Wang Juan-Juan, Qiu Lei, Cai Qing, Ying Sheng-Hua, Feng Ming-Guang
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China.
1] Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China [2] School of bioengineering, Qilu University of Technology, Jinan, Shandong, 250353, People's Republic of China.
Sci Rep. 2015 May 8;5:10108. doi: 10.1038/srep10108.
Transcriptional control of the cell cycle by forkhead (Fkh) transcription factors is likely associated with fungal adaptation to host and environment. Here we show that Fkh2, an ortholog of yeast Fkh1/2, orchestrates cell cycle and many cellular events of Beauveria bassiana, a filamentous fungal insect pathogen. Deletion of Fkh2 in B. bassiana resulted in dramatic down-regulation of the cyclin-B gene cluster and hence altered cell cycle (longer G2/M and S, but shorter G0/G1, phases) in unicellular blastospores. Consequently, ΔFkh2 produced twice as many, but smaller, blastospores than wild-type under submerged conditions, and formed denser septa and shorter/broader cells in aberrantly branched hyphae. In these hyphae, clustered genes required for septation and conidiation were remarkedly up-regulated, followed by higher yield and slower germination of aerial conidia. Moreover, ΔFkh2 displayed attenuated virulence and decreased tolerance to chemical and environmental stresses, accompanied with altered transcripts and activities of phenotype-influencing proteins or enzymes. All the changes in ΔFkh2 were restored by Fkh2 complementation. All together, Fkh2-dependent transcriptional control is vital for the adaptation of B. bassiana to diverse habitats of host insects and hence contributes to its biological control potential against arthropod pests.
叉头（Fkh）转录因子对细胞周期的转录调控可能与真菌对宿主和环境的适应性有关。在此我们表明，酵母Fkh1/2的直系同源物Fkh2协调丝状真菌昆虫病原体球孢白僵菌的细胞周期和许多细胞事件。球孢白僵菌中Fkh2的缺失导致细胞周期蛋白B基因簇显著下调，从而改变了单细胞芽生孢子的细胞周期（G2/M期和S期延长，但G0/G1期缩短）。因此，在液体培养条件下，ΔFkh2产生的芽生孢子数量是野生型的两倍，但体积较小，并且在异常分支的菌丝中形成更密集的隔膜和更短/更宽的细胞。在这些菌丝中，隔膜形成和分生孢子形成所需的成簇基因显著上调，随后气生分生孢子的产量更高且萌发更慢。此外，ΔFkh2表现出毒力减弱以及对化学和环境胁迫的耐受性降低，同时影响表型的蛋白质或酶的转录本和活性发生改变。Fkh2互补恢复了ΔFkh2中的所有变化。总之，Fkh2依赖性转录调控对于球孢白僵菌适应宿主昆虫的不同栖息地至关重要，因此有助于其对节肢动物害虫的生物防治潜力。
