FLOWERING LOCUS C-like mediates low-ambient-temperature-induced late flowering in chrysanthemum.

The flowering time of Chrysanthemum morifolium predominantly depends on day length but is also sensitive to ambient temperature. However, the mechanisms underlying the response of chrysanthemum to ambient temperature are mainly unknown. This study identified a MADS-box transcription factor called CmFLC-like, a representative low ambient temperature-responsive factor induced in chrysanthemum leaves and shoot apical meristems at 15°C. Subsequently, CmFLC-like localizes to the cell nucleus and membrane and functions as a transcriptional repressor. CmFLC-like overexpression made plants more sensitive to low-temperature-induced late flowering, whereas the chimeric activator CmFLC-like-VP64 was less sensitive at 15°C, indicating that CmFLC-like was involved in thermosensory flowering. Transcriptome profiling of CmFLC-like transgenic plants suggested that the potential target genes for low ambient temperature-responsive CmFLC-like regulation are predominantly flowering integrators, MADS-box transcription factors, and AP2 genes. Subsequent examination revealed that the orchestrated repression of CmAFL1 and CmFTL3 by CmFLC-like was mediated by its direct binding to the CArG-box element of their promoters. This study offers novel insights into the molecular mechanisms underlying chrysanthemum flowering and highlights the essential role of CmFLC-like proteins in the thermosensory pathway.