Meiotic recombination in sexual diploid and apomictic triploid dandelions (Taraxacum officinale L.).
Meiotic recombination in sexual diploid and apomictic triploid dandelions (Taraxacum officinale L.).
复制标题
有性二倍体和无融合生殖三倍体蒲公英（Taraxacum officinale L.）的减数分裂重组。
作者：
P. Baarlen;Peter J. van Dijk;Rolf F Hoekstra;J. D. Jong
蒲公英是一种生机勃勃的欧洲杂草，其二倍体有性种群分布在欧洲南部地区，二倍体有性种群和三倍体或四倍体无融合生殖种群部分重叠分布在中部和北部地区。以前的研究表明，在无融合生殖群体中，遗传变异水平出人意料地高，这表明在无融合生殖个体中发生了遗传分离和(或)有性个体和无融合生殖个体之间的杂交。在这项研究中，我们分析了有性二倍体和无融合生殖三倍体植物的减数分裂，以寻找可以解释无融合生殖中高水平遗传变异的机制。三倍体无融合生殖小孢子细胞的显微镜观察表明，减数分裂前期I的染色体配对和交叉形成水平低于有性二倍体，但仍足以假定同源体之间的重组。Nomarski DIC(差分干涉对比)显微镜观察到无融合生殖体内光学清晰的大孢子细胞偶然形成四分体，这表明杂交可以发生在三倍体的无融合生殖中。
Taraxacum officinale L. (dandelion) is a vigorous weed in Europe with diploid sexual populations in the southern regions and partially overlapping populations of diploid sexuals and triploid or tetraploid apomicts in the central and northern regions. Previous studies have demonstrated unexpectedly high levels of genetic variation in the apomictic populations, suggesting the occurrence of genetic segregation in the apomicts and (or) hybridization between sexual and apomictic individuals. In this study we analysed meiosis in both sexual diploid and apomictic triploid plants to find mechanisms that could account for the high levels of genetic variation in the apomicts. Microscopic study of microsporocytes in the triploid apomicts revealed that the levels of chromosome pairing and chiasma formation at meiotic prophase I were lower than in that of the sexual diploids, but still sufficient to assume recombination between the homologues. Nomarski DIC (differential interference contrast) microscopy of optically cleared megasporocytes in the apomicts demonstrated incidental formation of tetrads, which suggests that hybridization can occur in triploid apomicts.