Functional Analysis Of Citrinin Biosynthesis Oxydoreductase MaCtnB In Metarhizium Anisopliae

Metarhizium anisopliae is one of the most important genera of entomopathogenic fungi, it has a considerable application potential as an insect biocontrol agent. In natural conditions, M. anisopliae controls pests by spores mainly, the spore of quality and virulence determine whether can infect or not, and do the speed of infection.The factors(long time of spore mature, the high production cost of spore, vulnerable impact of environment, slow pesticidal speed) restrict large-scale production and application of microbial pesticides widely. Although it is easy to be influenced by adverse conditions(high temperature, nutritional deficiency and so on), filamentous fungi have the capability of microcycle conidiation. Microcycle conidiation is that filamentous fungus makes a self-protection mechanism which asexual spores germinates secondary spores directly without formation of mycelium when encounters the stress conditions. It has the advantages of a more uniform size spores, larger conidia quantity, faster spore production over that of normal conidiation. The related genes reported with the mechanisms are still little.In order to clarify the mechanism of microcycle conidiation, we subtracted c DNA library during microcycle conidiation and sporulation paradigm shift association with the library which constructed by our group in M. anisopliae at early period. We found that citrinin biosynthesis oxydoreductase Ctn B(Ma Ctn B) both upregulated expression. Therefore, we cloned the full-length DNA of citrinin biosynthesis oxidoreductase gene Ma Ctn B on the basis of the known entire M. anisopliae genome and by using gene knockout strategy analysed the function of Ma Ctn B.The main achievements are as follows:① Ma Ctn B affected conidial production and the way of sporulation on microcycle conidiaton medium(SYA), and influenceed conidial germination on PDA media.② Citrinin affected the way of sporulation of M. anisopliae.③ Ma Ctn B increased the sensitivity to UV radiation and heat shock, but did not affect the radial growth on PDA and supplemented with 6mmol/L H2O2, 1.0mol/L Sor, 0.01% SDS, 50μg/m L CFW.④ Ma Ctn B influenced the virulence of M. anisopliae. The mechanism was that there was a certain influence with germination, appressorium formation and appressorium collapse during the stage of entering host body; however, there was the main impact in vivo which influenced the fungal growth rate, the number of haemocytes, haemocytes types and ingestion of fungal body in host haemolymph. Thus it impacted host immune responses and reduced the virulence.