Regulation of the transition from active growth to dormancy in white spruce trees

北温带森林树种将其年度生长周期与当地环境条件同步的能力对该物种的长期可持续性至关重要。芽形成的时间和向休眠的过渡是适应性特征，代表了获得抗寒性和活跃生长持续时间之间的权衡，而活跃生长是生产力的决定因素。由于秋季物候转换只能在多年生植物中进行研究，我们对芽形成、生长停止、冷驯化和休眠获得等过程的分子事件知之甚少。 我的研究的长期目标是描绘在一种具有重要经济和环境意义的针叶树--白云杉--从活跃生长到休眠转变过程中发生的分子事件，并了解这些过程是如何受到日长和温度的调节的。对白云杉秋季物候转变的机械性理解可以为树木改良和保护计划提供信息，特别是在面对预测的气候变化情景时。基于最近的研究进展，我提出了四个目标。(1)确定日长和温度如何调节秋季物候转换。我们将测试特定的日长和温度控制芽的发育、生长停止、储备积累、冷驯化和芽、茎和根的休眠获得的假设。(2)识别休眠生物标志物。目前，确定一棵树是否处于休眠状态的唯一方法是评估在有利条件下的再生。为了克服这一局限，我们将发现其表达模式与休眠状态相关的基因。(3)通过基因功能鉴定发现秋季物候转换的调控因子。我们利用基因组学来确定白云杉花芽发育的候选调控因子，我们发现与拟南芥开花调节因子类似的白云杉转录因子可能调控白云杉的花芽形成。我们建议描述我们假设调控芽形成和休眠获得的其他候选调控因子。(4)构建调控秋季物候转换的转录网络。我们将使用我们发现的调控芽形成或休眠获得的转录因子来发现调节其表达的新转录因子，建立调节白云杉活动-休眠转换的调控网络。 研究成果将在分子、细胞和整个植物尺度上为白云杉秋季物候转换过程中发生的事件提供机械性的见解。这一新知识将有助于推动该领域从观察物候模式转向了解物候过程，为旨在提高森林弹性的管理实践提供信息。

The ability of north-temperate forest tree species to synchronize their annual growth cycle to local environmental conditions is critical for long term persistence of the species. Timing of bud formation and transition to dormancy are adaptive traits that represent a trade-off between acquisition of winter hardiness and duration of active growth, which is a determinant of productivity. Because autumnal phenology transitions can only be studied in perennial plants, we know surprisingly little about molecular events that underpin processes such as bud formation, growth cessation, cold acclimation and dormancy acquisition. The long term goals of my research are to delineate molecular events that occur during the transition from active growth to dormancy in an economically and environmentally important conifer, white spruce, and to understand how these processes are regulated by daylength and temperature. A mechanistic understanding of autumnal phenology transitions in white spruce can inform tree improvement and conservation programs, particularly in the face of predicted climate change scenarios. I propose four objectives that build upon recent research progress. (1) Determine how day length and temperature regulate autumnal phenology transitions. We will test the hypotheses that specific day lengths and temperatures govern bud development, growth cessation, reserve accumulation, cold acclimation and dormancy acquisition in buds, stems and roots. (2) Identify dormancy biomarkers. Currently, the only method to determine whether a tree is dormant is to assess regrowth under favorable conditions. To overcome this limitation, we will discover genes whose expression patterns correlate with dormancy status. (3) Discover regulators of autumnal phenology transitions through gene functional characterization. We used genomics to identify candidate regulators of white spruce bud development, and we showed that white spruce transcription factors similar to Arabidopsis flowering regulators may regulate bud formation in white spruce. We propose to characterize other candidate regulators that we hypothesize regulate bud formation and dormancy acquisition. (4) Construct transcriptional networks regulating autumnal phenology transitions. We will use transcription factors that we discover to regulate bud formation or dormancy acquisition to uncover new transcription factors that regulate their expression, building regulatory networks that mediate activity-dormancy transition in white spruce. Research outcomes will yield mechanistic insights for events that are invoked during autumnal phenology transition in white spruce at molecular, cellular and whole plant scales. This new knowledge will help move the field from observation of phenology patterns to understanding of phenology processes, informing management practices that aim to enhance resiliency of our forests.