Comprehensive analysis of a red-peel kiwi berry mutant reveals key genes are responsible for anthocyanin biosynthesis in fruit

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Actinidia arguta is an important kind of kiwifruit species with good fruit quality and high economic value. New cultivars of kiwi berry and kiwifruit with high accumulation of anthocyanins in fruit are becoming more and more popular mainly due to the benefit of anthocyanins to human health. Here, a red-peel A. arguta mutant, CG 1, was identified, and its fruit quality was determined. The genetic variation of CG 1 was confirmed by kiwifruit Simple Sequence Repeats (SSR) molecular marker analysis. The peel color of mature fruit in this mutant changed into red, while it was green for the wild type. In addition, the total contents of anthocyanins in peel and pulp tissues of the mutant were both significantly higher when comparing with that of the wild type. Especially, the amount of anthocyanins in fruit peel of CG 1 was 7.49 mg g−1 fresh weight (FW), almost 9.4 times higher than that of the wild type. Further study by transcriptome sequencing and quantitative real-time PCR (qRT-PCR) analysis indicated that the expression patterns of five genes involved in anthocyanin biosynthesis were highly consistent with the anthocyanins contents in peel tissues of the two genotypes. We deduce that those five candidate genes are responsible for the high accumulation of anthocyanins in fruit of the red-peel kiwi berry mutant. This research provides useful methods to identify new kiwi berry mutant. And the comprehensive analysis reveals that the promoted anthocyanins accumulation in the mutant is dependent on the high transcriptional regulations of several key genes involved in anthocyanin biosynthesis pathway.