Catalases negatively regulate methyl jasmonate signaling in guard cells

Methyl jasmonate (MeJA)-induced stomatal closure is accompanied by the accumulation of hydrogen peroxide (H2O2) in guard cells. In this study, we investigated the roles of catalases (CATs) in MeJA-induced stomatal closure using cat mutants cat2, cat3-1 and cat1 cat3, and the CAT inhibitor, 3-aminotriazole (AT). When assessed with 2′,7′-dichlorodihydrofluorescein, the reduction of catalase activity by means of mutations and the inhibitor accumulated higher basal levels of H2O2 in guard cells whereas they did not affect stomatal aperture in the absence of MeJA. In contrast, the cat mutations and the treatment with AT potentiated MeJA-induced stomatal closure and MeJA-induced H2O2 production. These results indicate that CATs negatively regulate H2O2 accumulation in guard cells and suggest that inducible H2O2 production rather than constitutive elevation modulates stomatal apertures in Arabidopsis.