Abstract
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 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,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 H2O2 production compared to WT plants. Our data suggest that AtCuAOδ is involved in the H2O2 production related to ABA-induced stomatal closure.
Highlights
Copper amine oxidases (CuAOs) are dimeric proteins of 140–180 kDa, containing a copper ion and a redox-active organic cofactor 2,4,5-trihydroxyphenylalanine quinone (TPQ) for each monomer
A promoter region of approximately 2.7 kb upstream of the Arabidopsis thaliana CuAOδ (AtCuAOδ) start codon was analyzed in silico for the presence of cis-acting elements by the Arabidopsis eFP Browser
AtCuAOδ mRNA in guard cells, whose level increased upon abscisic acid (ABA)-treatment
Summary
Copper amine oxidases (CuAOs) are dimeric proteins of 140–180 kDa, containing a copper ion and a redox-active organic cofactor 2,4,5-trihydroxyphenylalanine quinone (TPQ) for each monomer. These enzymes catalyze the intracellular and extracellular terminal catabolism of amines, including monoamines, diamines, and polyamines (PAs), by oxidizing the carbon next to the primary amino group, with the subsequent reduction of molecular oxygen to hydrogen peroxide (H2 O2 ) and the production of the corresponding aldehydes and ammonia [1,2]. CuAOs have been found at high expression levels in several species of Fabaceae, especially in the cell wall of pea (Pisum sativum), chickpea (Cicer arietinum), lentil (Lens culinaris), and soybean (Glycine max) seedlings, from which these enzymes have been purified and characterized [3]. CuAOs have been described in Arabidopsis (Arabidopsis thaliana) [5,6,7,8], tobacco (Nicotiana tabacum) [8,9], and apple (Malus domestica) [10], and a latex CuAO has been characterized from Mediterranean spurge (Euphorbia characias) [11], with diverse substrate affinities and specificities [12].
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