Suppressors of an Arabinose-Sensitive Mutant ofArabidopsis thaliana

Studies of an arabinose-sensitive mutant, ara1-1, of Arabidopsis thaliana, which has reduced arabinose kinase activity, are reviewed. Further studies describe the isolation of suppressor mutations of the arabinose-sensitive phenotype. Neither the ability to metabolise arabinose nor arabinose kinase activity is restored in these suppressed mutants, demonstrating that they are not true revertants. In contrast, in a number of suppressor mutants the ability to metabolise arabinose is further reduced and, in one case, arabinose kinase activity is also further reduced. This observation and genetic studies which show the suppressor mutations are closely linked to the original ara1-1 mutation indicate that both these mutations lie in the same gene. A likely explanation for these observations is that the suppressor mutations block the transport of arabinose into the cell. This suggests a direct or indirect role for the ARA1 gene product in arabinose transport. Further mapping studies of the ARA1 locus are described.