Function Analysis Of UvSUN1 Gene In Vegetative Growth And Pathogenicity Of Ustilaginoidea Virens And Inhibitory Effect Of Farnesol On Ustilaginoidea Virens

Rice false smut(RFS),a rice panicle disease caused by Ustilaginoidea virens,has an impact on both quantitative and qualitative losses.This disease has become one of the main rice diseases in China,seriously endangering the food security.Extension and application of resistant rice varieties to RFS is an effective way to resist the occurrence of the RFS.However,at present,there are still some peoblems,such as the unclear prevalence and pathogenesis of U.virens,and the lack of green control technology and products of RFS.Clarified the pathogenic mechanism of U.virens on rice and the molecular mechanism of the interaction between rice variety and the pathogen,can provide a theoretical basis for the control of U.virens.However,due to the slow growth rate,difficult to detection of pathogenicity,and smut ball as the only visible symptom of RFS,the unique pathogenic mechanism of U.virens still needs to be further studied.SUN protein is an unique protein family of Ascomycetes,which is involved in a variety of physiological activities,such as cell separation,cell wall morphogenesis,and stress response.In order to study the function of SUN protein in U.virens,we first predicted the UvSUN1 gene in the genome of U.virens with the conserved SUN domain.The UvSUN1 contains a conserved SUN domain,indicating that the protein belongs to SUN family.Using CRISPR-Cas9 system and homologous recombination,gene knockout mutants of UvSUN1 was obtained.We analyzed the biological phenotypes of wild-type strain P1 and knockout mutants of U.virens,and found that the knockout mutants showed the reduced of the growth rate,the conidia production,the cell wall integrity,the extracellular matrix of mycelium and the pathogenicity.Transcriptome analysis of the differentially expressed genes of P1 and knockout mutants at mycelial growth stage showed the consistent with the phenotype.Furthermore,we found that several glucose metabolism signaling pathways were affected in the knockout mutants,which was consistent with the predicted β-(1,3)-glucosidase activity of SUN family Group-I protein.Therefore,it is speculated that UvSUN1 gene is involved in the regulation of cell wall integrity of U.virens and affects the vegetative growth of the pathogen.Disruption of the UvSUN1 gene produces the decrease of extracellular matrix and the expression of sugar metabolism and transport related genes,affecting the adhesion and nutrient utilization,therefore reducing U.virens virulence.The results provide a theoretical basis for the study of pathogenic mechanism of U.virens.Due to the shortage of resistant rice germplasm resouces,limited resistant varieties to RFS could be used at present.Application of agrochemical to control RFS is still the main control method.The development of high-efficiency and green chemistry is of great significance to control RFS.Farnesol is a natural organic compound,which can be found in plants and some fungi.We studied the effect of farnesol on the growth and pathogenicity of U.virens.It was found that farnesol had a strong inhibitory effect on conidial germination,mycelial growth,and the adhesion of U.virens to abiotic surfaces.At the same time,farnesol can inhibit the pathogenicity.s.This was the first study to show the function of SUN protein in the growth and pathogenicity of U.virens,which provided a theoretical basis for the study of pathogenic mechanism of U.virens.On the other hand,it was the first time to study the effect of farnesol on the growth and pathogenicity of U.virens,which provides provided a valuable idea for developing new fungicides against this pathogen.