Hu Yujing, Cheng Hao, Zhang Yan, Zhang Jie, Niu Shuqing, Wang Xingsui, Li Wenjing, Zhang Jie, Yao Yuncong
Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing University of Agriculture, Beijing, 102206, China.
College of Plant Science and Technology, Beijing University of Agriculture, Beijing, 102206, China.
New Phytol. 2021 Aug;231(3):1105-1122. doi: 10.1111/nph.17431. Epub 2021 May 24.
Light induces anthocyanin accumulation and hence decides the coloration of apple fruit. It also plays a key role in regulating the biosynthesis of other secondary metabolites. However, the crosstalk between anthocyanin and lignin metabolism during light induction, which affects the edible quality and visual quality of apple fruit, respectively, have rarely been characterized. In this study, we identified and functionally elucidated the roles of miR7125 and its target, cinnamoyl-coenzyme A reductase gene (CCR), in regulating the homeostasis between anthocyanin and lignin biosynthesis during light induction. Overexpressing miR7125 or inhibiting CCR transiently in apple fruit promoted anthocyanin biosynthesis but reduced lignin production under light-induced conditions. Consistently, opposite results were observed under the background of repressed miR7125 or overexpressed CCR. We found that the repressor MdMYB16 and the activator MdMYB1 bound to the miR7125 promoter. Transient repression of MdMYB16 upregulated miR7125 expression significantly, accompanied by decreased levels of MdCCR transcript, resulting in a reduction in the lignin biosynthesis and an increase in anthocyanin accumulation. However, transient overexpression of MdMYB16 produced the opposite effects to MdMYB16-RNAi. The results reveal a novel mechanism by which the MdMYB16/MdMYB1-miR7125-MdCCR module collaboratively regulates homeostasis between anthocyanin and lignin biosynthesis under light induction in apple.
光诱导花青素积累，从而决定苹果果实的着色。它在调节其他次生代谢产物的生物合成中也起着关键作用。然而，光诱导过程中花青素和木质素代谢之间的相互作用，分别影响苹果果实的食用品质和视觉品质，却鲜有研究报道。在本研究中，我们鉴定并功能解析了miR7125及其靶标肉桂酰辅酶A还原酶基因（CCR）在光诱导过程中调节花青素和木质素生物合成稳态的作用。在苹果果实中过表达miR7125或瞬时抑制CCR，在光诱导条件下促进了花青素的生物合成，但减少了木质素的产生。同样，在miR7125受抑制或CCR过表达的背景下观察到相反的结果。我们发现阻遏蛋白MdMYB16和激活蛋白MdMYB1与miR7125启动子结合。瞬时抑制MdMYB16显著上调miR7125表达，同时MdCCR转录水平降低，导致木质素生物合成减少，花青素积累增加。然而，MdMYB16的瞬时过表达产生了与MdMYB16-RNAi相反的效果。结果揭示了一种新机制，即MdMYB16/MdMYB1-miR7125-MdCCR模块在光诱导下协同调节苹果中花青素和木质素生物合成的稳态。
