Project description:Although most known mycoviruses are asymptomatic or reduce the virulence of their host fungi, those that confer hypervirulence to entomopathogenic fungus still need to be explored. Here, we discovered and studied a novel mycovirus in Metarhizium flavoviride, isolated from Laodelphax striatellus. Based on molecular analysis, we tentatively designated the mycovirus as Metarhizium flavoviride partitivirus 1 (MfPV1), a novel species in genus Gammapartitivirus, family Partitiviridae. MfPV1 has two double-stranded (ds) RNAs as its genome, 1,775 and 1,575 bp in size respectively, encapsidated in isometric particles. When we transfected commercial strains of M. anisopliae and M. pingshaense with MfPV1, conidiation was significantly enhanced (t-test; P-value < 0. 01), and the significantly higher mortality rates of the larvae of Plutella xylostella and Spodoptera frugiperda, two important lepidopteran pests were found in virus-transfected strains (ANOVA; P-value < 0.05). Transcriptomic analysis showed that transcript levels of pathogenesis-related genes in MfPV1-infected M. anisopliae were obviously altered, suggesting increased production of metarhizium adhesin-like protein, hydrolyzed protein and destruxin synthetase. Further studies are required to elucidate the mechanism whereby MfPV1 enhances the expression of pathogenesis-related genes and virulence of Metarhizium to lepidopteran pests. This study presents experimental evidence that the transfection of other entomopathogenic fungal species with a mycovirus can confer significant hypervirulence and provides a good example that mycoviruses could be used as synergistic agent to enhance the biocontrol activity of entomopathogenic fungi.
Project description:The presence of genetic groups of the entomopathogenic fungus Metarhizium anisopliae in soil is shaped by its adaptability to specific soil and habitat types, and by soil insect populations. Although the entomopathogenic life style of this fungus is well studied, its saprophytic life style has received little consideration. While a set of functionally related genes can be commonly expressed for the adaptability of this fungus to different environments (insect cuticle, insect blood and root exudates), a different subset of genes is also expected for each environment. In order to increase the knowledge of the potential use of M. anisopliae as a rhizosphere competent organism, in this study we evaluated the genetic expression of this fungus while growing on plant root exudates in laboratory conditions during a time course. One fungal strain: Metarhizium anisopliae ARSEF 2575; Five time conditions: 0h, 1h, 4h, 8h, 12h; Five-condition experiment: Time0h vs. Time1h, Time1h vs. Time4h, Time4h vs. Time8h, Time8h vs. Time12h and Time12h vs. Time0h. Two Biological replicates: independently grown and harvested. Three replicates per array. Dye-swap was performed on replicate 2.
Project description:Exopolysaccharide galactosaminogalactan (GAG) is a fungal cell wall component composed of α-1,4 linked galactose, N-acetyl galactosamine and galactosamine, which has been demonstrated in Aspergillus fumigatus in association with fungal adhesion, biofilm formation and virulence. The gene cluster responsible for GAG biosynthesis has only been characterized in Aspergillus fungi. We found that the highly conserved gene cluster for GAG biosynthesis is also present in the insect pathogenic fungi Metarhizium species. Functional investigations in M. robertsii revealed that GAG is only produced on fungal cell wall during fungal germination, filamentation and the formation of the infection structure appressoria. Gene deletions revealed that, relative to the wild-type (WT), the appressorial mucilage production was abolished in the null mutant of M. robertsii. Since multiple enzymes are produced in appressorial mucilages, appressorial samples of the WT and mutant formed on cicada wings were collected and subjected to iTRAQ comparative proteomic analysis. We found that different protein families were up- or down-regulated in the null mutant when compared with the WT.
Project description:Transcription factor Msn2 played crucial roles in mediating fungal stress tolerance, a determinant to the biocontrol potential of fungal entomopathogens. We characterized for the first time the functions of Beauveria bassiana Msn2 (BbMsn2) and Metarhizium robertsii (MrMsn2) by analyzing multi-phenotypic changes in Msn2-deletion and investigating transcription patterns of WT versus ΔMsn2 of B. bassiana and M. robertsii under thermal and oxidative stresses by using high throughput sequencing (RNA-Seq). Our transcriptional profiles revealed that numerous differentially expressed genes (DEGs), of which involved in transportation, detoxification, signal transduction, and energy metabolism, were significantly repressed in expression level.
Project description:A spontaneously phenotypically degenerated strain of M. robertsii strain ARSEF 2575 (M. robertsii lc2575; lc = low conidiation) showed a reduction in conidiation and fungal virulence after successive subculturing on artificial medium. However, the conidial production and fungal virulence of a phenotypically degenerated M. robertsii were recovered by serially passaging through a plant host. The DNA methylation level of phenotypically degenerated Metarhizium robertsii M. robertsii lc2575 and this fungi after solider bean passages were tested through the whole genome bisulfite sequencing. The results showed that approximately 0.379 % of cytosines are methylated in the fungi after bean passages, almost the same as the DNA methylation level in M. robertsii lc2575 (0.375%). The distribution of different methylated regions located more on intergenic regions of fungi after bean passages than M. robertsii lc2575. Gene Ontology (GO) analysis and KEGG analysis of DMR-associated genes revealed that amino acid, carbohydrate and fatty acid metabolism.