Function Research Of WD40 Repeat Protein CreC Gene In Metarhizium Robertsii

Metarhizium robertsii,as one of the biocontrol fungi of pests,plays a very important role in pest control of agriculture.It has been widely studied by scientists for many years because of many advantages,such as safety,environmental protection,easy production and long shelf life.However,its large-scale application is limited by its low insecticidal efficiency,long lethal time and unstable control effect.Therefore,we should have a systematic and deep understanding of the pathogenic and stress resistant mechanism in the M.robertsii,meanwhile,its genetic improvement has become an urgent way.The CreC gene of WD40 repeat protein is a very important regulator in the pathway of CCR.It was found that inhibition of carbon catabolism was closely related to the growth and pathogenicity of entomopathogenic fungus.In this experiment,we used M.robertsii as a wild type strain and obtained CreC mutant strains by gene knockout technology.And analyzed how CreC affects the growth,development and pathogenicity of M.robertsii.The results showed that compared with wild type,the colony diameter of mutant strains on different nutrition medium decreased significantly;the conidial product decreased 65%,moreover,RT-PCR results showed that the transcription levels of major genes related to sporulation in knockout strains were significantly reduced;Compared with wild type,Growth was inhibited more obviously on media containing Congo red,H2O2,KCL and NaCL,the relative inhibition rates increased by 14%,8%,7%and 8%respectively;After ultraviolet irradiation,the spore germination of mutant strains was earlier than that of wild type for 6h,RT-PCR analysis showed that the expression of major ultraviolet-related genes in knockout plants increased sharply at 12 h;but there was no significant difference with wild type strains after heat shock;After surface infection and in vivo injection,the death rate of the knockout strain was slowed down,and the half-lethal time was respectively delayed by 41 h and 29 h,Further studies showed that the rate of appressorium formation of mutant strain also decreased by 63%and the RT-PCR data showed that the transcription level of virulence-related genes decline,so the CreC gene affected the infectivity of M.robertsii in insect surface.In conclusion,the CreC gene affects the growth,sporulation,stress resistance and toxicity of M.robertsii.The effect of CreC gene on appressorium and expression of virulence-related genes on insects infection is one of the reasons for the decrease of insecticidal virulence.