Heterotrimeric G-proteins involved in the MeJA regulated ion flux and stomatal closure in Arabidopsis thaliana

Heterotrimeric G-proteins play an important role in plant signalling pathways. The plant hormone methyl jasmonate (MeJA) can induce stomatal closure in many plant species. The signal cascade in MeJA-induced stomatal closure has been studied previously. However, the function of G proteins in this process has not yet been evaluated. In this study, the stomatal movement induced by MeJA in the wild-type Arabidopsis thaliana (L. Heynh.) (WS), G alpha subunit loss-of-function mutant gpa1-1 and gpa1-2 guard cells were measured. Further, the transmembrane ion flux (H+, Ca2+ and K+) and reactive oxygen species (ROS) experiments were performed in guard cells from WS, GDP-beta-S pre-treated WS, gpa1-1 and gpa1-2 using non-invasive micro-test technique (NMT) and confocal technique. It was observed that the MeJA-induced stomatal closure was abolished in guard cells of gpa1 mutants. GDP-beta-S pre-treatment and gpa1 mutants impaired the MeJA-activatedH(+) efflux, Ca2+ influx and K+ efflux. The accumulation of ROSin gpa1-1 and gpa1-2 guard cells was also lower than that in WS guard cells under MeJA treatment. These results suggested that G alpha subunits are involved in regulating the signal events in JA signal pathway and stomatal closure.