Modulation of lignin and anthocyanin homeostasis by <i>GTP cyclohydrolase1</i> in maize

Maize is a key biomass resource with wide agricultural applications. Anthocyanins, potent antioxidants, offer health benefits like reducing oxidative stress. The biosynthesis of anthocyanins competes with that of lignin for shared metabolic precursors, which can lead to trade-offs in plant growth and feed quality. Higher lignin content can decrease silage digestibility, posing challenges for livestock feed. The maize brown midrib 6 (bm6) mutant, known for reduced lignin, has an unclear genetic basis. Here, we identify ZmGCH1 as the candidate gene for bm6 through fine mapping. Mutations in ZmGCH1 shift precursors from lignin to anthocyanin biosynthesis. Furthermore, we show that ZmGCH1 interacts with ZmPEBP15 to modulate chalcone synthase activity, thereby stabilizing the allocation of precursors between lignin and anthocyanin pathways. To evaluate the practical implications of our findings, we introduced the bm6 mutation into Zhengdan958 and Xianyu335. In vitro rumen digestion assays confirmed that the introduction of the bm6 mutation significantly improved silage digestibility. This discovery not only holds great potential for enhancing silage digestibility but also provides a broader strategy for optimizing maize production to better meet the increasing demands of both the food and livestock feed.