Study Of Pathogenic Mechanism In The Midgut Of Locusta Migratoria Manilensis Infected By Metarhizium Anisopliae

Metarhizium anisopliae is an important entomopathogenic fungus widely applied in China and abroad,which has a broad host range. More than 200 kinds of pests can be effectively prevented and controlled by Metarhizium anisopliae. Metarhizium anisopliae has a higher pathogenicity to Locusta migratoria manilensis. The mechanism how Metarhizium anisopliae infects locusts through body wall has been thoroughly studied, but it is a controversial topic whether Metarhizium anisopliae can infect insects through digestive tract. In this research midgut ultrapathological changes after infection of Metarhizium anisopliae were observed through TEM and enzyme activity changes in the midgut were masured to illuminate the infection mechanism of M. anisopliae on L. migratoria manilensis.The main results in this study are as follows:(1) We constructed Metarhizium IMI330189 mutant library containing 100 transformants by ATM, 12 of whose extracellular protease(acidic, neutral and alkaline), chitinase, phospholipase activity were measured. The results showed that Metarhizium extracellular protease activity was significantly related to virulence.(2)Feeding Metarhizium IPPM202 bait could destroy microvillus, cell nucleus, mitochondria and endoplasmic reticulum in midgut of locust. Pathological changes of organelles in different tissues were worse with the extension of time. Pathological changes of organelles included a serious loss of microvilli, uneven chromatin and degradation, reducing the number of mitochondria and degradation to vacuoles and endoplasmic arranged disorderly or even broken.(3) The enzyme activities of SOD, POD, CAT, PO, AchE and ESTs of L.migratoria manilensis showed different trends after infected by M. anisopliae, but they all showed an entire tendency that increased at first and then decreased. The changes of enzyme activities in L.migratoria manilensis midgut reflected competitive relation between M. anisopliae and L.migratoria manilensis, which may related to pathogenic mechanism of M. anisopliae.