橡胶树捕光叶绿素a/b结合蛋白基因CAB2的克隆与分析

Molecular Cloning and Analysis of HbCAB2, A Chlorophyll a/b-binding Protein-Encoding Gene from Hevea brasiliensis

  • 摘要: 基于电子克隆结果,采用RT-PCR技术从橡胶树的叶片中分离到1条858 bp的cDNA。结果表明:该序列含有1个798 bp的开放读码框,将基因命名为HbCAB2HbCAB2预测编码265个氨基酸,其中包含35个残基的叶绿体信号肽,成熟蛋白的理论分子量为24.66 kDa、等电点为4.99;前体蛋白含有1个保守的捕光叶绿素a/b结合蛋白结构域(Chloroa_b-bind,PF00504),包含3个跨膜螺旋和2个短螺旋、1个三聚化基序以及多个叶绿素和类胡萝卜素结合位点,可归为LHCB1亚类;HbCAB2HbCAB1属于反式串联重复,两者在蛋白水平的序列相似性高达97.0%。表达分析显示,HbCAB2倾向于在叶片和雌花中表达,且其表达水平随着叶片的成熟而逐渐增加,但在衰老叶片中显著下调。此外,基因的表达还受病原侵染、干旱和低温胁迫抑制。

     

    Abstract: Based on the in silico cloning result, an 858-bp cDNA that includes a 798-bp long ORF (open reading frame, designated HbCAB2) was isolated from the Hevea brasiliensis leaf by using the RT-PCR technique. Sequence analysis indicated that this gene putatively encodes 265 amino acids with a chloroplast signal peptide of 35 residues, and the mature protein was predicted to have a theoretical molecular weight (Mw) of 24.66 kDa and an isolectric point (pI) of 4.99. HbCAB2 can be categoried into subtype LHCB1, which was shown to contain one conserved light-harvesting chlorophyll a/b binding domain (Chloroa_b-bind, Pfam ID PF00504) as well as 3 transmembrane helices and 2 short helices, 1 trimerization motif, some chlorophyll and carotenoid binding sites. HbCAB2 was shown to be a reverse tandem duplication of HbCAB1, which shares a sequence similarity of 97.0% at the protein level. Expression analysis revealed that HbCAB2 was preferentially expressed in leaves and female flowers, with a gradually increased expression pattern during leaf maturity but a sharply decrease in senescent leaves. Additionally, its transcript level was shown to be inhibited by pathogen infection, low temperature, and drought stresses.

     

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