PDF(Pubmed)
Abstract：
BACKGROUND: Centromeres play a crucial and conserved role in cell division, although their composition and evolutionary history in green algae, the evolutionary ancestors of land plants, remains largely unknown.
RESULTS: We constructed near telomere-to-telomere (T2T) assemblies for two Trebouxiophyceae species, Chlorella sorokiniana NS4-2 and Chlorella pyrenoidosa DBH, with chromosome numbers of 12 and 13, and genome sizes of 58.11 Mb and 53.41 Mb, respectively. We identified and validated their centromere sequences using CENH3 ChIP-seq and found that, similar to humans and higher plants, the centromeric CENH3 signals of green algae display a pattern of hypomethylation. Interestingly, the centromeres of both species largely comprised transposable elements, although they differed significantly in their composition. Species within the Chlorella genus display a more diverse centromere composition, with major constituents including members of the LTR/Copia, LINE/L1, and LINE/RTEX families. This is in contrast to green algae including Chlamydomonas reinhardtii, Coccomyxa subellipsoidea, and Chromochloris zofingiensis, in which centromere composition instead has a pronounced single-element composition. Moreover, we observed significant differences in the composition and structure of centromeres among chromosomes with strong collinearity within the Chlorella genus, suggesting that centromeric sequence evolves more rapidly than sequence in non-centromeric regions.
CONCLUSIONS: This study not only provides high-quality genome data for comparative genomics of green algae but gives insight into the composition and evolutionary history of centromeres in early plants, laying an important foundation for further research on their evolution.
RESULTS: We constructed near telomere-to-telomere (T2T) assemblies for two Trebouxiophyceae species, Chlorella sorokiniana NS4-2 and Chlorella pyrenoidosa DBH, with chromosome numbers of 12 and 13, and genome sizes of 58.11 Mb and 53.41 Mb, respectively. We identified and validated their centromere sequences using CENH3 ChIP-seq and found that, similar to humans and higher plants, the centromeric CENH3 signals of green algae display a pattern of hypomethylation. Interestingly, the centromeres of both species largely comprised transposable elements, although they differed significantly in their composition. Species within the Chlorella genus display a more diverse centromere composition, with major constituents including members of the LTR/Copia, LINE/L1, and LINE/RTEX families. This is in contrast to green algae including Chlamydomonas reinhardtii, Coccomyxa subellipsoidea, and Chromochloris zofingiensis, in which centromere composition instead has a pronounced single-element composition. Moreover, we observed significant differences in the composition and structure of centromeres among chromosomes with strong collinearity within the Chlorella genus, suggesting that centromeric sequence evolves more rapidly than sequence in non-centromeric regions.
CONCLUSIONS: This study not only provides high-quality genome data for comparative genomics of green algae but gives insight into the composition and evolutionary history of centromeres in early plants, laying an important foundation for further research on their evolution.
摘要：
背景：着丝粒在细胞分裂中起着至关重要和保守的作用，虽然它们在绿藻中的组成和进化史，陆地植物的进化祖先，仍然很大程度上未知。
结果：我们为两种树目植物构建了端粒到端粒（T2T）组件，小球藻NS4-2和小球藻蛋白核DBH，染色体数为12和13，基因组大小为58.11Mb和53.41Mb，分别。我们使用CENH3ChIP-seq鉴定并验证了它们的着丝粒序列，类似于人类和高等植物，绿藻的着丝粒CENH3信号显示出低甲基化模式。有趣的是,这两个物种的着丝粒主要由转座因子组成，尽管它们的组成有很大差异。小球藻属中的物种显示出更多样化的着丝粒组成，主要成员包括LTR/Copia的成员，LINE/L1和LINE/RTEX系列。这与绿藻形成鲜明对比，包括莱茵衣藻，球藻次椭圆，和嗜铬动物，其中着丝粒成分具有明显的单元素成分。此外，我们观察到小球藻属内具有强烈共线性的染色体之间着丝粒的组成和结构存在显着差异，表明着丝粒序列比非着丝粒区域的序列进化更快。
结论：这项研究不仅为绿藻的比较基因组学提供了高质量的基因组数据，而且还深入了解了早期植物着丝粒的组成和进化史。为进一步研究它们的演化奠定了重要基础。
结果：我们为两种树目植物构建了端粒到端粒（T2T）组件，小球藻NS4-2和小球藻蛋白核DBH，染色体数为12和13，基因组大小为58.11Mb和53.41Mb，分别。我们使用CENH3ChIP-seq鉴定并验证了它们的着丝粒序列，类似于人类和高等植物，绿藻的着丝粒CENH3信号显示出低甲基化模式。有趣的是,这两个物种的着丝粒主要由转座因子组成，尽管它们的组成有很大差异。小球藻属中的物种显示出更多样化的着丝粒组成，主要成员包括LTR/Copia的成员，LINE/L1和LINE/RTEX系列。这与绿藻形成鲜明对比，包括莱茵衣藻，球藻次椭圆，和嗜铬动物，其中着丝粒成分具有明显的单元素成分。此外，我们观察到小球藻属内具有强烈共线性的染色体之间着丝粒的组成和结构存在显着差异，表明着丝粒序列比非着丝粒区域的序列进化更快。
结论：这项研究不仅为绿藻的比较基因组学提供了高质量的基因组数据，而且还深入了解了早期植物着丝粒的组成和进化史。为进一步研究它们的演化奠定了重要基础。
