Abstract:

The self_incompatibility (S) loci from the Solanaceae, Rosaceae and Scrophulariaceae encode a class of ribonucleases, known as S Rnases, which have been shown to control the pistil expression of self_incompatible reaction. In the former two families, the S loci have been shown to be located near centromere. However, the chromosomal location of the S locus in Antirrhinum, a species of the Scrophulariaceae, is not known. To determine its chromosomal location and genomic organization, an S2 Rnase gene and its corresponding 63 kb BAC clone were separately used for fluorescence in situ hybridization (FISH) of mitotic metaphase chromosomes of a self_incompatible Antirrhinum line of S2S5. The results showed that the S2 Rnase detected a doublet signal near the centromere of the smallest chromosome (2n=16). Two separate doublet signals of the tested BAC sequence were shown on both sides of the centromeres of all eight pairs of the chromosomes, suggesting that the Antirrhinum S locus is located in a pericentromeric region. Furthermore, a retrotransposon, named RIS1 (retrotransposon in the S locus), which has not been identified yet in Antirrhinum, was found next to S2 Rnase. Taken together, the centromeric location of the S locus from the three S_Rnase_based self_incompatible families provides a further support on a common origin of their evolution as well as suppressed recombination.

金鱼草自交不亲和位点位于着丝粒的周边区
马闻师 周君莉 赖钊 张燕生 薛勇彪
（中国科学院遗传与发育研究所，北京100080）
摘要： 在蔷薇科、茄科和玄参科配子体自交不亲和中，编码花柱的S RNase控制花柱的自交不亲和性。在前两科植物中，自交不亲和（s）位点定位于着丝粒的附近，但在玄参科植物金鱼草（Antirrhinum）中自交不亲和位点至今未知。为了确定它在染色体上的位置和基因组结构，以基因型S₂S₅金鱼草根尖为材料，进行染色体的制备观察，利用地高辛标记的S₂RNase和含有其全长的&JE 克隆（S₂BAC）为探针进行荧光染色体原位杂交（FISH），发现S₂RNase 杂交信号位于染色体的着丝粒附近，而S₂BAC的杂交信号位于每条染色体的着丝粒的周边区，呈对称的4个，表明金鱼草! 位点位于着丝粒的周边区。对S₂BAC 预测基因的分析表明，发现一个金鱼草新的反转座子（RLS1）。结果显示，金鱼草S位点位于染色体着丝粒的周边区，富含转座子和反转座子，和其他两类配子体自交不亲和的位置类似，预示它们的共同起源和具有抑制重组的能。
关键词： 金鱼草；自交不亲和位点；着丝粒周边区；反转座子；荧光染色体原位杂交