Gene Cloning Of TaJAZ1 And Research On The Mechanism Of TaJAZ1-regulated Resistance Against Powdery Mildew In Wheat(triticum Aestivum L.)

Bread wheat(Triticum aestivum L.)is a major staple crop worldwide.Powdery mildew,caused by the biotrophic fungal pathogen Blumeria graminis f.sp.tritici,is a major limitation for wheat yield.The bread wheat capacities to adapt to biotic and abiotic stresses are important agronomic traits.To improve bread wheat resistance against powdery mildew,it is useful to identify the key regulators for bread wheat defense responses.However,the molecular mechanisms underlying wheat resistance against powdery mildew remain largely unclear.The phytohormone Jasmonic acid(JA)and its derivatives are key regulators of the response to stresses.In this study,we report the role of JASMONATE-ZIM domain protein Ta JAZ1 in regulating bread wheat resistance against powdery mildew and provide a molecular framework for JA signaling in bread wheat.The major results are as following:1.We generated the transgenic bread wheat lines over-expressing the truncated Ta JAZ1 without the Jas motif.After inoculation with powdery mildew,we observed increased resistance to powdery mildew in transgenic lines.The results of the q RT-PCR assay showed increased Ta PR1/2 gene expression and reactive oxygen species accumulation,leading to enhanced resistance against powdery mildew.2.Simultaneously,we identified a Jasmonic acid(JA)-induced b HLH transcription factor Ta MYC4 in bread wheat.We demonstrated that Ta JAZ1 directly interacts with Ta MYC4 to repress its transcriptional activity.We also show the interaction between C-terminal of Ta JAZ1 and N-terminal of Ta MYC4.3.Meanwhile,we showed that the ZIM domain of Ta JAZ1 interacts with the C terminus of Ta NINJA,whereas the N-terminal EAR motif of Ta NINJA interacts with the transcriptional co-repressor Ta TPL.Collectively,our work pinpoints Ta JAZ1 as a favorable gene to enhance bread wheat resistance toward powdery mildew,and provides a molecular framework for JA signaling in bread wheat.Our model proposes that under normal conditions,Ta NINJA directly links transcriptional repressor Ta JAZ1 to the transcriptional co-repressor Ta TPL for repression of the transcriptional activity of Ta MYC4.After Bgt inoculation,Ta JAZ1 is degraded and Ta MYC4 is released to regulate resistance against Bgt through repressing ROS accumulation and Ta PRs expression.