Fiorin F G, Ruas P M, Ortiz M A, Urtubey E, Matzenbacher N I, Ruas C F
Departamento de Biologia Geral, Centro de Ciências Biológicas, Universidade Estadual de Londrina, Londrina, PR, Brasil.
Genet Mol Res. 2013 Jun 11;12(2):1849-58. doi: 10.4238/2013.January.4.4.
Hypochaeris is an excellent system for studying different modes of chromosome evolution in plants. We carried out a cytogenetic analysis on populations of 2 Hypochaeris species, comprising 10 populations of H. catharinensis and 5 of H. lutea, to assess possible changes on chromosome organization in this interesting genus. Conventional Feulgen staining and fluorescent banding revealed that the general aspects of chromosome morphology for all populations of both species were similar, evidence of the typical bimodal karyotypes with 2n = 8 chromosomes that characterize the South American Hypochaeris. Comparative analysis of the karyotypes identified minor variations in the absolute size and arm ratio of corresponding chromosome pairs. One population of H. lutea was entirely polyploid adding a novel cytotype to this species. Fluorescent banding revealed strong chromomycin A3 (CMA3)-positive signals on both arms of chromosomes 3 and 4 of H. catharinensis, revealing a new pattern for the distribution of GC-rich heterochromatin in Hypochaeris. A strong CMA-positive signal was observed on the short arm of chromosome 3 in one population of H. lutea, while the other populations validated the CMA3 pattern already described for this species. While the overall karyotype similarities of the 2 species are in compass with all South American Hypochaeris, the presence of unusual large blocks of GC-rich heterochromatin suggests that chromosome rearrangements, related to dispersion of heterochromatin, are taking place in the karyotype of H. catharinensis. The novel polyploid cytotype identified in H. lutea provides support that polyploidization is an active process in the mode of chromosome evolution in Hypochaeris.
猫儿菊属是研究植物染色体进化不同模式的优秀体系。我们对2种猫儿菊属植物的种群进行了细胞遗传学分析，其中包括10个卡氏猫儿菊种群和5个黄花猫儿菊种群，以评估这个有趣属中染色体组织可能发生的变化。传统的福尔根染色和荧光带型分析表明，这两个物种所有种群的染色体形态总体特征相似，这是具有2n = 8条染色体的典型双峰核型的证据，该核型是南美猫儿菊属的特征。核型的比较分析确定了相应染色体对在绝对大小和臂比上的微小差异。黄花猫儿菊的一个种群完全是多倍体，为该物种增添了一种新的细胞型。荧光带型分析显示，卡氏猫儿菊第3和第4号染色体的两条臂上都有强烈的嗜铬霉素A3（CMA3）阳性信号，揭示了猫儿菊属中富含GC的异染色质分布的新模式。在黄花猫儿菊的一个种群中，在第3号染色体的短臂上观察到一个强烈的CMA阳性信号，而其他种群则验证了该物种已描述的CMA3模式。虽然这两个物种的总体核型相似性与所有南美猫儿菊属一致，但富含GC的异染色质异常大片段的存在表明，与异染色质分散相关的染色体重排在卡氏猫儿菊的核型中正在发生。在黄花猫儿菊中鉴定出的新型多倍体细胞型支持了多倍体化是猫儿菊属染色体进化模式中的一个活跃过程。
