Hypothetical protein MAA_07646 is required for stress resistance and pathogenicity in Metarhizium robertsii.

Metarhizium robertsii, a vital entomopathogenic fungus for pest management, relies on various virulence-related proteins for infection. Identifying these proteins, especially those with unknown functions, can illuminate the fungus's virulence mechanisms. Through RNA-seq, we discovered that the hypothetical protein MAA_07646 was significantly upregulated during appressorium formation in M. robertsii. In this study, we characterized MAA_07646, finding its presence in both the nucleus and cytoplasm. Surprisingly, it did not affect vegetative growth, conidiation, or chemical tolerance. However, it played a role in heat and UV radiation sensitivity. Notably, ΔMAA_07646 exhibited reduced virulence in Galleria mellonella larvae due to impaired appressorium formation and decreased expression of virulence-related genes. In conclusion, MAA_07646 contributes to thermotolerance, UV resistance, and virulence in M. robertsii. Understanding its function sheds light on the insecticidal potential of M. robertsii's hypothetical proteins.

Metarhizium robertsii MrAbaA affects conidial pigmentation via regulating MrPks1 and MrMlac1 expression.

Pigments of conidia play a crucial role in fungal defense against environmental stressors such as UV radiation. The molecular basis of conidial pigmentation has been studied in the entomopathogenic fungus Metarhizium robertsii, while limited information been reported on function mechanisms transcription factors governing conidial pigmentation. Here, we identified transcription factor MrAbaA binding to the promoter regions of both MrPks1 and MrMlac1 in M. robertsii using yeast one-hybrid technology. Chromatin immunoprecipitation quantitative PCR assays further confirmed the interaction. Furthermore, overexpression of MrAbaA in M. robertsii resulted in increased conidial pigment accumulation and enhanced tolerances to UV stress by upregulated the MrPks1 and MrMlac1 expression. Taken together, MrAbaA affects conidial pigmentation by interacting with the promoter regions of both MrPks1 and MrMlac1 in M. robertsii. This work advances the understanding of the regulation mechanism for conidial pigmentation in entomopathogenic fungi.