Figure 2.

Diurnal oscillations of poplar genes showing height-associated SNPs serve to unravel potential regulators of the photoperiodic control of shoot apical growth. (A) Clusters of poplar genes showing height-associated SNPs based on the phase of peak expression from the diurnal expression database. A total of 12 clusters were obtained covering the 24 h of the day and grouping phases every 2 h starting at cluster 1 (including phases 0 and 1). The central circadian circle shows the temporal succession of the clusters including identified poplar orthologs of known Arabidopsis flowering time regulators. (B) List of poplar genes orthologous to Arabidopsis flowering time regulators. Arabidopsis mutations in these genes gave rise to altered expression levels of FT. Poplar and Arabidopsis expression phases are shown (12:12 h light/dark, LDHC, cutoff 0.8). (C) Schematic representation of the leaf-localized photoperiod measurement mechanism in poplar. (1) Photosensory pathway, (2) circadian clock system, and (3) mobile photoperiodic mediator signal. (D) Schematic representation of poplar known and predicted photoperiod measurement components. Continuous lines represent experimentally supported links in poplar. Dashed lines represent experimentally supported links in Arabidopsis.