A fruit ripening-associated transcription factor CsMADS5 positively regulates carotenoid biosynthesis in citrus
A fruit ripening-associated transcription factor CsMADS5 positively regulates carotenoid biosynthesis in citrus
复制标题
果实成熟相关转录因子 CsMADS5 正向调节柑橘类胡萝卜素生物合成
DOI：
10.1093/jxb/erab045
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发表时间：
2021-02-05
影响因子：
6.9
通讯作者：
Deng, Xiuxin
中科院分区：
文献类型：
--
作者：
Lu, Suwen;Ye, Junli;Deng, Xiuxin
柑橘中的类胡萝卜素有助于果实的品质，但其转录调控机制相当未知。在这里，我们的特点是柑橘FRUITFULL亚枝MADS基因，CsMADS 5，这是成熟诱导，并作为一个核本地化的反式激活因子。在柑橘中瞬时过表达CsMADS 5诱导果实着色和提高类胡萝卜素浓度。在过表达CsMADS 5的果实果皮中，包括八氢番茄红素合成酶（PSY）、八氢番茄红素去饱和酶（PDS）和番茄红素β-环化酶1（LCYb 1）在内的胡萝卜素生成基因的表达增加。从番茄果实和柑橘愈伤组织中稳定过表达CsMADS 5观察到类似的结果，即使CsMADS 5对转基因柑橘愈伤组织中类胡萝卜素代谢的影响是有限的。进一步的生化分析表明，CsMADS 5激活PSY，PDS和LCYb 1的转录直接结合到他们的启动子。我们的结论是，CsMADS 5积极调节类胡萝卜素的生物合成在水果中直接激活胡萝卜素基因的转录。此外，CsMADS 5物理相互作用的正调节CsMADS 6，表明CsMADS 5可能形成一个增强子复合体与CsMADS 6协同促进类胡萝卜素的积累。这些发现扩展了我们对果实成熟过程中类胡萝卜素生物合成的复杂转录调控层次的理解。
Carotenoids in citrus contribute to the quality of the fruit, but the mechanism of its transcriptional regulation is fairly unknown. Here, we characterized a citrus FRUITFULL sub-clade MADS gene, CsMADS5, that was ripening-inducible and acted as a nucleus-localized trans-activator. Transient overexpression of CsMADS5 in citrus induced fruit coloration and enhanced carotenoid concentrations. The expression of carotenogenic genes including phytoene synthase (PSY), phytoene desaturase (PDS), and lycopene beta-cyclase 1 (LCYb1) was increased in the peels of fruits overexpressing CsMADS5. Similar results were observed from stable overexpression of CsMADS5 in tomato fruits and citrus calli, even though the effect of CsMADS5 on carotenoid metabolism in transgenic citrus calli was limited. Further biochemical analyses demonstrated that CsMADS5 activated the transcription of PSY, PDS, and LCYb1 by directly binding to their promoters. We concluded that CsMADS5 positively regulates carotenoid biosynthesis in fruits by directly activating the transcription of carotenogenic genes. Moreover, CsMADS5 physically interacted with a positive regulator CsMADS6, indicating that CsMADS5 may form an enhancer complex with CsMADS6 to synergistically promote carotenoid accumulation. These findings expand our understanding of the complex transcriptional regulatory hierarchy of carotenoid biosynthesis during fruit ripening.