A banana R2R3-MYB transcription factor MaMYB3 is involved in fruit ripening through modulation of starch degradation by repressing starch degradation-related genes and MabHLH6
A banana R2R3-MYB transcription factor MaMYB3 is involved in fruit ripening through modulation of starch degradation by repressing starch degradation-related genes and MabHLH6
复制标题
涉及香蕉 R2R3-MYB 转录因子 MaMYB3
DOI：
10.1111/tpj.14099
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发表时间：
2018-12-01
期刊：
影响因子：
7.2
通讯作者：
Chen, Jian-Ye
中科院分区：
文献类型：
--
作者：
Fan, Zhong-Qi;Ba, Liang-Jie;Chen, Jian-Ye
香蕉果实成熟过程中淀粉降解是决定果实品质的一个必要过程。许多与淀粉降解相关的基因已被研究。然而，香蕉果实成熟过程中淀粉降解的转录调控仍然知之甚少。在本研究中，我们鉴定了一个MYB转录因子（TF），命名为MaMYB 3，作为一个推定的蛋白结合的启动子MaGWD 1，葡聚糖水双激酶（GWD）家族的成员，已被证明是一个重要的淀粉降解酶。MaMYB 3是成熟和乙烯抑制的，其表达与淀粉降解呈负相关。MaMYB 3作为一个核定位的转录抑制因子，通过直接与MaGWD 1、MaSEX 4、MaBAM 7-MaBAM 8、MaAMY 2B、MaAMY 3、MaAMY 3A、MaAMY 3C、MaMEX 1和MapGlcT 2 -1等10个淀粉降解相关基因的启动子结合来抑制其转录。有趣的是，之前发现的淀粉降解相关基因的激活剂MabHLH 6也被MaMYB 3抑制。MaMYB 3在番茄中的异位过表达下调了淀粉降解相关基因的表达，抑制了淀粉降解，延缓了果实成熟。基于这些发现，我们得出结论，MaMYB 3通过直接抑制淀粉降解相关基因和MabHLH 6来负面影响淀粉降解，从而延迟香蕉果实成熟。总的来说，我们的研究扩展了我们对水果成熟过程中调节淀粉降解的复杂转录调控层次的理解。
Starch degradation is a necessary process determining banana fruit quality during ripening. Many starch degradation-related genes are well studied. However, the transcriptional regulation of starch degradation during banana fruit ripening remains poorly understood. In this study, we identified a MYB transcription factor (TF) termed MaMYB3, as a putative protein binding the promoter of MaGWD1, a member of glucan water dikinase (GWD) family which has been demonstrated as an important enzyme of starch degradation. MaMYB3 was ripening- and ethylene-repressible, and its expression was negatively correlated with starch degradation. Acting as a nucleus-localized transcriptional repressor, MaMYB3 repressed the transcription of 10 starch degradation-related genes, including MaGWD1, MaSEX4, MaBAM7-MaBAM8, MaAMY2B, MaAMY3, MaAMY3A, MaAMY3C, MaMEX1, and MapGlcT2-1, by directly binding to their promoters. Interestingly, a previously identified activator of starch degradation-related genes, MabHLH6, was also suppressed by MaMYB3. The ectopic overexpression of MaMYB3 in tomato down-regulated the expression of starch degradation-related genes, inhibited starch degradation and delayed fruit ripening. Based on these findings, we conclude that MaMYB3 negatively impacts starch degradation by directly repressing starch degradation-related genes and MabHLH6, and thereby delays banana fruit ripening. Collectively, our study expands our understanding of the complex transcriptional regulatory hierarchy modulating starch degradation during fruit ripening.