Molecular Mechanism Of Wheat Xingzi9104 Adult Plant Resistance To Stripe Rust

Stripe rust,caused by Puccinia striiformis.f.sp.tritici(Pst),is one of the most damaging wheat diseases worldwide.It has been proved that the use of resistance cultivars is the most economic way to control the disease.Adult plant resistance(APR)has recently received much attention due to its durable resistance and practical potentials.Previous studies on plant APR to pathogens mainly focus on the genetics of plant disease resistance,but the current knowledge deciphering molecular mechanism of plant APR to pathogens were largely limited.The wheat cultivar XingZi9104 possesses APR to stripe rust.To elucidate the molecular mechanism of APR and screen the key APR genes,the high-throughput transcriptome sequencing and digital gene expression profiling(DGE)technology were utilized to interrogate the interaction of wheat-Pst at seedling and adult stage.This research might provide a theoretical and practical significance for the breeding of improved cultivars and the sustainable control of stripe rust.The main results are as follows:1.With transcriptome sequencing for seedling and adult stage mock 0 hours post inoculation(hpi)samples,157689 Unigenes were obtained and 27204 differentially expressed genes(DEGs)were screened.Transcription was the second classes genes(9.58%)in COG function classification,indicated that transcription play a key role in biological activity.GO functional enrichment analysis showed that more genes were enriched in response to biotic stimulus,chitin and cell wall related biological process in DEGs.It is indicated that more basic resistence related genes were activate at adult stage.2.Twelve inoculated and mock inoculated RNA samples for seedling and adult stage were sequenced by DGE analysis,and 4966,4936 and 721 DEGs were screened for 24,48 and 120 hpi,respectively.Signal transduction,disease/defence,metabolism and transcription genes,respectively focused on kinase,resistence gene,glycometabolism and WRKY TFs,were able to take part in the APR by gene annotation.GO functional enrichment analysis showed that more genes were enriched in signal transduction,especially for kinases molecular function,vesicle cellular component and phosphorylation proces ontology in DEGs,indicated that kinases,vesicle and phosphorylation play a key role in APR.Fifty six DEGs were analysed by qRT-PCR.The results show that fourteen DEGs were induced only at adult stage,nine DEGs were induced only at seedling stage,and other genes shared the same expression pattern at adult and seedling stage.It is indicated that these DEGs may contribute to the APR or susceptible reaction at seedling stage in different degrees with different pattern.3.Transcriptome sequencing and DGE revealed that the transcription levels of WRKY TFs changed in after inoculation with Pst.To clarify whether WRKY TFs are involved in wheat APR to Pst,we cloned and characterized thirteen wheat WRKY TFs(TaWRKY1B?2?4?5?22?27?40?41?50?57?70?73?79).The TaWRKY41 transcript levels were sharply elevated at the early infection stage in adult plants.Meanwhile,the growth of Pst hyphae was increased and wheat disease resistance was weakened.These results suggested that TaWRKY41 act as a positive regulator for wheat APR to Pst.The TaWRKY79 transcript levels were sharply elevated at the early infection stage in seedling.Meanwhile,the growth of Pst hyphae were weakened.These results suggested that TaWRKY79 takes part in wheat susceptible reaction at seedling stage.However,there were no obvious change in transcript levels and BSMV-VIGS system for other eleven genes,indicated that they may play a minor role in wheat basic resistence to Pst.4.Comprehensive assays were performed for TaWRKY41 and TaWRKY79 according to the above results.Genome analysis revealed that there is one single copy for two genes in the wheat genome,located on chromosome 5D and 7D,respectively.TaWRKY41 protein possesses two WRKY domains and TaWRKY79 possesses one,but they both possess a separate region for mediating transcriptional activation.Subcellular localization revealed that two genes both are exclusively localized on the nucleus.Furthermore,the expression of TaWRKY41 was highly induced after treating adult plants with exogenous SA.The TaPRl transcript level was significantly reduced and the TaPAL was not affected in TaWRKY41-knockdown adult plants,however,when TaPAL was silenced in adult plants,TaWRKY41 expression was decreased.These results indicated that TaWRKY41 likely participates in the SA-mediated signaling pathway and functions downstream of TaPAL and upstream of TaPR1.However,the expression of TaWRKY79 was highly reduced after treating with exogenous SA and induced after treating with exogenous JA at seedling stage.Taken together,these results suggested that TaWRKY79 likely participates in wheat susceptible reaction at seedling stage by SA and JA-mediated signaling pathway.