GABA支路在柑橘果实采后品质保持中行使了某些特殊功能，但调控GABA代谢的机制还不清楚。前期研究中我们获得了HB柚×Fairchild橘F1分离群体的高酸和低酸果实，本项目拟其为材料，亲本为参照，从GABA生物合成、向线粒体的转运及线粒体对GABA的响应三个环节系统研究柑橘采后GABA代谢的限速步骤和关键基因，在此基础上着重研究线粒体GABA转运蛋白质CgGABP的生物学功能。对比分析GABP在高酸和低酸柑橘果实中的序列结构、表达水平、启动子元件及转录活性；从DNA、转录和翻译等不同水平揭示柑橘GABP的转运活性调控机制。另外，我们还将利用免疫胶体金技术跟踪GABA进入线粒体后的时空分布特征，同时分离和富积线粒体，从线粒体超微结构、蛋白质组和代谢组水平解析线粒体对外源GABA的响应。阐明GABA对柑橘果实有机酸代谢的调控机制对柑橘贮藏保鲜和耐贮藏新品种培育均具有重要的理论意义和应用价值。

Gamma-aminobutyric acid (GABA) plays peculiar roles in maintaining postharvest citrus fruit quality. To date, the regulation mechanisms underling the metabolism of GABA shunt in postharvest citrus fruit are still unclear. In previous studies, we obtained two groups of hybrid strains with high and low acid contents in the fruits from the F1 population of HB pummelo × Fairchild tangerine. In present project, the high and low acid contents fruits with very similar genetic background will be selected as materials. To explore the rate-limiting step and key genes related to GABA shunt, the bio-processes of GABA biosynthesis, GABA transfer from the cytoplasm to mitochondria and the subsequent response of the mitochondria to exogenous GABA will be studied systemically. Further work will focus in the bio-function of CgGABP, a mitochondrial specific GABA transfer protein. In order to unravel the regulatory mechanisms of GABA shunt activity differences between high and low acid strains, the sequences structures, gene expressions, promoter elements, and activities of transcription will be parallelly analyzed. Foremore, the space-time characters of GABA distribution after it been transferred into the mitochondria will be tracked by using immune colloidal gold technique. In addition, intact mitochondria will be isolated (or enriched), and mitochondria response to exogenous GABA will be investigated via mitochondrial ultra structure observation, as well as proteomics and metabomics approaches. Elucidating organic acid metabolism mechanism regulated by GABA shunt was expected to have important theoretic and practical impacts on both citrus postharvest biotechnology and novel cultivar breeding in citrus industry.