Abstract
Studies on organic acid metabolism have been mainly concentrated on the fruit, whereas, few have focused on the mechanism of high organic acids content in the fruit of Actinidia eriantha. Fruits of ‘Ganmi 6’ harvested at eleven developmental periods were used as materials. The components and content of organic acids were determined by high-performance liquid chromatography (HPLC) system, the activities of the related enzyme were detected, and gene expression levels were measured by quantitative real-time PCR (qRT-PCR). Components of ascorbic acid (AsA) and eight kinds of organic acids were detected. These results showed that quinic acid and citric acid were the main organic acids in the fruit of ‘Ganmi 6’. Correlation analysis showed that NADP-Quinate dehydrogenase (NADP-QDH), NADP-Shikimate dehydrogenase (NADP-SDH), and Cyt-Aconitase (Cyt-Aco) may be involved in regulating organic acids biosynthesis. Meanwhile, the SDH gene may play an important role in regulating the accumulation of citric acid. In this study, the activities of NADP-SDH, Mit-Aconitase (Mit-Aco), and NAD-Isocitrate dehydrogenase (NAD-IDH) were regulated by their corresponding genes at the transcriptional level. The activity of Citrate synthase (CS) may be affected by post-translational modification. Our results provided new insight into the characteristics of organic acid metabolism in the fruit of A. eriantha.
Highlights
China is the origin and distribution center of kiwifruit
Correlation analysis showed that the content of quinic acid and citric acid were significantly correlated with the content of total organic acids, which is consistent with the results on A. chinensis, A. deliciosa and A. arguta [16]
The relative gene expression level of Shikimate dehydrogenase (SDH) was significantly positively correlated with the activities of Nicotinamide adenine dinucleotide phosphate (NADP)-Quinate dehydrogenase (QDH) and NADP-SDH, which is consistent with the results on Citrus [16,40]. These results suggested that quinic acid may be synthesized at the early periods of fruit development and the activities of NADP-QDH and NADP-SDH may be regulated by SDH gene, DQS gene did not have a decisive effect on the quinic acid accumulation in the fruit of ‘Ganmi 6’
Summary
China is the origin and distribution center of kiwifruit. It has abundant germplasm resources of kiwifruit [1]. Kiwifruit is rich in organic acids, sugars, mineral elements, and other nutrients, which play important roles in human health [2]. Actinidia eriantha belongs to the family Actinidiaceae, genus. Actinidia, which is a unique kiwifruit germplasm resource in China [3]. A. eriantha has attracted much attention, due to its green flesh, strong fruit flavor, high ascorbic acid (AsA) content, easy peeling and ornamental value of pink corolla [4]. ‘Ganmi 6’ is a new kiwifruit cultivar which was selected from wild A. eriantha in Yihuang County, Jiangxi Province, China by Institute of kiwifruit, Jiangxi
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