Copper Amine Oxidase Catalyzes The Hydrogen Peroxide Involved In The Ethylene-induced Stomatal Closure

Stomatal is the main channel in plant leaves for gas exchange with the outside world, stomatal movement is regulated by multiple environment factors and internal cues including phytohormone ethylene and important signal molecule hydrogen peroxide (H2O2). Previous study has indicated that copper amine oxidase (CuAO) in Vicia faba guard cells is an essential enzymatic source for H2O2 production in ABA-induced stomatal closure via the degradation of putrescine, and ethylene-induced stomatal closure has also been shown to be dependent on H2O2 generated by the nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase. However, up to data, it is unclear whether H2O2 generated by CuAO participates in ethylene-induced stomatal closure. In the present study, using the abaxial epidermis of Vicia faba as materials, by means of the epidermal strip bioassay. laser scanning confocal microscopy (LSCM) and determination of CuAO activity, the role of H2O2 generated by CuAO in ethylene-induced stomatal closure was investigated. The main conclusions are as follows:1. Ethylene release agent ethephon. ethylene precursor 1-aminocyclopropane-l-carboxylic acid (ACC) and ethylene induced stomatal closure significantly.2. Aminoguanidine (Aminoguanidine. AG) and 2-bromine ethylamine (2-Bromoethylamine. BEA), two specific inhibitor of CuAO. obviously inhibited ethephon-, ACC-and ethylene-induced stomatal closure.3. Among four catalytic products of CuAO. only H2O2 significantly reversed the inhibitory effects of AG and BEA on ethephon-, ACC-and ethylene-induced stomatal closure.4. Putrescine (Put), a substrate of CuAO, had no significant effect on ethephon-, ACC-and ethylene-induced stomatal aperture.5. Ethephon, ACC and ethylene induced increase in apoplastic CuAO activity, and the effects of ethephon, ACC and ethylene on CuAO activity were significantly prevented.6. Ethephon. ACC and ethylene induced H2O2 production in guard cells, and the effects of ethephon. ACC and ethylene on H2O2 production in guard cells were significantly suppressed.In summary, our results demonstrate that ethylene-induce stomatal closure is associated with CuAO-dependent H2O2 production.