Functional Analysis Of Serine/Threonine Protein Kinase MaPsk1 In Metarhizium Acridum

Due to the fact that insect pests are less resistant and are environmentally friendly,biological pesticides are expected to become alternatives to chemical pesticides in the future.Entomopathogenic fungi are biological pesticides with the most potential application in biocontrol in agriculture.However,biopesticides generally have drawbacks of long killing time and unstable control effects,which severely restrict their application in agriculture.Entomopathogenic fungi,mostly derived from Ascomycetes in the genera Metarhizium and Beauveria,have been developed as environmentally friendly alternatives to chemical pesticides for a wide range of agricultural.Therefore,exploring the mechanisms of pathogenicity,sporulation,and stress tolerance of entomopahotgenic fungi is helpful for the development of biological pesticides.Serine/threonine protein kinases are one type of important kinases.Through phosphorylation of its downstream substrates,they participate in the regulation of nutrition absorption,growth and development,and stress tolerance.In yeast,serine/threonine protein kinase Psk1 regulated the glucose application,responded to metabolism and cell integrity signals,and participates in cell growth and proliferation.Up to now,there has been no report on function of Psk1 in pathogenicity and regulation mechanisms in fungi.In this study,we explored the function of Psk1 in entomopathogenic fungus Metarhizium acridum using gene disruption technique.The proteins interacted with MaPsk1 were screened and verified using yeast two-hybrid method.The signalosome complex subunit 5（MaCsn5）was proved to interact with MaPsk1.The main conclusions obtained in this study are as follows:1.The full length of MaPsk1 is 1542 bp（Accession number MAC＿03775）,encoding a protein of 513 amino acids with 1 S＿TKc catalytic domain and S＿TK＿X structural domain.No intron was in MaPsk1.2.MaPsk1 is located in lipid droplets,disruption of the MaPsk1 resulted in a significant decrease in the expression of the lipid droplet surface-specific protein gene MPL1,indicating that MaPsk1 may be involved in the lipid metabolism in M.acridum;3.Disruption of the MaPsk1 affects the fungal growth,sporulation and stress tolerance.TheΔMaPsk1 has smaller colony and the conidiation significantly decreased compared with the wild type.ΔMaPsk1 was less tolerance to UV-B irradiation,heat stress and chemical reagents SOR and H₂O_2.4.MaPsk1 affects the virulence of M.acridum.ΔMaPsk1 had significantly decreased virulence,the appressorium formation rate,glycerol content and turgor pressure compared to WT.5.RNA-Seq data analysis showed that MaPsk1 participated in the regulation of multiple biological processes,affected multiple signaling pathways,involved in lipid metabolism,amino acid metabolism,cell growth and development,and nutrient synthesis and metabolism.6.Yeast two-hybrid assay showed that MaPsk1 interacted with MaCsn5.Similar asΔMaPsk1,ΔMaCsn5 has significantly decreased virulence,less tolerance to SOR and H₂O₂ stresses.In summary,MaPsk1 affects the growth,sporulation,stress resistance and virulence in M.acridum by regulation of multiple signaling pathways in M.acridum.MaPsk1regulated these fungal characteristics by interaction with MaCsn5.