水稻eIF3大亚基(eIF3a)编码基因的克隆及其表达模式分析

ISOLATION AND EXPRESSION PATTERN ANALYSIS OF RICE AUXIN-INDUCED eIF3a CODING GENE

真核生物翻译起始因子(eIFs)在蛋白合成中起关键作用,在已经鉴定的13个因子中eIF3(由8个或更多的亚基组成)是分子量最大的一个并在翻译起始过程中起着核心作用。eIF3a是eIF3中最大的亚基并介导了eIF3的大多数的功能的实现。利用荧光-差异显示PCR法对生长素处理后的水稻材料进行分析发现eIF3a的表达可被生长素诱导,进一步通过筛选cDNA文库分离出水稻编码eIF3a的全长cDNA(命名为OseIF3a1),OseIF3a1含3459碱基(含5’和3’非翻译区)并编码一个986氨基酸的蛋白,与基因组序列比较表明OseIF3a1基因存在有12个内含子。OSeIF3a1与玉米和烟草的同源蛋白一致性分别为82.4%和70.1%并与其他真核生物eIF3a蛋白具较高一致性。以组织材料进行的RT-PCR结果表明OseIF3a1在根、幼苗、幼穗、茎和叶中表达,启动子-报告基因的转基因结果进一步表明OseIF3a1在根尖及幼嫩叶片表达较高,进一步的RTPCR分析确证了生长素对OseIF3a1的诱导,表明生长素在调控植物生长时可能涉及了翻译水平上的调节。

Eukaryotic initiation factors (eIFs) are key elements in protein synthesis. Among identified 13 initiation factors, eIF3, composed of 8 or more subunits, is the largest one and plays a central role in the initiation of translation. As the largest subunit, eIF3a mediates most functions of eIF3. Based on the experiments that rice eIF3a gene could be induced by auxin (through fluorescent differential display PCR), a cDNA coding for rice eIF3a, named OseIF3a\ , was isolated. OseIF3al cDNA, with a length of 3459bp (including 5' and 3'-UTR) and encoding a 986-aa polypeptide, shared sequence identity of 82. 4% and 70. 1 % with that in maize and tobacco. Comparison of cDNA and genomic sequence revealed the presence of 13 exons and 12 in-trons in OseIF3a1 gene. Reverse transcript PCR (RT-PCR) analysis indicated the expression of OseIF3a1 in root, shoots, young spike, stem and leaf tissues, promoter-GUS fusion studies further confirmed its expression in root tip, leaf, glume and stigma. The induction of OseIF3a1 by auxin suggested that function of auxin on growth may involve the regulation on translation level.