Fonsêca Artur, Richard Manon M S, Geffroy Valérie, Pedrosa-Harand Andrea
Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Universidade Federal de Pernambuco, Recife, Brazil.
Cytogenet Genome Res. 2014;143(1-3):168-78. doi: 10.1159/000360572. Epub 2014 Apr 15.
The common bean (Phaseolus vulgaris L.) is the main representative of its genus and one of most important sources of proteins in African and Latin American countries. Although it is a species with a small genome, its pericentromeric and subtelomeric heterochromatin fractions are interspersed with single-copy sequences and active genes, suggesting a less compartmentalized genome organization. The present study characterized its chromatin fractions, associating the distribution of repetitive sequences and resistance genes with histone and DNA epigenetic modifications with and without biotic stress. Immunostaining with H3K4me3 and H4K5ac were generally associated with euchromatic regions, whereas H3K9me2, H3K27me1, and 5mC preferentially labeled the pericentromeric heterochromatin. The 45S rDNA and centromeric DNA sequences were hypomethylated as were most of the terminal heterochromatic blocks. The largest of them, which is associated with resistance genes, was also hypomethylated after the plants were infected with virulent and avirulent strains of the fungus Colletotrichum lindemuthianum, suggesting no correlation with control of resistance gene expression. The results highlighted the differences between subtelomeric and pericentromeric heterochromatin as well as variation within the pericentromeric heterochromatin.
普通菜豆（Phaseolus vulgaris L.）是其所属豆科的主要代表物种，也是非洲和拉丁美洲国家最重要的蛋白质来源之一。尽管它是一个基因组较小的物种，但其着丝粒周围和亚端粒异染色质部分散布着单拷贝序列和活跃基因，这表明其基因组组织的区室化程度较低。本研究对其染色质部分进行了表征，将重复序列和抗性基因的分布与有无生物胁迫下的组蛋白和DNA表观遗传修饰联系起来。用H3K4me3和H4K5ac进行免疫染色通常与常染色质区域相关，而H3K9me2、H3K27me1和5mC则优先标记着丝粒周围的异染色质。45S rDNA和着丝粒DNA序列以及大多数末端异染色质区域均发生低甲基化。其中与抗性基因相关的最大区域，在植株被致病力强和致病力弱的炭疽菌（Colletotrichum lindemuthianum）菌株感染后也发生了低甲基化，这表明其与抗性基因表达的调控无关。结果突出了亚端粒和着丝粒周围异染色质之间的差异以及着丝粒周围异染色质内部的变异。
