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八氢番茄红素脱氢酶(PDS)是苹果类胡萝卜素生物合成途径的关键酶。本研究运用电子克隆与RACE技术克隆得到‘澳洲青苹’苹果Md PDS基因(Gen Bank登录号:KU508828),该c DNA序列全长2 005 bp,包含1 725个碱基(121~1 845 bp)的完整开放阅读框,编码575个氨基酸。氨基酸同源性分析表明,Md PDS编码的氨基酸序列与其他植物的PDS蛋白具有很高的同源性;其同样含有一个二核苷酸结合域和一个类胡萝卜素结合域。系统进化树分析表明,Md PDS与杏、碧桃和草莓蛋白亲缘关系较近,聚为一类。实时荧光定量PCR结果表明,Md PDS在‘澳洲青苹’苹果不同组织均有表达,其在树皮、果皮及叶片中的表达要明显高于花中的表达。此外,Md PDS在着色期套袋果实果皮中的表达量随果色增加而上升,而在非套袋果皮中的表达则变化不明显。上述结果表明Md PDS在苹果果实色泽发育过程中起着重要作用,也为进一步研究其生物学功能奠定了基础。
Phytoene desaturase (PDS) is a key enzyme in apple carotenoid biosynthesis pathway. In this study, we cloned the Md PDS gene from GenBank (Gen Bank Accession No: KU508828) by using electronic cloning and RACE technology. The full-length cDNA is 2 005 bp in length and contains 1 725 bases (121-1 845 bp ) Complete open reading frame, encoding 575 amino acids. Amino acid homology analysis revealed that the amino acid sequence encoded by Md PDS has high homology to the PDS protein of other plants; it also contains a dinucleotide binding domain and a carotenoid binding domain. Phylogenetic tree analysis showed that Md PDS was closely related to apricot, tope and strawberry proteins and clustered together. Real-time PCR results showed that Md PDS was expressed in different tissues of ’Greenpea’ apple, and its expression in the bark, pericarp and leaves was significantly higher than that in the flower. In addition, the expression of Md PDS in the pericarp of bagged fruit increased with the increase of fruit color while the expression of Md PDS did not change significantly in the non-bagged peel. The above results indicate that Md PDS plays an important role in the development of apple fruit color and lays the foundation for further study of its biological functions.