棉花多聚半乳糖醛酸酶抑制蛋白基因克隆、序列及表达谱分析

Cloning,Sequencing and Expression Profile Analysis of A Polygalacturonase-inhibiting Protein (PGIP) Gene in Cotton

植物的多聚半乳糖醛酸酶抑制蛋白(PGIPs)在植物的抵抗疾病机制中起着重要作用,能够高效、专一的结合病原体侵染时分泌的多聚半乳糖醛酸酶,抑制其活性。克隆了棉花(苏棉9号)的一段长993bpPGIP基因,命名为GhPGIP1,它能够编码一段长330个氨基酸残基,分子量与等电点分别为37.0kDa与8.30的蛋白质。核酸和蛋白质序列与其他9个物种的同源性分别为65.6%～70.3%和63.4%～68.6%。蛋白GhPGIP1有10个N端、C端半胱氨酸残基,6个可能的N糖基化位点和5个保守的亮氨酸重复结构域(LRR)。在所有的保守LRR域中,L是高度保守的。半定量RT-PCR试验结果显示,GhPGIP1在棉花的根、茎、叶中均表达,其中以叶中表达量最多。

Plant polygalacturonase-inhibiting proteins （PGIPs） play an important role in the defense system by effectively and specifically binding to and inhibiting the endopolygalacturonases secreted by pathogen during its invasion. In this study,a gene encoding the PGIP of cotton （Gossypium hirsutum）, named GhPGIP1 ,was cloned and sequenced, which had 993bp in length and encoded a peptide of 330 amino acids with a molecular weight of 37.0 kDa and pI of 8.30. Compared with the corresponding genes from other 9 species, the nucleotide and amino acid homologies were 65.6%-70.3% and 63.4%-68.6%,respectively. The deduced protein sequence had 6 potential N--glycosylation sites and 10 cysteine residues in N-- and C--terminal. The sequence alignment of deduced amino acid of GhPGIP1 with those of other 9 species indicated that there were 5 conservative leucine rich repeat （LRR） domains,the typical character of proteins with defense ability and most of the Leucines being highly conserved. Semi-quantitative RT--PCR disclosed that GhPGIP1 were constitutively expressed in root, stem and leaf, and the expressed amount in leaf was the most.