Identifying the S96 gene locus by map-based cloning. A, The S96 gene locus was closely linked to the ciw12 marker on chromosome I. B, The ACT1 coding region showing the location of the act1-6 mutation identified in line S96. Locations of the act1-1 and act1-5 mutations are also shown. Black boxes indicate exons, and lines indicate introns. C, Genotyping the S96 mutant by the fab1 CAPS and S96 dCAPS markers. D, The act1-6 mutation causes an amino acid change (A257T) in a conserved domain of the ACT1 protein, immediately adjacent to the putative glycerol-3-phosphate binding pocket motif (underlined). T-DNA, Transfer DNA; WT, wild type.