Vohanka Jaroslav, Simecková Katerina, Machalová Eliska, Behenský Frantisek, Krause Michael W, Kostrouch Zdenek, Kostrouchová Marta
Laboratory of Molecular Biology and Genetics, Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Gene Expr Patterns. 2010 Sep;10(6):227-36. doi: 10.1016/j.gep.2010.05.001. Epub 2010 May 10.
The genome of Caenorhabditis elegans encodes more than 280 nuclear hormone receptors (NHRs) in contrast to the 48 NHRs in humans and 18 NHRs in Drosophila. The majority of the C. elegans NHRs are categorized as supplementary nuclear receptors (supnrs) that evolved by successive duplications of a single ancestral gene. The evolutionary pressures that lead to the expansion of NHRs in nematodes, as well as the function of the majority of supnrs, are not known. Here, we have studied the expression of seven genes organized in a cluster on chromosome V: nhr-206, nhr-208, nhr-207, nhr-209, nhr-154, nhr-153 and nhr-136. Reverse transcription-quantitative PCR and analyses using transgenic lines carrying GFP fusion genes with their putative promoters revealed that all seven genes of this cluster are expressed and five have partially overlapping expression patterns including in the pharynx, intestine, certain neurons, the anal sphincter muscle, and male specific cells. Four genes in this cluster are conserved between C. elegans and Caenorhabditis briggsae whereas three genes are present only in C. elegans, the apparent result of a relatively recent expansion. Interestingly, we find that a subset of the conserved and non-conserved genes in this cluster respond transcriptionally to fasting in tissue-specific patterns. Our results reveal the diversification of the temporal, spatial, and metabolic gene expression patterns coupled with evolutionary drift within supnr family members.
与人类的48种核激素受体（NHRs）和果蝇的18种核激素受体相比，秀丽隐杆线虫的基因组编码超过280种核激素受体。秀丽隐杆线虫的大多数NHRs被归类为补充核受体（supnrs），它们是由单个祖先基因的连续复制进化而来的。导致线虫中NHRs扩张的进化压力以及大多数supnrs的功能尚不清楚。在这里，我们研究了位于第五条染色体上成簇排列的7个基因的表达：nhr-206、nhr-208、nhr-207、nhr-209、nhr-154、nhr-153和nhr-136。逆转录定量PCR以及使用携带与其推定启动子的GFP融合基因的转基因品系进行的分析表明，该簇中的所有7个基因均有表达，其中5个具有部分重叠的表达模式，包括在咽部、肠道、某些神经元、肛门括约肌和雄性特异性细胞中。该簇中的4个基因在秀丽隐杆线虫和briggsae秀丽隐杆线虫之间是保守的，而3个基因仅存在于秀丽隐杆线虫中，这显然是相对近期扩张的结果。有趣的是，我们发现该簇中保守和非保守基因的一个子集以组织特异性模式对禁食作出转录反应。我们的结果揭示了supnr家族成员中时间、空间和代谢基因表达模式的多样化以及进化漂移。
