The Roles Of The JA, ET And SA Pathways In The Fusarium Head Blight Resistance Of Wheat Landrace Wangshuibai

Resistance to Fusarium head blight (FHB) is a very complex process in wheat, including huge numbers of genes’ expressions and involved in multiple pathways. Transcriptome analysis of wheat spikes during infection by Fusarium pathogen will help us to better understand the mechanism underlying FHB resistance and identify genes related to FHB resistance. To study the roles of the JA, ET and SA pathways in resistance to FHB of Wheat Landrace Wangshuibai, gene expression patterns of the key genes involved in the three pathways from FHB resistant wild-type Wangshuibai and its FHB susceptible mutant NAUH117 after infection by F. graminearum pathogen were profiled and compared based on gene-chip, digital gene expression profiling system and Q-PCR technology. The application of exogenous JA, ET and SA were used to validate their function in FHB resistance of wheat spikes. The results obtained were as follows:1. The roles of the JA pathways in resistance to FHB of wheatThe microarray assay and DGE profiling data showed that several key genes involoved in Jasmonic acid (JA), Ethylene (ET) and Salicylic acid (SA) pathway were differentially expressed in Wangshuibai and NAUH117. For the JA synthesis pathway, AOS (Allene oxide synthase), AOC (Allene oxide cyclase),12-OPR (12-oxophytodienoate reductase) and LOX (lipoxygenase) were up-regulated in both Wangshuibai and its mutant upon the F. graminearum infection. For JA signal pathway, COI1 (CORONATINE-INSENSITIVE 1) and JAZ (Jasmonate ZIM domain) were up-regulated only in Wangshuibai, while down-regulated or not changed in the mutant. The expression pattern of the above differentially expressed genes was verified by qRT-PCR. It implied that the JA pathway was important in resistance to FHB of wheat, and the inactivation of JA pathway probably caused the susceptibility of NAUH117. In the previous results, NAUH117 was characterized to have a deletion at Fhbl locus on chromosome 3BS which lead to its susceptibility (Xiao et al.,2011). It is proposed that the JA signal pathway may be mediated by or related to Fhb1. The application of exogenous JA on the spikes followed by inoculation of F. graminearum showed that resistant of NAUH117 enhanced to a similar level as that of Wangshuibai. This further confirmed the important role of the JA pathways in resistance to FHB of wheat.2. The roles of the ET pathways in resistance to FHB of wheatFor ET pathway, the key genes for ET biosystheses including SAM, ACS and A CO, and the key genes for ET signal pathway such as EIN2, EIL, ERF and ChiBwere up-regulated only in NAUH117 while not in Wangshuibai. The results demonstrated that ET pathway was not activated in Wangshuibai and may be not pivotal in defense to FHB, especially for Fhbl mediated FHB resistance. Moreover, the mutant became more susceptible to FHB when applicating the exogenous ET on the spikes before F. graminearum inoculation, indicating that the ET pathway contributed to the FHB susceptibility of wheat.3. The roles of the SA pathways in resistance to FHB of wheatThe key gene PAL for SA synthesis pathway was up-regulated in Wangshuibai, and no significant changes were detected in the mutant. On the contrary, the marker gene of SA signal pathway, PR-1, was up-regulated in NAUH117, while no significant change was detected in Wangshuibai. Application of exogenous SA on the spikes followed by F. graminearum inoculationled to increased FHB resistance of NAUHl 17, indicating the positive roles of SA pathway in resistance to FHB. The relationship of SA pathway with Fhb1-mediated resistance needs to be further studied.