Mbp1, a component of the MluI cell cycle box‐binding complex, contributes to morphological transition and virulence in the filamentous entomopathogenic fungus Beauveria bassiana

Abstract

The Mbp1 protein functions as a DNA-binding protein in the MluI cell cycle box-binding complex and plays significant roles in yeast development. In this study, an ortholog of yeast Mbp1, BbMbp1, was characterized in a filamentous insect mycopathogen, Beauveria bassiana. BbMbp1 plays an important role in morphological changes under aerial and liquid environments. On the aerial surface, BbMbp1 was indispensable for the biogenesis of conidiophores and conidiation. Under submerged conditions, the ΔBbMbp1 mutant displayed abnormal spore-producing structures, with a dramatic decrease in blastospore yield (~95%). The virulence of the ΔBbMbp1 mutant was notably weakened, which might be due to the defect in in vivo blastospore formation in the insect. Moreover, disruption of BbMbp1 resulted in a substantial reduction in hyphal growth on cadavers. Comparative transcriptomics revealed that BbMbp1 mediated different transcriptomes during the formation processes of conidia and blastospores. Yeast one-hybrid assays demonstrated that BbMbp1 was required for transcriptional control of a cell wall protein gene, BbCwp, and an integral membrane protein gene, BbImp that played significant roles in conidiation and blastospore formation respectively. Our results demonstrate that BbMbp1 contributes to the morphological transitions in the pathogenic and saprophytic growth of B. bassiana via different genetic pathways. Received

Transcriptomic analyses reveal comprehensive responses of insect hemocytes to mycopathogen Beauveria bassiana, and fungal virulence-related cell wall protein assists pathogen to evade host cellular defense

“…Conidia were obtained from 7-d old culture on SDAY plates. In the previous study, conidial concentration was 10 5 conidia/ml [7]. In this study, conidial concentration was adjusted to 10 6 and 10 7 conidia/ml.…”

“…Total RNA was extracted from the hemocyte sample. cDNA libraries were constructed as described previously [7]. Briefly, mRNA molecules were purified by using magnetic oligo(dT) beads and used as templates to synthesize first-strand cDNA using random hexamer primers, which was followed by second-strand cDNA synthesis.…”

“…The larvae of the greater wax moth Galleria mellonella are excellent host models for studying the pathogenesis of mycopathogens [5], and have been widely used to study the mechanisms involved in the interaction of B. bassiana and its hosts [6,7]. In response to microbial invasion, G. mellonella adopts two types of innate immunity, i.e., humoral and cellular immunity [8].…”

“…Many differentially expressed genes (DEGs) were uncovered to be involved in the host cellular immunity. Of particular interest, a virulence-related cell-wall protein (BbCwp) [7] was found to assist B. bassiana to colonize in insect hemocoel by evasion of the host immune defense.…”

Transcriptomic Analysis of the Brown Planthopper, Nilaparvata lugens, at Different Stages after Metarhizium anisopliae Challenge

“…Several reports have shown the development of transgenic fungi for insect control with greater efficiency than that of naturally occurring fungi [27]. The virulence of fungi can be enhanced substantially by the integration of genes such as the insecticidal scorpion toxin (Bjα IT) [28,29]. Although these entomopathogenic fungal agents have been used to control different insect pest species, there are few desirable fungal strains for rice planthopper control.…”