Identification Of SA Signaling Involved In FHB Resistance By BSMV Induced Gene Silencing(VIGS)

Fusarium head blight?FHB?is a major fungal disease on the spikes of wheat in the whole world.In recent years,the threat of FHB to the global wheat production and food security has become more and more severe,as the change of global climate and tillage.Sumai3 and its derivatives,the most representative of FHB type II resistance,are the major source of FHB resistant materials used in the breeding program.So we conducted these experiments with sumai 3 and the near-isogenic line Apogee/Apogee73S2 derived from Sumai 3.In this study,we firstly established the barley stripe mosaic virus induced gene silencing?BSMV-VIGS?in wheat spikes and applied it on FHB resistance.Using Sumai 3 and Fhb1near-isogenic line Apogee/Apogee73S2,the marker genes in SA signal transduction were identified for FHB resistance via VIGS.The results are as follows:1.BSMV-VIGS system had been successfully established in wheat leaves and spikes using TaPDS as a reporter gene.Through the photobleaching phenotype resulted by the silence of TaPDS gene,we analyzed that it is optimum for gene silencing of wheat spikes to rub inoculation on wheat flag leaves in booting stage.Besides,we successfully silenced the PDS gene of wheat relative species,including wild emmer wheat and Aegilops tauschii,with the recombinant virus carrying TaPDS gene fragment,which provides an important technical method for the study of the functional gene in Aegilops tauschii and wild emmer wheat.2.In order to reduce the influence of BSMV infection to the FHB resistance,we inoculated the BSMV:00 plants with four different pathogenic F.g isolates.The results showed that the scap resistance of BSMV:00 infected plants could not be significantly affected when inoculated with the F.g strain of SF06-1 with moderate pathogenicity.3.It was found that Sumai 3 enhanced the sensivity to F.g with either of gene silencing of TaNPR2,TaNPR3 and TaICS,but not with the TaNPR1.Moreover,Kenong 199 improved the resistance to powdery mildew after the silencing of TaICS.It indicated that TaNPR2,TaNPR3 and TaICS probably had a certain effect on the resistance to Fusarium head blight,while TaICS might reduce the resistance to powdery mildew.4.The TaICS transgenic T₂ plants of Brachypodiam distachyon improved their resistance to FHB by the inoculation of F.g,which further proved the effect of TaICS on the resistance to Fusarium head blight.5.Exogenous SA treatment could slow down the morbidity of wheat scab,which mainly occurred in the early stage of the occurrence of Fusarium head blight.In addition,SA could also promote the occurrence of HR reaction and form necrotic spots in the infected area of wheat,to inhibit the spread of FHB to the uninfected parts.6.Expression analysis showed that TaNPR2,TaNPR3 and TaICS were differentially expressed in the isogenic lines Apogee/Apogee73S2 by the F.g induction,while it was consistent with TaNPR1'expression level in the above isogenic lines.TaNPR1 expression was little down-regulated in Sumai 3 induced by exogenous SA,while the expression level of TaNPR2 and TaNPR3 showed a trend of gradually increased first and then decreased.But the expression of TaICS gene was rapidly inhibited and the greatest inhibition was happened at 3hours after SA treatment,then the inhibitory degree decreases gradually.In this study,the BSMV-VIGS was successfully applied in identification of genes involed in FHB resistance.Using this system,the marker genes in SA signaling were confirned to play positive roles to scap resistance.