Polyamine Oxidation Is Indispensable for Wheat (Triticum aestivum L.) Oxidative Response and Necrotic Reactions during Leaf Rust (Puccinia triticina Eriks.) Infection

Hydrogen peroxide is a signal and effector molecule in the plant response to pathogen infection. Wheat resistance to Puccinia triticina Eriks. is associated with necrosis triggered by oxidative burst. We investigated which enzyme system dominated in host oxidative reaction to P. triticina infection. The susceptible Thatcher cultivar and isogenic lines with defined resistance genes were inoculated with P. triticina spores. Using diamine oxidase (DAO) and polyamine oxidase (PAO) inhibitors, accumulation of H(2)O(2) was analyzed in the infection sites. Both enzymes participated in the oxidative burst during compatible and incompatible interactions. Accumulation of H(2)O(2) in guard cells, i.e., the first phase of the response, depended on DAO and the role of PAO was negligible. During the second phase, the patterns of H(2)O(2) accumulation in the infection sites were more complex. Accumulation of H(2)O(2) during compatible interaction (Thatcher and TcLr34 line) moderately depended on DAO and the reaction of TcLr34 was stronger than that of Thatcher. Accumulation of H(2)O(2) during incompatible interaction of moderately resistant plants (TcLr24, TcLr25 and TcLr29) was DAO-dependent in TcLr29, while the changes in the remaining lines were not statistically significant. A strong oxidative burst in resistant plants (TcLr9, TcLr19, TcLr26) was associated with both enzymes’ activities in TcLr9 and only with DAO in TcLr19 and TcLr26. The results are discussed in relation to other host oxidative systems, necrosis, and resistance level.