Dynamic Changes of Phenolic Compounds and Their Associated Gene Expression Profiles Occurring during Fruit Development and Ripening of the Donghong Kiwifruit

The newly released Donghong kiwifruit is a promising commercial cultivar. The dynamic changes of major phenolic compounds (flavonols, flavanols, phenolic acids, and anthocyanins) during the representative stages of fruit development and ripening of the Donghong kiwifruit were determined by high-performance liquid chromatography. The corresponding time-course transcriptional changes were evaluated using the combined analysis of RNA-Seq and qRT-PCR. The most predominant phenolic compound in the Donghong kiwifruit was epicatechin. Cyanidin 3-O-[2-O-(β-xylosyl)-β-galactoside] and cyanidin 3-O-β-galactoside were two essential anthocyanins detected. Candidate genes and pathways involved in phenolic compounds biosynthesis were highlighted. The structural genes (AcLDOX2, Ac5GGT1, and Ac5AT2) and the transcription factor (bHLH74-2) were strongly associated with anthocyanin biosynthesis. AcMYB4-1 may be a novel transcription factor that reduces anthocyanin accumulation. Results from the study may be a very useful supplement to current knowledge of molecular mechanisms to elucidate coloration in the red-fleshed kiwifruit and could help breeders modify the kiwifruit germplasm.

最新发布的东红猕猴桃是一款极具商业化开发潜力的栽培品种。本研究采用高效液相色谱法（high-performance liquid chromatography）测定了东红猕猴桃果实发育与成熟典型阶段内主要酚类物质（黄酮醇、黄烷醇、酚酸及花青素）的动态变化规律，并通过RNA测序（RNA-Seq）与实时荧光定量PCR（qRT-PCR）的联合分析，对其对应的时序转录调控变化进行了解析。东红猕猴桃中含量最为丰富的酚类物质为表儿茶素，本研究共检测到两种核心花青素成分：矢车菊素3-O-[2-O-(β-木糖基)-β-半乳糖苷]与矢车菊素3-O-β-半乳糖苷。本研究重点梳理了参与酚类物质生物合成的候选基因与代谢通路，其中结构基因AcLDOX2、Ac5GGT1及Ac5AT2与转录因子bHLH74-2均与花青素生物合成过程显著相关；AcMYB4-1或为一类新型的可抑制花青素积累的转录因子。本研究结果可为阐明红肉猕猴桃果实着色的分子调控机制提供重要补充，同时可为育种人员改良猕猴桃种质资源提供关键理论参考。