Seligmann Igor C A, Furo Ivanete O, Dos Santos Michelly S, Tagliarini Marcella M, Araujo Cristiane C D, O''Brien Patricia C M, Ferguson-Smith Malcolm A, de Oliveira Edivaldo H C
Cytogenet Genome Res. 2019;159(1):32-38. doi: 10.1159/000503019. Epub 2019 Sep 20.
Despite the variation observed in the diploid chromosome number of storks (Ciconiiformes, Ciconiidae), from 2n = 52 to 2n = 78, most reports have relied solely on analyses by conventional staining. As most species have similar macrochromosomes, some authors propose that karyotype evolution involves mainly fusions between microchromosomes, which are highly variable in species with different diploid numbers. In order to verify this hypothesis, in this study, the karyotypes of 2 species of storks from South America with different diploid numbers, the jabiru (Jabiru mycteria, 2n = 56) and the maguary stork (Ciconia maguary, 2n = 72), were analyzed by chromosome painting using whole chromosome probes from the macrochromosomes of Gallus gallus (GGA) and Leucopternis albicollis (LAL). The results revealed that J. mycteria and C. maguary share synteny within chromosome pairs 1-9 and Z. The syntenies to the macrochromosomes of G. gallus are conserved, except for GGA4, which is homologous to 2 different pairs, as in most species of birds. A fusion of GGA8 and GGA9 was observed in both species. Additionally, chromosomes corresponding to GGA4p and GGA6 are fused to other segments that did not hybridize to any of the macrochromosome probes used, suggesting that these segments correspond to microchromosomes. Hence, our data corroborate the proposed hypothesis that karyotype evolution is based on fusions involving microchromosomes. In view of the morphological constancy of the macrochromosome pairs in most Ciconiidae, we propose a putative ancestral karyotype for the family, including the GGA8/GGA9 fusion, and a diploid number of 2n = 78. The use of probes for microchromosome pairs should be the next step in identifying other synapomorphies that may help to clarify the phylogeny of this family.
尽管鹳形目鹳科鸟类的二倍体染色体数目存在差异，从2n = 52到2n = 78，但大多数报告仅依赖于传统染色分析。由于大多数物种具有相似的大染色体，一些作者提出核型进化主要涉及微小染色体之间的融合，而微小染色体在具有不同二倍体数目的物种中高度可变。为了验证这一假设，在本研究中，使用家鸡（GGA）和白颈林鹳（LAL）大染色体的全染色体探针进行染色体涂染，分析了来自南美洲的两种二倍体数目不同的鹳的核型，即大裸颈鹳（Jabiru mycteria，2n = 56）和马瓜里鹳（Ciconia maguary，2n = 72）。结果显示，大裸颈鹳和马瓜里鹳在1 - 9号染色体对和Z染色体上具有同线性。与家鸡大染色体的同线性是保守的，除了GGA4，它与两对不同的染色体同源，这与大多数鸟类物种情况相同。在这两个物种中均观察到GGA8和GGA9的融合。此外，与GGA4p和GGA6相对应的染色体与未与所用任何大染色体探针杂交的其他片段融合，表明这些片段对应于微小染色体。因此，我们的数据证实了所提出的假设，即核型进化基于涉及微小染色体的融合。鉴于大多数鹳科动物大染色体对的形态稳定性，我们提出了该科的一个假定祖先核型，包括GGA8/GGA9融合，二倍体数目为2n = 78。使用微小染色体对的探针将是识别其他可能有助于阐明该科系统发育的共衍征的下一步。
