Studies Of UvXlnR And UvHxt1 Regulating Sugar Utilization In Ustilaginoidea Virens

Rice is the main food crop in China and its yield and quality not only affect agricultural economic benefits,but also threat to national food security.Ustilaginoidea virens is one of the destructive diseases of rice,threatening the safe rice production.In addition,the ustiloxins produced by U.virens are harmful to humans and animals.Currently,the main control measure of U.virens is the application of chemical fungicides.However,too much fungicide usages may cause environmental pollution and occurrence of fungicide resistance.Therefore,exploring the pathogenic mechanisms of U.virens may contribute to developing new fungicides and resistant varieties.U.virens absorbs nutrition to promote infection and colonization.Therefore,in this study,two kinds of sugar-related genes were investigated to make sure whether they are involved in growth and pathogenicity.The main results of the study are as follows:1.Zn(II)Cys6 zinc finger protein family was identified in U.virens,and the function of xylanase transcription factor encoding gene UvXlnR was studied.The expression level of UvXlnR at the infection stage showed that after inoculation,the expression of UvXlnR increased significantly with two peaks at 3 and 13 dpi,suggesting that UvXlnR gene plays important roles in both the infection and colonization in rice.UvXlnR knockout transformants exhibited accelerated growth rate,decreased conidiation,the changed conidial morphology,weak virulence,and decreased tolerance to cell wall stress,osmotic stress,and oxidative stress.It was also found that the extracellular xylanase activity and utilization rate of different carbon sources were decreased in UvXlnR knockout transformants.These results indicated that the UvXlnR regulated multiple metabolic pathways involving in growth,conidiation,pathogenicity,stress tolerance,and sugar utilization in U.virens.2.Seven hexose transporters were identified in U.virens.Through ectopic expression of UvHxts in hexose transporter deficient yeast mutants,it was found that UvHxt1 had the best ability to recover the sugar transport function,and thus was selected for further studies.After inoculation,the expression level of UvHxt1 reached the peak at 13 dpi.The UvHxt1 knockout transformants showed decreased growth rate,conidia production and virulence,which indicated that the gene played positive regulatory roles in the pathogenicity.Meanwhile,UvHxt1 regulated responses to cell wall stress,osmotic stress,and oxidative stress,and participated in utilizing different sugar sources.These results showed that UvHxt1 gene was involved in a variety of metabolic pathways regulating the growth,sporulation,pathogenicity,and sugar absorption in U.virens.In summary,sugar utilization proteins UvXlnR and UvHxt1,play an important role in the growth and pathogenicity of U.virens.It provides a research basis for the nutrient transport,pathogenic mechanism,the prevention and control of U.virens.