Wound healing in plants: Cooperation of copper amine oxidase and flavin-containing polyamine oxidase.

Copper amine oxidases (CuAO) and flavin-containing amine oxidases (PAO) are hydrogen peroxide (H(2)O(2))-producing enzymes responsible for the oxidative de-amination of polyamines. Currently, a key role has been ascribed to apoplastic amine oxidases in plants, i.e., to behave as H(2)O(2)-delivering systems in the cell wall during cell growth and differentiation as well as in the context of host-pathogen interactions. Indeed, H(2)O(2) is the co-substrate for the peroxidase-driven reactions during cell-wall maturation and a key signalling molecule in defence mechanisms. We recently demonstrated the involvement of an apoplastic PAO in the wound-healing process of the Zea mays mesocotyl. Experimental evidence indicated a similar role for an apoplastic PAO in Nicotiana tabacum. In this addendum we suggest that a CuAO activity is also involved in this healing event.