Facultad de Ciencias Agrarias, Instituto de Botánica del Nordeste (UNNE-CONICET), Corrientes, Argentina.
Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA.
Planta. 2019 May;249(5):1405-1415. doi: 10.1007/s00425-019-03096-4. Epub 2019 Jan 24.
The most conspicuous difference among chromosomes and genomes in Arachis species, the patterns of heterochromatin, was mainly modeled by differential amplification of different members of one superfamily of satellite DNAs. Divergence in repetitive DNA is a primary driving force for genome and chromosome evolution. Section Arachis is karyotypically diverse and has six different genomes. Arachis glandulifera (D genome) has the most asymmetric karyotype and the highest reproductive isolation compared to the well-known A and B genome species. These features make A. glandulifera an interesting model species for studying the main repetitive components that accompanied the genome and chromosome diversification in the section. Here, we performed a genome-wide analysis of repetitive sequences in A. glandulifera and investigated the chromosome distribution of the identified satellite DNA sequences (satDNAs). LTR retroelements, mainly the Ty3-gypsy families "Fidel/Feral" and "Pipoka/Pipa", were the most represented. Comparative analyses with the A and B genomes showed that many of the previously described transposable elements (TEs) were differently represented in the D genome, and that this variation accompanied changes in DNA content. In addition, four major satDNAs were characterized. Agla_CL8sat was the major component of pericentromeric heterochromatin, while Agla_CL39sat, Agla_CL69sat, and Agla_CL122sat were found in heterochromatic and/or euchromatic regions. Even though Agla_CL8sat belong to a different family than that of the major satDNA (ATR-2) found in the heterochromatin of the A, K, and F genomes, both satDNAs are members of the same superfamily. This finding suggests that closely related satDNAs of an ancestral library were differentially amplified leading to the major changes in the heterochromatin patterns that accompanied the karyotype and genome differentiation in Arachis.
在花生属物种中，染色体和基因组之间最显著的区别在于异染色质的模式，主要是由一个卫星 DNA 超家族的不同成员的差异扩增形成的。重复 DNA 的多样性是基因组和染色体进化的主要驱动力。花生属在染色体组型上具有多样性，有六个不同的基因组。与广为人知的 A 组和 B 组物种相比，花生腺毛种（D 基因组）的染色体组型最不对称，生殖隔离程度最高。这些特征使花生腺毛种成为研究该属中伴随基因组和染色体多样化的主要重复成分的理想模式物种。在这里，我们对花生腺毛种的重复序列进行了全基因组分析，并研究了鉴定出的卫星 DNA 序列（satDNA）在染色体上的分布。LTR 反转录转座子，主要是 Ty3-gypsy 家族的“Fidel/Feral”和“Pipoka/Pipa”，是最主要的代表。与 A 组和 B 基因组的比较分析表明，许多先前描述的转座元件（TEs）在 D 基因组中的表达存在差异，这种变化伴随着 DNA 含量的变化。此外，还鉴定了四个主要的 satDNA。Agla_CL8sat 是着丝粒周围异染色质的主要成分，而 Agla_CL39sat、Agla_CL69sat 和 Agla_CL122sat 则存在于异染色质和/或常染色质区域。尽管 Agla_CL8sat 属于不同于在 A、K 和 F 基因组异染色质中发现的主要 satDNA（ATR-2）的家族，但这两种 satDNA 都属于同一个超家族。这一发现表明，密切相关的祖先文库中的 satDNA 被差异扩增，导致伴随花生属染色体组型和基因组分化的异染色质模式的主要变化。
