<i>BRITTLE PLANT1</i> is required for normal cell wall composition and mechanical strength in rice

A series of nucleotide sugar interconversion enzymes (NSEs) generate the activated donors required for biosynthesis cell wall matrix polysaccharides and glycoproteins. UDP-glucose 4-epimerases (UGEs) are NSEs that function in (UDP-Glc) UDP-galactose (UDP-Gal). The roles monocots remain unclear due to redundancy pathways. Here, we report a brittle plant (bp1) rice mutant exhibits leaves culms at all growth stages. had reduced levels rhamnogalacturonan I, homogalacturonan, arabinogalactan proteins. Moreover, altered contents uronic acids, neutral noncellulosic monosaccharides, cellulose. Map-based cloning demonstrated OsBP1 encodes 4-epimerase (OsUGE2), cytosolic protein. We also show BP1 can form homo- hetero-protein complexes with other UGE family members transporters 2 (OsUGT2) 3 (OsUGT3), which may facilitate channeling Gal proteoglycans. Our results demonstrate participates regulating composition structure walls.