Wheat MYB28 Regulates Wax Biosynthesis And Resistance To Insect And Pathogen Attacks

Wheat is a popular gramineous crop in the world,and plays an important role in food security and our production and life.Food has always been the focus of global attention.The infestation of pests and diseases has seriously affected the yield and quality of crops.From the research of disease-resistant and insect-resistant drugs to the cultivation of excellent varieties,the research of disease-resistant and insect-resistant drugs and the increase of yield has always been the focus of people’s research.Plant MYB transcription factors regulate phloem-based defense（PBD）and affect plant growth and development.As a form of plant defense response,PBD plays a defensive role against systemic infection of pathogenic microorganisms,and is an effective mechanism against powdery mildew pathogen infection and feeding of wheat aphid.PBD consists of two key components: phloem protein（PP）and β-1,3-glucan.The protein complex formed by PP and the callose formed by the aggregation of β-1,3-glucan play the role of blocking the sieve and preventing pathogen invasion.The waxy layer on plant surface plays an important role in all stages of plant growth and development,and is also an important barrier for plants to resist external biological and abiotic stress.When plants are infected by pests and diseases,the waxy layer plays a first-line defense role Alkanes are important components of wax synthesis.The wax synthesis gene TaCER1-1A found in wheat regulates the types and contents of alkanes and aldehydes by participating in the decarbonyl pathway The MYB transcription factor TaMYB28 regulates the synthesis of wax.It was demonstrated by chromatin immunoprecipitation that MYB transcription factor TaMYB28 can interact with the wax gene TaCER1-1A in wheat.Can TaMYB28 interact with TaCER1-1A to affect the formation of wax layer in wheat and play a defense role against plant diseases and insect pests ? In this study,the silencing and overexpression vectors of TaMYB28 and TaCER1-1A were constructed by using virus-mediated gene silencing and virus-mediated gene overexpression techniques,and corresponding silencing and overexpression plants TaMYB28 i,TaMYB28 OE,TaCER1-1Ai and TaCER1-1AOE were obtained.The effects of TaMYB28 on the synthesis of wax layer and the roles of TaMYB28 and TaCER1-1A in the response to powdery mildew infection and the feeding of wheat aphid were studied by fluorescence quantitative PCR detection of wax crystal scanning and chlorophyll leaching experiment.The results showed that TaMYB28 was involved in the synthesis of wax layer and affected the number and morphology of wax crystal.Both TaMYB28 and TaCER1-1A had a positive regulation effect on the wax layer thickening against pathogen invasion during powdery mildew infection and feeding of wheat aphid.In addition,TaMYB28,as an upstream regulator,can regulate the synthesis of wax layer and participate in the regulation of phloem defense response.After feeding on TaMYB28 i and TaMYB28 OE plants,the glucan synthase encoding gene GSL2,GSL10,GSL12 and phloem lectin protein encoding gene Hfr-1.The expression levels of Wci-1 and other phloem defense response-related genes were significantly different from those of the wild type,while the expression levels of these genes were not significantly different from those of the wild type after aphid fed TaCER1-1Ai and TaCER1-1AOE,suggesting that TaCER1-1A was not involved in the regulation of PBD process.This study revealed the mechanism of wheat TaMYB28 resistance to disease and insect infestation,providing a favorable molecular genetic basis for wheat agricultural production prevention of disease and insect infestation and selection of superior varieties.