Cascant-Lopez Emma, Crosthwaite Susan K, Johnson Louise J, Harrison Richard J
Genetics, Genomics and Breeding, NIAB EMR, East Malling, United Kingdom.
The School of Biological Sciences, University of Reading, Reading, United Kingdom.
Front Microbiol. 2020 Aug 28;11:1977. doi: 10.3389/fmicb.2020.01977. eCollection 2020.
Many organisms harbor circadian clocks that promote their adaptation to the rhythmic environment. While a broad knowledge of the molecular mechanism of circadian clocks has been gained through the fungal model , little is known about circadian clocks in other fungi. belongs to the same class as many important plant pathogens including the vascular wilt fungus . We identified homologs of clock proteins in , which showed high conservation in key protein domains. However, no evidence for an endogenous, free-running and entrainable rhythm was observed in the daily formation of conidia and microsclerotia. In the () gene encodes a central clock protein expressed rhythmically and in response to light. In contrast, expression of is not light-regulated. Temporal gene expression profiling over 48 h in constant darkness and temperature revealed no circadian expression of key clock genes. Furthermore, RNA-seq over a 24 h time-course revealed no robust oscillations of clock-associated transcripts in constant darkness. Comparison of gene expression between wild-type and a Δ mutant showed that genes involved in metabolism, transport and redox processes are mis-regulated in the absence of . In addition, Δ mutants display growth defects and reduced pathogenicity in a strain dependent manner. Our data indicate that if a circadian clock exists in Verticillium, it is based on alternative mechanisms such as post-transcriptional interactions of VdFRQ and the WC proteins or the components of a FRQ-less oscillator. Alternatively, it could be that whilst the original functions of the clock proteins have been maintained, in this species the interactions that generate robust rhythmicity have been lost or are only triggered when specific environmental conditions are met. The presence of conserved clock genes in genomes should not be taken as definitive evidence of circadian function.
许多生物体都拥有生物钟，以促进它们适应有节律的环境。虽然通过真菌模型已经对生物钟的分子机制有了广泛的了解，但对于其他真菌中的生物钟却知之甚少。[该真菌名称]与许多重要的植物病原体属于同一类，包括维管束枯萎病菌。我们在[该真菌名称]中鉴定出了生物钟蛋白的同源物，它们在关键蛋白结构域中显示出高度保守性。然而，在分生孢子和微菌核的日常形成过程中，未观察到内源性、自由运行且可被调节的节律的证据。在[另一种真菌名称]中，[基因名称]基因编码一种核心生物钟蛋白，其表达有节律且对光有反应。相比之下，[另一基因名称]的表达不受光调节。在恒定黑暗和温度条件下进行的48小时时间基因表达谱分析显示，关键生物钟基因没有昼夜节律表达。此外，在24小时时间进程中的RNA测序显示，在恒定黑暗条件下，与生物钟相关的转录本没有强烈的振荡。野生型[该真菌名称]和Δ突变体之间的基因表达比较表明，在没有[相关基因名称]的情况下，参与代谢、运输和氧化还原过程的基因被错误调节。此外,Δ突变体以菌株依赖的方式表现出生长缺陷和致病性降低。我们的数据表明，如果黄萎病菌中存在生物钟，它是基于诸如VdFRQ和WC蛋白的转录后相互作用或无FRQ振荡器的组件等替代机制。或者，情况可能是，虽然生物钟蛋白的原始功能得以保留，但在这个物种中，产生强烈节律性的相互作用已经丧失，或者只有在满足特定环境条件时才会触发。基因组中保守生物钟基因的存在不应被视为昼夜节律功能的确凿证据。
