옥수수 5-methyltryptophan 저항성 돌연변이주(MR1)의 Anthranilate Synthetase 특성

5-methyltryptophan(5MT) resistant mutant plants (MR1) were analyzed for characterization of anthranilate synthetase (AS) and tryptophan synthetase (TS) enzymes. The enzyme was measured in crude extracts from MR1 and control seedlings of Danggin inbred line. There was no significant difference in the level of AS between MRl and control seedlings when grown on MS medium without 5MT. However, MRl seedlings grown on MS medium with 25mg/L 5MT showed the level of AS twice higher than that of control seedlings. The activity of AS was inhibited to 50% in untreated plants when 4mg/L L-tryptophan was added to their extracts. Extracts from MRl plants required about four times higher concentration of amino acid to cause equal inhibition. In the TS assay, the activity observed in MRl seedlings was four times higher than that of control seedlings. We have also isolated and sequenced the gene which encoding the tryptophan synthetase B subunit (TSB) from maize. The gene encodes polypeptides with high homology to TSB isolated from other plants, and is expressed in all the developmental stages examined. Northern hybridization analysis indicated that the gene expression in MRl seedlings grown on MS medium showed a higher level than in control seedlings.