香蕉谷氨酸脱羧酶基因克隆与表达

Cloning and Expression Analysis of MaGAD1 Gene from Banana Fruit

根据抑制缩减杂交文库获得的香蕉谷氨酸脱羧酶基因片段,利用RACE技术,首次从香蕉果实中克隆了谷氨酸脱羧酶基因的cDNA全长.结果表明,该cDNA的ORF全长1 500 bp,编码499个氨基酸.Blast分析表明,该基因所推导的氨基酸序列与水稻、柑橘、白杨、番茄等具有较高的一致性,分别为82%、81%、79%、78%,推测其编码的蛋白质分子量为56.25 kD,等电点5.21,具有与钙调蛋白结合的C端延伸区域和磷酸吡哆醛结合位点.组织特异性和果实采后正常成熟不同阶段表达结果显示,该基因在香蕉根、茎、叶、花、果实中均有表达,果实中的表达量较高,正常成熟表达量的增加可能受内源乙烯诱导并促进乙烯生物合成,推测其可能在不同的生理过程中起作用,并且与果实成熟及乙烯生物合成密切相关.

The GAD gene was isolated from banana fruit （Musa acuminata L. AAA group cv. Brazilian） and designated as MaGAD1. The full length of MaGAD1 cDNA is 1 500 bp with an open reading frame encoding 499 amino acids that shared high identities with the GAD from Oryza sativa ,Citrus sinensis ,Populus alba and Solanurn lycopersicum （82% ,81%,79% and 78%）. Amino acid alignment indicated MaGAD1 has a CaM binding domain at the carboxy terminus and a putative PLP-binding motif. RT-PCR analysis showed that MaGAD1 is expressed in roots, stems, leaves, flowers and fruits. The expression lever is higher in fruits than in other organs. Real time quantitative RT-PCR analysis and measure of ethylene production indicated that the expression levels of MaGAD1 are induced by ethylene production from fruit and improve ethylene biosynthesis in banana fruit natural ripeness.