Unveiling equal importance of two 14-3-3 proteins for morphogenesis, conidiation, stress tolerance and virulence of an insect pathogen

Two conserved 14-3-3 proteins orthologous to Saccharomyces cerevisiaeBmh1/2 are poorly understood in filamentous fungi. Here we show that Bmh1 and Bmh2 contribute equally to the fundamental biology and physiology of Beauveria bassiana by targeting many sets of proteins/enzymes. Single Bmh deletion caused similar upregulation of another. Excellent knockdown (approximate to 91%) expressions of Bmh1 in Bmh2 and Bmh2 in Bmh1 resulted in equally more severe multiphenotypic defects than the single deletions, including G(2)/M transition, blastospore size, carbon/nitrogen utilization, conidiation, germination and conidial tolerances to high osmolarity, oxidation, cell wall stress, high temperature and UV-B irradiation. All the deletion and deletion/knockdown mutants showed similar defects in blastospore yield and density, hyphal septation and cell size, hyphal responses to most chemical stresses and virulence. All the defects were evident with altered transcripts of phenotype-related genes and well restored by each Bmh complementation. Our Bmh1- and Bmh2-specific transcriptomes generated under osmotic and oxidative stresses revealed up to 6% genes differentially expressed by at least twofold in the fungal genome. Many of those were greatly depressed or co-depressed in Bmh1 and Bmh2. Our findings provide a thorough insight into the functions and complementary effects of the two 14-3-3 proteins in the filamentous entomopathogen.