Mirosinases, TGG1 and TGG2, redundantly function in ABA and MeJA signaling in Arabidopsis guard cells

Abstract

Thioglucosid glucohydrolase (myrosinase), TGG1, is a strikingly sbundant protein in Arabidopsis guard cells. We investigated responses of tgg1-3, tgg2-1 and tgg1-3 tgg2-1 double mutants to ABA and MeJA to clarify whether two myrosinases, TGG1 and TGG2, function during stomatal closure. ABA, MeJA and H₂O₂ induced stomatal closure in wild ype, tgg1-3 and tgg2-1, but failed to induce stomatal closure in tgg1-3 tgg2-1. All mutants and wild type showed Ca²⁺-induced stomatal closure and ABA-induced reactive oxygen species (ROS) production. A model is discussed in which two myrosinases redundantrly function downstream of ROS production and upstream of cytosolic Ca²⁺ elevation in ABA and MeJA signaling in guard cells.