Jing Bin

Nuclear Factor Y (NF-Y) is a class of heterotrimeric transcription factors composed of three subunits: NF-A, NF-YB, and NF-YC. NF-YC family members play crucial roles in various developmental processes, particularly in the regulation of flowering time. However, their functions in petunia remain poorly understood. In this study, we isolated four PhNF-YC genes from petunia and confirmed their subcellular localization in both the nucleus and cytoplasm. We analyzed the transcript abundance of all four PhNF-YC genes and found that PhNF-YC2 and PhNF-YC4 were highly expressed in apical buds and leaves, with their transcript levels decreasing before flower bud differentiation. Silencing PhNF-YC2 using VIGS resulted in a delayed flowering time and reduced chlorophyll content, while PhNF-YC4-silenced plants only exhibited a delayed flowering time. Furthermore, we detected the transcript abundance of flowering-related genes involved in different signaling pathways and found that PhCO, PhGI, PhFBP21, PhGA20ox4, and PhSPL9b were regulated by both PhNF-YC2 and PhNF-YC4. Additionally, the transcript abundance of PhSPL2, PhSPL3, and PhSPL4 increased only in PhNF-YC2-silenced plants. Overall, these results provide evidence that PhNF-YC2 and PhNF-YC4 negatively regulate flowering time in petunia by modulating a series of flowering-related genes.

Nuclear Factor Y, Subunit C (NF-YC) transcription factors are conserved in most plants, and play essential roles in plant growth and development, especially in flowering regulation. Chrysanthemums are important commercial plants, and their market value is strongly impacted by flowering time. Until now, no details regarding the NF-YC family in the Chrysanthemum genus have been available. In this study, five NF-YC genes were cloned from Chrysanthemum indicum. Multiple alignments showed that CiNF-YCs had the highly conserved characteristic regions. Phylogenetic analyses identified a pair of paralogue NF-YC proteins in chrysanthemums. Gene structure and conserved motifs were also analyzed for functional understanding. According to the results of the expression experiments, CiNF-YC1 and CiNF-YC5 were mainly expressed in leaves or flowers, and their expression levels varied greatly from the seedling to flower bud differentiation stage. Arabidopsis overexpressing CiNF-YC1 and CiNF-YC3 showed significantly delayed flowering, accompanied by other morphological alterations. RT-qPCR analysis revealed that genes associated with photoperiod, vernalization, aging, and gibberellin pathways were downregulated in CiNF-YC1-OX lines, relative to the wild type, whereas in CiNF-YC3-OX lines, only SHORT VEGETATIVE PHASE (AtSVP), the key factor in the ambient temperature pathway, was upregulated. Taken together, these findings suggest that CiNF-YC1 and CiNF-YC3 negatively regulate flowering in Arabidopsis via different flowering pathways.