Laboratory of Pomology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Plant Physiol. 2011 Sep;157(1):485-97. doi: 10.1104/pp.111.181982. Epub 2011 Jul 27.
Bud endodormancy in woody plants plays an important role in their perennial growth cycles. We previously identified a MADS box gene, DORMANCY-ASSOCIATED MADS box6 (PmDAM6), expressed in the endodormant lateral buds of Japanese apricot (Prunus mume), as a candidate for the dormancy-controlling gene. In this study, we demonstrate the growth inhibitory functions of PmDAM6 by overexpressing it in transgenic poplar (Populus tremula × Populus tremuloides). Transgenic poplar plants constitutively expressing PmDAM6 showed growth cessation and terminal bud set under environmental conditions in which control transformants continued shoot tip growth, suggesting the growth inhibitory functions of PmDAM6. In the Japanese apricot genome, we identified six tandemly arrayed PmDAM genes (PmDAM1-PmDAM6) that conserve an amphiphilic repression motif, known to act as a repression domain, at the carboxyl-terminal end, suggesting that they all may act as transcriptional repressors. Seasonal expression analysis and cold treatment in autumn indicated that all PmDAMs were repressed during prolonged cold exposure and maintained at low levels until endodormancy release. Furthermore, PmDAM4 to PmDAM6 responses to a short period of cold exposure appeared to vary between low- and high-chill genotypes. In the high-chill genotype, a short period of cold exposure slightly increased PmDAM4 to PmDAM6 expression, while in the low-chill genotype, the same treatment repressed PmDAM4 to PmDAM6 expression. Furthermore, PmDAM4 to PmDAM6 expression was negatively correlated with endodormancy release. We here discuss the genotype-dependent seasonal expression patterns of PmDAMs in relation to their involvement in endodormancy and variation in chilling requirements.
木本植物的芽休眠在其多年生长周期中起着重要作用。我们之前鉴定了一个 MADS 框基因，休眠相关 MADS 框 6（PmDAM6），在日本杏（Prunus mume）的休眠侧芽中表达，作为休眠控制基因的候选基因。在这项研究中，我们通过在转基因杨树（Populus tremula × Populus tremuloides）中过表达 PmDAM6 来证明其生长抑制功能。在控制转化体继续进行茎尖生长的环境条件下，组成型表达 PmDAM6 的转基因杨树表现出生长停止和顶芽形成，表明 PmDAM6 具有生长抑制功能。在日本杏基因组中，我们鉴定了六个串联排列的 PmDAM 基因（PmDAM1-PmDAM6），它们在羧基末端保守一个亲脂性抑制基序，已知该基序作为抑制结构域起作用，表明它们都可能作为转录抑制剂起作用。季节性表达分析和秋季的冷处理表明，所有 PmDAMs 在长时间的冷暴露下均被抑制，并保持在低水平，直到休眠解除。此外，PmDAM4 到 PmDAM6 对短时间冷暴露的反应似乎在低冷和高冷基因型之间有所不同。在高冷基因型中，短时间的冷暴露略微增加了 PmDAM4 到 PmDAM6 的表达，而在低冷基因型中，相同的处理抑制了 PmDAM4 到 PmDAM6 的表达。此外，PmDAM4 到 PmDAM6 的表达与休眠解除呈负相关。我们在这里讨论了 PmDAMs 与休眠和冷需求变化相关的基因型依赖性季节性表达模式。
