猕猴桃维生素C高效合成与积累的分子机理研究

Kiwifruit (Actinidia) is an economically and nutritionally important fruit crop with remarkably high content of ascorbic acid (Vitamin C, Vc). Although marked difference in Vc contents between Actinidia species as well as between interspecific cultivars of Actinidia chinensis was found, the molecular mechanisms of Vc hyperaccumulation in the fruit of Actinidia are unknown and have been paid great attention. Based on the tremendous datasets of the genome sequencing and RNA-seq transcriptome of "Hongyang", a widely cultivated variety derived from Actinidia chinensis, we plan to further investigate the potential molecular mechanisms of Vc hypersynthesis and hyperaccumulation in kiwifruit. Multiple approaches and cutting-edge techniques including comparative genomics, transcriptomics, forward and reverse genetics, biochemical and molecular methods as well as transgenic technology will be extensively adopted in our study to elucidate effects of Vc-associated gene duplication, gene transcriptional capacity, rate-limiting enzyme activities, as well as its metabolic intermediates and its associated redox enzymes on the hyperaccumulation of Vc. Hence, our aim is to identify the key structural genes and/or regulatory genes which could be used to enhance Vc accumulation not only in the fruit of Actinidia but also in other crops and/or vegetables via molecular breeding and genetic modification.

猕猴桃因富含维生素C（Vc）而受到广泛关注。已经完成的中华猕猴桃（Actinidia chinensis）代表品种"红阳"的基因组和转录组数据揭示猕猴桃基因组中与Vc合成代谢相关基因发生了显著的数量倍增，但其转录活性、生化与生物学功能还不清楚。本项研究将利用组学和正、反向遗传学、生化与分子生物学以及转基因技术系统探讨基因培增、转录时空调控、限速酶活性、Vc代谢中间产物消长与终产物的积累以及氧化态和还原态（Vc）循环再利用等影响猕猴桃Vc高效合成和积累的分子调控机理，鉴定分离新的Vc合成代谢和积累的重要功能基因，为园艺植物品质改良和分子设计育种提供新的技术途径。

利用三代测序技术组装完成毛花猕猴桃基因组精细图谱，建立了中华猕猴桃基因组数据库（http://bdg.hfut.edu.cn/kir/），揭示了2次全基因组近代倍增是猕猴桃Vc代谢通路基因数量增多的基因组学机制。对4个显著扩增的基因家族（脱氢抗坏血酸还原酶基因DHAR、抗坏血酸过氧化物酶APX、单脱氢抗坏血酸还原酶MDHAR和醛糖酸内酯酶Alase）的20个成员进行了详尽的研究，包括各个基因的表达模式、亚细胞定位、酶活性以及异位表达后的生理生化及生物学功能，研究工作取得了丰硕的研究成果。