Huang Jie, Katz Laura A
Department of Biological Sciences, Smith College, Northampton, MA 01063, USA; Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Department of Biological Sciences, Smith College, Northampton, MA 01063, USA; Program in Organismic and Evolutionary Biology, UMass-Amherst, Amherst, MA 01003, USA.
Protist. 2014 Aug;165(4):445-51. doi: 10.1016/j.protis.2014.04.005. Epub 2014 May 9.
In some ciliates, extensive genome fragmentation leads to a macronucleus (i.e. somatic nucleus) containing gene-sized chromosomes that vary in copy number. Yet the relationship between copy number and expression level is not well understood as previous work has shown a variety of patterns. For example, nanochromosome copy numbers are positively correlated to mRNA levels in spirotrichous ciliates, while one study of Chilodonella uncinata suggested that they were inversely correlated. To study further copy number and expression levels in C. uncinata, we analyzed 11 members in five gene families (SSU-rDNA, actin, alpha-tubulin, histidine acid phosphatase family protein and a protein kinase domain containing protein) from one strain. We find that macronuclear copy numbers of these genes range from hundreds to thousands per cell, and that copy number does not correlate with expression level as measured by steady-state RNA in predominantly-vegetative cultures. We also compared six of these genes to their orthologs in a second genetically-isolated strain of C. uncinata to reveal that patterns of nanochromosome and transcript copy numbers are conserved between strains. Our data suggest that nanochromosome copy number may be related to a feature like nuclear architecture.
在一些纤毛虫中，广泛的基因组片段化导致大核（即体细胞核）含有基因大小的染色体，其拷贝数各不相同。然而，由于先前的研究显示了多种模式，拷贝数与表达水平之间的关系尚未得到很好的理解。例如，在螺旋毛纲纤毛虫中，纳米染色体的拷贝数与mRNA水平呈正相关，而一项对曲钩斜管虫的研究表明它们呈负相关。为了进一步研究曲钩斜管虫中的拷贝数和表达水平，我们分析了来自一个菌株的五个基因家族（小亚基核糖体DNA、肌动蛋白、α-微管蛋白、组氨酸酸性磷酸酶家族蛋白和一种含有蛋白激酶结构域的蛋白）中的11个成员。我们发现这些基因的大核拷贝数在每个细胞中从数百到数千不等，并且在主要为营养型的培养物中，拷贝数与通过稳态RNA测量的表达水平不相关。我们还将其中六个基因与其在曲钩斜管虫的第二个遗传隔离菌株中的直系同源基因进行了比较，以揭示纳米染色体和转录本拷贝数的模式在不同菌株之间是保守的。我们的数据表明，纳米染色体拷贝数可能与核结构等特征有关。
