Abstract：
Carotenoids are essential for photosynthesis and photoprotection. Plants must evolve multifaceted regulatory mechanisms to control carotenoid biosynthesis. However, the regulatory mechanisms and the regulators conserved among plant species remain elusive. Phytoene synthase (PSY) catalyzes the highly regulated step of carotenogenesis and geranylgeranyl diphosphate synthase (GGPPS) acts as a hub to interact with GGPP-utilizing enzymes for the synthesis of specific downstream isoprenoids. Here, we report a function of Nudix hydrolase 23 (NUDX23), a Nudix domain-containing protein, in post-translational regulation of PSY and GGPPS for carotenoid biosynthesis. NUDX23 expresses highly in Arabidopsis (Arabidopsis thaliana) leaves. Overexpression of NUDX23 significantly increases PSY and GGPPS protein levels and carotenoid production, whereas knockout of NUDX23 dramatically reduces their abundances and carotenoid accumulation in Arabidopsis. NUDX23 regulates carotenoid biosynthesis via direct interactions with PSY and GGPPS in chloroplasts, which enhances PSY and GGPPS protein stability in a large PSY-GGPPS enzyme complex. NUDX23 was found to co-migrate with PSY and GGPPS proteins and to be required for the enzyme complex assembly. Our findings uncover a regulatory mechanism underlying carotenoid biosynthesis in plants and offer promising genetic tools for developing carotenoid-enriched food crops.
摘要：
类胡萝卜素对光合作用和光保护至关重要。植物已经进化出多方面的调节机制来控制类胡萝卜素的生物合成。然而,植物物种之间保守的监管机制和监管机构仍然难以捉摸。植烯合酶（PSY）催化高度调节的类胡萝卜素生成步骤，而香叶基香叶基二磷酸合酶（GGPPS）充当枢纽，与利用GGMP的酶相互作用，以合成特定的下游类异戊二烯。这里,我们报告了Nudix水解酶23(NUDX23)的功能，一种含有Nudix结构域的蛋白质，在类胡萝卜素生物合成的PSY和GGPPS的翻译后调节中。NUDX23在拟南芥(Arabidopsisthaliana)叶片中高度表达。过表达NUDX23显著增加PSY和GGPPS蛋白水平和类胡萝卜素产量,而敲除NUDX23会显著降低其在拟南芥中的丰度和类胡萝卜素积累。NUDX23通过与叶绿体中PSY和GGPPS的直接相互作用来调节类胡萝卜素的生物合成，在大型PSY-GGPPS酶复合物中增强PSY和GGPPS蛋白的稳定性。发现NUDX23在高分子量复合物中与PSY和GGPPS蛋白共迁移，并且是酶复合物组装所必需的。我们的发现揭示了植物中类胡萝卜素生物合成的调节机制，并为开发富含类胡萝卜素的粮食作物提供了有希望的遗传工具。
