The TFL2-BZIP43-ERF21 module mediated regulation of seasonal growth in Pinus tabuliformis

As perennial evergreen non-deciduous plants, conifer face severe challenges from cold and drought stresses during autumn and winter. Understanding how conifers balance growth and stress responses is crucial for forest conservation and tree genetic improvement under climate change. While TFL2 has been identified as a core regulatory factor mediating dormancy with distinct seasonal rhythmic expression in conifers, its downstream regulatory mechanisms remain largely unknown. Here, we systematically screened the TFL2 interactome via Y2H-seq at the whole-transcriptome scale, identifying 448 non-redundant interacting proteins, including 76 transcription factors (TFs) and 16 transcriptional regulators (TRs). Among these, PtbZIP43 and PtERF21 were confirmed as direct interactors of PtTFL2, displaying temporal expression patterns highly correlated with PtTFL2, peaking sequentially in autumn. This hierarchy forms a PtTFL2-PtbZIP43-PtERF21 cascade module that binds to downstream gene promoters to regulate seasonal growth transitions. Overexpression of the PtTFL2, PtbZIP43 and PtERF21 significantly delayed flowering time while enhancing resistance to cold and drought stresses of transgenic plants. These findings demonstrate that the PtTFL2-PtbZIP43-PtERF21 module enhancing conifer tolerance to autumn/winter stresses by coordinates growth and stress responses. This study elucidates a hierarchical transcriptional network integrating seasonal cues with stress adaptation in conifers, offering targets for genetic improvement of forest tree resilience.