermost layer of defense. When aphids repeatedly probe and puncture the epidermal cells with their stylets, or beaks, they take up the flavonoids that lead to their demise.

The findings, published online in the Journal of Chemical Ecology, indicate flavonoids can potentially be deployed as potent insect deterrents to protect crops, Chopra suggested.

“Sorghum plants have evolved to precisely emit compounds offering defenses against harmful predatory insects that threaten them, and yet these chemicals in their defenses don’t hurt beneficial insects,” said Chopra. “If we could develop nontoxic insecticides, it would be a game changer — given that the toxicity of synthetic pesticides is of great concern, and they are considered to be dangerous to human health.”

Chopra, supported by Penn State, has applied for a patent on using flavonoids as insect deterrents. He pointed out that while much more research needs to be done, the most important consideration is that flavonoids are natural plant products that do not cause any pollution and are not harmful to human or animal health.

This research may be an early step toward developing new phytochemicals for crop defenses, Chopra believes. “How well the flavonoids work against other herbivores is being researched, but we know with corn leaf aphids they are very, very potent,” he said.

Read the paper: Journal of Chemical Ecology

Article source: Penn State

Image: USDA

Hedges, flowering strips and other seminatural habitats provide food and nesting places for insects and birds in agricultural landscapes. This also has advantages for agriculture: bees, flies, beetles and other animal groups pollinate crops and control pest insects in adjacent fields.

But how much of these habitats is necessary and how should they be arranged to make use of these nature-based ecosystem services?

This question has been addressed by a new study from the Chair of Animal Ecology and Tropical Biology at the Biocenter of Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany. The results are published in the journal “Ecology Letters”.

Small-scale land use is advantageous

According to the study, biodiversity, pollination, and pest control can be improved in landscapes even with a relatively small amount of non-crop habitat. To reach this effect, these habitats must be arranged to create a small-scale agricultural landscape.

For this study, Dr. Emily A. Martin‘s team took a closer look at data from ten European countries and 1,515 different agricultural landscapes. This clearly showed that small-scale land use is advantageous: it leads to a greater density of beneficial insects and spiders. And it increases the services provided by ecosystems for agriculture – pollination and natural pest control.

Creating a web of seminatural habitats

“In order to reduce pests and promote biodiversity, increasing the density of seminatural habitat elements can be an ideal solution for farms. You don’t have to remove much land from cultivation to reach a significant effect,” says Dr. Martin.

“The implementation of these findings would be an important step forward in the effort to achieve a sustainable and biodiversity-friendly agriculture”, Professor Ingolf Steffan-Dewenter, head of the Chair of Animal Ecology and Tropical Biology and co-author of the study, emphasises.

The JMU research team is now focusing on intensified cooperation with agricultural and environmental stakeholders. The scientists want to help implement a landscape management system that benefits everyone – nature and mankind.

Read the paper: Ecology Letters

Article source: University of Würzburg

Image: Matthias Tschumi

A large portion of a plant is hidden below the ground. This buried root system is essential for the plant: it provides stability, water, and food. In contrast to mammals, where the body plan is final at birth, the formation of new root branches ensures that the root system keeps growing throughout a plant’s life. The labs of Prof. Ive De Smet and Prof. Tom Beeckman (VIB-UGent Center for Plant Systems Biology), together with researchers from the University of Nottingham (UK), Heidelberg University (Germany) and the University of Copenhagen (Denmark) identified a novel component that controls the development of root branches supporting plants. Their findings will be published in the journal Proceedings of the National Academy of Sciences of the United States of America.

Prof. Ive De Smet and his team investigate how plants deal with changing environments, specifically with temperature extremes and drought stress. Prof. Tom Beeckman and his team explore how (lateral) roots evolved and develop. In plants, new organs are formed all the time. To do this, there must be a tight regulation of when and where a new organ is formed, and of how the cells that will make up this organ need to grow and divide.

To investigate organ formation in plants, the researchers used root branching as a model system. This process occurs continuously along the growing root, endlessly increasing the root system, and requires an extremely fine-tuned coordination of asymmetric cell divisions in cells that can give rise to new roots, together with the synchronization of processes in surrounding tissues. This ensures that the roots grow in the best possible way to take advantage of the nutrients and water in the soil.

Dr. Ramakrishna (University of Nottingham), who is the first author of the study, explains how the team discovered a new component through which plants control this: “To identify novel factors involved in governing root branching, we explored which genes are expressed during the early stages of the process. This led to the identification of a cell wall modifying enzyme – a molecule that regulates chemical reactions – that controls the cell divisions leading to the growth of a new root. Mutations in the gene that codes for this enzyme led to swelling of root cells that give rise to a new lateral root and resulted in subsequent defects in the first asymmetric cell divisions during the formation of root branches.”

These results show that a very tight regulation of cell size impacts the position of cell divisions, and thus the location and growth of new root branches. The identification of a cell wall enzyme acting in the extracellular space mediating plant stem cell divisions suggests we need to take into account a much broader range of proteins in our future search to disentangle the process of root branching.

Prof. Tom Beeckman (VIB-UGent) adds: “Identifying this enzyme is only a first step. The next challenge is to unravel how these cell wall modifications control cell size and how this is coordinated with other molecular processes during root branching.”

Prof. Ive De Smet (VIB-UGent) continues: “Ultimately, we strive to understand how plants respond to their ever-changing environment. Improving root architecture can contribute to stabilization of plant yield under adverse environmental conditions.”

This study, and the new research avenues it opens up, could lead to innovative techniques to improve root architecture in favor of higher crop yields and plants more resistant to drought and nutrient stress.

Read the paper: PNAS

Article source: VIB-UGent

Image: Pixabay

Dense rainforests, maple-blanketed mountains and sweeping coniferous forests demonstrate the growth and proliferation of trees adapted to specific conditions. The regional dominance of tree species we see on the surface now, however, might actually have been determined underground long ago.

Princeton University researchers report that the organization of forests worldwide — such as conifers in northern boreal forests or the broad-leafed trees of the tropics — are based on the ancient relationships that plant species forged with soil-dwelling microbes such as fungi and bacteria. These tiny organisms, known as symbionts, enhance the roots’ uptake of the crucial nutrients nitrogen and phosphorus.

The researchers reported in the journal Nature Ecology and Evolution that trees and shrubs came to dominate specific biomes by evolving the most competitive arrangement with local soil microbes — and cutting competing plants out of the action.

The biome-specific dynamics between plants and soil microbes could help scientists understand how ecosystems may shift as climate change brings about warmer temperatures that alter the interplay between trees, microbes and soil, the researchers report. Because the most competitive symbiotic arrangements for a particular biome triumph, scientists would only need to understand how an ecosystem is changing to gauge which vegetation will be moving in and which will be moving out. The research was supported by the Carbon Mitigation Initiative based within the Princeton Environmental Institute (PEI).

“The pattern we found can be used to tell us the landscapes that are more sensitive to human disturbance,” said senior author Lars Hedin, the George M. Moffett Professor of Biology and professor of ecology and evolutionary biology and the Princeton Environmental Institute. “It will predict what communities of trees will go where, their effect on the environment, and how they will respond in the future to climate change and increased carbon dioxide.”

First author Mingzhen Lu, a postdoctoral research associate in the Hedin lab, said that symbioses arose because plants needed microbes to unlock the nutrients — particularly nitrogen and phosphorus — released through soil decomposition. In return, the fungi and bacteria thrive on the carbohydrates that plants provide from photosynthesis. Lichen — the frilly white-green algae-fungus amalgamations that grow on rocks and trees — are an early example of this cooperation.

“The moment plants colonized the land, they formed symbioses,” Lu said. “The evolution of those new, powerful symbioses allowed plants to colonize new lands. This biology powers the global carbon and nutrient cycle.”

Lu and Hedin focused on trees and shrubs and found that as the plants spread across the globe, they carved out biomes using the nutrient advantage their relationship with microbes bestowed on them, Lu said. For example, maple trees will set conditions so that competing trees can’t grow in the areas maples inhabit.

“This is a perfect example of how biological organisms can shape the surrounding environment in favor of themselves,” Lu said. “This suggests to us that once the correct biological mechanisms are included, changes in the land can be predicted, but those forecasts need to capture belowground dynamics. By figuring out the most competitive symbiosis under specified conditions, we can determine how plant communities will evolve and develop in that biome in the future.”

Lu and Hedin used a game-theory model that allowed plants to use different belowground strategies for acquiring nutrients. Their model examined trees and shrubs — known as dominant vegetation — in tropical, temperate and boreal forests. They looked at biome conditions such as sunlight and nutrient turnover to examine the most competitive symbioses that will emerge if ecosystems are allowed to change and mutate naturally. They factored in the amount of carbon and nutrients that cycle through a particular biome, as well as how it responds to disturbances and how plant populations replace each other through succession.

Their model revealed that specific local interactions between plants, soil and nutrients are suitable for those areas. For instance, boreal trees have developed symbiotic relationships tailored for spongy boreal soils, but not the sodden soil of a tropical forest.

“Our findings show that the relationship between plants and their symbionts is central to understanding the organization and history of the land biosphere,” Hedin said.

The Hedin lab at Princeton previously found that plants may have a more active role in their evolution — and the formation of natural systems — than they are given credit for. In February 2018, Hedin and Lu reported in the journal Natur that the proliferation of plant life across the globe may have been propelled by root adaptations that allowed plants to become more efficient and independent.

In 2015, a paper in Nature Plants suggested that plants found in areas otherwise unsuitable for them — such as nitrogen-poor rainforest soils — use secretions to invite soil bacteria known as rhizobia to infect their roots cells. In a give-give relationship similar to that described in the latest publication, the rhizobia convert atmospheric nitrogen into fertilizer in exchange for carbohydrates. This interplay creates a nitrogen cycle that benefits surrounding vegetation.

“Plants have long created the conditions for their own success. What’s important is that we are now better understanding how this works based on our models,” Hedin said.

“Our new model shows that plants have competed for soil resources and in doing so they have harnessed the help of symbiosis and this has made them successful,” he said. “The resulting relationship has been so powerful that not only have they helped other trees and plants, but they also have transformed the environment.”

Read the paper: Nature Ecology and Evolution

Article source: Princeton University

Image: Mingzhen Lu, Princeton Ecology and Evolutionary Biology

Pre-crop values for a high number of previous and following crop combinations originating from farmers’ fields are, for the first time, available to support diversification of currently monotonous crop sequencing patterns in agriculture. The groundbreaking method utilizing satellite images was developed by Natural Resources Institute Finland (Luke) in collaboration with Finnish Geospatial Research Institute (FGI).

Luke has developed together with FGI a dynamic method to derive Normalized Difference Vegetation Index (NDVI) values to estimate pre-crop values on a field parcel scale from open Copernicus Sentinel-2 data. “The method is based on estimation of NDVI-gap, which was originally developed for Luke’s Land Use Optimization -tool available for each Finnish farmer on EconomyDoctor-portal”, says Research Professor Pirjo Peltonen-Sainio.

Pre-crop value is a measure that indicates the benefits of a previous crop for a subsequent crop in crop sequencing. Thereby, understanding on pre-crop values facilitates diversification of crop production. This again is a core measure for sustainable intensification of agricultural systems.

Digitalization can replace resource intensive field experimentation

Traditionally, long-term multi-locational field experiments are needed to identify pre-crop values. Such experiments are very resource intensive and therefore, they evaluate pre-crop values only for a limited number of previous and subsequent crops. With the new method data on pre-crop values can be updated and expanded every year, and implemented across continents.

“To develop the novel method, a total of 240.000 NDVI-values were used. With such vast data pre-crop values were determined for an exceptionally high number of previous and subsequent crop combinations”, describes Luke’s Senior Scientist Lauri Jauhiainen.

For the test-region in the South-West of Finland, the pre-crop values ranged from +16% to -16%. Especially grain legumes and rapeseed were valuable as pre-crops, which is well in line with results from field experiments.

Many opportunities – also rising from limitations

The method had some limitations as well. “For example, there is insufficient data on crops mostly cultivated in monoculture rotations for estimation of the value of a high number of alternative previous crops”, says Peltonen-Sainio. This was especially true for potatoes and sugar beet in Finland, for which spring and winter cereals were the only pre-crops with sufficient data for their pre-crop values.

“Data on pre-crop values can, however, be updated and regionally expanded every year. Now we just concentrated on developing the method per se”, reminds Jauhiainen. Scarce knowledge on pre-crop choices may limit farmers’ actions towards diversification of monotonous potato and sugar beet sequencing. On the other hand, these findings emphasize that the future experiments should focus on estimating pre-crop values for such previous and following crop combinations which suffer from insufficient on-farm data.

Read the paper: Frontiers in Plant Science

Article source: Natural Resources Institute Finland (Luke)

Image: CCO Public domain

What will a three-degree-warmer world look like? How will plants fare in more extreme weather conditions? When experiencing stress or damage from various sources, plants use chloroplast-to-nucleus communication to regulate gene expression and help them cope.

Now, Salk Institute researchers have found that GUN1—a gene that integrates numerous chloroplast-to-nucleus retrograde signaling pathways—also plays an important role in how proteins are made in damaged chloroplasts, which provides a new insight into how plants respond to stress. The paper was published in the Proceedings of the National Academy of Sciences (PNAS), and may help biologists breed plants that can better withstand environmental stressors.

“Climate change holds the potential to affect our food system dramatically. When plants are stressed, like in a drought, they produce lower crop yields. If we understand how plants respond to stress, then perhaps we can develop a way to increase their resistance and keep food production high,” says Salk Professor Joanne Chory, director of the Plant Molecular and Cellular Biology Laboratory and senior author of the paper.

In plant cells, structures called chloroplasts convert energy from sunlight into chemical energy (photosynthesis). Normally, the nucleus of the cell transmits information to the chloroplasts to maintain steady energy production. However, in a stressful environment, chloroplasts send an alarm back to the cell nucleus using retrograde signaling (creating a chloroplast-to-nucleus communication feedback loop). This SOS prompts a response that helps regulate gene expression in the chloroplasts and the nucleus to optimize energy production from sunlight.

Previously, the Chory lab identified a group of genes, including GUN1, that influence other genes’ expression in the cell when the plant experiences stress. GUN1 accumulates under stressful conditions but the exact molecular function of GUN1 has been difficult to decipher, until now.

“Plants often experience environmental stressors, so there must be a chloroplast-to-nucleus communication pathway that helps the plant know when to conserve energy when injury occurs,” says Xiaobo Zhao, first author and postdoctoral fellow in Chory’s lab. “GUN1 turns out to play a big role in this.”

To understand how GUN1 regulates chloroplast-to-nucleus communication, the scientists observed plants with functional and nonfunctional GUN1 under pharmacological treatments that could damage chloroplasts. In plants without GUN1, gene expression changed, as did RNA editing in chloroplasts. (RNA editing is a modification of the RNA that changes the identity of nucleotides, so that the information in the mature RNA differs from that defined in the genome, altering the instructions for making proteins.) Some areas of RNA had more editing and other locations had less editing—suggesting that GUN1 plays a role in regulating chloroplast RNA editing.

After further analysis, the team unexpectedly found that GUN1 partners with another protein, MORF2 (an essential component of the plant RNA editing complex), to affect the efficiency of RNA editing during chloroplast-to-nucleus communication in damaged chloroplasts. Greater activity of MORF2 led to widespread editing changes as well as defects in chloroplast and leaf development even under normal growth conditions (see image). During periods of stress and injury, MORF2 overproduction also led to disruption of chloroplast-to-nucleus communication.

“Taken together, these findings suggest a possible link between chloroplast-to-nucleus communication and chloroplast RNA editing, which are important regulatory functions for flowering plants, especially during stress,” says Chory, Howard Hughes Medical Institute investigator and holder of the Howard H. and Maryam R. Newman Chair in Plant Biology.

Next, the researchers plan to examine the mechanism of how the RNA editing changes in chloroplasts activate signals that can be relayed to the nucleus, and how these modifications alter the ability of the plant to respond to stress.

Other authors included Jianyan Huang, a postdoctoral fellow in the Chory lab.

Read the paper: PNAS

Article source: The Salk Institute

Image: Salk Institute