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Plant Physiology Preview Published on November 9, 2007; 10.1104/pp.107.108902
Received September 13, 2007 Involvement of Polyamine Oxidase in Wound Healing
Dipartimento di Biologia, Universita "Roma Tre" Viale G. Marconi 446, 00146 Roma, Italy; Istituto di Cristallografia, Consiglio Nazionale delle Ricerche, Monterotondo, 00016 Roma, Italy; Dipartimento Farmaco Chimico Tecnologico, Universita degli Studi di Siena, Via A. Moro, 53100 Siena, Italy * Corresponding author; email: cona{at}uniroma3.it.
Hydrogen peroxide (H2O2) is involved in plant defense responses which follow mechanical damage, such as those which occur during herbivore or insect attacks, as well as pathogen attack. H2O2 accumulation is induced during wound healing processes as well as by treatment with the wound signal jasmonic acid. Plant polyamine oxidases (PAOs) are H2O2 producing enzymes supposedly involved in cell-wall differentiation processes and defense responses. Zea mays PAO (ZmPAO) is a developmentally regulated flavoprotein abundant in primary and secondary cell walls of several tissues. In this study, we investigated the effect of wounding on ZmPAO gene expression in the outer tissues of the maize mesocotyl and provide evidence that ZmPAO enzyme activity, protein and mRNA levels increased in response to wounding as well as jasmonic acid treatment. Histochemically detected ZmPAO activity especially intensified in the epidermis and in the wound periderm, suggesting a tissue-specific involvement of ZmPAO in wound healing. The role played by ZmPAO-derived H2O2 production in peroxidase-mediated wall stiffening events was further investigated by exploiting the in vivo use of N-prenylagmatine (G3), a selective and powerful ZmPAO inhibitor, representing a reliable diagnostic tool in discriminating ZmPAO-mediated H2O2 production from that generated by peroxidase, oxalate oxidase or by NADPH oxidase activity. Here, we demonstrate that G3 inhibits wound-induced H2O2 production and strongly reduces lignin and suberin polyphenolic domain deposition along the wound, while it is ineffective in inhibiting the deposition of suberin aliphatic domain. Moreover, ZmPAO ectopic expression in the cell wall of transgenic tobacco plants strongly enhanced lignosuberization along the wound periderm, providing evidence for a causal relationship between PAO and peroxidase-mediated events during wound-healing.
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