A xanthophyll-derived apocarotenoid regulates carotenogenesis in tomato chromoplasts.
A xanthophyll-derived apocarotenoid regulates carotenogenesis in tomato chromoplasts.
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DOI：
10.1016/j.plantsci.2022.111575
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发表时间：
2022-12
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通讯作者：
C. D’Ambrosio;Adriana Lucia Stigliani;J. Rambla;Sarah Frusciante;G. Diretto;Eugenia M. A. Enfissi;A. Granell;P. Fraser;G. Giorio
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作者：
C. D’Ambrosio;Adriana Lucia Stigliani;J. Rambla;Sarah Frusciante;G. Diretto;Eugenia M. A. Enfissi;A. Granell;P. Fraser;G. Giorio
类胡萝卜素具有重要的生物功能，使它们成为人类饮食的基本成分。β-胡萝卜素和其他一些类胡萝卜素具有维生素A活性，而叶黄素和玉米黄质，通常被称为黄斑色素，与良好的视力和延缓与年龄相关的眼病的发生有关。为了创造生产玉米黄质的番茄果实，对两个转基因品系进行了遗传杂交，其中一个转基因品系具有高β-胡萝卜素环化酶活性，另一个转基因品系具有高β-胡萝卜素羟基酶活性。由此产生的后代的成熟果实中含有大量的紫黄质、花黄质和叶黄素酯。然而，它们的玉米黄质含量并不像预期的那样高，类胡萝卜素的总水平仅为对照品系成熟果实中类胡萝卜素的25%。靶向转录分析和类胡萝卜素测定表明，类胡萝卜素合成途径的转录调控或降解不是杂交果实类胡萝卜素含量低的原因，而是类胡萝卜素生物合成显著减少的结果。值得注意的是，杂交果实中一种未知的羟基环状(C13)类胡萝卜素的含量是对照果实的13倍。此外，基于GC-MS的代谢物图谱显示，成熟的杂交水果中胡萝卜素的生成受到干扰，与该途径的一个阻断相一致。此外，对一组携带hp3突变的实验品系的叶片、果实和花瓣样本进行的类胡萝卜素分析表明，结合两个转基因，花瓣和果实染色体中的类胡萝卜素生物合成是可以调控的。总之，这些数据与番茄有色体类胡萝卜素途径的调控假说是一致的，该假说是通过叶黄素衍生的类胡萝卜素介导的反馈抑制机制来调节的。由于玉米黄质和类胡萝卜素信号的前体玉米黄质和心黄质的异常产生，这种色质特异的转录后转录机制被揭示在胡萝卜杂交的转基因果实中。提出了一个描述番茄有色质体内类胡萝卜素途径调控的模型。
Carotenoids possess important biological functions that make them essential components of the human diet. β-Carotene and some other carotenoids have vitamin A activity while lutein and zeaxanthin, typically referred to as the macular pigments, are involved in good vision and in delaying the onset of age-related eye diseases. In order to create a zeaxanthin-producing tomato fruit, two transgenic lines, one with a high β-carotene cyclase activity and the other with a high β-carotene hydroxylase activity, have been genetically crossed. Ripe fruits from the resulting progeny contained significant levels of violaxanthin, antheraxanthin, and xanthophyll esters. However, their zeaxanthin content was not as high as expected, and the total level of carotenoids was only 25% of the carotenoids found in ripe fruits of the comparator line. Targeted transcript analysis and apocarotenoids determinations indicated that transcriptional regulation of the pathway or degradation of synthesized carotenoids were not responsible for the low carotenoid content of hybrid fruits which instead appeared to result from a substantial reduction of carotenoid biosynthesis. Notably, the content of an unidentified hydroxylated cyclic (C13) apocarotenoid was 13 times higher in the hybrid fruits than in the control fruits. Furthermore, a GC-MS-based metabolite profiling demonstrated a perturbation of carotenogenesis in ripening hybrid fruits compatible with a block of the pathway. Moreover, carotenoid profiling on leaf, fruit, and petal samples from a set of experimental lines carrying thehp3mutation, in combination with the two transgenes, indicated that the carotenoid biosynthesis in petal and fruit chromoplasts could be regulated. Altogether the data were consistent with the hypothesis of the regulation of the carotenoid pathway in tomato chromoplasts through a mechanism of feedback inhibition mediated by a xanthophyll-derived apocarotenoid. This chromoplast-specific post-transcriptional mechanism was disclosed in transgenic fruits of HU hybrid owing to the abnormal production of zeaxanthin and antheraxanthin, the more probable precursors of the apocarotenoid signal. A model describing the regulation of carotenoid pathway in tomato chromoplasts is presented.