Late flowering in chrysanthemum induced by low ambient temperature is mediated by FLOWERING LOCUS C - like

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 FLOWERING LOCUS C-like (CmFLC-like), a representative low ambient temperature-responsive factor induced in Chrysanthemum leaves and shoot apical meristems at 15 °C. Subsequently, CmFLC-like localized to the cell nucleus and membrane and functioned as a transcriptional repressor. Overexpression of CmFLC-like increased plants sensitivity 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 APETALA2 genes. Subsequent examination revealed that the orchestrated repression of CmAFL1 and FLOWERING LOCUS T-like 3 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 of flowering in Chrysanthemum, and highlights the essential role of CmFLC-like proteins in the thermosensory pathway.