BARLEY CHALCONE FLAVONONE ISOMERASE GENE: ISOLATION, COMPARATIVE SEQUENCE AND PUTATIVE MUTANT ANALYSIS

¹ Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164 USA

² Department of Genetics and Cell Biology, Washington State University, Pullman, WA 99164 USA

³ Clemson University Genomics Institute, 100 Jordan Hall, Clemson, SC 29634 USA

Chalcone flavonone isomerase (CHI; EC 5.5.1.6) is one of the key enzymes in flavonoid biosynthesis. It is responsible for converting chalcones to flavonones which serve as a precursors for many diverse compounds downstream of the methabolic pathway. Numerous physiological consequences due to blocked flavonone synthesis include UV-B sensitivity, increased susceptibility to various pathogens, growth retardation and sterility. Many barley mutants with drastically reduced flavonoid levels have been identified. Detailed biochemical analysis suggests that in some of them the CHI gene most probably is mutated (Reuber et al 1998). The CHI gene has been cloned from many plant species and shows relatively high levels of homology (50-80%). Nevertheless, attempts to isolate barley gene using partial rice cDNA and maize gDNA clones failed because of poor cross-hybridization. We isolated and sequenced a rice CHI genomic clone from cv Nipponbare BAC library and by comparing it to the maize and other available CHI gene sequences selected a highly conservative region. This region was used to isolate barley genomic clone from cv Morex BAC library. The CHI gene maps to barley chromosome 7L(5HL) subtelomeric region and rice chromosome 3. Comparative sequence analysis of monocot and dicot CHI genes as well as barley putative CHI mutant gene analysis will be presented.