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Summary: The domestication gene Q is largely responsible for the widespread cultivation of wheat because it confers multiple domestication traits. However, the underlying molecular mechanisms of how Q regulates these domestication traits remain unclear.In this study, we identify a Q‐interacting protein TaLAX1, a basic helix–loop–helix transcription factor, through yeast two‐hybrid assays. Using biochemical and genetic approaches, we explore the roles of TaLAX1 in regulating wheat domestication traits.Overexpression of TaLAX1 produces phenotypes, reminiscent of the q allele; loss‐of‐function Talax1 mutations confer compact spikes, largely similar to the Q‐overexpression wheat lines. The two transcription factors TaLAX1 and Q disturb each other's activity to antagonistically regulate the expression of the lignin biosynthesis‐related gene TaKNAT7‐4D. More interestingly, a natural variation (InDel, +/− TATA), which occurs in the promoter of TaLAX1, is associated with the promoter activity difference between the D subgenome of bread wheat and its ancestor Aegilops tauschii accession T093.This study reveals that the transcription factor TaLAX1 physically interacts with Q to antagonistically regulate wheat domestication traits and a natural variation (InDel, +/− TATA) is associated with the diversification of TaLAX1 promoter activity. [ABSTRACT FROM AUTHOR]