ASR proteins (abscissic acid, stress, ripening induced) are involved in plant responses to developmental and environmental signals but their biological functions remain to be elucidated. Grape ASR gene (VvMSA) encodes a new transcription factor regulating the expression of a glucose transporter. Here, we provide evidence for some polymorphism of grape ASRs and their identification as chromosomal non-histone proteins. By the yeast two-hybrid approach, a protein partner of VvMSA is isolated and characterized as an APETALA2 domain transcription factor. Interaction of the two proteins is further demonstrated by the BiFC approach and the exclusive nuclear localization of the heterodimer is visualized.