de Chastonay Y, Müller F, Tobler H
Institute of Zoology, University of Fribourg, Switzerland.
Gene. 1990 Sep 14;93(2):199-204. doi: 10.1016/0378-1119(90)90225-g.
Two families of highly reiterated satellite nucleotide (nt) sequences have been found in the genome of the sexually separated nematode Panagrellus redivivus. The repeats are arranged in tandem arrays but the different satellites are not intermingled. Monomeric lengths are of 155 bp for one kind and 167 bp for the other; they were named E155 and E167. The A + T content is elevated in both families (i.e., 59.5%, and 65.3%, respectively). No similarity was found between the two satellites nor to other known highly repetitive elements. Furthermore, nt methylation as well as transcriptional activity were negative. An internal subrepeating unit, about 30 bp long, was observed in E167, implying that it could have evolved from a shorter sequence. Reiteration frequencies are approx. 30,000 and 40,000 copies per haploid genome, for E155 and E167, respectively, constituting together about 17% of the total DNA. This figure is astonishingly high, considering a C-value of 70,000 kb in P. redivivus, which is thought to be the lower limit for metazoans. Hence, the genome complexity is approx. 58,000 kb. In contrast to the nematodes Ascaris lumbricoides and Parascaris equorum, however, P. redivivus does not seem to eliminate large blocks of satellite DNA in the presomatic cells during early development.
在有性分离的线虫类小杆线虫（Panagrellus redivivus）的基因组中发现了两类高度重复的卫星核苷酸（nt）序列。这些重复序列以串联阵列的形式排列，但不同的卫星序列并不相互混杂。一类单体长度为155 bp，另一类为167 bp；它们分别被命名为E155和E167。两类序列的A + T含量均有所升高（即分别为59.5%和65.3%）。这两类卫星序列之间以及与其他已知的高度重复元件之间均未发现相似性。此外，核苷酸甲基化以及转录活性均为阴性。在E167中观察到一个约30 bp长的内部亚重复单元，这意味着它可能是由一个较短的序列进化而来。E155和E167的重复频率分别约为每单倍体基因组30,000份和40,000份，总共约占总DNA的17%。考虑到小杆线虫的C值为70,000 kb（这被认为是后生动物的下限），这个数字高得惊人。因此，基因组复杂度约为58,000 kb。然而，与线虫蛔虫（Ascaris lumbricoides）和马副蛔虫（Parascaris equorum）不同的是，小杆线虫在早期发育过程中似乎不会在体细胞前体细胞中消除大片段的卫星DNA。
