The double mutations in SYP31 and SYP32 cause pollen abortion. A, Schematic diagram of the SYP31 and SYP32 gene structures and T-DNA insertion sites. Black boxes represent exons. Gray lines represent introns. White boxes represent untranslated regions (UTRs). Triangles indicate T-DNA insertion sites. B, Alexander staining of MP. Arrows indicate aborted pollen. C, Statistical analysis of abnormal pollen from WT and indicated mutants (n > 500 pollen from three individual plants was counted for each line), values represent the means SD. D, Quartets from the syp31/+ syp32/+ qrt1/− triple mutant lines. Arrowheads indicate deformed pollen. Bars = 10 μm in (B) and (D).