A forest in Idyllwild, California. Credit: Sean Brenner
Two new studies this week—one from England, the other from California—have come to the same conclusion about how to protect plants from extreme climate change: just “talk” to them.
Biologists at UCLA deciphered a secret “language” in leaves and woody stems that points to plants’ optimal habitats—information that could be exploited to protect existing habitats and establish new populations. At the University of Cambridge, researchers demonstrated that they can activate a plant's natural defense mechanism, or immune response, using colored light as a stimulus.
Predictive power
In a new study published in Functional Ecology, researchers at UCLA developed a statistical model that estimates each plant species’ preferred temperature and amount of rainfall based on its height; the size, wilting point, anatomy and chemical composition of its leaves; and the density of its wood. This data allows scientists to how much rain each species prefers—not merely what it can tolerate. The model also allows the team to estimate how mismatched a plant is from its native climate.
For the study, the team analyzed 10 distinct leaf and wood traits from more than 100 species in a range of environments mostly within the University of California Natural Reserve System. The ecosystem types the scientists analyzed—desert, coastal sage scrub, chaparral, montane wet forest, mixed riparian woodland and mixed conifer broadleaf forest—cover about 70% of California’s land area.
They found that species native to warmer, drier climates tend to be shorter in stature, with thicker and denser leaves and lower wilting points—traits that enable them to continue photosynthesis when water is scarce and to grow faster when water is more readily available. They also found that many plants were occupying locations that differed in climate from what was estimated to be their optimal niche.
“As climate change ensues, we think this will tend to aggravate the sensitivity of many species, including common trees like the California buckeye and shrubs like the purple sage and California lilacs,” said senior author Lawren Sack, a UCLA professor of ecology and evolutionary biology.
There have been previous studies on whether plants’ functional traits could be used to accurately predict their climate preferences. However, this is the first to combine all the available state-of-the art measurement technologies—such as vapor-pressure osmometry to determine plants’ wilting points—with advanced statistical modeling to do so. The researchers say this gave them “unprecedented predictive power.”
“Now that we know this, if you give us a leaf and a piece of wood, we can give a good scientific prediction of where the plant prefers to live,” said Sack. “We are tuning in to what the plants are telling us about their preferences, in the language of their tissues and physiology, aiming to help them survive escalating climate challenges.”
Optogenetics as a language
To understand cellular activity, biologists need to be able to control biomolecular processes at the cellular level. Optogenetics is a technique that uses a light stimulus to activate or deactivate a specific process. To do this, scientists engineer light-sensitive photoreceptors to control a target process and then deliver these optogenetic actuators to the cells they want to control.
But, optogenetics has been difficult to apply to plants since they’re already responsive to light with a plethora of photoreceptors and the need for a wide spectrum of light to grow.
Thus, the University of Cambridge team looked for an optogenetic gene expression switch that could be applied under normal horticultural light conditions without impacting endogenous plant physiology and development.
Collaborating with UC Davis, the team ended up repurposing the prokaryotic CcaS-CcaR optogenetic system into a eukaryotic CcaS-CcaR optogenetic system. And while the prokaryotic CcaS-CcaR optogenetic system uses green (on) - red (off) light signals, the team suddenly detected an unexpected blue-off behavior in the eukaryotic version.
According to the study published in PLoS Biology, in addition to the original red-green sensing domain, CcaS had a domain with homology to blue-light photosensors called phototropins. The team’s engineering efforts inadvertently unlocked a latent CcaS blue sensing behavior—providing an alternate way to control CcaS-CcaR activity.
Currently “Highlighter,” as the system is called, is inactive under blue light conditions and active in the dark and under white light, green light and, mysteriously, red light conditions. Further work is planned, but the team has already demonstrated optogenetic control over plant immunity, pigment production and a yellow fluorescent protein, the latter at cellular resolution.
“If we could warn plants of an impending disease outbreak or pest attack, plants could then activate their natural defense mechanisms to prevent widespread damage,” said study author Alexander Jones. “We could also inform plants about approaching extreme weather events, such as heatwaves or drought, allowing them to adjust their growth patterns or conserve water. This could lead to more efficient and sustainable farming practices and reduce the need for chemicals.”