| Metarhizium acridum, belonging to Metarhizium spp , is an entomopathogenic fungi with virulence. It has the advantages of no residue, agents easy to produce and longer persistence, having broad application prospects. Appressorium is one of the most important structures in entomophthogenic fungus. The formation of appressoria are the key step during the successfully infection of M. acridum.The cDNA library of M. acridum germinating and differentiating on locust wing has been constructed in our laboratory. In this study, the Magas1 gene GenBank accession number: DQ496227) was selectd from this library for further analysis. The Magas1 gene has an open reading frame of 954 bp encoding a protein of 317 amino acid residues. Homology analysis showed highly similarity with gas2 (AF264035) in Magnaporthe grisea and mas1 (XP747144) in Aspergillus fumigatus by NCBI blast.Semi-quantitative RT-PCR analysis shows strong expression of the Magas1 gene during appressorium formation stage of the infection process, and weak signal of the Magas1 gene in germinated spores and hyphae. The Magas1 could not be detected in hyphal body inside insect, conidia collected from artificial medium and surface of the infected locusts.The Magas1-EGFP fusion expression under the control of Magas1 promoter was inspected with confocal microscopy. Visible green fluorescence was detected in the cytoplasm of the appresorium in the Magas1-EGFP fusion expression construct.The Magas1 deletion mutant showed a retard in the formation of conidiogenous structure on the 1/4 SDAY medium, but no significant difference on the germination rate and appressorium formation compared with wild type. The Magas1 detelion mutant had a significant decrease in virulence against Locusta migratoria compared to the wild type, indicating Magas1 is a virulence factor in M. acridum,But the loss of Magas1 resulted in dramatic reduction of turgor pressure sounding that Magas1 referred in theprocess of penetration. Furhter study of Magas1 would contribute to better understand the mechanism of appresorium formation and penetration of entomopathogenicn fungi. |
