Orange: a target gene for regulating carotenoid homeostasis and increasing plant tolerance to environmental stress in marginal lands

Carotenoids (类胡萝卜素) play essential roles in various light-harvesting (光捕获) processes in plants and help protect the photosynthetic machinery from photo-oxidative (光氧化) damage. Orange genes, which play a role in carotenoid accumulation, were recently isolated from several plant species, and their functions were intensively investigated. The Orange gene (IbOr) from sweetpotato [Ipomoea batatas (L.) Lam 甘薯] helps maintain carotenoid homeostasis to improve plant tolerance to environmental stress. IbOr, a protein with strong holdase chaperone activity, directly interacts with phytoene synthase (IbPSY; 八氢番茄红素合成酶), a key enzyme involved in carotenoid biosynthesis, in plants under stress conditions, resulting in increased carotenoid accumulation and abiotic stress tolerance. In addition, IbOr interacts with the oxygen-evolving enhancer protein 2-1 (PsbP; 放氧增强蛋白), a member of a protein complex in photosystem II (PSII) that is denatured (变性) under heat stress. Transgenic sweetpotato plants overexpressing IbOr showed enhanced tolerance to high temperatures (47°C). These findings indicate that IbOr protects plants from environmental stress, not only by controlling carotenoid biosynthesis, but also by directly stabilizing PSII. In this review, we discuss the functions of IbOr and Or proteins in other plant species and their possible biotechnological applications for molecular breeding for sustainable development on marginal lands.

类胡萝卜素在植物光捕获过程中扮演着非常重要的作用，帮助植物的光合作用免受光氧化的损害。Orange基因在类胡萝卜素的积累中发挥重要作用，近期在一些植物中成功分离出了Orange基因，并且对其功能进行了一定的研究。甘薯的Orange基因IbOr帮助稳定类胡萝卜素的内稳态以增强植物对于环境胁迫的耐性。IbOr蛋白具有很强的分子伴侣活性，在胁迫条件下的植株中直接与一个类胡萝卜素生物合成中的关键酶八氢番茄红素合成酶IbPSY互作，导致类胡萝卜素积累和非生物胁迫抗性的增加。另外，IbOr还会与放氧增强蛋白PsbP互作，PsbP蛋白是光合系统II中蛋白复合物的一员，在热胁迫条件下会变性。过表达IbOr基因的转基因甘薯植株显示47°C高温下的耐性。本文的发现揭示了IbOr不仅通过控制类胡萝卜素的生物合成，还通过直接稳定PSII来保护植株免受环境胁迫。在本综述中，作者讨论了IbOr和Or蛋白在其他植物中的功能，以及这两个蛋白在贫瘠土地可持续发展的分子植物育种中可能的生物技术应用。

通讯：Sang-Soo Kwak (https://www.researchgate.net/profile/Sang_Soo_Kwak)

doi: https://doi.org/10.1093/jxb/ery023