Heterotrimeric G protein mediates ethylene‐induced stomatal closure via hydrogen peroxide synthesis in Arabidopsis

Summary Heterotrimeric G proteins function as key players in hydrogen peroxide (H 2 O 2 ) production in plant cells, but whether G proteins mediate ethylene‐induced H 2 O 2 production and stomatal closure are not clear. Here, evidences are provided to show the Gα subunit GPA 1 as a missing link between ethylene and H 2 O 2 in guard cell ethylene signalling. In wild‐type leaves, ethylene‐triggered H 2 O 2 synthesis and stomatal closure were dependent on activation of Gα. GPA 1 mutants showed the defect of ethylene‐induced H 2 O 2 production and stomatal closure, whereas wG α and cG α overexpression lines showed faster stomatal closure and H 2 O 2 production in response to ethylene. Ethylene‐triggered H 2 O 2 generation and stomatal closure were impaired in RAN 1 , ETR 1 , ERS 1 and EIN 4 mutants but not impaired in ETR 2 and ERS 2 mutants. Gα activator and H 2 O 2 rescued the defect of RAN 1 and EIN 4 mutants or etr1‐3 in ethylene‐induced H 2 O 2 production and stomatal closure, but only rescued the defect of ERS 1 mutants or etr1‐1 and etr1‐9 in ethylene‐induced H 2 O 2 production. Stomata of CTR 1 mutants showed constitutive H 2 O 2 production and stomatal closure, but which could be abolished by Gα inhibitor. Stomata of EIN 2 , EIN 3 and ARR 2 mutants did not close in responses to ethylene, Gα activator or H 2 O 2 , but do generate H 2 O 2 following challenge of ethylene or Gα activator. The data indicate that Gα mediates ethylene‐induced stomatal closure via H 2 O 2 production, and acts downstream of RAN 1, ETR 1, ERS 1, EIN 4 and CTR 1 and upstream of EIN 2, EIN 3 and ARR 2. The data also show that ETR 1 and ERS 1 mediate both ethylene and H 2 O 2 signalling in guard cells.