Planta ( IF 3.6 ) Pub Date : 2022-10-29 , DOI: 10.1007/s00425-022-04016-9 Yu-Min Zhang 1 , Rong-Hua Wu 1 , Lu Wang 1 , Ya-Hui Wang 1 , Hui Liu 1 , Ai-Sheng Xiong 1 , Zhi-Sheng Xu 1
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Main conclusion
Distinct plastid types and ultrastructural changes are associated with differences in carotenoid pigment profiles in differently coloured carrots, and a variant of the OR gene, DcOR3Leu is vital for chromoplast biogenesis.
Abstract
Accumulation of different types and amounts of carotenoids in carrots impart different colours to their taproots. In this study, the carotenoid pigment profiles, morphology, and ultrastructure of plastids in 25 carrot varieties with orange, red, yellow, or white taproots were investigated by ultra-high performance liquid chromatography as well as light and transmission electron microscopy. α-/β-Carotene and lycopene were identified as colour-determining carotenoids in orange and red carrots, respectively. In contrast, lutein was identified as the colour-determining carotenoid in almost all tested yellow and white carrots. The latter contained only trace amounts of lutein as a unique detectable carotenoid. Striking differences in plastid types that coincided with distinct carotenoid profiles were observed among the differently coloured carrots. Microscopic analysis of the different carotenoid pigment-loaded plastids revealed abundant crystalloid chromoplasts in the orange and red carrots, whereas amyloplasts were dominant in most of the yellow and white carrots, except for the yellow carrot ‘Yellow Stone’, where yellow chromoplasts were observed. Plastoglobuli and crystal remnants, the carotenoid sequestering substructures, were identified in crystalloid chromoplasts. Crystal remnants were often associated with a characteristic undulated internal membrane in orange carrots or several undulated membranes in red carrots. No crystal remnants, but some plastoglobuli, were observed in the plastids of all tested yellow and white carrots. In addition, the presence of chromoplast in carrot taproots was found to be associated with DcOR3Leu, a natural variant of DcOR3, which was previously reported to be co-segregated with carotene content in carrots. Knocking out DcOR3Leu in the orange carrot ‘Kurodagosun’ depressed chromoplast biogenesis and led to the generation of yellow carrots. Our results support that DcOR3Leu is vital but insufficient for chromoplasts biogenesis in carrots, and add to the understanding of the formation of chromoplasts in carrots.
中文翻译：
不同颜色胡萝卜的质体多样性和有色体生物发生：DcOR3Leu 基因的作用
主要结论
不同质体类型和超微结构变化与不同颜色胡萝卜中类胡萝卜素色素谱的差异有关，而OR基因的变体DcOR3 Leu对于有色体生物发生至关重要。
抽象的
胡萝卜中不同类型和数量的类胡萝卜素的积累赋予其主根不同的颜色。在这项研究中，通过超高效液相色谱以及光学和透射电子显微镜研究了 25 个具有橙色、红色、黄色或白色主根的胡萝卜品种的类胡萝卜素色素谱、形态和质体超微结构。α-/β-胡萝卜素和番茄红素分别被鉴定为橙色和红色胡萝卜中的决定颜色的类胡萝卜素。相比之下，叶黄素被确定为几乎所有测试的黄色和白色胡萝卜中的决定颜色的类胡萝卜素。后者仅含有微量的叶黄素作为一种独特的可检测类胡萝卜素。在不同颜色的胡萝卜中观察到与不同类胡萝卜素特征一致的质体类型的显着差异。对载有不同类胡萝卜素色素的质体进行的显微镜分析显示，橙色和红色胡萝卜中含有丰富的晶体有色体，而淀粉体在大多数黄色和白色胡萝卜中占主导地位，但黄色胡萝卜“黄石”除外，其中观察到黄色有色体。在晶体有色体中发现了质体球和晶体残余物，即类胡萝卜素螯合子结构。晶体残余物通常与橙色胡萝卜中特征性的波状内膜或红色胡萝卜中的几个波状膜相关。在所有测试的黄色和白色胡萝卜的质体中没有观察到晶体残留物，但观察到一些质体球。此外，发现胡萝卜主根中有色体的存在与DcOR3 Leu是DcOR3的天然变体，此前曾报道其与胡萝卜中的胡萝卜素含量共分离。敲除橙色胡萝卜“Kurodagosun”中的DcOR3 Leu会抑制有色体生物发生并导致黄色胡萝卜的产生。我们的结果支持DcOR3 Leu对胡萝卜中的有色体生物发生至关重要但不足，并增加了对胡萝卜中有色体形成的理解。
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