Metabolic Rewiring of the Shikimate Pathway Enables Rose-Scented Rice

Rice fragrance is a key determinant of grain quality, yet the aroma profile of cultivated rice is highly uniform and largely dominated by the popcorn-like compound 2-acetyl-1-pyrroline. Here we expanded the aromatic repertoire of rice by engineering a rose-like fragrance through reconstruction of the phenylalanine-derived 2-phenylethanol (2-PE) pathway in the endosperm. To increase phenylalanine precursor supply, we co-expressed an engineered G211R/G212S variant of the rice 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase isoform OsDHS2 (LOC_Os08g37790; mOsDHS2) with heterologous phenylacetaldehyde synthase (PAAS) and phenylacetaldehyde reductase (PAR) in the endosperm. As a result, the engineered grains accumulated up to 2014 μg/kg 2-PE, conferring a distinct rose-like aroma. Unexpectedly, metabolic rewiring also reshaped grain composition, resulting in nearly doubled soluble protein content and increased levels of several vitamin B6-related metabolites, including the active coenzyme forms pyridoxal 5'-phosphate and pyridoxamine 5'-phosphate. These findings reveal extensive associated metabolic coordination between aromatic amino acid pathways and central seed metabolism. Our work establishes a strategy for creating designer fragrances in staple crops while simultaneously improving nutritional traits, providing a versatile platform for producing high-value metabolites in cereal grains.