Southern blot analysis. Genomic DNA was digested with the following restriction enzymes: SalI (lane 1), XhoI (lane 2), XbaI (lane 3), ClaI (lane 4), and BamHI (lane 5). Complete cDNA of gtt1 was used as a probe. Single bands were detected, unless enzymes which cut the gtt1 sequence were used, such as SalI and XhoI.