MOLECULAR ANALYSIS AND MAPPING OF 2 GENES ENCODING MAIZE GLUTATHIONE S-TRANSFERASES (GST-I AND GST-II)

Maize glutathione S-transferase (GST) isozymes are encoded by a gene f amily comprising at least five genes, three of which (Gst I, II and II I) have recently been isolated and sequenced. The enzymes are active a s homo or heterodimers and exhibit intraspecific polymorphism includin g a ''null'' variant for the two major isoforms expressed in roots. No rthern blot analyses performed on total root RNA from ''null'' and ''p lus'' genotypes, using Gst I- and Gst II-specific probes, indicated th at the Gst I gene controls the expression of the two major GST isoform s expressed in roots. Gst I and Gst II were mapped by RFLP analysis us ing an F-2 population of 149 individuals previously characterized. Gst I was localized on the long arm of chromosome 8, while two putative G st II loci were mapped to chromosomes 8 (70 cM from Gst I) and 10, res pectively.