TaPGS1 Driven Flavonol Accumulation Delays Endosperm Cellularization and Enlarges Wheat Grains

Flavonols play a crucial role in seed development by regulating multiple physiological processes, including seed coat pigmentation, dormancy, fertilization, and endosperm formation. Notably, flavonols influence the polar transport of auxin, thereby affecting seed growth dynamics. In our previous work, we found that overexpression of the wheat bHLH transcription factor TaPGS1 results in increased grain size; however, the underlying mechanism remained unclear. In this study, metabolomic and transcriptomic analyses of TaPGS1 overexpressing wheat lines revealed enhanced flavonol accumulation and upregulation of key flavonol biosynthetic genes. Further investigations suggested that flavonol accumulation in the seed coat may disrupt auxin transport, leading to localized auxin buildup, delayed endosperm cellularization, and an increase in endosperm cell number. These changes collectively contribute to grain enlargement. Our findings uncover a TaPGS1 flavonol regulatory module that links auxin distribution to endosperm development and seed size control in wheat.