Figure 1.

The gpa7 mutant has a defect in storage protein transport to the PSV. A and B, Comparison of representative WT and gpa7 dry seeds. Bars, 1 mm. C, Scanning electron microscopy images of transverse sections of WT and gpa7 grains. Bars, 10 μm. D, Protein profiles of WT and gpa7 dry seeds on SDS–PAGE gels stained by Coomassie blue. pGT, 57-kDa proglutelins; αGT, 40-kDa glutelin acidic subunits; αGlb, 26-kDa α-globulin; βGT, 20-kDa glutelin basic subunits; Pro, prolamins. E, Immunoblot analysis of storage proteins in WT and gpa7 dry seeds with anti-glutelin acidic subunits and anti-α-globulin antibodies. Arrowhead denotes 57-kDa proglutelins, while arrow indicates glutelin acidic subunits. F, Immunoblot analysis of WT and gpa7 dry seeds with anti-molecular chaperone (BIP1 and PDI1-1) antibodies. Anti-EF1-α antibodies were used as a loading control in (E) and (F). G, Images of WT and gpa7 seedlings grown for 5 d on half strength MS medium. Bar, 1 cm. H, Light microscopy observation of WT and gpa7 grain sections stained with Coomassie blue. Black and red arrowheads indicate irregularly shaped PBIIs and round-shaped PBIs. SG, starch grains. Bars, 5 μm. I, Immunofluorescence microscopy images showing the distribution of glutelins and prolamins in WT and gpa7 developing subaleurone cells. Secondary antibodies conjugated with Alexa fluor 488 (green) and Alexa fluor 555 (red) were used to trace the antigens recognized by the anti-glutelin acidic subunits and anti-prolamin antibodies. Arrows indicate PBIs, while arrowheads indicate PBIIs. PMB structures are indicated by asterisks. Bars, 5 μm. J and K, Measurement of the diameters of PBIIs (J) and PBIs (K). Values are means ± sd. Asterisks indicate the statistical significance between the WT and gpa7 values, as determined by Student’s t test (**P < 0.01; n > 300).