Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Pernambuco, Brazil.
Laboratory of Plant Genome Evolution and Domestication, Department of Plant Biology, Faculty of Agronomy, University of the Republic, Montevideo, Uruguay.
Planta. 2021 Apr 1;253(4):86. doi: 10.1007/s00425-021-03598-0.
While two lineages of retrotransposons were more abundant in larger Passiflora genomes, the satellitome was more diverse and abundant in the smallest genome analysed. Repetitive sequences are ubiquitous and fast-evolving elements responsible for size variation and large-scale organization of plant genomes. Within Passiflora genus, a tenfold variation in genome size, not attributed to polyploidy, is known. Here, we applied a combined in silico and cytological approach to study the organization and diversification of repetitive elements in three species of this genus representing its known range in genome size variation. Sequences were classified in terms of type and repetitiveness and the most abundant were mapped to chromosomes. We identified long terminal repeat (LTR) retrotransposons as the most abundant elements in the three genomes, showing a considerable variation among species. Satellite DNAs (satDNAs) were less representative, but highly diverse between subgenera. Our results clearly confirm that the largest genome species (Passiflora quadrangularis) presents a higher accumulation of repetitive DNA sequences, specially Angela and Tekay elements, making up most of its genome. Passiflora cincinnata, with intermediate genome and from the same subgenus, showed similarity with P. quadrangularis regarding the families of repetitive DNA sequences, but in different proportions. On the other hand, Passiflora organensis, the smallest genome, from a different subgenus, presented greater diversity and the highest proportion of satDNA. Altogether, our data indicates that while large genomes evolved by an accumulation of retrotransposons, the smallest genome known for the genus has evolved by diversification of different repeat types, particularly satDNAs.
虽然两种逆转录转座子谱系在较大的西番莲基因组中更为丰富，但卫星体在分析的最小基因组中更为多样和丰富。重复序列是普遍存在且快速进化的元素，负责植物基因组的大小变化和大规模组织。在西番莲属内，已知基因组大小存在十倍的变化，而不是归因于多倍体。在这里，我们应用了一种组合的计算和细胞学方法来研究三个代表该属已知基因组大小变化范围的物种中重复元件的组织和多样化。序列根据类型和重复次数进行分类，最丰富的序列被映射到染色体上。我们确定长末端重复（LTR）逆转录转座子是三个基因组中最丰富的元素，在物种间表现出相当大的差异。卫星 DNA（satDNA）的代表性较低，但在亚属之间高度多样化。我们的结果清楚地证实，最大基因组的物种（Passiflora quadrangularis）具有更高的重复 DNA 序列积累，特别是 Angela 和 Tekay 元件，占其基因组的大部分。基因组中等且来自同一亚属的 Passiflora cincinnata 与 P. quadrangularis 在重复 DNA 序列家族方面具有相似性，但比例不同。另一方面，最小基因组的 Passiflora organensis 来自不同的亚属，表现出更高的多样性和最高比例的 satDNA。总之，我们的数据表明，虽然大基因组通过逆转录转座子的积累进化而来，但该属已知的最小基因组通过不同重复类型的多样化进化而来，特别是 satDNA。
