The study aimed to identify the wheat vernalization gene VRN1, which controls the flowering response in winter wheat. Using 6,190 gametes, the researchers found VRN1 to be linked to MADS-box genes AP1 and AGL1G, flanked by genes Cysteine and Cytochrome B5. The wheat AP1 and AGL1G genes were similar to Arabidopsis meristem identity genes AP1 and AGL2, respectively. AP1 transcription was regulated by vernalization in both apices and leaves, with the progressive increase in AP1 transcription consistent with the progressive effect of vernalization on flowering time. Vernalization was required for AP1 transcription in apices and leaves in winter wheat but not in spring wheat. AGL1G transcripts were detected during spike differentiation but not in vernalized apices or leaves, suggesting that AP1 acts upstream of AGL1G. No differences were found between genotypes with different VRN1 alleles in the coding regions of AP1 and AGL1G, but three independent deletions were found in the promoter region of AP1. These results suggest that AP1 is a better candidate for VRN1 than AGL1G. The epistatic interactions between VRN1 and VRN2 genes were also studied, leading to a model where VRN2 represses AP1 expression directly or indirectly. The model explains the evolution of vernalization requirements in Triticaceae species and the recurrent occurrence of dominant spring growth habit alleles.The study aimed to identify the wheat vernalization gene VRN1, which controls the flowering response in winter wheat. Using 6,190 gametes, the researchers found VRN1 to be linked to MADS-box genes AP1 and AGL1G, flanked by genes Cysteine and Cytochrome B5. The wheat AP1 and AGL1G genes were similar to Arabidopsis meristem identity genes AP1 and AGL2, respectively. AP1 transcription was regulated by vernalization in both apices and leaves, with the progressive increase in AP1 transcription consistent with the progressive effect of vernalization on flowering time. Vernalization was required for AP1 transcription in apices and leaves in winter wheat but not in spring wheat. AGL1G transcripts were detected during spike differentiation but not in vernalized apices or leaves, suggesting that AP1 acts upstream of AGL1G. No differences were found between genotypes with different VRN1 alleles in the coding regions of AP1 and AGL1G, but three independent deletions were found in the promoter region of AP1. These results suggest that AP1 is a better candidate for VRN1 than AGL1G. The epistatic interactions between VRN1 and VRN2 genes were also studied, leading to a model where VRN2 represses AP1 expression directly or indirectly. The model explains the evolution of vernalization requirements in Triticaceae species and the recurrent occurrence of dominant spring growth habit alleles.