RIKEN Innovation Center, Wako, Saitama 351-0198, Japan.
G3 (Bethesda). 2012 Oct;2(10):1269-78. doi: 10.1534/g3.112.003749. Epub 2012 Oct 1.
The dioecious plant Silene latifolia has heteromorphic sex chromosomes, and comparison of the positions of sex-linked genes indicates that at least three large inversions have occurred during the evolution of the Y chromosome. In this article, we describe the isolation of a new sex-linked gene from S. latifolia, which provides new information on the evolution of this plant's young sex chromosomes. By using reverse-transcription polymerase chain reaction degenerate primers based on the Arabidopsis thaliana sequence of WUSCHEL, a flower-development gene, we found two copies in S. latifolia, which we named SlWUS1 and SlWUS2. Southern blot and genetic segregation analysis showed that SlWUS1 is located on the X chromosome and SlWUS2 is autosomal. No Y-linked copy of SlWUS1 was found by either Southern blot analysis under low-stringency conditions or polymerase chain reaction with degenerate primers, so we conclude that SlWUS1 probably has no Y-linked homolog. It is unknown whether the Y chromosome lost the SlWUS1 copy by degeneration of this individual gene or whether deletion of a larger genome region was involved. Several tests lead us to conclude that dosage compensation has not evolved for this sex-linked gene. We mapped the ortholog in the nondioecious relative S. vulgaris (SvWUS1), to compare the location in a species that has no history of having sex chromosomes. SvWUS1 maps to the same linkage group as other fully X-linked genes, indicating that it was not added to the X, but was lost from the Y. Its location differs in the maps from the two species, raising the possibility that the X chromosome, as well as the Y, may have been rearranged.
雌雄异株的植物长柱菀（Silene latifolia）具有异型性染色体，对性连锁基因位置的比较表明，在 Y 染色体的进化过程中至少发生了三次大的倒位。本文描述了从长柱菀中分离出的一个新的性连锁基因，该基因提供了关于该植物年轻性染色体进化的新信息。通过使用基于拟南芥（Arabidopsis thaliana）WUSCHEL 花发育基因的反转录聚合酶链反应简并引物，我们在长柱菀中发现了两个拷贝，我们将其命名为 SlWUS1 和 SlWUS2。Southern 印迹和遗传分离分析表明，SlWUS1 位于 X 染色体上，SlWUS2 位于常染色体上。通过 Southern 印迹在低严格条件下或使用简并引物进行聚合酶链反应，都没有发现 SlWUS1 的 Y 连锁拷贝，因此我们推断 SlWUS1 可能没有 Y 连锁同源物。尚不清楚 Y 染色体是通过单个基因的退化失去了 SlWUS1 拷贝，还是涉及更大基因组区域的缺失。几项测试使我们得出结论，这个性连锁基因没有进化出剂量补偿。我们将同源基因在非雌雄异株的近缘种普通菀（S. vulgaris）中的定位（SvWUS1）进行了映射，以比较在一个没有性染色体历史的物种中的位置。SvWUS1 与其他完全 X 连锁基因位于同一连锁群，这表明它不是添加到 X 染色体上，而是从 Y 染色体上丢失的。它在两个物种的图谱中的位置不同，这增加了 X 染色体和 Y 染色体可能发生重排的可能性。
