UDP-glucosyltransferase 71C4 controls the flux of phenylpropanoid metabolism to shape cotton seed development.

Seeds play a crucial role in plant reproduction, making it essential to identify genes that affect seed development. In this study, we focused on UDP-glucosyltransferase 71C4 (UGT71C4) in cotton, a member of the glycosyltransferase family that shapes seed width, length, and therefore, seed index and seed cotton yield. Overexpression of UGT71C4 results in seed enlargement due to its glycosyltransferase activity on flavonoids, which redirects metabolic flux from lignin to flavonoid metabolism. This shift promotes cell proliferation of ovule via accumulation of flavonoid glycoside, significantly enhancing seed cotton yield with the seed index increasing from 10.66 g to 11.91 g. In contrast, knockout of UGT71C4 leads to smaller seeds owing to activation of the lignin metabolism pathway, and redirection of metabolic flux back to lignin synthesis. This redirection leads to increased ectopic lignin deposition in the ovule, inhibiting ovule growth and development, and alters yield component, increasing the lint percentage from 41.42% to 43.40% but reducing the seed index from 10.66 g to 8.60 g. Our research sheds new light on seed size development and opens potential pathways for enhancing plant seed yield.