#Deciphering how light controls stomatal production in plants

NUS biologists have discovered the mechanism of how light regulates stomatal production on the leaf surface, a process critical for the adaptation and fitness of plants.

Stomata are pores found on the outer layer (epidermis) of leaves and stems that control the rate of gas exchange in land plants. The number, size and distribution of stomata vary widely and change with external factors, enabling plants to adapt to diverse environments. It is widely accepted that light, as a critical external signal on plant development, triggers production of stomata for carbon dioxide uptake. However, the detailed mechanism of how light signals are linked to stomatal production remains unclear.

Extensive studies have found that a gene ELONGATED HYPOCOTYL 5 (HY5) plays important roles in light-mediated developmental changes in plants. Prof Lau On Sun and his team from the Department of Biological Sciences, National University of Singapore have established a link between HY5 and light-triggered stomatal production. The researchers found that under light, HY5 positively regulates stomatal development at early stages. Interestingly, they discovered that HY5 is expressed in the inner tissue of leaves (mesophyll) and activates STOMAGEN, which is secreted into the extracellular space and in turn stabilizes the master regulator of stomatal development SPEECHLESS (SPCH) on the epidermis. This leads to enhanced stomatal production (see Figure). The exciting results from this research reveal that environmental stimuli could modify gene expression in cells from one tissue and subsequently influence cell development from another tissue.

Prof Lau said, “The findings are intriguing as it suggests there is tight coordination between tissue layers in plants when they respond to the environment. Embarking on this, we plan to investigate if other stimuli, including plant hormones and temperature changes, may play a role in stomatal development through HY5 and STOMAGEN. The regulatory module uncovered here could also serve as an entry point for improving plant vigor in diverse growing conditions.”