Functional characterization of Citrus PSY gene in Hongkong kumquat (Fortunella hindsii Swingle)
Functional characterization of Citrus PSY gene in Hongkong kumquat (Fortunella hindsii Swingle)
复制标题
香港金橘（FortunellahinsiiSwingle）柑橘PSY基因的功能特征
DOI：
10.1007/s00299-009-0774-3
复制
发表时间：
2009-11-01
影响因子：
6.2
通讯作者：
Deng, Xiuxin
中科院分区：
文献类型：
--
作者：
Zhang, Jiancheng;Tao, Nengguo;Deng, Xiuxin
柑橘富含类胡萝卜素，按年总产量计算是最重要的水果作物。在类胡萝卜素生物合成途径中，八氢番茄红素合酶（PSY，EC 2.5.1.32）催化两分子的牻牛儿基牻牛儿基焦磷酸（GGPP）二聚形成八氢番茄红素，并且已被证明是类胡萝卜素合成的一种限速酶。在本研究中，我们通过在含有产生GGPP质粒的大肠杆菌中异源表达，研究了红肉脐橙（Citrus sinensis Osbeck）中CsPSY的催化活性。此外，还在转基因山橘（Fortunella hindsii Swingle）中对CsPSY过表达对类胡萝卜素积累的影响进行了功能分析。所得转基因植株结出橙色果实，来自4株过表达植株果实的提取物中八氢番茄红素平均增加2.5倍，含量约为71.38μg/g鲜重。转基因果实中的番茄红素、β -胡萝卜素和β -隐黄质也显著增加，而叶黄素和紫黄质水平几乎保持不变，变化在1.1 - 1.3倍之间。CsPSY过表达植株中类胡萝卜素生物合成基因的转录水平除了PDS和ZDS略有增加外，其余均未改变。本研究表明CsPSY在柑橘类胡萝卜素生物合成中起关键作用，可作为改良水果作物以生产类胡萝卜素的一种手段。
Citrus, rich in carotenoids, is the most important fruit crop based on the total annual production. In the carotenoid biosynthesis pathway, phytoene synthase (PSY, EC 2.5.1.32) catalyzes the dimerization of two molecules of geranylgeranyl pyrophosphate (GGPP) to phytoene and has been shown to be a rate-limiting enzyme for the synthesis of carotenoids. In this study, we investigated catalytic activity of CsPSY from Cara Cara navel orange (Citrus sinensis Osbeck) by heterologous expression in Escherichia coli containing a GGPP-producing plasmid. Moreover, the effects of CsPSY overexpression on carotenoid accumulation were also functionally analyzed in transgenic Hongkong kumquat (Fortunella hindsii Swingle). The resulting transgenic plants produced orange fruits, and extracts from the fruits of four overexpressing plants had a 2.5-fold average increase of phytoene with the content approximately 71.38 microg/g fresh weight. Lycopene, beta-carotene, and beta-cryptoxanthin in transgenic fruits were also markedly increased, whereas the levels of lutein and violaxanthin kept nearly unchanged with 1.1-1.3 folds variation. Transcript levels of carotenoid biosynthetic genes in the CsPSY overexpressed plants remained unaltered except that PDS and ZDS showed a minor increase. This study suggests that CsPSY plays a crucial role in citrus carotenoid biosynthesis and could be used as a means of engineering fruit crop for the production of carotenoids.