背景回顾：In temperate and boreal regions, perennials adapt their annual growth cycle to the change of seasons. These adaptations ensure survival in harsh environmental conditions, allowing growth at different latitudes and altitudes, and are therefore tightly regulated. Populus tree species cease growth and form terminal buds in autumn when photoperiod falls below a certain threshold. This is followed by establishment of dormancy and cold hardiness over the winter. At the center of the photoperiodic pathway in Populus is the gene FLOWERING LOCUS T2 (FT2), which is expressed during summer and harbors significant SNPs in its locus associated with timing of bud set. The paralogous gene FT1, on the other hand, is hyper-induced in chilling buds during winter. Even though its function is so far unknown, it has been suggested to be involved in the regulation of flowering and the release of winter dormancy. 

主要发现：In this study, we employ CRISPR-Cas9-mediated gene editing to individually study the function of the FT-like genes in Populus trees. 

结果：We show that while FT2 is required for vegetative growth during spring and summer and regulates the entry into dormancy, expression of FT1 is absolutely required for bud flush in spring. Gene expression profiling suggests that this function of FT1 is linked to the release of winter dormancy rather than to the regulation of bud flush per se. 

结论：These data show how FT duplication and sub-functionalization have allowed Populus trees to regulate two completely different and major developmental control points during the yearly growth cycle.

 摘 要 

在温带和北方地区，多年生植物会根据季节的变化调整年生长周期。植物的这种适应能力保证其在恶劣环境条件下的生存，使得其能够在不同的纬度和经度区域生长，因此也受到了十分严格的调控。当秋季的光周期低于一定的阈值后，杨属物种会停止生长并形成顶芽。随后，杨属植物在整个冬季保持休眠状态，并具备较强的耐寒性。杨属光周期通路的核心基因是FT2，该基因在夏季表达，并且在其与封顶时间变异相关的位点上存在丰富的SNPs。另一方面，其旁系同源基因FT1在冬季寒冷的芽中受到高诱导表达。尽管这些基因具体的功能还不清楚，但是其被认为参与了开花的调控以及冬季休眠的解除。本文中，作者利用CRISPR/Cas9技术介导的基因编辑技术单独研究了杨属中FT-like基因的功能。作者发现，FT2作用于杨属植物在春夏两季的营养生长，并且调控杨属植物进入休眠，而FT1则作用于杨属植物在春季的芽萌发。基因表达谱显示，FT1基因的这一功能与冬季休眠的解除更加相关，而非芽萌发本身的调控。本文的研究结果揭示了FT基因的复制及亚功能化使得杨树能够调控两个完全不同，但又是年生长周期中最为重要的两个发育控制点。

 Ove Nilsson