Table_1_Time-Resolved Analysis of Candidate Gene Expression and Ambient Temperature During Bud Dormancy in Apple.XLSX

Winter dormancy – a period of low metabolic activity and no visible growth – appears as an adaptation to harsh winter conditions and can be divided into different phases. It is tightly controlled by environmental cues, with ambient temperature playing a major role. During endodormancy, a cultivar-specific amount of cold needs to be perceived, and during ecodormancy, heat hours accumulate before bud burst and anthesis in spring. Expression analysis, performed in several key fruit tree species, proved to be very useful in elucidating the molecular control of onset and release of dormancy. However, the time resolution of these experiments has been limited. Therefore, in this study, dense time-series expression analysis was conducted for 40 candidate genes involved in dormancy control, under the cool-temperate climate conditions in Dresden. Samples were taken from the cultivars ‘Pinova’ and ‘Gala,’ which differ in flowering time. The set of candidate genes included well-established dormancy genes such as DAM genes, MdFLC-like, MdICE1, MdPRE 1, and MdPIF4. Furthermore, we tested genes from dormancy-associated pathways including the brassinosteroid, gibberellic acid, abscisic acid (ABA), cytokinin response, and respiratory stress pathways. The expression patterns of well-established dormancy genes were confirmed and could be associated with specific dormancy phases. In addition, less well-known transcription factors and genes of the ABA signaling pathway showed associations with dormancy progression. The three ABA signaling genes HAB1_chr15, HAI3, and ABF2 showed a local minimum of gene expression in proximity of the endodormancy to ecodormancy transition. The number of sampling points allowed us to correlate expression values with temperature data, which revealed significant correlations of ambient temperature with the expression of the Malus domestica genes MdICE1, MdPIF4, MdFLC-like, HAB1chr15, and the type-B cytokinin response regulator BRR9. Interestingly, the slope of the linear correlation of temperature with the expression of MdPIF4 differed between cultivars. Whether the strength of inducibility of MdPIF4 expression by low temperature differs between the ‘Pinova’ and ‘Gala’ alleles needs to be tested further.

冬季休眠——指代谢活动低下且无可见生长的阶段——是植物对严酷冬季环境的适应性策略，可划分为多个不同阶段。该过程受环境信号的严格调控，其中环境温度发挥核心调控作用。在内休眠（endodormancy）阶段，植物需感知品种特异性的冷需求量；而在生态休眠（ecodormancy）阶段，则需积累暖温时数，直至春季芽萌发与开花。针对多种核心果树物种开展的表达分析，已被证实为解析休眠启动与解除的分子调控机制的有效手段，但此类实验的时间分辨率始终受限。因此，本研究在德国德累斯顿的冷温带气候条件下，针对40个参与休眠调控的候选基因开展了高密度时间序列表达分析。实验样本取自开花时间存在差异的两个苹果品种「皮诺瓦（Pinova）」与「嘎拉（Gala）」。该候选基因集包含已被广泛验证的休眠调控基因，例如DAM基因、MdFLC-like、MdICE1、MdPRE1以及MdPIF4。此外，本研究还检测了参与休眠相关通路的基因，涵盖油菜素类固醇、赤霉素、脱落酸（ABA）、细胞分裂素响应以及呼吸胁迫通路相关基因。本研究验证了已被广泛认知的休眠调控基因的表达模式，并将其与特定休眠阶段建立了关联。此外，部分此前研究较少的转录因子以及脱落酸信号通路基因，也被发现与休眠进程存在关联。三个脱落酸信号通路基因HAB1_chr15、HAI3与ABF2的表达量在内休眠向生态休眠转变的临界阶段呈现局部表达低谷。本次实验的采样点数充足，使得研究团队能够将基因表达量与温度数据进行关联分析，结果显示环境温度与苹果（Malus domestica）基因MdICE1、MdPIF4、MdFLC-like、HAB1_chr15以及B型细胞分裂素响应调节因子BRR9的表达量存在显著相关性。值得注意的是，环境温度与MdPIF4表达量之间的线性相关斜率在两个品种间存在显著差异。「皮诺瓦」与「嘎拉」两个品种的MdPIF4等位基因受低温诱导表达的强度是否存在差异，仍需后续实验进一步验证。