Tomato fruit ripening is controlled by the hormone ethylene and by a group of transcription factors, acting upstream of ethylene. During ripening, the linear carotene lycopene accumulates at the expense of cyclic carotenoids. Fruit-specific overexpression of LYCOPENE β-CYCLASE (LCYb) resulted in increased β-carotene (provitamin A) content. Unexpectedly, LCYb-overexpressing fruits also exhibited a diverse array of ripening phenotypes, including delayed softening and extended shelf life. These phenotypes were accompanied, at the biochemical level, by an increase in abscisic acid (ABA) content, decreased ethylene production, increased density of cell wall material containing linear pectins with a low degree of methylation, and a thicker cuticle with a higher content of cutin monomers and triterpenoids. The levels of several primary metabolites and phenylpropanoid compounds were also altered in the transgenic fruits, which could be attributed to delayed fruit ripening and/or to ABA. Network correlation analysis and pharmacological experiments with the ABA biosynthesis inhibitor, abamine, indicated that altered ABA levels were a direct effect of the increased β-carotene content and were in turn responsible for the extended shelf life phenotype. Thus, manipulation of β-carotene levels results in an improvement not only of the nutritional value of tomato fruits, but also of their shelf life.

中文翻译：

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操纵番茄果实中的β-胡萝卜素水平会导致ABA含量增加和货架期延长。

番茄果实的成熟受激素乙烯和一组在乙烯上游起作用的转录因子的控制。在成熟过程中，线性胡萝卜素番茄红素的积累以环状类胡萝卜素为代价。果实特定的番茄红素β-环化酶（LCYb）的过表达导致β-胡萝卜素（蛋白原A）含量增加。出乎意料的是，过表达LCYb的果实还表现出各种各样的成熟表型，包括延迟的软化和延长的保质期。这些表型在生化水平上伴随着脱落酸（ABA）含量的增加，乙烯产量的降低，甲基化程度低的含有线性果胶的细胞壁材料密度的增加以及高含量的角质层的表皮变厚。角质单体和三萜。转基因果实中几种主要代谢物和苯丙烷化合物的含量也发生了变化，这可能归因于果实成熟和/或ABA的延迟。使用ABA生物合成抑制剂阿巴胺的网络相关性分析和药理实验表明，改变的ABA水平是增加β-胡萝卜素含量的直接作用，并进而导致货架期延长。因此，β-胡萝卜素水平的控制不仅改善了番茄果实的营养价值，而且改善了其货架期。指出改变的ABA水平是β-胡萝卜素含量增加的直接影响，并且反过来又导致延长的货架期表型。因此，β-胡萝卜素水平的控制不仅改善了番茄果实的营养价值，而且改善了其货架期。指出改变的ABA水平是β-胡萝卜素含量增加的直接影响，并且反过来又导致延长的货架期表型。因此，β-胡萝卜素水平的控制不仅改善了番茄果实的营养价值，而且改善了其货架期。