Modification of cell cycle in entomopathogenic fungi is likely crucial for host infection and environmental adaptation. Here we show that Wee1 and Cdc25 can balance cell cycle-required cyclin-dependent kinase 1 (Cdk1) activity in Beauveria bassiana. The Cdk1 phosporylation signal was strong in Δcdc25 but very weak in Δwee1 and absent in Δwee1Δcdc25. Consequently, cell cycles, septation patterns and many septation-dependent gene transcripts of these mutants were reversely changed. Hyphal cells were short in Δwee1, slender in Δcdc25 and short and swollen in Δwee1Δcdc25. Conidiation was most defective in Δwee1, followed by Δcdc25. Their conidia and yeast-like blastospores also altered antagonistically in both size and complexity, accompanied with abnormally branched germlings in Δwee1 and Δwee1Δcdc25. Conidial thermotolerance and UV-B resistance decreased much more in Δwee1Δcdc25 than in Δwee1 but significantly increased in Δcdc25. The double deletion and the point mutation Cdk1(T14A/P15F) for inhibitory phosphorylation caused most defective virulence, followed by wee1 deletion. All the changes were restored by ectopic gene complementation. Virulence changes in all the mutants and control strains were highly correlated to those in blastospore size or complexity. Taken together, Wee1 and Cdc25 control cell cycle, morphogenesis, asexual development, stress tolerance and virulence of B. bassiana by balancing the Cdk1 activity.

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Phytochromes (Phy) in filamentous fungi are Group VIII histidine kinases that share a unique N-terminal photosensory core, but their functions are largely unknown. Here we show that Beauveria bassiana Phy (Bbphy) is functionally vital for growth, conidiation and multistress tolerance of the fungal entomopathogen lacking sexual stage. Colony growth of ΔBbphy was significantly slower in a nutrition-rich medium but faster in several minimal media. Conidial yield of ΔBbphy in the rich medium increased at the fitted rate of 3.4 × 10(7) conidia h(-1) white light in the light/dark cycles of 0:24 to 16:8 h, decreased greatly in the short-, long- and full-day cycles of red/far-red light, but was unaffected under full-day blue light. Moreover, ΔBbphy showed higher osmosensitivity, increased antioxidant capability, and decreased conidial thermotolerance and UV-B resistance, accompanied with downregulation of Hog1 phosphorylation and of four Hog1-related genes under osmotic stress, and upregulation of five superoxide dismutases and four catalases under oxidative stress. All the changes were restored by the gene complementation. Taken together, Bbphy controls conidiation by responding to daylight length and red/far-red light and regulates multistress responses perhaps because of an involvement in Hog1 pathway. Our findings highlight diverse functions of Bbphy in B. bassiana.

Histone lysine acetylation orchestrates transcriptional activity essential for diverse cellular events across organisms, but it remains poorly understood how an acetylated lysine affects cellular functions in filamentous fungal pathogens. Here, we show the functions of a histone acetyltransferase that is phylogenetically close to Mst2 in fission yeast and specifically acetylates histone H3K14 in Beauveria bassiana, a fungal insect pathogen widely applied in arthropod pest management. Deletion of mst2 in B. bassiana resulted in moderate growth defects on rich and minimal media, delayed conidiation, and drastic reduction (75%) in conidiation capacity under normal culture conditions. The Δmst2 conidia suffered slower germination, decreased hydrophobicity, attenuated virulence, and reduced thermotolerance and UV-B resistance. The Δmst2 mutant also displayed increased sensitivities to DNA damaging, oxidative, cell wall perturbing, and osmotic stresses during conidial germination and colony growth at optimal 25 °C. Intriguingly, the phenotypic changes were accompanied with transcriptional repression of related gene sets, which are required for asexual development and conidial hydrophobicity or cascaded for CWI and HOG pathways, and encode the families of superoxide dismutases (SOD), catalases, heat-shock proteins, and trehalose or mannitol-metabolizing enzymes. Consequently, total SOD and catalase activities, trehalose and mannitol contents, and hydrophobicity were remarkably lowered in the hyphal cells or conidia of Δmst2. All of these changes were well restored by targeted mst2 complementation. Our results indicate that Mst2 enables to mediate global gene transcription and/or post-translation through H3K14 acetylation and plays an essential role in sustaining the biological control potential of B. bassiana against arthropod pests.

O-Mannosylation dependent on the protein O-mannosyltransferase (Pmt) family is an essential post-translational modification process in eukaryotes, but their connection to the biocontrol potential of a filamentous entomopathogen against arthropod pests is not understood. Here, we characterized the functions of three Pmt orthologues (Pmt1, Pmt2 and Pmt4) in the Pmt family of Beauveria bassiana and found that they were positive, but differential, regulators of the fungal growth, conidiation, multi-stress tolerance and virulence. Three Pmt2 knockdown mutants (ΔPmt2 was lethal), ΔPmt1 and ΔPmt4 grew 20-79% slower on nutrition-rich and limited media. Their conidial yields on a standard medium were reduced by 17-62%, accompanied with delayed germination. All the mutants became significantly less tolerant to most stresses of cell wall perturbation, high osmolarity, oxidation, wet heat and UV-B irradiation during colony growth and conidial germination and lost virulence by 53-62% via cuticle infection, although their virulence via hemocoel injection was not affected. Strikingly, these phenotypic defects were accompanied with remarkable cell wall damage, including thinner cell wall, lower conidial hydrophobicity and altered cell wall composition. All the changes were well restored to wild-type levels by targeted Pmt1 or Pmt4 complementation. Our results indicate for the first time that Pmt1, Pmt2 and Pmt4 are all required for the full biocontrol potential of B. bassiana despite differential contributions.