Cheng Zhi-Jun, Murata Minoru
Core Research for Evolutionary Science and Technology Program, Japan Science Technology Corporation, Tokyo 103-0027, Japan.
Genetics. 2003 Jun;164(2):665-72. doi: 10.1093/genetics/164.2.665.
From a wild diploid species that is a relative of wheat, Aegilops speltoides, a 301-bp repeat containing 16 copies of a CAA microsatellite was isolated. Southern blot and fluorescence in situ hybridization revealed that approximately 250 bp of the sequence is tandemly arrayed at the centromere regions of A- and B-genome chromosomes of common wheat and rye chromosomes. Although the DNA sequence of this 250-bp repeat showed no notable homology in the databases, the flanking or intervening sequences between the repeats showed high homologies (>82%) to two separate sequences of the gag gene and its upstream region in cereba, a Ty3/gypsy-like retroelement of Hordeum vulgare. Since the amino acid sequence deduced from the 250 bp with seven CAAs showed some similarity ( approximately 53%) to that of the gag gene, we concluded that the 250-bp repeats had also originated from the cereba-like retroelements in diploid wheat such as Ae. speltoides and had formed tandem arrays, whereas the 300-bp repeats were dispersed as a part of cereba-like retroelements. This suggests that some tandem repeats localized at the centromeric regions of cereals and other plant species originated from parts of retrotransposons.
从小麦的近缘野生二倍体物种斯卑尔脱山羊草（Aegilops speltoides）中分离出一个含有16个CAA微卫星拷贝的301 bp重复序列。Southern杂交和荧光原位杂交显示，该序列约250 bp串联排列在普通小麦A和B基因组染色体以及黑麦染色体的着丝粒区域。尽管这个250 bp重复序列的DNA序列在数据库中未显示出显著同源性，但重复序列之间的侧翼或间隔序列与大麦（Hordeum vulgare）的Ty3/gypsy类反转录元件cereba的gag基因及其上游区域的两个独立序列具有高度同源性（>82%）。由于从含有7个CAA的250 bp推导的氨基酸序列与gag基因的氨基酸序列有一定相似性（约53%），我们得出结论，250 bp重复序列也起源于二倍体小麦如斯卑尔脱山羊草中的cereba样反转录元件，并形成了串联阵列，而300 bp重复序列则作为cereba样反转录元件的一部分分散存在。这表明一些位于谷物和其他植物物种着丝粒区域的串联重复序列起源于反转录转座子的部分序列。
