Harpke Doerte, Peterson Angela
Biozentrum Martin-Luther-University of Halle/Wittenberg, Weinbergweg 22, 06120 Halle/Saale, Germany.
Mol Phylogenet Evol. 2006 Dec;41(3):579-93. doi: 10.1016/j.ympev.2006.05.036. Epub 2006 Jun 6.
Molecular studies of 21 species of the large Cactaceae genus Mammillaria representing a variety of intrageneric taxonomic levels revealed a high degree of intra-individual polymorphism of the internal transcribed spacer region (ITS1, 5.8S rDNA, ITS2). Only a few of these ITS copies belong to apparently functional genes, whereas most are probably non-functional (pseudogenes). As a multiple gene family, the ITS region is subjected to concerted evolution. However, the high degree of intra-individual polymorphism of up to 36% in ITS1 and up to 35% in ITS2 suggests a non-concerted evolution of these loci in Mammillaria. Conserved angiosperm motifs of ITS1 and ITS2 were compared between genomic and cDNA ITS clones of Mammillaria. Some of these motifs (e.g., ITS1 motif 1, 'TGGT' within ITS2) in combination with the determination of GC-content, length comparisons of the spacers and ITS2 secondary structure (helices II and III) are helpful in the identification of pseudogene rDNA regions.
对仙人掌科大型乳突球属21个物种进行的分子研究，这些物种代表了该属内不同的分类水平，结果显示内部转录间隔区（ITS1、5.8S rDNA、ITS2）存在高度的个体内多态性。这些ITS拷贝中只有少数属于明显有功能的基因，而大多数可能是无功能的（假基因）。作为一个多基因家族，ITS区域经历协同进化。然而，ITS1中高达36%、ITS2中高达35%的高度个体内多态性表明这些位点在乳突球属中存在非协同进化。在乳突球属的基因组和cDNA ITS克隆之间比较了ITS1和ITS2保守的被子植物基序。其中一些基序（例如，ITS1基序1、ITS2内的'TGGT'）结合GC含量的测定、间隔区长度比较和ITS2二级结构（螺旋II和III）有助于鉴定假基因rDNA区域。
