毛竹PSⅡ大量捕光天线蛋白基因克隆及其表达分析

Cloning and Molecular Characterization of the Major Light Harvesting Antenna Protein Genes of PSⅡ in Phyllostachys edulis

采用RT-PCR和RACE技术,从一年生毛竹(Phyllostachys edulis)新鲜叶片中分离到3个捕光色素结合蛋白基因cab-PhE2、cab-PhE3和cab-PhE6,GenBank登记号分别为EF207230、EF405877和EF628209。序列分析表明,3个基因分别与其它植物如水稻、玉米、大麦等PSⅡ的lhcb2、lhcb1、lhcb3基因有着较高的一致性,其编码的蛋白属于大量捕光天线。蛋白结构预测表明,3个基因编码的蛋白均由导肽和成熟蛋白组成,其中成熟蛋白的二级结构均包含4个α螺旋结构、3个类胡萝卜素结合位点,以及相应的叶绿素a、b结合位点。组织特异性表达检测表明,3个基因在叶片、叶鞘和幼茎中均有表达,且在叶片中最高,而在根中未检测到表达。在强光照射(1500μmo.l m-2.s-1)条件下,3个基因的表达量均呈下调趋势,不同基因间存在着一定的差异,其中cab-PhE3和cab-PhE2的表达丰度在光照4 h内下降较快,至6 h cab-PhE2接近于零,而cab-PhE6经光照4 h表达丰度仍为对照的70%以上,但之后2 h后很快降至对照的5%以下。

Three light harvesting chlorophyll a/b-binding protein genes（cab-PhE2,cab-PhE3 and cab-PhE6） were isolated from fresh leaves of Phyllostachys edulis by RT-PCR and RACE methods.The GenBank accession numbers were EF207230,EF405877 and EF628209,respectively.They shared high identities,with lhcb2,lhcb1,and lhcb3 genes encoding the major antenna proteins of PSⅡ from other plants such as Oryza sativa,Zea mays,and Hordeum vulgare.Secondary structure analysis showed that all the deduced proteins consisted of signal peptide and mature protein containing four α helices,three carotenoid binding sites and chlorophyll a/b-binding sites.The expression of these genes was detected in leaf（highest）,sheath,and stem,but was undetectable in root.The genes were all down-regulated in leaf treated with strong light（1500 μmol·m-2·s-1）,although they showed differences during treatment.The expression of cab-PhE3 and cab-PhE2 decreased rapidly during the first four hours,and cab-PhE2 dropped nearly to zero after six hours ＇ treatment.However,the expression level of cab-PhE6 was more than 70% that of the control after four hours,after which it reduced to less than 5% during the following two hours.