Wee1 and Cdc25 control morphogenesis, virulence and multistress tolerance of Beauveria bassiana by balancing cell cycle-required cyclin-dependent kinase 1 activity

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 cdc25 but very weak in wee1 and absent in wee1cdc25. Consequently, cell cycles, septation patterns and many septation-dependent gene transcripts of these mutants were reversely changed. Hyphal cells were short in wee1, slender in cdc25 and short and swollen in wee1cdc25. Conidiation was most defective in wee1, followed by cdc25. Their conidia and yeast-like blastospores also altered antagonistically in both size and complexity, accompanied with abnormally branched germlings in wee1 and wee1cdc25. Conidial thermotolerance and UV-B resistance decreased much more in wee1cdc25 than in wee1 but significantly increased in cdc25. 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.