New live analysis system for plant stomata, signals exciting progress in climate-change resistant crop development
Stomata, the holes on the surface of a plant’s leaves, are essential for controlling the exchange of gases between the plant and the atmosphere. Stomata with the right characteristics can increase a plant’s adaptability and resistance to challenging conditions such as drought, which may be a particularly desirable characteristic with the prospect of climate change looming.
Selective plant breeding and genetic analysis are both methods by which plants’ characteristics can be adapted to their environment, but in order to make these processes work, it is necessary to identify specimens with the desired stomatal characteristics. Unlike larger parts of plants such as leaves or seeds, stomata have to be examined under a microscope, which is incredibly time consuming when performed by hand.
Scientists at Yokohama City University Kihara Institute for Biological Research and Nagoya University Institute of Transformative Bio-molecules (WPI-ITbM) have developed a new AI analysis method which allows the live imaging and simultaneous analysis of wheat stomata. By using a dedicated processing unit that analyzes the stomata as they pass beneath the microscope, this new system removes the previous greatest obstacle to rapid analysis: the need to store and process images via a separate server or computer system, which is time-consuming and expensive. The system is inexpensive and can be operated using equipment present in most modern imaging laboratories.
The principal application of this system will be in identifying plant specimens with desirable characteristics and using them to develop crops, both through selective breeding and genome analysis, which will be more resistant to environmental stressors such as drought in a future where climate change may outpace plants’ ability to evolve resistance naturally. As its development moves forward, it should also be able to be applied to other areas of plants whose characteristics’ visual analysis may prove useful.
It is hoped that the development of this system represents a significant step towards preventing future food shortages and ensuring that people in areas of the globe vulnerable to climate change are not left without viable crops.
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JOURNAL
Frontiers in Plant Science
ARTICLE TITLE
An Affordable Image-Analysis Platform to Accelerate Stomatal Phenotyping During Microscopic Observation
ARTICLE PUBLICATION DATE
28-Jul-2021
Survival strategy of starving spruces trees: The critical role of reserves
Trees continue to form reserves even during long periods of starvation, study shows
Peer-Reviewed PublicationIMAGE: HEALTHY, GROWN-UP TREES OF THE ORIGINAL SPRUCE CLONES USED FOR THE EXPERIMENT. view more
CREDIT: MPI-BGC
During climate extremes, plants cannot produce sufficient energy-rich carbon compounds through photosynthesis and they become dependent on stored reserves. According to current understanding, these reserves are only formed when the supply of photosynthesis products exceeds demand to support processes like growth. Scientists from the Max Planck Institute for Biogeochemistry demonstrate that trees continue to form reserves even during long periods of starvation. To achieve this, trees stop growing and even digest non-essential energy-rich components. This knowledge can be used to improve predictions of how trees will respond to climate change.
Trees and entire forests worldwide are threatened by increasing climate extremes and ensuing insect infestations. As sessile organisms, trees cannot escape threatening environmental conditions and must adapt their metabolic processes to confront the threats. Crucially important for plants is the production of energy-rich sugar molecules (carbohydrates) by photosynthesis. These compounds serve as both energy sources and basic building blocks for all metabolic processes. During climate extremes such as prolonged drought or heat, photosynthesis is impaired and trees produce less carbohydrates, because CO2 uptake declines and water is scarce. The demand for energy-rich sugars is then not met and plants have to rely on stored reserves to maintain vital metabolic processes. When reserves become depleted, plants may starve to death or become vulnerable to disease and insect attacks as the defense system fails.
Despite their critical role, it was assumed until now that reserves like soluble sugars, starch or fats are only formed when photosynthetic conditions are favorable and their rate of production exceeds the demand from other functions such as growth. "From an evolutionary perspective that doesn't make sense. Trees have to survive for decades before they can reproduce, and a reliable source of quickly available reserves plays a crucial role in surviving frequent unfavorable periods" underlines Dr. Henrik Hartmann, group leader at the Max Planck Institute for Biogeochemistry (MPI-BGC) in Jena. "Why should a tree invest in growth instead of ensuring immediate and future survival by accumulating more reserves?"
To investigate the importance of storage for tree survival, Dr. Jianbei Huang, postdoctoral researcher in the research group and first author of the recent study published in Proc.Natl.Acad.Sci.USA, subjected young spruce trees to a starvation treatment by growing them at very low CO2 concentrations for several weeks. This allowed him to simulate reduced photosynthetic rates that occur during climate extremes when studying the plants’ carbohydrates. Initially, readily available storage compounds decreased as expected, since they were used for metabolism and could not be replenished under reduced CO2 supply. Surprisingly, as CO2 starvation progressed, the storage compounds stabilized at a constant level and trees stopped growing. "When photosynthetic output became too low to adequately supply carbon to all functions, the trees reduced their growth and diverted available resources to storage," Huang concludes.
CAPTION
Experimental set-up used for CO2-starving and analyzing the spruce seedlings (right).
CREDIT
MPI-BGC
Three to 5 weeks after the onset of CO2 starvation, the researchers also examined the genetic activity of plant cells, in particular expression of genes that encode enzymes involved in metabolic processes. "We found for the first time that after prolonged starvation the production of enzymes responsible for fast-access storage compounds was increased" Huang says. In contrast, gene expression of enzymes involved in growth processes, such as cellulose and lignin production, was greatly reduced, thus confirming the trade-off between storage and growth at the molecular level.
Even more surprising, metabolic pathways for alternative energy production were boosted, as found by an increased production of enzymes responsible for the conversion of complex fat molecules into energy-rich carbohydrates. "It seems that plants prefer to sacrifice expendable structures and apparently even digest themselves, rather than to give up on storage formation" says Hartmann. "So the strategy for energy production and storage, while shutting down unnecessary energy consumption for growth, is consistently implemented during CO2 starvation". How long trees may survive climate extremes using this strategy and whether apparently healthy looking trees might already be in the emergency mode of self-digestion, are follow-up questions that research should urgently tackle. Altogether, the novel finding that carbon-starved spruce trees build up reserves gives hope that this adaptation allows forests to recover from climate stress.
Previous studies on storage strategies in plants were limited to short-lived herbaceous species like Arabidopsis, covering only hours to a few days. However, for long-lived plants that take decades to reproduce and that are continuously exposed to changing seasons and sporadic climate extremes, findings on Arabidopsis may be of little relevance. "Of course, trees must follow a storage strategy that allows them to survive longer than biennial herbs" says Huang, "how else have they managed to persist on Earth for nearly 400 million years?"
Conifers, such as the spruce trees studied here, dominate many Northern Hemisphere ecosystems and have other very important ecological functions besides absorbing and storing the greenhouse gas carbon dioxide. Yet, many conifer species are not adapted to the warmer and drier conditions imposed by climate change, and are thus particularly threatened. Their survival and overall forest development is simulated in vegetation models. However, these are based on the older ideas that photosynthesis supply directly drives growth, ignoring allocation of energy-rich sugars into storage and reserves. "Building on our new findings, such models can now be designed more realistically," Hartmann emphasizes, "and more reliable model outcomes are extremely important to predict the future of our forests, especially under advancing climate change."
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JOURNAL
Proceedings of the National Academy of Sciences
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Storage of carbon reserves in spruce trees is prioritized over growth in the face of carbon limitation.
ARTICLE PUBLICATION DATE
16-Aug-2021
