植物中HECT和U-box基因的结构与进化研究

发布时间：2018-11-14 14:17

【摘要】：E3泛素连接酶构成了高度多样的重要酶群,它们和26S蛋白酶体一同参与泛素化蛋白酶体途径。E3泛素连接酶促进了泛素基团向底物蛋白的转移,这种泛素标记可使底物蛋白降解。通过这种方式,E3泛素连接酶在很多植物细胞学和生理学过程中起到重要的调控作用。HECT(homologous to E6-associated protein C-terminus)和U-box(a modified RING motif without the full complement of Zn2+-binding ligands)是两类重要的E3泛素连接酶。目前这两类E3泛素连接酶在植物基因组中的分布、结构和进化及其功能尚不完全清楚。本研究以植物基因组中HECT和U-box基因的预测为中心,深入分析了这些植物HECT和U-box基因的结构和进化,以及它们可能的生物学功能。1.大豆基因组中HECT基因的结构与进化系统分析了大豆基因组中HECT基因的序列结构和进化过程。结果发现大豆基因组中有19个HECT基因。根据系统发育关系和结构域组织情况,可将这些基因分为7个组。重要的是,这些大豆HECT基因数量的增加都是因为进化历程上的片段重复事件导致。在大豆的14个组织中,有15个HECT基因都检测到有表达。这15个检测到的HECT基因在花组织和芽组织中表达相对较高,而在其它组织中表达相对较低。对每个检测到的大豆HECT基因来说,组VI的HECT基因在大部分组织中表达都相对较高。2.其它植物基因组中HECT基因的结构与进化预测了40个植物物种的HECT基因,发现在所有检测的植物中都含有HECT基因,但数量差异较大。高等植物中的HECT基因可根据进化关系分为7组。除了组II之外,每个HECT组,都有对应的拟南芥的直系同源基因。所有植物HECT基因的HECT结构域都非常保守,并且含有大量高度保守的氨基酸残基。此外,直系同源HECT基因的选择压力分析结果表明这些基因都受到强烈的负选择,并且在三对并系同源亚组间发生了功能分歧。3.大豆基因组中U-box基因的结构与进化系统分析了大豆基因组中U-box基因的序列结构和进化。结果表明,大豆基因组中有127个U-box基因。这些U-box基因根据进化关系和结构域组织情况可以分为3个亚家族。亚家族I主要含有Kinase结构域,亚家族II主要含有ARM结构域,亚家族III家族只含有U-box结构域。研究还发现,这些基因的扩增主要是由大豆进化历程中的片段重复事件和串联重复事件引起的。在大豆中表达的98个U-box基因中,大部分基因在花组织、幼叶组织、根组织、根瘤组织以及不同时期的豆荚组织中表达相对较高,而在不同时期的种子组织中表达都相对较低。综上所述,本研究采用生物信息学的研究方法预测了植物基因组中HECT和U-box基因,系统分析了它们的结构和进化。研究结果可以进一步加深对E3连接酶在植物基因表达调控过程中发挥的重要功能的认识。
[Abstract]:E3 ubiquitin ligase is a highly diverse and important enzyme group, and they are involved in the ubiquitin proteasome pathway together with 26s proteasome. E3 ubiquitin ligase promotes the transfer of ubiquitin group to substrate protein. This ubiquitin label degrades the substrate protein. In this way, E3 ubiquitin ligase (. HECT (homologous to E6-associated protein C-terminus) and U-box (a modified RING motif without the full complement of Zn2-binding ligands) are two important E3 ubiquitin ligases which play an important role in many plant cytological and physiological processes. At present, the distribution, structure, evolution and function of E3 ubiquitin ligases in plant genomes are not completely clear. Based on the prediction of HECT and U-box genes in plant genomes, the structure and evolution of HECT and U-box genes in these plants and their possible biological functions were analyzed. The structure and evolution of HECT gene in soybean genome were analyzed. The sequence structure and evolution process of HECT gene in soybean genome were analyzed. The results showed that there were 19 HECT genes in soybean genome. According to phylogenetic relationship and domain organization, these genes can be divided into 7 groups. Importantly, the increase in the number of HECT genes in these soybeans is due to repeated events in evolutionary processes. Fifteen HECT genes were detected in 14 soybean tissues. The 15 detected HECT genes were relatively high in floral and bud tissues, but relatively low in other tissues. For each detected soybean HECT gene, the HECT gene of group VI was relatively high in most tissues. 2. 2. The structure and evolution of HECT gene in other plant genomes predicted the HECT gene of 40 plant species. It was found that HECT gene was found in all the tested plants, but there was a great difference in quantity. HECT genes in higher plants can be divided into 7 groups according to their evolutionary relationships. In addition to group II, each HECT group had corresponding lineal homologous genes of Arabidopsis thaliana. The HECT domain of HECT gene in all plants is very conserved and contains a large number of highly conserved amino acid residues. In addition, the selection pressure analysis of homologous HECT genes showed that these genes were strongly negatively selected, and the functional differences occurred between the three pairs of homologous subgroups. 3. The structure and evolution of U-box gene in soybean genome were analyzed. The results showed that there were 127 U-box genes in soybean genome. These U-box genes can be divided into three subfamilies according to evolutionary relationship and domain organization. Subfamily I mainly contains Kinase domain, subfamily II mainly contains ARM domain, and subfamily III family only contains U-box domain. It was also found that the amplification of these genes was mainly caused by repeated fragment events and tandem repeats in the evolution of soybean. Most of the 98 U-box genes expressed in soybean were relatively high in flower tissue, young leaf tissue, root nodule tissue and pod tissue at different stages. However, the expression was relatively low in the seed tissues at different stages. In conclusion, HECT and U-box genes in plant genomes were predicted by bioinformatics, and their structures and evolution were systematically analyzed. The results of the study can further deepen the understanding of the important function of E3 ligase in the regulation of plant gene expression.
【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：Q943.2

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