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

北温带森林树种的年生长周期与当地环境条件同步的能力对物种的长期持久性至关重要。芽形成的时间和向休眠的过渡是一种适应性性状，代表了冬寒性的获得和积极生长的持续时间之间的权衡，这是生产力的决定因素。由于秋季物候变化只能在多年生植物中进行研究，我们对诸如芽形成、生长停止、冷驯化和休眠获取等过程的分子事件知之甚少。***我研究的长期目标是描述在经济和环境重要的针叶树，白云杉中从活跃生长到休眠的转变过程中发生的分子事件，并了解这些过程是如何受白昼长度和温度调节的。对白云杉秋季物候变化的机制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变化。我们将测试特定的白天长度和温度控制芽发育、生长停止、储备积累、冷驯化和芽、茎和根的休眠获取的假设。(2)确定休眠生物标志物。目前，确定树木是否休眠的唯一方法是评估有利条件下的再生情况。为了克服这一限制，我们将发现其表达模式与休眠状态相关的基因。(3)通过基因功能表征，发现秋季物候转变的调控因子。我们利用基因组学方法鉴定了白云杉芽发育的候选调控因子，发现与拟南芥开花调控因子相似的白云杉转录因子可能调控白云杉芽的形成。我们建议描述其他候选调节因子，我们假设调节芽形成和休眠获得。(4)构建调控秋季物候变化的转录网络。我们将利用我们发现的调控芽形成或休眠获得的转录因子来发现新的调控其表达的转录因子，构建调节白云杉活动-休眠转变的调控网络。***研究结果将在分子、细胞和整个植物尺度上对白云杉秋季物候转变过程中所调用的事件产生机制见解。这一新知识将有助于将该领域从对物候模式的观察转向对物候过程的理解，为旨在增强森林复原力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. ********