Institute of Agrobiotechnology, CERTH, Thermi-Thessaloniki, Greece.
BMC Plant Biol. 2010 Apr 21;10:73. doi: 10.1186/1471-2229-10-73.
Epigenetic phenomena have been associated with the regulation of active and silent chromatin states achieved by modifications of chromatin structure through DNA methylation, and histone post-translational modifications. The latter is accomplished, in part, through the action of PcG (Polycomb group) protein complexes which methylate nucleosomal histone tails at specific sites, ultimately leading to chromatin compaction and gene silencing. Different PcG complex variants operating during different developmental stages have been described in plants. In particular, the so-called FIE/MEA/FIS2 complex governs the expression of genes important in embryo and endosperm development in Arabidopsis. In our effort to understand the epigenetic mechanisms regulating seed development in barley (Hordeum vulgare), an agronomically important monocot plant cultivated for its endosperm, we set out to characterize the genes encoding barley PcG proteins.
Four barley PcG gene homologues, named HvFIE, HvE(Z), HvSu(z)12a, and HvSu(z)12b were identified and structurally and phylogenetically characterized. The corresponding genes HvFIE, HvE(Z), HvSu(z)12a, and HvSu(z)12b were mapped onto barley chromosomes 7H, 4H, 2H and 5H, respectively. Expression analysis of the PcG genes revealed significant differences in gene expression among tissues and seed developmental stages and between barley cultivars with varying seed size. Furthermore, HvFIE and HvE(Z) gene expression was responsive to the abiotic stress-related hormone abscisic acid (ABA) known to be involved in seed maturation, dormancy and germination.
This study reports the first characterization of the PcG homologues, HvFIE, HvE(Z), HvSu(z)12a and HvSu(z)12b in barley. All genes co-localized with known chromosomal regions responsible for malting quality related traits, suggesting that they might be used for developing molecular markers to be applied in marker assisted selection. The PcG differential expression pattern in different tissues and seed developmental stages as well as in two barley cultivars with different seed size is suggestive of a role for these genes in barley seed development. HvFIE and HvE(Z) were also found to be induced by the plant hormone ABA implying an association with ABA-mediated processes during seed development, germination and stress response.
表观遗传现象与活性和沉默染色质状态的调节有关，通过 DNA 甲基化和组蛋白翻译后修饰来实现染色质结构的修饰。后者部分通过 PcG（多梳组）蛋白复合物的作用来完成，该复合物在特定位置甲基化核小体组蛋白尾部，最终导致染色质紧缩和基因沉默。在植物中，已经描述了在不同发育阶段起作用的不同 PcG 复合物变体。特别是，所谓的 FIE/MEA/FIS2 复合物控制着拟南芥胚胎和胚乳发育中重要基因的表达。在我们努力理解调控大麦（Hordeum vulgare）种子发育的表观遗传机制时，大麦是一种重要的单子叶农业作物，其胚乳被培育出来，我们开始描述编码大麦 PcG 蛋白的基因。
鉴定并结构和系统发育地描述了四个大麦 PcG 基因同源物，分别命名为 HvFIE、HvE(Z)、HvSu(z)12a 和 HvSu(z)12b。相应的基因 HvFIE、HvE(Z)、HvSu(z)12a 和 HvSu(z)12b 分别被定位到大麦染色体 7H、4H、2H 和 5H 上。PcG 基因的表达分析表明，在组织和种子发育阶段以及种子大小不同的大麦品种之间，基因表达存在显著差异。此外，HvFIE 和 HvE(Z)基因的表达对与非生物胁迫相关的激素脱落酸（ABA）有反应，ABA 已知参与种子成熟、休眠和萌发。
本研究首次在大麦中描述了 PcG 同源物 HvFIE、HvE(Z)、HvSu(z)12a 和 HvSu(z)12b 的特性。所有基因都与已知的负责麦芽质量相关性状的染色体区域共定位，表明它们可能被用于开发分子标记，应用于标记辅助选择。不同组织和种子发育阶段以及两个种子大小不同的大麦品种中 PcG 的差异表达模式表明，这些基因在大麦种子发育中可能发挥作用。还发现 HvFIE 和 HvE(Z)被植物激素 ABA 诱导，这意味着它们与种子发育、萌发和应激反应过程中的 ABA 介导过程有关。
