| Puccinia striiformis f.sp.tritici（Pst）is one of the most devastating obligate biotrophic pathogens that threatens global wheat production.At present,resistance breeding is the most economical and effective strategy for preventing and controlling stripe rust caused by Pst.But the resistant varieties applied to agricultural production quickly"lost"their resistance due to the rapid mutation of Pst races.From obligate biotrophic fungi’s perspective,the deletion or mutation of some susceptible genes will break the balance established between the host and the pathogen.However,this balance will take a long time,or even impossible to rebuild.Therefore,the deletion or mutation of the susceptible gene will produce more durable and broad-spectrum resistance.Research on susceptible genes can enrich the gene resource pool for plant resistance improvement.In the preliminary work of screening wheat stripe rust-susceptible genes,we selected a candidate susceptible gene—TaMYB24（MYB transcription factor,TF）.Firstly,TaMYB24encodes an R2R3 type MYB protein of 237 amino acids（714 nucleotides）.Subcellular localization assay indicated that TaMYB24 was localized in the nucleus of N.benthamiana and Triticum aestivum mesophyll cell.The result of transactivation assay supported that TaMYB24 had transcriptional activation activity.Tissue-specific expression analysis showed that TaMYB24 was differentially expressed in wheat roots,stems and leaves,and was induced in the early stages of Pst infection.After silencing of TaMYB24 by BSMV-VIGS（Virus induced gene silencing）system,the hyphal length and infection area in the silenced plants were decreased to varying degrees compared to control plants both in the incompatible and compatible interactions at different time points.Meanwhile,the expression of pathogenesis-related genes was significantly up-regulated.The H2O2 accumulation in the silenced plants was increased in the compatible interaction.The VIGS results show that after silencing of TaMYB24,the resistance of wheat to Pst is enhanced.The results of VIGS indicating that TaMYB24 negatively regulates the immune defense response of wheat to Pst infection,exercising susceptible function.At the same time,we explored the susceptibility mechanism of TaCIPK2（Calcineurin B-Like protein interacting protein kinases）confirmed its susceptible function in preliminary work.Firstly,in the all of four TaCIPK2’s candidate targets screened from c DNA yeast library,TaSY5 was verified to interact with TaCIPK2 through yeast two-hybrid assay,bimolecular fluorescence complementation（Bi FC）assay and luciferase complementation（LUC）assay.And than,we analysised the function of TaSYT5.TaSYT5 encodes a synaptotagmin protein of 562 amino acids,which is a transporter protein.Domain feature analysis showed that TaSYT5 consisted of three different domains,TM,SMP and C2domains.Subcellular localization assay indicated that TaSYT5 was located in cytoplasm.TaSYT5 was induced upon exogenous application of ABA and at the early stages of Pst infection.After silencing of TaSYT5 using VIGS system,wheat resistance to Pst infection was enhanced in the compatible incompatible interaction,,and the susceptibility of wheat to strip rust was weakened in the compatible interaction.Based on these findings,we speculate that the TaCIPK2 may affect the intracellular material transport of host plant by regulating TaSYT5,thereby playing a susceptible role in the process of Pst infecting wheat. |
