Er. Radwanski et al., CHARACTERIZATION OF TRYPTOPHAN SYNTHASE ALPHA-SUBUNIT MUTANTS OF ARABIDOPSIS-THALIANA, MGG. Molecular & general genetics, 253(3), 1996, pp. 353-361
Three mutations in the Arabidopsis thaliana gene encoding the alpha su
bunit of tryptophan synthase were isolated by selection for resistance
to 5-methylanthranilate or 5-fluoroindole, toxic analogs of tryptopha
n pathway intermediates. Plants homozygous for trp3-1 and trp3-2 are l
ight-conditional tryptophan auxotrophs, while trp3-100 is a more leaky
mutant. Genetic complementation crosses demonstrated that the three m
utations are allelic to each other, and define a new complementation g
roup. All three mutants have decreased steady-state levels of tryptoph
an synthase alpha protein, and the trp3-100 polypeptide exhibits alter
ed electrophoretic mobility. All three mutations were shown to be in t
he TSA1 (tryptophan synthase alpha subunit) structural gene by several
criteria. Firstly, the trp3-1 mutation is linked to TSA1 on the botto
m of chromosome 3. Secondly, the trp3-1 mutation was complemented when
transformed with the wild-type TSA1 gene. Finally, DNA sequence analy
sis of the TSA1 gene revealed a single transition mutation in each trp
3 mutant.