Marinho Rafaela C, Mendes-Rodrigues Clesnan, Balao Francisco, Ortiz Pedro L, Yamagishi-Costa Júlia, Bonetti Ana M, Oliveira Paulo E
Instituto de Genética e Bioquímica, Universidade Federal de Uberlândia, Uberlândia-MG 38400-902, Brazil.
Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia-MG 38400-902, Brazil.
Am J Bot. 2014 Sep;101(9):1456-65. doi: 10.3732/ajb.1400248. Epub 2014 Sep 11.
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Whole genome duplication (WGD) and specific polyploidy events marked turning points for angiosperm genome structure and evolution. Therefore, cytogenetic studies of polyploidy-prone groups such as the tropical Malvaceae and plant formations such as as the Brazilian Cerrado have gained further importance. We present new chromosome counts for Cerrado Bombacoideae and revised chromosome numbers for the Malvaceae s.l., compare these between subfamilies, and relate them to phylogenetic signal.•
We studied the chromosome number of Eriotheca candolleana, E. gracilipes, E. pubescens, Pachira glabra, Pseudobombax longiflorum, and P. tomentosum. We also compared Eriotheca species ploidy levels using flow cytometry. We compiled chromosome numbers for 557 species of Malvaceae s.l., including 37 Bombacoideae species. We included this information in a phylogenetic reconstruction based on chloroplast matK-trnK DNA to evaluate chromosome evolution of the Malvaceae s.l. and the Bombacoideae in particular.•
The Cerrado Bombacoideae presented consistently high chromosome numbers. Numbers for Eriotheca species were among the highest and varied among populations. Flow cytometry analyses showed similar 1Cx DNA for all cytotypes and indicated neopolyploidy. Chromosome numbers differed between subfamilies, with the lowest numbers in the Malvoideae and Byttnerioideae and the highest in Tilioideae. Chromosome numbers had significant phylogenetic signal for Bombacoideae but not for Malvoideae or Malvaceae s.l.•
Clearly distinct chromosome numbers allied to monophyly provide some support for a circumscription of the Bombacoideae and distinction within the Malvaceae. The phylogenetic signal for chromosome number supports the idea of an ancient WGD and further neopolyploidy events as important evolutionary trends for the Bombacoideae.
研究前提：全基因组复制（WGD）和特定的多倍体事件标志着被子植物基因组结构和进化的转折点。因此，对易发生多倍体的类群（如热带锦葵科）和植物区系（如巴西塞拉多）进行细胞遗传学研究变得更加重要。我们给出了塞拉多木棉亚科新的染色体计数以及广义锦葵科修订后的染色体数目，比较了各亚科之间的这些数据，并将它们与系统发育信号相关联。
方法：我们研究了坎多勒毛蕊木、细柄毛蕊木、柔毛毛蕊木、光瓜栗、长花假木棉和绒毛假木棉的染色体数目。我们还使用流式细胞术比较了毛蕊木属物种的倍性水平。我们汇总了广义锦葵科557个物种的染色体数目，其中包括37个木棉亚科物种。我们将这些信息纳入基于叶绿体matK - trnK DNA的系统发育重建中，以评估广义锦葵科尤其是木棉亚科的染色体进化。
主要结果：塞拉多木棉亚科的染色体数目一直很高。毛蕊木属物种的染色体数目是最高的之一，且在不同种群间存在差异。流式细胞术分析表明，所有细胞型的1Cx DNA相似，并表明存在新多倍体现象。各亚科的染色体数目不同，其中锦葵亚科和柄翅果亚科的数目最低，椴树亚科的数目最高。染色体数目对木棉亚科有显著的系统发育信号，但对锦葵亚科或广义锦葵科则没有。
结论：与单系性相关的明显不同的染色体数目为木棉亚科的界定以及锦葵科内的区分提供了一些支持。染色体数目的系统发育信号支持这样一种观点，即古老的全基因组复制和进一步的新多倍体事件是木棉亚科重要的进化趋势。
