Leaf-Wounding Long-Distance Signaling Targets AtCuAOβ Leading to Root Phenotypic Plasticity

The Arabidopsis gene AtCuAO beta (At4g14940) encodes an apoplastic copper amine oxidase (CuAO) highly expressed in guard cells of leaves and flowers and in root vascular tissues, especially in protoxylem and metaxylem precursors, where its expression is strongly induced by the wound signal methyl jasmonate (MeJA). The hydrogen peroxide (H2O2) derived by the AtCuAO beta-driven oxidation of the substrate putrescine (Put), mediates the MeJA-induced early root protoxylem differentiation. Considering that early root protoxylem maturation was also induced by both exogenous Put and leaf wounding through a signaling pathway involving H2O2, in the present study we investigated the role of AtCuAO beta in the leaf wounding-induced early protoxylem differentiation in combination with Put treatment. Quantitative and tissue specific analysis of AtCuAO beta gene expression by RT-qPCR and promoter::green fluorescent protein-beta-glucuronidase fusion analysis revealed that wounding of the cotiledonary leaf induced AtCuAO beta gene expression which was particularly evident in root vascular tissues. AtCuAO beta loss-of-function mutants were unresponsive to the injury, not showing altered phenotype upon wounding in comparison to wild type seedlings. Exogenous Put and wounding did not show synergy in inducing early root protoxylem maturation, suggesting their involvement in a shared signaling pathway.