Function Analysis Of MapacC,A Transcription Factor In Metarhizium Acridum

As an important biocontrol resource,entomopathogenic fungi had great potential.The conidial yield and quality,stress tolerance and virulence of entomopathogenic fungi are important indicators for measuring the efficacy of insecticidal fungi pesticides.Studies had shown that the C₂H₂ transcription factor pacC/Rim101 plays an important role in the growth of fungi in alkaline pH environment,sporulation and infection,and its function is different in different fungi.Until now,the function of pacC in the model entomopathogenic fungus Metarhizium acridum had not been reported.This study used the disruption and complementary strategies to clarify the function of the transcription factor pacC.This study found that,similar to pacC in other fungi,the pacC protein in M.acridum contains three C₂H₂-type zinc finger structures,which play an important role in the adaptation of M.acridum to alkaline environment growth.The identification and functional characterization of MapacC indicated that MapacC had the highest expression level during post-penetration in vivo growth（hyphal bodies）in the initial stage of inoculated locusts of M.acridum.It is speculated that MapacC may play an important role in the adaptation of M.acridum to the insect environment or avoiding the host immune response.After MapacC disrupted,the conidial yield of M.acridum was reduced,and the UV-B resistance was unchanged,however,the expression of some genes defense heat shock increased significantly,resulting in increased thermotolerance of M.acridum.Fluorescent staining showed that the conidial surface structure was different among the wild-type strain,ΔMapacC mutant and complementary strain.The disruption of MapacC reduced the virulence of M.acridum.The penetration process analysis found that the disruption of MapacC had slight effect on the appressorium formation of M.acridum,however,the proliferation rate ofΔMapacC mutant in locusts was significantly reduced.Compared with the locusts infected by the wild-type strain,the phenoloxidase（PO）activity in the locusts haemolymph inoculated with the conidia ofΔMapacC mutant was significantly increased,also,the number of nodules on the locusts’inner body walls was significantly increased.The above phenomenon indicates that MapacC may play an important role in the immune recognition process of M.acridum to avoid locusts.Interestingly,it was also found thatΔMapacC mutant no longer microcycle conidiation（MC）under MC induced conditions.A total of 44 genes were differentially expressed between wild-type strain andΔMapacC mutant were screened by RNA-seq analysis,of which 27 genes were up-regulated and 17 genes were down-regulated after MapacC disrupted.According to the analysis of 34 genes with annotation information,MapacC may affect the conidiation pattern shift of M.acridum by regulating proteins which play important roles in cell division and mycelial growth.In summary,this study clarified the role of MapacC,which had an important contribution to the biocontrol potential in M.acridum.The results of this study will provide a theoretical basis for further elucidation of the pathogenic mechanism of entomopathogenic fungi and the mechanism of conidiation pattern shift in filamentous fungi,and it was expected to provide new candidate genes for molecular improvement of entomopathogenic fungi,which had important theoretical significance and practical application value.