State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, Shandong, People's Republic of China.
Plant Mol Biol. 2014 Aug;85(6):627-38. doi: 10.1007/s11103-014-0207-8. Epub 2014 Jun 4.
Volatile esters are major factors affecting the aroma of apple fruits, and alcohol acyltransferases (AATs) are key enzymes involved in the last steps of ester biosynthesis. The expression of apple AAT (MdAAT2) is known to be induced by salicylic acid (SA) or ethylene in apple fruits, although the mechanism of its transcriptional regulation remains elusive. In this study, we reveal that two apple transcription factors (TFs), MdMYB1 and MdMYB6, are involved in MdAAT2 promoter response to SA and ethylene in transgenic tobacco. According to electrophoretic mobility shift assays, MdMYB1 or MdMYB6 can directly bind in vitro to MYB binding sites in the MdAAT2 promoter. In vivo, overexpression of the two MYB TFs can greatly enhance MdAAT2 promoter activity, as demonstrated by dual luciferase reporter assays in transgenic tobacco. In contrast to the promoter of MdMYB1 or MdMYB6, the MdAAT2 promoter cannot be induced by SA or ethephon (ETH) in transgenic tobacco, even in stigmas in which the MdAAT2 promoter can be highly induced under normal conditions. However, the induced MYB TFs can dramatically enhance MdAAT2 promoter activity under SA or ETH treatment. We conclude that MdMYB1 and MdMYB6 function in MdAAT2 responses to SA and ethylene in transgenic tobacco, suggesting that a similar regulation mechanism may exist in apple.
挥发性酯类是影响苹果果实香气的主要因素，而醇酰基转移酶（AATs）是参与酯类生物合成最后步骤的关键酶。已知苹果 AAT（MdAAT2）的表达受苹果果实中水杨酸（SA）或乙烯的诱导，尽管其转录调控机制仍不清楚。在本研究中，我们揭示了两个苹果转录因子（TFs），MdMYB1 和 MdMYB6，参与了 SA 和乙烯在转基因烟草中对 MdAAT2 启动子的响应。根据电泳迁移率变动分析，MdMYB1 或 MdMYB6 可以直接在体外与 MdAAT2 启动子中的 MYB 结合位点结合。在体内，通过双荧光素酶报告基因检测在转基因烟草中，两个 MYB TFs 的过表达可以极大地增强 MdAAT2 启动子活性。与 MdMYB1 或 MdMYB6 的启动子不同，SA 或乙烯（ETH）不能在转基因烟草中诱导 MdAAT2 启动子，即使在正常条件下 MdAAT2 启动子可以在柱头中被高度诱导的情况下也是如此。然而，诱导的 MYB TFs 可以在 SA 或 ETH 处理下显著增强 MdAAT2 启动子活性。我们得出结论，MdMYB1 和 MdMYB6 在转基因烟草中参与了 MdAAT2 对 SA 和乙烯的响应，这表明在苹果中可能存在类似的调控机制。
