Carotenoids are indispensable for both human health and plant survival. Citrus, is one of the fruit crops richest in carotenoid compounds, with approximately 115 kinds of carotenoids; tremendous diversity in carotenoids composition and concentration exists among various species, showing different colors from nearly white to crimson. The carotenoid biosynthetic pathway and the key carotenogenic genes have been identified in citrus; however, the underlying regulatory mechanisms remain unclear. In this study, among the main species of genus Citrus (primitive, wild, and cultivated), we detected carotenoids in flavedo using High-Performance Liquid Chromatography, and analyzed variations in cis-acting elements in the promoters of key carotenoid pathway genes. Intriguingly, both carotenoid composition and content were generally increased during the evolution of citrus, and the corresponding variations in the promoters were identified, including the gain or loss of critical environmental stress-responsive elements and hormone-responsive elements, which are closely associated with carotenoid enhancement. In addition, pummelo has the most heat-responsive elements, but the Mangshan mandarin does not have this element in the promoters of PSY, which is highly related to their geographical origin and indicate that temperature is a critical environmental signal influencing carotenoid accumulation. Moreover, the abscisic acid-responsive motif was rich in almost all the seven species, but the ethylene-responsive motif was deficient, which demystified the unique phytohormone regulation mechanism of carotenoid accumulation in citrus. Overall, our study provides new insights into the molecular regulatory mechanism of carotenoid enhancement in the evolution of citrus, which can facilitate breeding and cultivation efforts to improve the nutritional quality and esthetic value in citrus and hopefully other fruit crops.

类胡萝卜素对于人类健康和植物生存都是必不可少的。柑橘是最丰富的类胡萝卜素化合物的水果作物之一，约有115种类胡萝卜素。不同物种之间的类胡萝卜素组成和浓度存在巨大差异，从近白色到深红色都显示出不同的颜色。类胡萝卜素的生物合成途径和关键的类胡萝卜素基因已经在柑橘中鉴定出来。但是，基本的监管机制仍不清楚。在这项研究中，我们使用高效液相色谱法在柑橘属（原始，野生和栽培）的主要物种中检测了黄褐藻中的类胡萝卜素，并分析了顺式的变化。关键类胡萝卜素途径基因的启动子中的α-作用元件。有趣的是，类胡萝卜素的组成和含量通常在柑橘的进化过程中都增加了，并且鉴定出启动子的相应变化，包括与类胡萝卜素紧密相关的关键环境胁迫响应元件和激素响应元件的得失。增强。此外，柚子具有最强的热响应性元素，但是芒山普通话在PSY的启动子中没有这种元素。，这与它们的地理起源高度相关，并表明温度是影响类胡萝卜素积累的关键环境信号。此外，脱落酸反应基序几乎在所有七个物种中都丰富，而乙烯反应基序却缺乏，这揭开了柑橘类胡萝卜素积累中独特的植物激素调节机制的神秘性。总的来说，我们的研究提供了对柑橘进化过程中类胡萝卜素增强的分子调控机制的新见解，这可以促进育种和栽培工作，以改善柑橘和希望其他水果作物的营养质量和美学价值。