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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Involvement of Polyamine Oxidase in Wound Healing^1,2,[W]

Dipartimento di Biologia, Università Roma Tre, Viale G. Marconi 446, 00146 Rome, Italy (R.A., A.T., M.M.C., R.F., A.C.); Istituto di Cristallografia, Consiglio Nazionale delle Ricerche, Monterotondo, 00016 Rome, Italy (G.R.); and Dipartimento Farmaco Chimico Tecnologico, Università degli Studi di Siena, Via A. Moro, 53100 Siena, Italy (M.B.)

Hydrogen peroxide (H₂O₂) is involved in plant defense responses that follow mechanical damage, such as those that 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. Maize (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 (Nicotiana tabacum) plants strongly enhanced lignosuberization along the wound periderm, providing evidence for a causal relationship between PAO and peroxidase-mediated events during wound healing.

² This work is dedicated to the memory of Daniele Liberatori.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Alessandra Cona (cona{at}uniroma3.it).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.108902

^* Corresponding author; e-mail cona{at}uniroma3.it.

Received September 13, 2007; accepted October 29, 2007; published November 9, 2007.