The Forkhead Box Gene, , Negatively Regulates UV- and Thermo-Tolerances and Is Required for Microcycle Conidiation in .

Insect pathogenic fungi have shown great potential in agricultural pest control. Conidiation is crucial for the survival of filamentous fungi, and dispersal occurs through two methods: normal conidiation, where conidia differentiate from mycelium, and microcycle conidiation, which involves conidial budding. The conidiation process is related to cell separation. The forkhead box gene in plays a crucial role in cell separation. Nevertheless, the function of Sep1 has not been clarified in filamentous fungi. Here, MaSep1, the homolog of Sep1 in , was identified and subjected to functional analysis. The findings revealed that conidial germination of the -deletion strain (Δ) was accelerated and the time for 50% germination rate of conidial was shortened by 1 h, while the conidial production of Δ was considerably reduced. The resistances to heat shock and UV-B irradiation of Δ were enhanced, and the expression of some genes involved in DNA damage repair and heat shock response was significantly increased in Δ. The disruption of had no effect on the virulence of . Interestingly, Δ conducted the normal conidiation on the microcycle conidiation medium, SYA. Furthermore, 127 DEGs were identified by RNA-Seq between the wild-type and Δ strains during microcycle conidiation, proving that MaSep1 mediated the conidiation pattern shift by governing some genes associated with conidiation, cell division, and cell wall formation.