Function Of FgScs2 In Gowth Dvelopment And Pthogenicity In Fusarium Graminearum

Wheat is an important crop widely planted worldwide.However,in recent years,Fusarium head blight has spread in many parts of the world,causing serious economic losses.Fusariurn graminearum,one of the major pathogens causing Fusarium head blight,has important research significance.Meanwhile,during plant infection,F.graminearum also produces a secondary metabolite--Deoxynivalenol(DON),which cause human and animals vomiting,anorexia and other symptoms,and therefore bring great safety risks to the ecological environment.Autophagy is a self-degrading mechanism in eukaryotes and is highly conserved,affecting many aspects of cell life activities.Previous studies have found that normal autophagy plays an important regulatory role in the pathogenicity of pathogens such as F.graminearum,which provides scientists with new strategies for research on Fusarium head blight control methods.Phosphatidylinositol 4-phosphate(PI4P),a phospholipid molecule,is widely distributed on the Golgi apparatus and plasma membrane.A large amount of research data shown that PI4P participates in regulating many basic physiological,such as cytoskeleton construction,vesicle transport,and Autophagy.In eukaryotes,PI4P and its multiple phosphorylation products are involved in regulating the formation of autophagosomes during autophagy.VAP proteins and homologous proteins(Scs2/Scs22 in Saccharomyces cerevisiae)in eukaryotes are involved in the transport of PI4P.In this study,the only homologous gene of the Scs2/Scs22 gene was identified in F.graminearum by amino acid sequence alignment,and named FgScs2.Through protein sequence alignment and SMART prediction,two important domains of FgScs2 were found,namely major sperm protein domain(MSP)and transmembrane domain(TMD),which are consistent with Scs2/Scs22 in S.cerevisiae.In order to globally elucidate the functions of FgScs2,we knocked out the FgSCS2 gene to obtain ΔFgscs2 mutant,and performed a series of biological function studies on the ΔFgscs2 mutant.The results showed that compared to the WT strain,the colony growth rate of the ΔFgscs2 mutant strain decreased by 70.6%,and the difference in colony phenotype was obvious;Meanwhile,the mycelial branches increased significantly,and the height of aerial hyphae decreased by 47.7%;The morphology of conidia was not deformed,but the length of conidia and spore production decreased by 25.8%and 29.4%,and the number of spore membranes was mostly three,it accounts for 61%of the total sample.The above results show that FgScs2 is very important for the vegetative growth of F.graminearum.The ΔFgscs2 mutant strains have phenotypes that promote growth on CM plates supplemented with 0.7 M KCl,0.7 M NaCl,1 M sorbitol,1 g/L Congo red,and 0.05%SDS,this indicates that the ΔFgscs2 mutant strain is more tolerant to the stress effects of different environmental factors.During plant infection,F.graminearum produces a large amount of DON that is essential for virulence.At present,TRI related genes have been shown to participate in the synthesis of DON,mainly including:TRI1,TRI4,TRI5,TRI6,TRI10 and so on.Quantitative real-time(qRT)-PCR analysis revealed that the expression of DON synthesis-related genes TRI4,TRI5,and TRI10 in ΔFgscs2 mutants decreased by 72%,40%,and 38%.At the same time,DON biosynthesis quantity was detected and found that the DON synthesis of the ΔFgscs2 mutant strain was 41.7%lower than that of the WT.This result indicates that FgScs2 is involved in the regulation of DON biosynthesis in F.graminearum.Many factors such as vegetative growth,sexual reproduction,and DON synthesis will affect the pathogenicity of pathogenic fungi.Experiments have shown that the pathogenicity ofΔFgscs2 mutant strains to wheat ears,wheat coleoptiles and tomatoes is greatly reduced,and the disease index is reduced by more than 90%compared with WT.In order to further explore the role of FgScs2 in the pathogenic mechanism,we conducted the following experiments and found:(1)FgScs2 not participate in the generation of toxisome and lipid droplet,suggesting that FgScs2 is involved in pathogenicity not by affecting toxisome synthesis.(2)After the deletion of FgSCS2 gene,the location of PI4P in the cells was obviously abnormal.The location of PI4P in the WT was mainly concentrated in the plasma membrane and diffused in the cytoplasm,while the PI4P in the ΔFgscs2 mutant strain was diffusely distributed in the cytoplasm.(3)Compared with the WT strain,this study further found that the process of autophagy protein FgAtg8 in the ΔFgscs2 mutant entered the vacuole was delayed,and it is not completely blocked.In addition,our result showed that the physical interaction between FgScs2 and autophagy protein FgAtg1 by yeast two-hybrid.These results suggest that FgScs2 may affect the pathogenicity of F.graminearum by participating in the localization of PI4P in mycelium and autophagy pathway.In summary,this study found that FgScs2 is involved in the regulation of vegetative growth,asexual reproduction,sexual reproduction,pathogenicity,PI4P transport and autophagy in F.graminearum.