College of Tropical Crops, Hainan University, Haikou 570228, China.
Key Laboratory of Breeding and Utilization of Kiwifruit in Sichuan Province, Sichuan Provincial Academy of Natural Resource Sciences, Chengdu 610065, China.
Int J Mol Sci. 2023 Jan 13;24(2):1573. doi: 10.3390/ijms24021573.
During the development of yellow-fleshed kiwifruit (), the flesh appeared light pink at the initial stage, the pink faded at the fastest growth stage, and gradually changed into green. At the maturity stage, it showed bright yellow. In order to analyze the mechanism of flesh color change at the metabolic and gene transcription level, the relationship between color and changes of metabolites and key enzyme genes was studied. In this study, five time points (20 d, 58 d, 97 d, 136 d, and 175 d) of yellow-fleshed kiwifruit were used for flavonoid metabolites detection and transcriptome, and four time points (20 d, 97 d, 136 d, and 175 d) were used for targeted detection of carotenoids. Through the analysis of the content changes of flavonoid metabolites, it was found that the accumulation of pelargonidin and cyanidin and their respective anthocyanin derivatives was related to the pink flesh of young fruit, but not to delphinidin and its derivative anthocyanins. A total of 140 flavonoid compounds were detected in the flesh, among which anthocyanin and 76% of the flavonoid compounds had the highest content at 20 d, and began to decrease significantly at 58 d until 175 d, resulting in the pale-pink fading of the flesh. At the mature stage of fruit development (175 d), the degradation of chlorophyll and the increase of carotenoids jointly led to the change of flesh color from green to yellow, in addition to chlorophyll degradation. In kiwifruit flesh, 10 carotenoids were detected, with none of them being linear carotenoids. During the whole development process of kiwifruit, the content of -carotene was always higher than that of -carotene. In addition, -cryptoxanthin was the most-accumulated pigment in the kiwifruit at 175 d. Through transcriptome analysis of kiwifruit flesh, seven key transcription factors for flavonoid biosynthesis and ten key transcription factors for carotenoid synthesis were screened. This study was the first to analyze the effect of flavonoid accumulation on the pink color of yellow-fleshed kiwifruit. The high proportion of -cryptoxanthin in yellow-fleshed kiwifruit was preliminarily found. This provides information on metabolite accumulation for further revealing the pink color of yellow-fleshed kiwifruit, and also provides a new direction for the study of carotenoid biosynthesis and regulation in yellow-fleshed kiwifruit.
在金艳猕猴桃（）的发育过程中，果实最初呈淡粉色，在生长最快的阶段粉红色逐渐褪去，逐渐变为绿色。在成熟阶段，它呈现出鲜艳的黄色。为了在代谢和基因转录水平上分析果肉颜色变化的机制，研究了颜色与代谢物和关键酶基因变化的关系。在这项研究中，使用了五个时间点（20 d、58 d、97 d、136 d 和 175 d）来检测金艳猕猴桃的类黄酮代谢物，并使用了四个时间点（20 d、97 d、136 d 和 175 d）来检测类胡萝卜素的靶向检测。通过分析类黄酮代谢物含量的变化，发现天竺葵素和矢车菊素及其各自的花青素衍生物的积累与幼果的粉红色有关，但与飞燕草素及其衍生物的花青素无关。在果肉中共检测到 140 种类黄酮化合物，其中花青素和 76%的类黄酮化合物在 20 d 时含量最高，从 58 d 开始显著下降，直到 175 d，导致果肉的淡粉色褪去。在果实发育的成熟阶段（175 d），除了叶绿素的降解外，叶绿素的降解和类胡萝卜素的增加共同导致果肉颜色从绿色变为黄色。在猕猴桃果肉中，检测到 10 种类胡萝卜素，其中没有一种是直链类胡萝卜素。在猕猴桃的整个发育过程中，β-胡萝卜素的含量始终高于β-胡萝卜素。此外，在 175 d 时，β-隐黄质是猕猴桃中积累最多的色素。通过猕猴桃果肉转录组分析，筛选到 7 个类黄酮生物合成关键转录因子和 10 个类胡萝卜素合成关键转录因子。本研究首次分析了类黄酮积累对金艳猕猴桃粉红色的影响。初步发现金艳猕猴桃中β-隐黄质的比例较高。这为进一步揭示金艳猕猴桃的粉红色提供了代谢物积累的信息，也为金艳猕猴桃类胡萝卜素生物合成和调控的研究提供了新的方向。
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