Nikolaou Elissavet, Agrafioti Ino, Stumpf Michael, Quinn Janet, Stansfield Ian, Brown Alistair J P
Aberdeen Fungal Group, School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, UK.
BMC Evol Biol. 2009 Feb 21;9:44. doi: 10.1186/1471-2148-9-44.
Microbes must sense environmental stresses, transduce these signals and mount protective responses to survive in hostile environments. In this study we have tested the hypothesis that fungal stress signalling pathways have evolved rapidly in a niche-specific fashion that is independent of phylogeny. To test this hypothesis we have compared the conservation of stress signalling molecules in diverse fungal species with their stress resistance. These fungi, which include ascomycetes, basidiomycetes and microsporidia, occupy highly divergent niches from saline environments to plant or mammalian hosts.
The fungi displayed significant variation in their resistance to osmotic (NaCl and sorbitol), oxidative (H2O2 and menadione) and cell wall stresses (Calcofluor White and Congo Red). There was no strict correlation between fungal phylogeny and stress resistance. Rather, the human pathogens tended to be more resistant to all three types of stress, an exception being the sensitivity of Candida albicans to the cell wall stress, Calcofluor White. In contrast, the plant pathogens were relatively sensitive to oxidative stress. The degree of conservation of osmotic, oxidative and cell wall stress signalling pathways amongst the eighteen fungal species was examined. Putative orthologues of functionally defined signalling components in Saccharomyces cerevisiae were identified by performing reciprocal BLASTP searches, and the percent amino acid identities of these orthologues recorded. This revealed that in general, central components of the osmotic, oxidative and cell wall stress signalling pathways are relatively well conserved, whereas the sensors lying upstream and transcriptional regulators lying downstream of these modules have diverged significantly. There was no obvious correlation between the degree of conservation of stress signalling pathways and the resistance of a particular fungus to the corresponding stress.
Our data are consistent with the hypothesis that fungal stress signalling components have undergone rapid recent evolution to tune the stress responses in a niche-specific fashion.
微生物必须感知环境压力，传导这些信号并产生保护性反应才能在恶劣环境中生存。在本研究中，我们检验了这样一个假设，即真菌应激信号通路已以一种与系统发育无关的生态位特异性方式快速进化。为了验证这一假设，我们比较了不同真菌物种中应激信号分子的保守性与其抗逆性。这些真菌包括子囊菌、担子菌和微孢子虫，占据从盐环境到植物或哺乳动物宿主等高度不同的生态位。
这些真菌在对渗透压（氯化钠和山梨醇）、氧化（过氧化氢和甲萘醌）和细胞壁应激（荧光增白剂和刚果红）的抗性方面表现出显著差异。真菌系统发育与抗逆性之间没有严格的相关性。相反，人类病原体往往对所有三种类型的应激更具抗性，白色念珠菌对细胞壁应激荧光增白剂敏感是个例外。相比之下，植物病原体对氧化应激相对敏感。我们研究了18种真菌中渗透压、氧化和细胞壁应激信号通路的保守程度。通过进行双向BLASTP搜索，鉴定了酿酒酵母中功能定义的信号成分的假定直系同源物，并记录了这些直系同源物的氨基酸同一性百分比。这表明，一般来说，渗透压、氧化和细胞壁应激信号通路的核心成分相对保守，而这些模块上游的传感器和下游的转录调节因子则有显著差异。应激信号通路的保守程度与特定真菌对相应应激的抗性之间没有明显的相关性。
我们的数据与以下假设一致，即真菌应激信号成分最近经历了快速进化，以一种生态位特异性方式调节应激反应。
