de Paula Cristina Maria Pinto, Souza Sobrinho Fausto, Techio Vânia Helena
Department of Biology/DBI, Federal University of Lavras (UFLA), Lavras, Minas Gerais, 37200000, Brazil.
Empresa Brasileira de Pesquisa Agropecuária, Embrapa Dairy Cattle, Juiz de Fora, Minas Gerais, Brazil.
Plant Cell Rep. 2016 Jun;35(6):1359-69. doi: 10.1007/s00299-016-1969-z. Epub 2016 Mar 25.
Assessment of chromosomal distribution of modified histones and 5-methylcytosine shown that there are diversification of chromosomal types among species of Brachiaria and its interspecific hybrids. Histone post-translational modifications and DNA methylation are epigenetic processes that are involved in structural and functional organization of the genome. This study compared the chromosomal distribution of modified histones and 5-methylcytosine (5-mCyt) in species and interspecific hybrids of Brachiaria with different ploidy levels and reproduction modes. The relation between H3K9me2 and 5-mCyt was observed in the nucleolus organizer region, centromeric central domain and pericentromeric region. H3K4me2 was detected in euchromatic domains, mainly in the terminal chromosomal regions. Comparison of chromosomal distribution among species and hybrids showed greater variation of chromosomal types for the H3K9me2 in B. decumbens (tetraploid and apomictic species) and the 963 hybrid, while, for the H3K4me2, the variation was higher in B. brizantha and B. decumbens (tetraploid and apomictic species) and 963 hybrid. The chromosome distribution of 5-mCyt was similar between B. brizantha and B. decumbens, which differ from the distribution observed in B. ruziziensis (diploid and sexual species). Significant alterations in DNA methylation were observed in the artificially tetraploidized B. ruziziensis and in the interspecific hybrids, possibly as result of hybridization and polyploidization processes. The monitoring of histone modifications and DNA methylation allowed categorizing nuclear and chromosomal distribution of these epigenetic marks, thus contributing to the knowledge of composition and structure of the genome/epigenome of Brachiaria species and hybrids. These data can be useful for speciation and genome evolution studies in genus Brachiaria, and represent important markers to explore relationships between genomes.
对修饰组蛋白和5-甲基胞嘧啶的染色体分布评估表明，臂形草属物种及其种间杂种存在染色体类型的多样化。组蛋白翻译后修饰和DNA甲基化是参与基因组结构和功能组织的表观遗传过程。本研究比较了不同倍性水平和繁殖方式的臂形草属物种及其种间杂种中修饰组蛋白和5-甲基胞嘧啶（5-mCyt）的染色体分布。在核仁组织区、着丝粒中央结构域和着丝粒周围区域观察到H3K9me2与5-mCyt之间的关系。在常染色质结构域中检测到H3K4me2，主要位于染色体末端区域。物种和杂种之间染色体分布的比较表明，俯仰臂形草（四倍体和无融合生殖物种）和963杂种中H3K9me2的染色体类型变异更大，而对于H3K4me2，在非洲臂形草和俯仰臂形草（四倍体和无融合生殖物种）以及963杂种中变异更高。B. brizantha和俯仰臂形草之间5-mCyt的染色体分布相似，这与在鲁齐兹臂形草（二倍体和有性生殖物种）中观察到的分布不同。在人工四倍体化的鲁齐兹臂形草和种间杂种中观察到DNA甲基化的显著变化，这可能是杂交和多倍体化过程的结果。对组蛋白修饰和DNA甲基化的监测使得能够对这些表观遗传标记的核分布和染色体分布进行分类，从而有助于了解臂形草属物种和杂种的基因组/表观基因组的组成和结构。这些数据对于臂形草属的物种形成和基因组进化研究可能是有用的，并且代表了探索基因组之间关系的重要标记。
