Fraudentali, I., Department of Science, Università Roma Tre, Roma, 00146, Italy; Carucci, A., Department of Science, Università Roma Tre, Roma, 00146, Italy; Tavladoraki, P., Department of Science, Università Roma Tre, Roma, 00146, Italy, Istituto Nazionale Biostrutture e Biosistemi (INBB), Rome, 00136, Italy; Angelini, R., Department of Science, Università Roma Tre, Roma, 00146, Italy, Istituto Nazionale Biostrutture e Biosistemi (INBB), Rome, 00136, Italy; Cona, A., Department of Science, Università Roma Tre, Roma, 00146, Italy, Istituto Nazionale Biostrutture e Biosistemi (INBB), Rome, 00136, Italy; Rodrigues-Pousada, R.A., Department of Life, Health, and Environmental Sciences, Università dell’Aquila, L’Aquila, 67100, Italy

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 CuAOδ (AtCuAOδ; At4g12290) in the ABA-mediated stomatal closure by genetic and pharmacological approaches. Obtained data show that AtCuAOδ is up-regulated by ABA and that two Atcuaoδ T-DNA insertional mutants are less responsive to this hormone, showing reduced ABA-mediated stomatal closure and H2 O2 accumulation in guard cells as compared to the wild-type (WT) plants. Furthermore, CuAO inhibitors, as well as the hydrogen peroxide (H2 O2) scavenger N,N1-dimethylthiourea, reversed most of the ABA-induced stomatal closure in WT plants. Consistently, AtCuAOδ over-expressing transgenic plants display a constitutively increased stomatal closure and increased H2 O2 production compared to WT plants. Our data suggest that AtCuAOδ is involved in the H2 O2 production related to ABA-induced stomatal closure. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.