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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Yellow flowers generated by expression of the aurone biosynthetic pathway
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Yellow flowers generated by expression of the aurone biosynthetic pathway

机译：通过金黄色生物合成途径的表达产生的黄色花朵

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摘要

Flower color is most often conferred by colored flavonoid pigments. Aurone flavonoids confer a bright yellow color on flowers such as snapdragon (Antirrhinum majus) and dahlia (Dahlia variabilis). A. majus aureusidin synthase (AmAS1) was identified as the key enzyme that catalyzes aurone biosynthesis from chalcones, but transgenic flowers overexpressing AmAS1 gene failed to produce aurones. Here, we report that chalcone 4'-O-glucosyltransferase (4'CGT) is essential for aurone biosynthesis and yellow coloration in vivo. Coexpression of the Am4'CGT and AmAS1 genes was sufficient for the accumulation of aureusidin 6-O-glucoside in transgenic flowers (Torenia hybrida). Furthermore, their coexpression combined with down-regulation of anthocyanin biosynthesis by RNA interference (RNAi) resulted in yellow flowers. An Am4'CGT-GFP chimeric protein localized in the cytoplasm, whereas the AmAS1(N1-60)-RFP chimeric protein was localized to the vacuole. We therefore conclude that chalcones are 4'-O-glucosylated in the cytoplasm, their 4'-O-glucosides transported to the vacuole, and therein enzymatically converted to aurone 6-O-glucosides. This metabolic pathway is unique among the known examples of flavonoid, including anthocyanin biosynthesis because, for all other compounds, the carbon backbone is completed before transport to the vacuole. Our findings herein not only demonstrate the biochemical basis of aurone biosynthesis but also open the way to engineering yellow flowers for major ornamental species lacking this color variant.
机译：花的颜色通常是由有色的类黄酮颜料赋予的。淡黄色的类黄酮使花朵如金鱼草（Antirrhinum majus）和大丽花（Dahlia variabilis）具有明亮的黄色。 Majus aureusidin合酶（AmAS1）被确定为催化从查耳酮中合成生物素的关键酶，但过表达AmAS1基因的转基因花无法产生金质。在这里，我们报告查尔酮4'-O-葡萄糖基转移酶（4'CGT）对于体内的金黄色生物合成和黄色着色至关重要。 Am4'CGT和AmAS1基因的共表达足以在转基因花（Torenia hybrida）中积累金黄色素6-O-葡萄糖苷。此外，它们的共表达与RNA干扰（RNAi）对花色苷生物合成的下调相结合，导致产生黄色花朵。 Am4'CGT-GFP嵌合蛋白位于细胞质中，而AmAS1（N1-60）-RFP嵌合蛋白位于液泡中。因此，我们得出的结论是，查耳酮在细胞质中被4'-O-糖基化，它们的4'-O-糖苷被转运至液泡，并在其中酶促转化为金酮6-O-糖苷。该代谢途径在已知的类黄酮实例中是唯一的，包括花青素的生物合成，因为对于所有其他化合物，碳主链在转运至液泡之前就已完成。我们在本文中的发现不仅证明了金莲花生物合成的生物化学基础，而且还为缺乏这种颜色变异的主要观赏物种开辟了黄色花的工程方法。

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