Wounding chickpea (Cicer arietinum) internodes or cotyledons resulted in an increase in the steady-state level of copper amine oxidase (CuAO) expression both locally and systemically. Dissection of the molecular mechanisms controlling CuAO expression indicated that jasmonic acid worked as a potent inducer of the basal and wound-inducible CuAO expression, whereas salicylic acid and abscisic acid caused a strong reduction of the wound-induced CuAO expression, without having any effect on the basal levels. Epicotyl treatment with the CuAO mechanism-based inhibitor 2-bromoethylamine decreased hydrogen peroxide (H 2 O 2 ) levels in all the internodes, as evidenced in vivo by 3,3Ј-diaminobenzidine oxidation. Moreover, inhibitor pretreatment of wounded epicotyls resulted in a lower accumulation of H 2 O 2 both at the wound site and in distal organs. In vivo CuAO inhibition by 2-bromoethylamine after inoculation of resistant chickpea cv Sultano with Ascochyta rabiei resulted in the development of extended necrotic lesions, with extensive cell damage occurring in sclerenchyma and cortical parenchyma tissues. These results, besides stressing the fine-tuning by key signaling molecules in wound-induced CuAO regulation, demonstrate that local and systemic CuAO induction is essential for H 2 O 2 production in response to wounding and indicate the relevance of these enzymes in protection against pathogens.Plant defense responses are accomplished by the deployment of a complex array of events that are differentially modulated depending on the incoming stress (Maleck and Dietrich, 1999). Wounding different plant organs or interaction with pathogens induce local and systemic accumulation of defenserelated proteins (Hammond-Kosack and Jones, 1996;Ryals et al., 1996;Ryan, 2000). The study of signaling events inducing local and systemic responses led to the discovery of systemin, jasmonates, ethylene, salicylic acid (SA), and abscisic acid (ABA) as signal molecules (Peñ a-Cortés et al., 1989; Farmer and Ryan, 1990; Pearce et al., 1991;Xu et al., 1994; O'Donnell et al., 1996;Schweizer et al., 1998;van Loon et al., 1998; Knoester et al., 1999).The existence of multiple defense strategies and complex signaling networks leads to an enhanced defense capacity of the plants. The signal transduction pathways of wounding and pathogen attack may be common, different, or exclusive, depending on the biological system, but likewise the establishment of defense mechanisms requires the presence or accumulation of hydrogen peroxide (H 2 O 2 ; Sutherland, 1991; Mehdy, 1994; Hammond-Kosack et al., 1996). In particular, H 2 O 2 behaves as a direct cytotoxic compound against pathogens and as a second messenger in the activation of defense genes (Lamb and Dixon, 1997). Moreover, this compound is involved in systemic acquired resistance and acts synergistically with NO in the induction of hypersensitive cell death (Delledonne et al., 1998). As a cosubstrate of the peroxidases, H 2 O 2 has been implicated in the oxidative cross-linking of apoplastic st...

No abstract