植物血红蛋白基因家族的分子进化研究  

Molecular Evolution of Hemoglobin Families

作　　者：齐小琼[1] 王艇[2] 

机构地区：[1]湖北第二师范学院化学与生命学院/植物抗癌活性物质提纯与应用湖北省重点实验室,武汉430205 [2]中国科学院武汉植物园,武汉430074

出　　处：《湖北农业科学》2014年第18期4447-4456,共10页Hubei Agricultural Sciences

基　　金：国家自然科学基金青年项目(31201242/C130405);湖北省教育厅科学研究计划项目(Q20143004)

摘　　要：植物血红蛋白(Hemoglobin)是一类由珠蛋白(Globin)和血红素(Ferroheme)组成的结合蛋白,广泛存在于植物界中。根据序列特征、表达模式及配基结合性质可将血红蛋白分为共生血红蛋白(Symbiotic hemoglobin,sHb)、非共生血红蛋白(Nonsymbiotic hemoglobin,NsHb)和截短的血红蛋白(Truncated hemoglobin,tHb)3大类,并对植物血红蛋白基因家族进行了分子系统发育分析和进化研究。结果表明,通过基因重复在被子植物中产生了class 1和class 2两类血红蛋白基因。该基因重复发生在单、双子叶植物分化之前,但由于class 2类基因在单子叶植物中发生了一次基因丢失事件,致使class1类基因广泛分布于单、双子叶植物中,而class 2类基因则仅见于双子叶植物;class 2类基因的进化速率高于class 1类基因,并分别在class 2、sHbs的祖先支上检测到了正选择的发生,表明基因重复发生后,class 2、sHbs通过插曲式进化和适应性进化获得了不同的功能;在class 1和class 2的功能性分歧位点检测中获得14个I类功能性分歧位点,但未能发现II类功能性分歧位点,这些功能性分歧位点是由正选择作用或者放松的选择限制产生的。该研究结果可以指导后续的试验工作,来验证那些具有重要功能的氨基酸置换位点和正选择位点,从而揭示功能性分歧和适应性进化的分子基础。Hemoglobins （Hbs） are combinative proteins consisted of globin and ferroheme,widespread in plants.Based on the sequence similarity,expression pattern and binding ligand property,Hbs can be divided into three groups including nonsymbiotic （NsHb）,symbiotic （sHb） and truncated Hbs （tHb）.Phylogenetic analyses and molecular evolution of hemoglobin families were conducted.The results showed that an ancient gene duplication produced two classes of hemoglobin in angiosperms：class 1 and class 2.The duplication event occurred before the divergence between monocots and eudicots.Class 2 genes were lost in monocots afterwards.The class 1 hemoglobin genes are widespread in both monocots and dicots,whereas the class 2 genes limited in dicots.The evolutionmy rate in class 2 is higher than that in class 1,especially in sHbs.Positive selection occurred on the ancestral branch leading to class 2 and sHbs.class 2 and sHbs acquired different functions through episodic evolution and adaptive evolution in certain sites,respectively.14 type-Ⅰ amino acid sites presumably submitted to altered functional constraints were detected by analyzing functional divergence.There was no evidence of type-Ⅱ functional divergence between class 1 and class 2.The results indicated that there were significantly site-specific rate shift between the two classes,leading to subgroup-specific functional diversification,either through positive selection or relaxation of selective constraints.These computational results can guide molecular experimentation,leading to the identification of functionally important amino acid substitutions and positively selected sites,which might help us to reveal the molecular basis of functional divergence and adaptive evolution.It will provide crucial evolutionary information.

关 键 词：血红蛋白基因 基因家族 分子进化分析 适应性进化 功能性分歧 

分 类 号：Q37[生物学—遗传学]