Institute of Microbiology, Zhejiang University, Hangzhou, 310058, China.
Chongqing Vocational College of Transportation, Chongqing, 402247, China.
Nat Commun. 2017 Nov 16;8(1):1565. doi: 10.1038/s41467-017-01756-1.
Metarhizium robertsii is a versatile fungus with saprophytic, plant symbiotic and insect pathogenic lifestyle options. Here we show that M. robertsii mediates the saprophyte-to-insect pathogen transition through modulation of the expression of a membrane protein, Mr-OPY2. Abundant Mr-OPY2 protein initiates appressorium formation, a prerequisite for infection, whereas reduced production of Mr-OPY2 elicits saprophytic growth and conidiation. The precise regulation of Mr-OPY2 protein production is achieved via alternative transcription start sites. During saprophytic growth, a single long transcript is produced with small upstream open reading frames in its 5' untranslated region. Increased production of Mr-OPY2 protein on host cuticle is achieved by expression of a transcript variant lacking a small upstream open reading frame that would otherwise inhibit translation of Mr-OPY2. RNA-seq and qRT-PCR analyses show that Mr-OPY2 is a negative regulator of a transcription factor that we demonstrate is necessary for appressorial formation. These findings provide insights into the mechanisms regulating fungal lifestyle transitions.
罗伯茨绿僵菌是一种多功能真菌，具有腐生、植物共生和昆虫病原性生活方式的选择。在这里，我们表明罗伯茨绿僵菌通过调节膜蛋白 Mr-OPY2 的表达来介导从腐生到昆虫病原的转变。丰富的 Mr-OPY2 蛋白启动附着胞的形成，这是感染的先决条件，而 Mr-OPY2 的产量减少则引发腐生生长和分生孢子形成。Mr-OPY2 蛋白产量的精确调节是通过转录起始位点的替代来实现的。在腐生生长过程中，一个长转录本通过其 5'非翻译区中的小上游开放阅读框产生。在宿主表皮上增加 Mr-OPY2 蛋白的产量是通过表达一种缺少小上游开放阅读框的转录本变体来实现的，否则该框会抑制 Mr-OPY2 的翻译。RNA-seq 和 qRT-PCR 分析表明，Mr-OPY2 是一个转录因子的负调节剂，我们证明该转录因子对于附着胞的形成是必要的。这些发现为调节真菌生活方式转变的机制提供了深入的了解。
