Avramova Zoya
School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA.
Int J Dev Biol. 2009;53(2-3):371-81. doi: 10.1387/ijdb.082664za.
The SET domain-containing genes of the TRITHORAX family encode epigenetic factors that maintain the expression of targeted genes. Trithorax homologs have been found in both animals and plants. Since these are thought to have evolved multicellularity independently, common mechanisms of epigenetic regulation must be evolutionarily ancient and derived from a common ancestor. In addition, each lineage has evolved unique mechanisms to expand the original repertoire of epigenetic functions. Phylogenetic analysis of SET domain proteins has outlined some intriguing evolutionary trends. In plants, epigenetic gene silencing mechanisms have been aggressively pursued. In contrast, studies of epigenetic mechanisms maintaining active gene expression have been scarce. The goal of this review is to draw attention to this gap. Trithorax function in plants are analyzed here in an evolutionary context tracing phylogenetic relationships between the histone methyltransferase activities in unicellular and multicellular domains of life. The involvement of two members of the Arabidopsis Trithorax family, ARABIDOPSIS HOMOLOG of TRITHORAX1 (ATX1), and ARABIDOPSIS HOMOLOG of TRITHORAX2 (ATX2), in developmental and adaptation processes of the plant is overviewed.
TRITHORAX家族中含SET结构域的基因编码维持靶基因表达的表观遗传因子。在动物和植物中均已发现Trithorax同源物。由于认为它们是独立进化出多细胞性的，因此表观遗传调控的共同机制在进化上必定古老且源自共同祖先。此外，每个谱系都进化出了独特的机制来扩展表观遗传功能的原始库。对SET结构域蛋白的系统发育分析揭示了一些有趣的进化趋势。在植物中，人们积极探索表观遗传基因沉默机制。相比之下，关于维持基因活性表达的表观遗传机制的研究却很少。本综述的目的是提请人们注意这一差距。本文在进化背景下分析了植物中的Trithorax功能，追溯了生命单细胞和多细胞领域中组蛋白甲基转移酶活性之间的系统发育关系。概述了拟南芥Trithorax家族的两个成员，即TRITHORAX1的拟南芥同源物（ATX1）和TRITHORAX2的拟南芥同源物（ATX2）在植物发育和适应过程中的作用。
