Figure 3.

Genetic and physical characterization of the VTC1 locus. (A) VTC1 was mapped to a position on chromosome 2, 0.9 cM centromere distal from cleaved amplified polymorphic sequence (CAPS) marker m429, placing it within a sequenced region of the genome. (B) A gene encoding a putative GDP-mannose pyrophosphorylase is located on the 92-kb BAC T5I7 at the centromere proximal end of this contig. The relative map positions of the VTC1 locus and a second genetically identified locus, TOPP4, on BAC T5I7 are shown. (C) The ≈3.4-kb ClaI–HindIII fragment from this BAC used to complement the vtc1-1 mutation by Agrobacterium-mediated transformation. The location of oligonucleotide primers used to amplify the VTC1 locus from vtc1-1 and vtc1-2 genomic DNA for sequence analysis are indicated with arrows. (D) The structure of the VTC1 transcribed region is shown along with the nucleotide substitution in vtc1-1 and vtc1-2; unshaded rectangles, noncoding sequences present in the VTC1 cDNA; shaded rectangles, exons encoding the GDP-mannose pyrophosphorylase; thin lines, the location of intron sequences.