Although abscisic acid (ABA) is a vital regulator of fruit ripening and several transcription factors have been reported to regulate ABA biosynthesis, reports of the effect of ABA on citrus ripening and the regulation of its biosynthesis by a multiple-transcription-factor complex are scarce. In the present study, a systematic metabolic, cytological, and transcriptome analysis of an ABA-deficient mutant (MT) of Citrus reticulata cv. Suavissima confirmed the positive effect of ABA on the citrus ripening process. The analysis of transcriptome profiles indicated that CrNAC036 played an important role in the ABA deficiency of the mutant, most likely due to an effect on the expression of 9-cis-epoxycarotenoid dioxygenase 5 (CrNCED5). Electrophoretic mobility shift assays and dual luciferase assays demonstrated that CrNAC036 can directly bind and negatively regulate CrNCED5 expression. Furthermore, yeast two-hybrid, bimolecular fluorescence complementation, and dual luciferase assays demonstrated that CrNAC036 interacted with CrMYB68, also down-regulating the expression of CrNCED5. Taken together, our results suggest that CrNAC036 and CrMYB68 synergistically inhibit ABA biosynthesis in citrus fruit by regulating the expression of CrNCED5.

中文翻译：

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NAC 转录因子及其相互作用蛋白通过协同抑制柑橘中的 NCED5 来阻碍脱落酸生物合成。


尽管脱落酸 (ABA) 是果实成熟的重要调节因子，并且已报道了多种转录因子可调节 ABA 生物合成，但关于 ABA 对柑橘成熟的影响以及多转录因子复合物对其生物合成的调节的报道很少。在本研究中，对柑橘 ( Citrus reticulata ) ABA 缺陷突变体 (MT) 进行了系统的代谢、细胞学和转录组分析。 Suavissima证实了 ABA 对柑橘成熟过程的积极影响。转录组谱分析表明，CrNAC036 在突变体的 ABA 缺陷中发挥了重要作用，很可能是由于对9-顺式环氧类胡萝卜素双加氧酶 5 ( CrNCED5 ) 表达的影响。电泳迁移率变动分析和双荧光素酶分析表明 CrNAC036 可以直接结合并负向调节CrNCED5 的表达。此外，酵母双杂交、双分子荧光互补和双荧光素酶测定表明 CrNAC036 与 CrMYB68 相互作用，也下调CrNCED5的表达。综上所述，我们的结果表明 CrNAC036 和 CrMYB68 通过调节CrNCED5的表达来协同抑制柑橘类水果中的 ABA 生物合成。