The Arabidopsis Rab protein RABC1 affects stomatal development by regulating lipid droplet dynamics

Abstract

Lipid droplets (LDs) are evolutionarily conserved organelles that serve as hubs of cellular lipid and energy metabolism in virtually all organisms. Mobilization of LDs is important in light-induced stomatal opening. However, whether and how LDs are involved in stomatal development remains unknown. We show here that Arabidopsis thaliana LIPID DROPLETS AND STOMATA 1 (LDS1)/RABC1 (At1g43890) encodes a member of the Rab GTPase family that is involved in regulating LD dynamics and stomatal morphogenesis. The expression of RABC1 is coordinated with the different phases of stomatal development. RABC1 targets to the surface of LDs in response to oleic acid application in a RABC1GEF1-dependent manner. RABC1 physically interacts with SEIPIN2/3, two orthologues of mammalian seipin, which function in the formation of LDs. Disruption of RABC1, RABC1GEF1 or SEIPIN2/3 resulted in aberrantly large LDs, severe defects in guard cell vacuole morphology and stomatal function. In conclusion, these findings reveal an aspect of LD function and uncover a role for lipid metabolism in stomatal development in plants.

COBL7 is required for stomatal formation via regulation of cellulose deposition in Arabidopsis

“…The analysis suggested that the phenotype of dsm1 mutant was caused by a recessive mutation of a single unknown gene. Therefore, dsm1 was selected for mutant gene cloning as described (He et al ., 2018; Lukowitz et al ., 2000; Ge et al ., 2022). Totally, 800 dsm1 phenotype seedlings were identified for fine gene mapping.…”

“…Stomatal apertures were measured as described (Geisler et al ., 2000; Ge et al ., 2022). Briefly, attach the abaxial side of the leaflet with light‐bodied vinylpolysiloxane dental resin (Elite HD+, Zhermack Clinical, Italy) and then remove it as soon as it dried.…”

“…Authors New Phytologist Ó 2023 New Phytologist Foundation New Phytologist (2024) 241: 227-242 www.newphytologist.comNew Phytologist these stomata had similar aperture size to stomata in WT under treatments of light or fusicoccin, a fungal toxin that opens stomata (Fig.S1d;Turner & Graniti, 1969;Ge et al, 2022).By positional cloning and DNA sequencing analysis, we identified a single point mutation (from G to A substitution) at nucleotide 1215 in the open reading frame of the COBL7 gene COBL7…”

Dynamic Regulation of Lipid Droplet Biogenesis in Plant Cells and Proteins Involved in the Process

“…When LD production is induced by oleic acid, SEIPIN2/3 is mainly located on the LD surface in wild-type, while very little SEIPIN2/3 was located on the LD surface in RABC1 mutants. Thus, together with its partner GEF, RABC1 negatively controls the dynamics and size of LDs in young stomata by regulating the localization of its effector factors SEIPIN2/3 [ 13 ].…”

“…Homologs of some regulatory proteins related to animal LD formation have been identified in plants, however, there is no experimental evidence to show whether they function the same way in plant LD formation [ 11 , 12 , 13 ]. It has been shown that plant and animal LD surface proteins are completely different ( Figure 1 ).…”