The wheat transcription factor Q functions in gibberellin biosynthesis and signaling and regulates height and spike length
Pan Liu, Shulin Xue, Jizeng Jia, Guangyao Zhao, Jie Liu, Yilong Hu, Cuizheng Kong, Dong Yan, Huan Wang, Liu Xu, Zefu Lu, Lifeng Gao
Abstract
The Q gene is a key domestication gene in wheat (Triticum aestivum) that regulates free-threshing habit, spike morphology, height, and other critical agronomic traits. However, the precise molecular mechanisms underlying its function remain unclear. In this study, we identified a Q allele with a missense mutation (G to A) in the fifth exon of the Q gene, resulting in reduced plant height and spike length. Further investigation revealed that this mutation causes a Gly-229-Ser amino acid substitution, which enhances Q protein stability. Furthermore, we discovered that Q directly binds to the promoter region of Gibberellin 3-oxidase 2 gene (TaGA3ox2) and represses its expression. Moreover, Q interacts with both REDUCED HEIGHT1 (RHT1) and GIBBERELLIN INSENSITIVE 2 (TaGID2), which may disrupt GID2-triggered RHT1 degradation. Collectively, these findings reveal the dual roles of Q in regulating both GA biosynthesis and signaling, providing insights into the molecular mechanisms through which Q modulates plant height and spike length in wheat.