Laboratório de Citogenética e Diversidade Vegetal, Departamento de Biologia Geral, Centro de Ciências Biológicas, Universidade Estadual de Londrina, Londrina, Paraná, 86097-570, Brazil.
Programa de Pós-graduação em Genética e Biologia Molecular, Centro de Ciências Biológicas, Universidade Estadual de Londrina, Londrina, Paraná, 86097-570, Brazil.
Mol Biol Rep. 2022 Sep;49(9):8785-8799. doi: 10.1007/s11033-022-07728-z. Epub 2022 Jul 9.
Cestrum species present large genomes (2 C = ~ 24 pg), a high occurrence of B chromosomes and great diversity in heterochromatin bands. Despite this diversity, karyotypes maintain the chromosome number 2n = 16 (except when they present B chromosomes), and a relative similarity in chromosome morphology and symmetry. To deepen our knowledge of the Cestrum genome composition, low-coverage sequencing data of C. strigilatum and C. elegans were compared, including cytogenomic analyses of seven species.
Bioinformatics analyses showed retrotransposons comprising more than 70% of the repetitive fraction, followed by DNA transposons (~ 17%), but FISH assays using retrotransposon probes revealed inconspicuous and scattered signals. The four satellite DNA families here analyzed represented approximately 2.48% of the C. strigilatum dataset, and these sequences were used as probes in FISH assays. Hybridization signals were colocalized with all AT- and GC-rich sequences associated with heterochromatin, including AT-rich Cold-Sensitive Regions (CSRs). Although satellite probes hybridized in almost all tested species, a satDNA family named CsSat49 was highlighted because it predominates in centromeric regions.
Data suggest that the satDNA fraction is conserved in the genus, although there is variation in the number of FISH signals between karyotypes. Except to the absence of FISH signals with probes CsSat1 and CsSat72 in two species, the other satellites occurred in species of different phylogenetic clades. Some satDNA sequences have been detected in the B chromosomes, indicating that they are rich in preexisting sequences in the chromosomes of the A complement. This comparative study provides an important advance in the knowledge on genome organization and heterochromatin composition in Cestrum, especially on the distribution of satellite fractions between species and their importance for the B chromosome composition.
香石竹属物种具有较大的基因组（2C=~24pg）、大量 B 染色体的出现以及异染色质带的多样性。尽管存在这种多样性，但其染色体组型保持 2n=16（当它们出现 B 染色体时除外），并且在染色体形态和对称性方面具有相对相似性。为了更深入地了解香石竹属的基因组组成，对 C. strigilatum 和 C. elegans 的低覆盖测序数据进行了比较，包括对七个物种的细胞遗传学分析。
生物信息学分析表明，逆转录转座子占重复部分的 70%以上，其次是 DNA 转座子（~17%），但使用逆转录转座子探针的 FISH 检测显示出不明显且分散的信号。在这里分析的四个卫星 DNA 家族代表了 C. strigilatum 数据集的约 2.48%，这些序列被用作 FISH 检测中的探针。杂交信号与所有与异染色质相关的富含 AT 和 GC 的序列（包括富含 AT 的冷敏感区 (CSRs)）共定位。尽管卫星探针几乎在所有测试的物种中都发生了杂交，但一个名为 CsSat49 的 satDNA 家族被突出显示，因为它在着丝粒区域占主导地位。
数据表明，尽管在染色体组型之间存在 FISH 信号数量的变化，但 satDNA 部分在属中是保守的。除了在两个物种中 CsSat1 和 CsSat72 探针没有 FISH 信号外，其他卫星出现在不同系统发育枝的物种中。一些 satDNA 序列已在 B 染色体中检测到，这表明它们富含 A 染色体组中染色体的现有序列。这项比较研究为香石竹属基因组组织和异染色质组成的知识提供了重要进展，特别是在物种之间卫星分数的分布及其对 B 染色体组成的重要性方面。
