Flavonoids are a major group of plant-specific metabolites that determine flower and seed coloration. In plant cells, flavonoids are synthesized at the cytosolic surface of the endoplasmic reticulum and are sequestered in the vacuole. It is possible that membrane trafficking, including vesicle trafficking and organelle dynamics, contributes to flavonoid transport and accumulation. However, the underlying mechanism has yet to be fully elucidated. Here we show that the Arabidopsis ECHIDNA protein plays a role in flavonoid accumulation in the vacuole and protein trafficking to the vacuole. We found defective pigmentation patterns in echidna seed, possibly caused by reduced levels of proanthocyanidins, which determine seed coloration. The echidna mutant has defects in protein sorting to the protein storage vacuole as well as vacuole morphology. These findings indicate that ECHIDNA is involved in the vacuolar trafficking pathway as well as the previously described secretory pathway. In addition, we found a genetic interaction between echidna and green fluorescent seed 9 (gfs9), a membrane trafficking factor involved in flavonoid accumulation. Our findings suggest that vacuolar trafficking and/or vacuolar development, both of which are collectively regulated by ECHIDNA and GFS9, are required for flavonoid accumulation, resulting in seed coat pigmentation.

中文翻译：

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拟南芥ECHIDNA蛋白参与种子的着色，蛋白转运至液泡和液泡生物发生。

类黄酮是决定花朵和种子着色的主要植物特异性代谢物。在植物细胞中，类黄酮在内质网的胞质表面合成，并被隔离在液泡中。膜运输，包括囊泡运输和细胞器动力学，可能有助于类黄酮的运输和积累。但是，尚未完全阐明其基本机制。在这里，我们显示拟南芥ECHIDNA蛋白在液泡中的类黄酮积累和向液泡的蛋白运输中起作用。我们发现针种子中的色素沉着模式存在缺陷，这可能是由于原花青素含量降低所致，而花色素的水平决定了种子的色泽。该针鼹突变体在蛋白质分类方面存在缺陷，例如蛋白质储存液泡和液泡形态。这些发现表明ECHIDNA参与液泡运输途径以及先前描述的分泌途径。此外，我们发现了针和绿色荧光种子9（gfs9）之间的遗传相互作用，绿色荧光种子9是参与类黄酮积累的膜运输因子。我们的发现表明，类黄酮的积累需要液泡运输和/或液泡发育，二者均受ECHIDNA和GFS9共同调控，从而导致种皮色素沉着。