Understanding the genetic basis of stomatal morphogenesis and function

Each formed by a pair of guard cells, stomata are microscopical pores that play fundamental roles in plant photosynthesis, water use efficiency and stress adaptation. The simple stomatal structure and specialised guard cell anatomy enable plants to respond and adapt to environmental changes rapidly. To identify genetic determinants involved in stomatal formation and maturation, we took advantage of forward genetic approaches and performed focused mutant screens. Here, we report the isolation and characterization of two mutants, lds1 and dsm1. LIPID DROPLETS AND STOMATA 1 (LDS1)/RABC1 (At1g43890) encodes a member of the Rab GTPase family that is involved in regulating lipid droplets (LD) dynamics. The expression of LDS1/RABC1 is coordinated with the different phases of stomatal development. RABC1 physically interacts with SEIPIN2/3, two orthologues of mammalian Seipin, which function in the formation of LD. Disruption of RABC1, RABC1GEF1, or SEIPIN2/3 resulted in aberrantly large LD, severe defects in guard cell vacuole morphology, stomatal movements. DEFORMED STOMATA 1 (DSM1) encodes COBRA-LIKE 7 (COBL7), a plant-specific glycosylphosphatidylinositol (GPI)-anchored protein. COBRA-LIKE 7 and its closest homologue, COBL8, are first enriched on the forming cell plates during cytokinesis, and then their subcellular distribution and abundance change are correlated with the progressive stages of stomatal pore formation. Furthermore, we demonstrated that COBL7 plays a predominant and functionally redundant role with COBL8 in stomatal formation through regulating cellulose deposition and ventral wall modification. Our work provides necessary insight into the regulatory mechanisms of stomatal morphogenesis and function in Arabidopsis.

Keywords: stomatal morphogenesis, cellulose, lipid droplets, ventral wall modification, plant development