Anh Tuan Pham, Bai Songling, Saito Takanori, Imai Tsuyoshi, Ito Akiko, Moriguchi Takaya
NARO Institute of Fruit Tree Science, Tsukuba, Ibaraki, 305-8605 Japan.
NARO Institute of Fruit Tree Science, Tsukuba, Ibaraki, 305-8605 Japan Present address: Institute of Fruit Science, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou, Zhejiang 310058, China.
Plant Cell Physiol. 2016 May;57(5):1038-47. doi: 10.1093/pcp/pcw041. Epub 2016 Mar 3.
In the Japanese pear (Pyrus pyrifolia Nakai) 'Kosui', three developmental stages of lateral flower buds have been proposed to occur during ecodormancy to the flowering phase, i.e. rapid enlargement, sprouting and flowering. Here, we report an APETALA2/ethylene-responsive factor (AP2/ERF) transcription factor gene, named pear EARLY BUD-BREAK (PpEBB), which was highly expressed during the rapid enlargement stage occurring prior to the onset of bud break in flower buds. Gene expression analysis revealed that PpEBB expression was dramatically increased during the rapid enlargement stage in three successive growing seasons. PpEBB transcript levels peaked 1 week prior to onset of bud break in 'Kosui' potted plants treated with hydrogen cyanamide or water under forcing conditions. Chromatin immunoprecipitation-quantitative PCR showed that higher levels of active histone modifications (trimethylation of the histone H3 tail at Lys4) in the 5'-upstream and start codon regions of the PpEBB gene were associated with the induced expression level of PpEBB during the rapid enlargement stage. In addition, we provide evidence that PpEBB may interact with and regulate pear four D-type cyclin (PpCYCD3) genes during bud break in 'Kosui' lateral flower buds. PpEBB significantly increased the promoter activities of four PpCYCD3 genes in a dual-luciferase assay using tobacco leaves. Taken together, our findings uncovered aspects of the bud break regulatory mechanism in the Japanese pear and provided further evidence that the EBB family plays an important role in bud break in perennial plants.
在日本梨（Pyrus pyrifolia Nakai）‘幸水’品种中，已提出在生态休眠至开花阶段，侧花芽会经历三个发育阶段，即快速膨大、萌芽和开花。在此，我们报道了一个APETALA2/乙烯响应因子（AP2/ERF）转录因子基因，命名为梨早期萌芽（PpEBB），其在花芽萌芽开始前的快速膨大阶段高度表达。基因表达分析表明，在连续三个生长季节的快速膨大阶段，PpEBB的表达显著增加。在强制条件下用氰胺或水处理的‘幸水’盆栽植物中，PpEBB转录水平在萌芽开始前1周达到峰值。染色质免疫沉淀-定量PCR显示，PpEBB基因5'-上游和起始密码子区域较高水平的活性组蛋白修饰（组蛋白H3尾巴赖氨酸4处的三甲基化）与快速膨大阶段PpEBB的诱导表达水平相关。此外，我们提供证据表明，在‘幸水’侧花芽萌芽过程中，PpEBB可能与梨四个D型细胞周期蛋白（PpCYCD3）基因相互作用并对其进行调控。在使用烟草叶片的双荧光素酶测定中，PpEBB显著增加了四个PpCYCD3基因的启动子活性。综上所述，我们的研究结果揭示了日本梨萌芽调控机制的一些方面，并进一步证明EBB家族在多年生植物的萌芽过程中起重要作用。
