URGT1 and URGT2 are involved in pectic galactan and seed mucilage formation, respectively. (A) Ruthenium red staining of dry WT and urgt2 seeds. (Scale bar: 200 μm.) (B) Sections of dry seeds stained with toluidine blue. WT seeds accumulate more mucilage in the apoplast in comparison to the URGT2 mutant lines. c, columella; m, mucilage; rw, radial wall. (Scale bars: 25 μm.) (C) Immunolabeling of dehydrated mucilage from dry seed sections using the antibody CCRC-M36, specific to unbranched RG-I. The labeling with CCRC-M36 antibody of WT seed mucilage is stronger in comparison to urgt2 lines. (D) Monosaccharide composition of hydrolyzed soluble mucilage derived from WT, urgt2-1, and urgt2-2 dry seeds. Data represent the mean and SD of n = 4 biological replicates. (E) Monosaccharide composition of hydrolysate of endo-β1,4-galactanase digested cell wall material derived from 35Spro:URGT1 plants. Res, residue; SN, supernatant. Data are the mean and SD of n = 4 replicates. *Significantly different (t test at P < 0.05).