4种大戟科植物PMK基因家族的全基因组鉴定与分析

甲羟戊酸-5-磷酸激酶（PMK）是甲羟戊酸（MVA）途径中的关键酶,其在ATP和Mg2＋等二价金属离子的存在下可逆地催化甲羟戊酸-5-磷酸（MVAP）磷酸化从而形成甲羟戊酸-5-焦磷酸（MVAPP）.基于已公布的基因组和EST数据,对蓖麻、麻疯树、木薯和橡胶树4种大戟科植物的PMK基因进行系统鉴定,分析其基因结构与进化特征.结果表明,蓖麻、麻疯树、木薯和橡胶树分别含有1、1、1和2个PMK基因,所有基因均含有9个内含子.根据同源性,PMK基因可分为2类,Ⅰ类广泛分布于绿色植物和部分古细菌、真细菌和真菌中,Ⅱ类则为动物所特有;虽然绝大多数绿色植物都含有PMK,但基因组范围内的搜索却未能在单细胞的绿藻中找到其同源基因;在大多基因组已测序的物种中,PMK主要以单拷贝的形式存在,其中包括蓖麻、麻疯树和木薯,但在橡胶树中基因出现了加倍现象,这与玉米和杨树类似.基因表达谱分析显示,在叶片、花、Ⅱ/Ⅲ期胚乳、Ⅴ/Ⅵ期胚乳和种子等组织中,RcPMK在Ⅱ/Ⅲ期胚乳中的表达丰度较高,叶片、种子和花次之,而在Ⅴ/Ⅵ期胚乳中的表达丰度最低.

Genome-Wide Identification and Analysis of PMK Gene Family of Four Euphorbiaceae Plants

The 5-phosphomevalonate kinase （PMK） is an essential enzyme in mevalonate （MVA） pathway that catalyzes the reversible phosphorylation of mevalonate 5-phosphate （MVAP） to form mevalonate-5-diphosphate （MVAPP） in the presence of ATP and divalent ion such as Mg2＋.Based on the released genome and EST data,a genome-wide search was carried out for the first time to identify PMK gene family of four Euphorbiaceae plant species i.e.,castor bean （Ricinus communis）,physic nut （Jatropha curcas）,cassava （Manihot esculenta） and rubber tree （Hevea brasiliensis）,and subsequently,the gene structure and evolutionary relationship were also analyzed.As a result,a number of 1,1,1 and 2 PMK gene （s） were identified from castor bean,physic nut,cassava and rubber tree,respectively,and all of them contained 9 introns.Homology analyses suggested that PMK genes can be divided into two types,and type Ⅰ is widely distributed in plants,some archaea,eubacteria and fungi,while type Ⅱ is specific to animals.Although PMK genes were identified in most green plants,no homologous genes were found in unicellular green algae.In most genome sequenced plants including castor bean,physic nut and cassava,a single copy of PMK gene was found,however,in rubber tree plant,two copies were identified just like that in maize （Zea mays） and poplar （Populus trichocarpa）.In castor bean,digital expression profiling suggested that in five examined tissues such as leaf,flower,Ⅱ/Ⅲ stage endosperm,Ⅴ/Ⅵ stage endosperm and seed,RcPMK was expressed strongly in Ⅱ/Ⅲ stage endosperm,moderately in leaf,seed and flower,weakly in Ⅴ/Ⅵ stage endosperm.