Gene structure and allele verification. A, AtSS2 gene map. The scaled linear map depicts the eight exons as black boxes and the seven introns as lines between the exons. The positions of the translational start and stop codons are noted. The locations of specific primer sequences used for PCR amplification are noted, as well as the locations of three T-DNA insertions in the gene. B, RT-PCR analysis of transcripts from the Atss2-3 mutant. Total RNA from leaves of WS wild type plants or the Atss2-3 mutant was amplified by RT-PCR using the indicated primer pairs. C, Immunoblot analysis. Total soluble proteins from crude leaf extracts were separated by anion exchange chromatography, then selected fractions were separated by SDS-PAGE and subjected to immunoblot analysis using anti-AtSSII antibody.