Evaluating the role of phenylpropanoid and octadecanoid signal transduction pathways and some components of cell wall-associated defense in wheat cultivars- Fusarium species interaction

Two species of Fusarium graminearum and F. culmorum are the main causal agents of wheat head blight worldwide. Currently, there is limited knowledge about the defense-signaling pathways and mechanisms involved in wheat cultivars basal resistance against Fusarium spp. Phenylalanine ammonia lyase (PAL) and lipoxygenase (LOX) enzymes, as main markers of phenylpropanoid and octadecanoid signal transduction pathways, may be involved in plant defense responses. In this research, the activity of two enzymes of PAL and LOX and expression of corresponding genes, also production of defense compounds such as phenolics and lignin were investigated in the leaves and spikes of susceptible (Falat) and partially resistant (Gaskozhen) wheat cultivars inoculated withtwo species of F. graminearum and F. culmorum. The results of this study showed that the activity of these two enzymes and production of phenolic compounds and lignin in leaves and spikes of Gaskozhen cultivar was higher than Falat. Expression analysis of the PAL and LOX genes revealed a direct correlation between enzymes activity and expression of the corresponding genes. In most of the studied times after inoculation, higher levels of enzymes activity, gene expression and phenolics and lignin production were observed in wheat-F. culmorum interaction. Application of PAL and LOX inhibitors increased disease development in both cultivars. These results provide novel information about the biochemical and molecular role of phenylpropanoid and octadecanoid signal transduction pathways in resistance of wheat against Fusarium spp.