DcCCD4 catalyzes the degradation of α-carotene and β-carotene to affect carotenoid accumulation and taproot color in carrot
DcCCD4 catalyzes the degradation of α-carotene and β-carotene to affect carotenoid accumulation and taproot color in carrot
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DOI：
10.1111/tpj.15498
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发表时间：
2021-10-28
期刊：
影响因子：
7.2
通讯作者：
Xiong, Ai-Sheng
中科院分区：
文献类型：
--
作者：
Li, Tong;Deng, Yuan-Jie;Xiong, Ai-Sheng
类胡萝卜素是一种重要的天然色素，能赋予植物鲜艳的色彩。类胡萝卜素积累的差异是胡萝卜主根不同颜色形成的关键因素之一。类胡萝卜素裂解双加氧酶（carotenoiccleavingdioxygenases，CCD）是植物中参与类胡萝卜素裂解的主要酶，包括CCD和9-顺式环氧类胡萝卜素双加氧酶。从胡萝卜基因组中已经注释了7个CCD基因。本研究通过表达分析发现，DcCCD 4在类胡萝卜素含量低的白色胡萝卜主根中的表达量显著高于类胡萝卜素含量高的橙子胡萝卜。在橙子胡萝卜中过表达DcCCD 4导致主根颜色变淡黄色，α-和β-胡萝卜素含量急剧下降。DcCCD 4功能缺失的突变体胡萝卜呈现黄色（对照胡萝卜的主根为白色）。在主根中也检测到β-胡萝卜素的积累。DcCCD 4酶的体外功能分析表明，它能够在9，10（9 '，10'）双键处切割α-和β-胡萝卜素。此外，与正常橙子胡萝卜相比，过表达DcCCD 4的转基因胡萝卜主根细胞中有色质体的数量显著减少。结果表明，DcCCD 4通过切割胡萝卜主根中的α-和β-胡萝卜素来影响类胡萝卜素的积累。
Carotenoids are important natural pigments that give bright colors to plants. The difference in the accumulation of carotenoids is one of the key factors in the formation of various colors in carrot taproots. Carotenoid cleavage dioxygenases (CCDs), including CCD and 9-cis epoxycarotenoid dioxygenase, are the main enzymes involved in the cleavage of carotenoids in plants. Seven CCD genes have been annotated from the carrot genome. In this study, through expression analysis, we found that the expression level of DcCCD4 was significantly higher in the taproot of white carrot (low carotenoid content) than orange carrot (high carotenoid content). The overexpression of DcCCD4 in orange carrots caused the taproot color to be pale yellow, and the contents of alpha- and beta-carotene decreased sharply. Mutant carrot with loss of DcCCD4 function exhibited yellow color (the taproot of the control carrot was white). The accumulation of beta-carotene was also detected in taproot. Functional analysis of the DcCCD4 enzyme in vitro showed that it was able to cleave alpha- and beta-carotene at the 9, 10 (9', 10') double bonds. In addition, the number of colored chromoplasts in the taproot cells of transgenic carrots overexpressing DcCCD4 was significantly reduced compared with that in normal orange carrots. Results showed that DcCCD4 affects the accumulation of carotenoids through cleavage of alpha- and beta-carotene in carrot taproot.