Chen Yixiong, Duan Zhibing, Chen Peilin, Shang Yanfang, Wang Chengshu
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Current address:Department of Neuroscience &Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway NJ, 08854, USA.
Sci Rep. 2015 May 29;5:10625. doi: 10.1038/srep10625.
Bax inhibitor 1 (BI-1) is a highly conserved protein originally identified as a suppressor of the proapoptotic protein Bax to inhibit cell death in animals and plants. The orthologs of BI-1 are widely distributed in filamentous fungi but their functions remain largely unknown. Herein, we report the identification and characterizations of MrBI-1, an ortholog of BI-1, in the entomopathogenic fungus Metarhizium robertsii. First, we found that MrBI-1 could partially rescue mammalian Bax-induced cell death in yeast. Deletion of MrBI-1 impaired fungal development, virulence and heat tolerance in M. robertsii. We also demonstrated that inactivation of MrBI-1 reduced fungal resistance to farnesol but not to hydrogen peroxide, suggesting that MrBI-1 contributes to antiapoptotic-like cell death via the endoplasmic reticulum stress-signaling pathway rather than the classical mitochondrium-dependent pathway. In particular, we found that unlike the observations in yeasts and plants, expression of mammalian Bax did not lead to a lethal effect in M. robertsii; however, it did aggravate the fungal apoptotic effect of farnesol. The results of this study advance our understanding of BI-1-like protein functions in filamentous fungi.
Bax抑制剂1（BI-1）是一种高度保守的蛋白质，最初被鉴定为促凋亡蛋白Bax的抑制剂，可抑制动植物中的细胞死亡。BI-1的直系同源物广泛分布于丝状真菌中，但其功能在很大程度上仍不清楚。在此，我们报告了昆虫病原真菌罗伯茨绿僵菌中BI-1的直系同源物MrBI-1的鉴定和特征。首先，我们发现MrBI-1可以部分挽救哺乳动物Bax诱导的酵母细胞死亡。在罗伯茨绿僵菌中缺失MrBI-1会损害真菌的发育、毒力和耐热性。我们还证明，MrBI-1的失活降低了真菌对法尼醇的抗性，但对过氧化氢没有抗性，这表明MrBI-1通过内质网应激信号通路而非经典的线粒体依赖性通路促成抗凋亡样细胞死亡。特别是，我们发现与在酵母和植物中的观察结果不同，哺乳动物Bax的表达在罗伯茨绿僵菌中不会导致致死效应；然而，它确实加剧了法尼醇对真菌的凋亡作用。这项研究的结果增进了我们对丝状真菌中BI-1样蛋白功能的理解。
