Component of the NF-Y/HAP transcription factor complex (By similarity). The NF-Y complex stimulates the transcription of various genes by recognizing and binding to a CCAAT motif in promoters (By similarity). Promotes the expression of heat stress-inducible genes by contributing to the formation of a heat stress-specific transcriptional complex with NF-Y subunits (e.g. DPB3-1, NF-YA2 and NF-YB3) and DREB2A at the promoter of target genes, thus promoting heat tolerance (PubMed:25490919). Heterotrimeric transcription factor composed of three components, NF-YA, NF-YB and NF-YC (By similarity). NF-YB and NF-YC must interact and dimerize for NF-YA association and DNA binding (By similarity). Component of a heat stress-inducible transcriptional complex with NF-YA and NF-YB subunits made, at least, of NFYA2, NFYB3 and DPB3-1 in cooperation with DREB2A (PubMed:25490919). Binds directly with DPB3-1 (PubMed:25490919). Present in both cytoplasm and nucleus under nonstress conditions but translocates in the nucleus upon heat stress. Ubiquitous (PubMed:11250072). Expressed in seedlings, petioles, hypocotyls, reproductive organ tissues and leaves (PubMed:25490919). In seedlings, first expressed in petioles and leaf blades of the cotyledons as well as tops and bottoms of the hypocotyls. Enhanced by heat stress but repressed by dehydration stress. Belongs to the NFYB/HAP3 subunit family.