Dehydrogenase WRD1 regulates plant growth by modulating cell wall formation, ROS homeostasis, and auxin signaling in rice.

Nucleotide sugars serve as the substrates for the biosynthesis of cell wall polysaccharides. Although the enzymes such as uridine diphosphate (UDP)-glucose dehydrogenase (UGD) involved in nucleotide sugar biosynthesis have been biochemically characterized, their biological roles in plants remain largely unexplored. In this study, we identify a rice mutant weakness and root hair defective 1 (wrd1), which exhibits pleiotropic phenotypes including dwarfism, reduced tiller number, and abnormal root architecture. WRD1 encodes a UGD that catalyzes the conversion of UDP-Glc to UDP-GlcA. The WRD1 mutation disrupts this enzymatic function and substantially reduces UGD activity in vivo, resulting in elevated UDP-Glc accumulation, decreased UDP-GlcA levels, and consequently an imbalance in their downstream derivatives. The aberrant UDP-sugar metabolism significantly impairs cell wall architecture and auxin glycosylation in the wrd1 mutant, accompanied by dysregulated reactive oxygen species (ROS) homeostasis and auxin-related gene expression. These combined effects lead to excessive ROS production and abnormal auxin signaling in root cells, resulting in programmed cell death and severe developmental defects. Our findings highlight the critical role of WRD1 in regulating cell wall formation and overall plant growth by modulating nucleotide sugars homeostasis, which provides new insights into the interplay between cell wall biosynthesis, auxin signaling, and ROS metabolism during plant development.