Identification and characterization of putative transposable DNA elements in solanaceous plants and Caenorhabditis elegans.

Several families of putative transposable elements (TrEs) in both solanaceous plants and Caenorhabditis elegans have been identified by screening the DNA data base for inverted repeated domains present in multiple copies in the genome. The elements are localized within intron and flanking regions of many genes. These elements consist of two inverted repeats flanking sequences ranging from 5 bp to > 500 bp. Identification of multiple elements in which sequence conservation includes both the flanking and internal regions implies that these TrEs are capable of duplicative transposition. Two of the elements were identified in promoter regions of the tomato (Lycoperiscon esculentum) polygalacturonase and potato (Solanum tuberosum) Win1 genes. The element in the polygalacturonase promoter spans a known regulatory region. In both cases, ancestral DNA sequences, which represent potential recombination target sequences prior to insertion of the elements, have been cloned from related species. The sequences of the inverted repeated domains in plants and C. elegans show a high degree of phylogenetic conservation. While frequency of the different elements is variable, some are present in very high copy number. A member of a single C. elegans TrE family is observed approximately once every 20 kb in the genome. The abundance of the described TrEs suggests utility in the genomic analysis of these and related organisms.

本研究通过在DNA数据库中筛查基因组内以多拷贝形式存在的反向重复结构域，在茄科植物（solanaceous plants）与秀丽隐杆线虫（Caenorhabditis elegans）中均鉴定得到多家族推定转座因子（putative transposable elements, TrEs）。该类转座因子定位于众多基因的内含子及侧翼区域，由两段反向重复序列侧翼连接长度介于5 bp至500 bp以上的序列构成。多个元件的序列保守性同时覆盖侧翼区域与内部区域，这表明此类转座因子具备复制型转座的能力。其中两个元件分别位于番茄（Lycopersicon esculentum）多聚半乳糖醛酸酶基因与马铃薯（Solanum tuberosum）Win1基因的启动子区域；多聚半乳糖醛酸酶启动子内的转座因子跨越了已知的调控区域。在这两种案例中，代表元件插入前潜在重组靶序列的祖先DNA序列，均已从相关物种中克隆获得。植物与秀丽隐杆线虫体内的反向重复结构域序列展现出高度的系统发育保守性。尽管不同转座因子的拷贝数存在差异，部分元件的拷贝数极高：秀丽隐杆线虫的单个转座因子家族成员在基因组中大约每20 kb即可出现一次。本次鉴定的转座因子丰度较高，表明其可应用于上述物种及近缘物种的基因组分析研究。