Institute of Fruit Tree and Tea Science, NARO, Tsukuba, Ibaraki 305-8605, Japan.
Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Zhejiang University, Hangzhou, Zhejiang 310058, China.
Plant Cell Physiol. 2017 Aug 1;58(8):1378-1390. doi: 10.1093/pcp/pcx074.
In the pear 'Kosui' (Pyrus pyrifolia Nakai), the dormancy-associated MADS-box (PpDAM1 = PpMADS13-1) gene has been reported to play an essential role in bud endodormancy. Here, we found that PpDAM1 up-regulated expression of 9-cis-epoxycarotenoid dioxygenase (PpNCED3), which is a rate-limiting gene for ABA biosynthesis. Transient assays with a dual luciferase reporter system (LUC assay) and electrophoretic mobility shift assay (EMSA) showed that PpDAM1 activated PpNCED3 expression by binding to the CArG motif in the PpNCED3 promoter. PpNCED3 expression was increased toward endodormancy release in lateral flower buds of 'Kosui', which is consistent with the induced levels of ABA, its catabolism (ABA 8'-hydroxylase) and signaling genes (type 2C protein phosphatase genes and SNF1-related protein kinase 2 genes). In addition, we found that an ABA response element (ABRE)-binding transcription factor, PpAREB1, exhibiting high expression concomitant with endodormancy release, bound to three ABRE motifs in the promoter region of PpDAM1 and negatively regulated its activity. Taken together, our results suggested a feedback regulation between PpDAM1 and the ABA metabolism and signaling pathway during endodormancy of pear. This first evidence of an interaction between a DAM and ABA biosynthesis in vitro will provide further insights into bud endodormancy regulatory mechanisms of deciduous trees including pear.
在梨品种‘Kosui’（Pyrus pyrifolia Nakai）中，休眠相关的 MADS-box（PpDAM1= PpMADS13-1）基因已被报道在芽休眠中起重要作用。在这里，我们发现 PpDAM1 上调了 9-顺式-环氧类胡萝卜素双加氧酶（PpNCED3）的表达，PpNCED3 是 ABA 生物合成的限速基因。双荧光素酶报告系统（LUC 测定）和电泳迁移率变动分析（EMSA）的瞬时测定表明，PpDAM1 通过结合 PpNCED3 启动子中的 CArG 基序来激活 PpNCED3 的表达。PpNCED3 的表达在‘Kosui’侧芽的休眠解除过程中增加，这与 ABA、其代谢物（ABA 8'-羟化酶）和信号基因（2C 型蛋白磷酸酶基因和 SNF1 相关蛋白激酶 2 基因）的诱导水平一致。此外，我们发现，一种 ABA 反应元件（ABRE）结合转录因子 PpAREB1，在休眠解除时表现出高水平表达，它结合 PpDAM1 启动子区域的三个 ABRE 基序，并负调控其活性。综上所述，我们的结果表明在梨芽休眠过程中，PpDAM1 与 ABA 代谢和信号通路之间存在反馈调节。这是首次在体外发现 DAM 与 ABA 生物合成之间的相互作用，将为包括梨在内的落叶树芽休眠调控机制提供进一步的见解。
