Identification of ZmNF-YC2 and its regulatory network in maize flowering time.

Flowering time is an important agronomic trait that determines the distribution and adaptation of plants. The accurate prediction of flowering time in elite germplasm is very critical for maize breeding. However, the molecular mechanisms underlying photoperiod response remain elusive in maize. Here we cloned the flowering time controlling gene, ZmNF-YC2, by map-based cloning and confirmed that ZmNF-YC2 is the protein of nuclear transcription factor Y subunit C-2 and a positive regulator of flowering time in maize under long-day conditions. Our results show that ZmNF-YC2 promotes the expression of ZmNF-YA3. ZmNF-YA3 negatively regulates the transcription of ZmAP2. ZmAP2 suppresses the expression of ZMM4 to delay flowering time. Then we developed a gene regulatory model of flowering time in maize using ZmNF-YC2, ZmNF-YA3, ZmAP2, ZMM4 and other key genes. The cascading regulation of ZmNF-YC2 on maize flowering time has not been reported in other species.