Beauveria bassiana CGMCC 7.34 Transcriptome or Gene expression

We characterized a novel filamentous fungal-specific transmembrane protein, Bbtmp1, which is controlled by Bbhog1 MAPK pathway and involved in regulation of intracellular ROS levels, oxidative and osmotic stress responses and the virulence in the insect fungal pathogen Beauveria bassiana. Bbtmp1 encodes a predicted hybrid membrane protein containing an AMP-binding domain, five putative transmembrane domains, and an experimentally-validated FAD/NAD(P)-binding domain, which was testified to be associated with mitochondria. Either disruption or overexpression of tmp1 caused a reduction in conidiation, but a dramatic difference in conidial development. ?tmp1 strain exhibited swollen conidia, rapid germination and thicken cell wall with increased total carbohydrate content, while the overexpression strain (OE-tmp1) showed smaller conidia, altered cell wall structure with reduction in chitin and ß-1,3/1,6-glucan composition. Disruption or overexpression of tmp1 caused an elevation in intracellular ROS level mostly due to interference with mitochondrial inner membrane potential. However, ?tmp1 and OE-tmp1 strains showed opposite response to external oxidants H2O2 and menadione, and osmotic stress, in which the former was more tolerant to oxidative and osmotic stresses, whereas the latter was hypersensitive to external oxidants and more sensitive to osmotic stress. Involvement of Bbtmp1 in osmotic stress might be partially related to mediation of compatible solute accumulation. Insect bioassay revealed increased virulence in the ?tmp1 strain but decreased virulence in OE-tmp1 strain using both topical and intrahemoceol injection assays. Localization and function analyses showed that Bbtmp1 is different from other orthologs characterized or predicted in sequenced fungi that are associated with peroxisome or cytoplast and positively mediate oxidative stress response and virulence, suggesting an exclusive protein. Furthermore, disruption of tmp1 in Bbhog1 mutant (?hog1) background partially restored the sensitivity to oxidative stresses, but did not influence the osmotic response, suggesting regulation relationship between Bbhog1 pathway and Bbtmp1, and a complex mechanism of osmotic stress mediated by Bbtmp1. The results of comparative transcriptome analyses suggested that Bbtmp1 might be involved in production of a regulatory signal that mediate signal transduction, gene transcription and gene expression and mediated fungal development and differentiation, cell wall integrity and response to adverse stresses, detoxification, virulence and likely other process. Collectively, we have discovered a Bbhog1 pathway-controlled novel protein which is involved in regulation of intracellular ROS homeostasis, and negatively control oxidative and osmotic stress responses and virulence in the insect fungal pathogen B. bassiana.