Structural basis for the dual roles of DPW in lipid and UDP-sugar metabolism during rice anther development

Fatty acids and uridine diphosphate (UDP)-sugars are essential metabolites involved in the biosynthesis of polysaccharides and lipids, both of which are critical for anther development in plants. Our previous study identified Defective Pollen Wall (DPW), a rice fatty acyl carrier protein reductase (FAR), as a key factor in pollen wall formation. In this study, we demonstrate that the structure of DPW in complex with its cofactor NADP⁺ exhibits structural similarities to that of UDP-glucose epimerase (UGE). In vitro enzymatic assays utilizing recombinant DPW confirmed its ability to interconvert UDP-glucose (UDP-Glc) and UDP-galactose (UDP-Gal) in an NADP(H)-dependent manner. Mutations in conserved NADP(H)-binding residues abolished both DPW's FAR and UGE activities. In vivo assays showed that the dpw mutation causes UDP-Glc accumulation, disrupting the balance between UDP-Glc and UDP-Gal in rice anthers. Taken together, our findings provide insights into the dual roles of DPW in lipid and UDP-sugar metabolism during rice anther development, shedding light on how plants integrate metabolic pathways through multifunctional enzymes to regulate male reproductive development.