Unravelling the molecular mechanisms underlying the superior performance of grass stomata

Trang Dang, Diana Santelia
Institute of Integrative Biology, ETH Zurich, 8092 Zurich, Switzerland

β-amylases (BAM, EC 3.2.1.2) are key enzymes of plastidial starch turnover extensively studied in Arabidopsis thaliana. One isoform of the Arabidopsis BAM family, BAM1, is predominantly expressed in guard cells (GCs), regulating GC starch diel turnover and facilitating rapid stomatal opening at dawn and under blue light. However, the role of BAM1 orthologs in other plant species remains underexplored. To address this, we examined GC starch metabolism in C3 grasses (Poaceae), which have unique dumbbell-shaped stomata and superior stomatal kinetics. Our research identified key enzymes for GC starch degradation in barley and revealed that subsidiary and mesophyll cells play a crucial role in GC starch metabolism under blue light, likely via SWEET family sugar transporters supplying carbohydrates to GCs. These findings advance our understanding of GC starch metabolism, offering insights into stomatal evolution and regulation, and suggesting future research directions for improving plant resilience to environmental stress.

Keywords: β-amylase, guard cells, subsidiary cells, starch metabolism, grass stomata