Azaiez Aïda, Bouchard Eric F, Jean Martine, Belzile François J
Département de Phytologie, Université Laval, QC G1K 7P4, Canada.
Genome. 2006 Nov;49(11):1366-73. doi: 10.1139/g06-099.
Microsatellites are simple, tandem DNA repeats that represent unstable regions of the genome. They undergo frequent changes in tract length by base additions or deletions due to DNA polymerase slippage during replication. To characterize factors affecting the frequency of spontaneous mutations occurring in microsatellites in plants, a reporter system was used in Arabidopsis thaliana and tomato (Lycopersicon esculentum). The beta-glucuronidase (GUS) reporter system was used to measure the mutation frequency in various microsatellites (G(7), G(10), G(13), G(16), and C(16)) in somatic tissues. Our results indicate that this frequency increases with the number of repeats: a G(16) tract was almost 80-fold more mutable than a G(7) tract. Furthermore, the frequency of mutations depends on repeat orientation, as G(16) was 3-fold more mutable than C(16). The mutation rate was also found to differ markedly in Arabidopsis and tomato for an identical microsatellite. Indeed, Arabidopsis showed a 5-fold higher mutation frequency than tomato with the same G(7) reporter construct. Finally, mutation in a G(16) tract was frequent enough that mutations transmitted germinally to the next generation could be detected at a relatively high frequency.
微卫星是简单的串联DNA重复序列，代表基因组的不稳定区域。由于复制过程中DNA聚合酶的滑动，它们通过碱基的添加或缺失使序列长度频繁变化。为了表征影响植物微卫星中自发突变频率的因素，在拟南芥和番茄（番茄）中使用了一个报告系统。β-葡萄糖醛酸酶（GUS）报告系统用于测量体细胞组织中各种微卫星（G(7)、G(10)、G(13)、G(16)和C(16)）的突变频率。我们的结果表明，这种频率随着重复次数的增加而增加：一个G(16)序列的突变率几乎是G(7)序列的80倍。此外，突变频率取决于重复方向，因为G(16)的突变率是C(16)的3倍。对于相同的微卫星，在拟南芥和番茄中也发现突变率有显著差异。事实上，使用相同的G(7)报告构建体时，拟南芥的突变频率比番茄高5倍。最后，G(16)序列中的突变足够频繁，以至于可以以相对较高的频率检测到向下一代传递的生殖系突变。
