Pectinase function in growth and stomatal dynamics

Pectin is a polymer that holds cell walls together and stiffens the walls, but what happens when those cell walls need to move, for example when cells (including guard cells) expand? Rui et al. started with a guard-cell specific transcriptome to identify genes encoding cell-wall modifying enzymes. They identified POLYGALACTURONASE INVOLVED IN EXPANSION3 (PGX3), a guard-cell enriched and ABA-inducible pectinase-encoding gene. The authors show that elevated PGX3 expression affects pectin molecular mass and abundance, thus affecting cell wall mechanics and leading to increased cell expansion and enhanced stomatal pore closure, whereas pgx3 mutants are delayed in stomatal closure. They present a model for how PGX3 affects cell wall stiffness and stomatal movements. Plant Cell 10.1105/tpc.17.00568