橡胶树Lhcb2基因的克隆与表达特性分析

基于从基因组中获得的基因序列，应用RT-PCR技术从橡胶树叶片中分离得到1条849bp的cDNA；该cDNA包含1个798bp的ORF，编码265个氨基酸，理论分子量为2866kD，等电点为542，属于叶绿体定位的类囊体膜蛋白；蛋白含有3个跨膜螺旋，2个C端螺旋，1个保守的捕光叶绿素a/b结合蛋白结构域，1个三聚化基序，以及多个类胡萝卜素和叶绿素结合位点，根据进化关系可归为LHCB2亚家族；蛋白与蓖麻、野草莓、可可、葡萄和棉花中同源蛋白的一致性均接近95%，在进化上显示出高度的保守性，将基因命名为HbLhcb21。表达分析显示，HbLhcb21倾向于在叶片中表达，且其转录水平随着叶片的成熟而逐渐增加，但随着叶片的衰老而明显下调。

Molecular Cloning and Expression Analysis of an Lhcb2 Gene from Hevea brasiliensis

Based on the gene sequence identified from the rubber tree (Hevea brasiliensis) genome, an 849 bp cDNA containing an ORF of 798 bp was isolated from the leaf tissue by using the RT PCR technique. The gene denoted HbLhcb21 was predicted to encode 265 amino acids with a theoretical molecular weight of 2866 kD and isolectric point of 542; the protein was promised to be a thylakoid protein of chloroplast; the protein contains one conserved light harvesting chlorophyll a/b binding protein domain, three transmembrane helices and two C terminal helices, a trimerization motif, several chlorophyll and carotenoid binding sites, which could be grouped into the LHCB2 subfamily based on the evolutionary relationship. Homologous analysis showed that HbLhcb21 shared an identity of about 95% with the homologs in Ricinus communis, Gossypium hirsutum, Vitis vinifera, Fragaria vesca or Theobroma cacao, suggesting a highly conserved evolution. Expression analysis indicated that HbLhcb21 was mainly expressed in the leaves, with a gradual increase as along with the leaf maturity, but a sharp decrease in senescing leaves.