Study On The Biological Function Of FvSwi4 And FvSwi6 In Fumarium Verticillioide

Fusarium verticillioides is an important pathogen of maize worldwide.The pathogen can cause a variety of plant stems and spike rot,especially for maize.More importantly,F.verticillioides produces various mycotoxins,such as fumonisins,which are extremely harmful to human and animal health.Fumonisin,which belongs to a polyketone mycotoxin,can damage the animal's immune system,resulting in damage of immune function and a variety of animal diseases.The International Agency for Research on Cancer(IARC)as declared fumonisin as"2B" toxin,(the possible carcinogens for human being),Since 1988,28 analogues of fumonis have been found.B series is not only one of the most important class,but also is the most widely in the natural conditions.It includes highly toxic FBI,FB2,FB3.In the eukaryotic,bHLH-like transcription factors are a class of widely distributed transcription factors that participate in many important intracellular signaling processes including differentiation,metabolism,and response to external environmental factors.This study identified the bHLH transcription factors FvSwi4 and FvSwi6.By konckouting the FvSwi4 and FvSwi6,we studied deeply the effects of FvSwi4 and FvSwi6 for Fusarium verticillioides on growth,stress resistance,pathogenicity,producton of fumonisin and the other secondary metabolites and the regulation pathway of FvSwi4 and FvSwi6 in Fusarium verticillioides.Results of current study include:Growth rate of the mutants ?FvSwi4 and ?FvSwi6 slowed down on the PDA,CM and MM medium,the sporulation decreased,and the ascospore could not be formed during sexual reproduction.And the FvSwi4 and FvSwiS also have influenced on resistance for environmental stress factor in Fusarium verticillioides.We found ?FvSwi4 and ?FvSwi6 show obviously resistance on the stress factors of cell wall and oxidation pressure.Further analysis revealed that the cell walls were thickened and the content of hydrogen peroxide in the two mutants reduced.By the CHIP analysis,it proved that proein FvSwi4 and FvSwi6 bind to the promoter region of chitinase-related genes and the catalase-related genes to regulate its effect.The pathogenicity of the mutants ?FvSwi4 and AFvSwi6 decrease,and the activity of amylase and cellulose declined significantly.Other more,the production of fumonisin also decreased.Furthermore,after ?FvSwi4 and ?FvSwi6 cultured on MM medium,by transmission electron microscopy,we found the increase of lipid droplet content in ?FvSwi4 and ?FvSwi6.Nile red staining and TAG content measurement prove the phenomenon,too.In addition,the of autophage AFvSwi4 and AFvSu,i6 also increased,this phenomenon may also be the main reason for the significant enhancement in the lipid content of the mutants ?FvSwi4 and AFvSwi6.Protein is a direct manifestation of the function of gene.By fluorescence localization,yeast two-hybrid,CO-IP and BIFC,we found FvSwi4 and FvSwi6 proteins are localized in the nucleus.The gene FvMgvl is the upstream of FvSwi4 and FvSwi6 on MAPK signaling pathway.And FvMgvl respectively interacts with FvSwi4 and FvSwi6 and is localized in the nucleus.FvSwi4 and FvSwi6 also occurred between the interaction and located in the nucleus.We identified phosphorylation sites of FvSwi4 and FvSwi6,the 562th serine of FvSwi4 and 264th threonine of FvSwi6.This study shows that bHLH transcription factors FvSwi4 and FvSwi6 regulate growth,pathogenicity,stress tolerance,secondary metabolism and other important life activities in Fusarium verticillioides.The pathogenesis of Fusarium verticillioides can provide a theoretical basis for the development of biological control agents.