Eliciting and signal transduction events of the Russian wheat aphid resistance response in wheat

[摘要] English: Features of the upstream defense response in the interaction between wheat (Triticumaestivum L.) and the Russian wheat aphid (RWA) (Diuraphis noxia, Mordvilko) wereinvestigated. The study was conducted in an attempt to shed light on the eliciting andsignal transduction events of the defense mechanism.It was found that the intercellular wash fluid (IWF) of infested resistant wheat plants(Tugela Dn 1), injected intercellularly into susceptible (Tugela) and resistant (TugelaDn 1) plants had much higher eliciting activity than the IWF of infested susceptible plants.The eliciting activity was measured in terms of the expression of downstream defenserelated peroxidase and β-1,3-glucanase activities. The defense related enzymes weredifferentially induced to higher levels in the resistant than susceptible plants. Fractionationof the IWF of infested resistant plants by C-18 reverse-phase and con A bindingchromatography revealed the elicitor to be a glycoprotein capable of inducing both localand systemic defense responses.The signaling role of salicylic acid (SA) in mediating the downstream defense responseswas also investigated. RWA infestation induced differential accumulation of SA to higherlevels in the resistant (421-fold) than susceptible (78-fold) plants. The increase in theactivity of the defense related peroxidase in infested resistant plants correlated well withthe increase in SA content. Intercellular application of H202 induced a 65% increase in SAcontent only in the resistant plants. As SA was accumulating, catalase activity wasdeclining. In addition, intercellularly applied SA also inhibited catalase activity by 49%.The results from this study indicated that the intercellular glycoproteins from infestedresistant plants can act as elicitors of the downstream defense responses and that SA ismost probably a signaling molecule in mediating these responses.

[发布机构] University of the Free State