Haring E, Hagemann S, Pinsker W
Institut für Allgemeine Biologie, Abteilung Genetik, Medizinische Fakultät, Universität Wien, Austria.
Gene. 1995 Oct 3;163(2):197-202. doi: 10.1016/0378-1119(95)00334-3.
Distribution and variation of two P-element subfamilies designated M-type and O-type elements were investigated in Drosophila bifasciata (Db) and its relatives. PCR screening revealed that full-sized and internally deleted elements of both types occur in three geographic Db strains and in the related species, D. imaii (Di). Molecular analyses indicate differences in the evolutionary behaviour of the two P-element types. Internally deleted M-type elements fall into two size classes present in all three Db strains. In contrast, internally deleted O-type elements vary between the strains in number and length. With respect to genomic location, M-type elements seem to be restricted to conserved euchromatic sites, whereas the positions of O-type elements appear to be geographically variable. In one strain of Db (Italy), O-type elements seem to accumulate in the heterochromatin. Sequencing of a 397-bp segment shows intra- and interspecific divergence of M-type elements. In a 452-bp segment of the O-type elements, no substitutions were found, neither within nor between species. This finding suggests recent introgression of O-type elements via hybridization between Db and Di. Sequence identity and variation in chromosomal locations among different copies imply that O-type elements are transpositionally active. For M-type elements, genomic mobility cannot be proved. In a survey of several other taxa, no O-type-related sequences were detected so far. Therefore, the origin of the O-type subfamily remains unknown, whereas the source of M-type elements can be traced back to the genus Scaptomyza.
在双带果蝇（Db）及其近缘种中研究了两种P元件亚家族（分别命名为M型和O型元件）的分布和变异情况。PCR筛选显示，这两种类型的全长和内部缺失元件存在于三个地理区域的Db菌株以及相关物种伊氏果蝇（Di）中。分子分析表明这两种P元件类型在进化行为上存在差异。内部缺失的M型元件分为两个大小类别，存在于所有三个Db菌株中。相比之下，内部缺失的O型元件在不同菌株之间数量和长度有所不同。就基因组位置而言，M型元件似乎局限于保守的常染色质位点，而O型元件的位置在地理上似乎是可变的。在Db的一个菌株（意大利）中，O型元件似乎在异染色质中积累。对一段397bp片段的测序显示了M型元件的种内和种间差异。在O型元件的一段452bp片段中，在种内和种间均未发现替换。这一发现表明O型元件是通过Db和Di之间的杂交最近渗入的。不同拷贝之间的序列同一性和染色体位置变异意味着O型元件具有转座活性。对于M型元件，无法证明其基因组移动性。在对其他几个分类群的调查中，到目前为止尚未检测到与O型相关的序列。因此，O型亚家族的起源仍然未知，而M型元件的来源可以追溯到Scaptomyza属。
