MaSln1, a Conserved Histidine Protein Kinase, Contributes to Conidiation Pattern Shift Independent of the MAPK Pathway in .

As a conserved sensor kinase in the HOG-MAPK pathway, Sln1 plays distinct functions in different fungi. In this study, the roles of MaSln1 in Metarhizium acridum were analyzed using gene knockout and rescue strategies. Deletion of did not affect conidial germination, conidial yield, or resistance to chemical agents. However, fungal tolerance to heat shock and UV-B were significantly reduced after deletion of . Insect bioassays showed that fungal pathogenicity was significantly impaired when was deleted. Further studies showed that MaSln1 did not affect either germination or appressorium formation of on locust wings, but it significantly increased appressorium turgor pressure. In addition, disruption of resulted in a conidiation pattern shift in . Microscopic observation revealed, however, that some genes located in the MAPK signaling pathway, including , , , and , were not involved in the conidiation pattern shift on SYA medium (microcycle medium). Meanwhile, of the 143 differently expressed genes (DEGs) identified by RNA-seq, no genes related to the MAPK pathway were found, suggesting that MaSln1 regulation of the conidiation pattern shift was probably independent of the conserved MAPK signaling pathway. It was found that 22 of the 98 known DEGs regulated by MaSln1 were involved in mycelial growth, cell division, and cytoskeleton formation, indicating that MaSln1 likely regulates the expression of genes related to cell division and morphogenesis, thus regulating the conidiation pattern shift in . The productivity and quality of conidia are both crucial for mycopesticides. In this study, we systematically analyzed the roles of in fungal pathogens. Most importantly, our results revealed that deletion of resulted in a conidiation pattern shift in . However, some other genes, located in the MAPK signaling pathway, were not involved in the conidiation pattern shift. RNA-seq revealed no genes related to the MAPK pathway, suggesting that the regulation of the conidiation pattern shift by MaSln1 was probably independent of the conserved MAPK signaling pathway. This study provided a new insight into the functions of Sln1 and laid a foundation for exploring the mechanisms of conidiation pattern shifts in .