Biologists at the National University of Singapore have figured out how plants inhibit the formation of stomata and microscopic pores on their surface to limit water loss during a drought. Pys.org portal.
Stomata, which are present on the surface of leaves, are important for gas exchange between plants and the atmosphere. However, they are also the main sources of water loss when it leaves the leaves as water vapour. When there is a shortage of water, plants perform two stomatal reactions to conserve water: they close the pores of existing stomata and limit the formation of new ones.
These responses, which are mediated by abscisic acid (ABA), are critical for plant adaptation to drought and are especially important for maintaining agricultural efficiency in a changing climate. However, it has not been previously studied exactly how ABA inhibits stomatal production.
In the latest release Science Advances A research team led by LAU Associate Professor On Sun from the Department of Biological Sciences at the National University of Singapore reported on the mechanism underlying this drought-mediated suppression of stomatal development.
The scientists found that the major drought-activated ABA signaling kinases directly phosphorylate the master stomatal regulator SPEECHLESS (SPCH). Phosphorylation refers to the addition of a phosphate group to a molecule. This ABA-induced phosphorylation of the SPCH protein occurs at two different sites and causes degradation of SPCH.
Because SPCH promotes stomatal development, SPCH phosphorylation leads to a decrease in SPCH levels and stomata number, and elimination of these sites (sample S240/271A) resulted in the opposite response. Importantly, the researchers also demonstrated that plants with altered SPCH phosphorylation sites exhibited differential drought tolerance.
These results show that a certain "code" underlies a key response of plants to conserve water. By manipulating it, we could fine-tune the drought tolerance of crop plants and help optimize them for a variety of growing conditions, from traditional to urban farming.