Functional Characterization Of Two Transcription Factor Genes,TaMYB77 And TaAP2-15,during Wheat-puccinia Striiformis F.sp.tritici Interaction

Wheat is one among of the most significant cereal crops to mankind as it is a stable of many diets.However,the production and productivity of wheat is constrained by both biotic and abiotic stresses.Among the biotic stresses,disease is the most yield limiting factor.The three wheat rust diseases,stem rust(Puccinia graminis f.sp.tritici),leaf rust(Puccinia triticina)and stripe rust(Puccinia striiformis f.sp.tritici(Pst))are the most threats to wheat production.Of these rust diseases,stripe rust is the most serious in many wheat producing areas of the globe.Plants have their own innate defense mechanisms against invading pathogens.The transcription factors(TFs)are involved in plant defense response against invading pathogens.Here,we identified two genes from Myeloblastosis(MYB)and APETALA2/AP2 families and characterized their functional roles during the Wheat-Pst interaction.Our work provides theoretical basis for sustainable control of wheat stripe rust.The main results were obtained as follows:MYB TFs are one of the largest TFs families that are involved in response to stresses.However,only limited information is available on the roles of MYB TFs on how wheat plant responses to Pst infection.Here,we reported the functional role of a novel R2R3 MYB TF,TaMYB77 during wheat-Pst interaction.Our data indicated that TaMYB77 is induced upon infection with both virulence and avirulence Pst isolates.It also induced by exogenous application of salicylic acid(SA)and Abscisic acid(ABA).TaMYB77 is localized in the nucleus of both wheat and N.benthamiana.Transient overexpression of TaMYB77 in N.benthamiana triggered hypersensitive response(HR)related program cell death accompanied by an increased electrolyte leakage,enormous accumulation of reactive oxygen species(ROS)and transcriptional accumulation of different hormone defense related-and HR-specific marker genes.Overexpression of TaMYB77 in wheat significantly enhanced wheat resistance to Pst through various ways of defense response as induction of pathogenesis-related genes,ROS accumulation and hypersensitive cell death.On the other hand,RNAi-mediated silencing of TaMYB77 improved wheat susceptibility to Pst associated with enhanced fungal growth.Furthermore,we found a RING-type E3 ligase,Ta BR,interact with TaMYB77 both in yeast(in vitro)and in planta(in vivo).Our results demonstrated that TaMYB77 acts as a positive regulator of hypersensitive response associated cell death and contributes to wheat resistance to Pst by regulating certain PR genes through SA-and ABA-signaling pathways.AP2 TFs have also plays crucial roles in development,reproductive growth,biotic and abiotic stress of plants.However,the role of TaAP2-15,under wheat-Pst scenario remains elusive.In this study,we isolated TaAP2-15 and characterized its function during the interaction between wheat and stripe rust fungus.TaAP2-15 was significantly induced upon infection with Pst.The transcriptional accumulation of TaAP2-15 was also significantly increased when treated with SA and other environmental stress elicitors.TaAP2-15 was localized in the nucleus of wheat and N.benthamiana.Silencing of TaAP2-15 by BSMV mediated VIGS(Virus-induced gene silencing)resulted in increased wheat susceptibility to Pst accompanied by enhanced Pst growth.We also confirmed that the transcript levels of pathogenesis-related genes(Ta PR1 and Ta PR2)were down-regulated,while ROS-scavenging genes(Ta CAT3 and Ta FSOD3D)were induced by quantitative real-time PCR(RT-qPCR)accompanied by reducing the accumulation of H₂O₂.Furthermore,TaAP2-15was found interacting with a Zinc finger protein(Ta RZFP34)that is a homolog of Os RZFP34 in rice.Together these findings demonstrated that the TaAP2-15 positively involved in wheat resistance to stripe rust fungus and provide new insights into the roles of AP2 in wheat-Pst interaction.