The Copper Amine Oxidase AtCuAOδ Participates in Abscisic Acid-Induced Stomatal Closure in Arabidopsis

Plant copper amine oxidases (CuAOs) are involved in wound healing, defense against pathogens, methyl-jasmonate-induced protoxylem differentiation, and abscisic acid (ABA)-induced stomatal closure. In the present study, we investigated the role of the Arabidopsis thaliana CuAO delta (AtCuAO delta; At4g12290) in the ABA-mediated stomatal closure by genetic and pharmacological approaches. Obtained data show that AtCuAO delta is up-regulated by ABA and that two Atcuao delta T-DNA insertional mutants are less responsive to this hormone, showing reduced ABA-mediated stomatal closure and H2O2 accumulation in guard cells as compared to the wild-type (WT) plants. Furthermore, CuAO inhibitors, as well as the hydrogen peroxide (H2O2) scavenger N,N-1-dimethylthiourea, reversed most of the ABA-induced stomatal closure in WT plants. Consistently, AtCuAO delta over-expressing transgenic plants display a constitutively increased stomatal closure and increased H2O2 production compared to WT plants. Our data suggest that AtCuAO delta is involved in the H2O2 production related to ABA-induced stomatal closure.