MOLECULAR CHARACTERIZATION OF DUPLICATE CYTOSOLIC PHOSPHOGLUCOSE ISOMERASE GENES IN CLARKIA AND COMPARISON TO THE SINGLE-GENE IN ARABIDOPSIS

The nucleotide sequence of PgiC1-a which encodes a cytosolic isozyme o f phosphoglucose isomerase (PGIC; EC 5.3.1.9) in Clarkia lewisii, a wi ldflower native to California, is described and compared to the previo usly published sequence of the duplicate PgiC2-a from the same genome. Both genes have the same structure of 23 exons and 22 introns located in identical positions, and they encode proteins of 569 amino acids. Exon and inferred protein sequences of the two genes are 96.4% and 97. 2% identical, respectively. Intron sequences are 88.2% identical. The high nucleotide similarity of the two genes is consistent with previou s genetic and biosystematic findings that suggest the duplication aros e within Clarkia. A partial sequence of PgiC2-b was also obtained. It is 99.5% identical to PgiC2-a in exons and 99.7% in introns. The nucle otide sequence of the single PgiC from Arabidopsis thaliana was also d etermined for comparison to the Clarkia genes. The A. thaliana PgiC ha s 21 introns located at positions identical to those in Clarkia PgiC1 and PgiC2, but lacks the intron that divides Clarkia exons 21 and 22. The A. thaliana PGIC protein is shorter, with 560 amino acids, and dif fers by about 17% from the Clarkia PGICs. The PgiC in A. thaliana was mapped to a site 20 cM from restriction fragment length polymorphism m arker 331 on chromosome 5.