Departamento de Ciências Biológicas, Centro de Biotecnologia e Genética, Universidade Estadual de Santa Cruz, Rodovia Jorge Amado, km 16, CEP, Ilhéus, BA, 45662-900, Brazil.
Centro de Ciências e Tecnologias Agropecuárias, Laboratório de Melhoramento Genético Vegetal, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, Brazil.
BMC Genet. 2018 Apr 11;19(1):25. doi: 10.1186/s12863-018-0610-2.
The Leguminosae family is the third-largest family of angiosperms, and Caesalpinioideae is its second-largest subfamily. A great number of species (approximately 205) are found in the Caesalpinia group within this subfamily; together with these species' phenotypic plasticity and the similarities in their morphological descriptors, make this a complex group for taxonomic and phylogenetic studies. The objective of the present work was to evaluate the karyotypic diversity and the 2C DNA content variation in 10 species of the Caesalpinia group, representing six genera: Paubrasilia, Caesalpinia, Cenostigma, Poincianella, Erythrostemon and Libidibia. The GC-rich heterochromatin and 45S rDNA sites (which are used as chromosome markers) were located to evaluate the karyotype diversity in the clade. The variation in the 2C DNA content was determined through flow cytometry.
The fluorochrome banding indicated that the chromomycin A/4',6-diamidino-2-phenylindole blocks were exclusively in the terminal regions of the chromosomes, coinciding with 45S rDNA sites in all analyzed species. Physical mapping of the species (through fluorescence in situ hybridization) revealed variation in the size of the hybridization signals and in the number and distribution of the 45S rDNA sites. All hybridization sites were in the terminal regions of the chromosomes. In addition, all species had a hybridization site in the fourth chromosome pair. The 2C DNA content ranged from 1.54 pg in Erythrostemon calycina to 2.82 pg in the Paubrasilia echinata large-leaf variant. The Pa. echinata small-leaf variant was isolated from the other leaf variants through Scoot-Knott clustering.
The chromosome diversity and the variation in the 2C DNA content reinforce that the actual taxonomy and clustering of the analyzed taxa requires more genera that were previously proposed. This fact indicates that taxonomy, phylogeny and cytoevolutionary inference related to the complex Caesalpinia group have to be done through integrative evaluation.
豆科是被子植物的第三大科，云实亚科是其第二大亚科。在该亚科的云实属中发现了大量物种（约 205 种）；加上这些物种的表型可塑性和形态描述符的相似性，使得这个群体成为分类学和系统发育研究的一个复杂群体。本研究的目的是评估 10 种云实属物种的核型多样性和 2C DNA 含量变异，这些物种代表了六个属：Paulbrasia、Caesalpinia、Cenostigma、Poincianella、Erythrostemon 和 Libidibia。用 GC 丰富的异染色质和 45S rDNA 位点（用作染色体标记）来评估进化枝中的核型多样性。通过流式细胞术测定 2C DNA 含量的变化。
荧光染料带分析表明，色霉素 A/4'，6-二脒基-2-苯吲哚带仅位于染色体的末端区域，与所有分析物种的 45S rDNA 位点一致。通过荧光原位杂交对物种进行物理作图显示，杂交信号的大小、45S rDNA 位点的数量和分布存在差异。所有杂交位点均位于染色体的末端区域。此外，所有物种的第四对染色体都有一个杂交位点。2C DNA 含量范围为 1.54 pg（Erythrostemon calycina）至 2.82 pg（Paubrasilia echinata 大叶变型）。通过 Scoot-Knott 聚类，从小叶变型中分离出 Pa. echinata 小叶变型。
染色体多样性和 2C DNA 含量的变化表明，分析类群的实际分类学和聚类需要更多以前提出的属。这一事实表明，与复杂的云实属相关的分类学、系统发育和细胞进化推断必须通过综合评估来进行。
