Genetical and physiological studies of an auxin resistant mutant of Arabidopsis thaliana
The genetical and physiological characterisation of an auxin-resistant mutant (aux-1) of Arabidopsis thaliana has been completed.aux-1 exhibits segregation ratios typical of a single recessive gene. Genetic analysis, using both trisomics and single gene markers, localised aux-1 on chromosome 2.Compared with wild-type seedling roots aux-1 roots have a 14-fold increased resistance to 2,4-D, an increased growth rate and lack a normal geotropic response.- 14C72,4-D uptake experiments showed how uptake of 2,4-D in the mutant lagged behind that of wild-type but confirmed that 2,4-D does enter mutant seedlings. Seedling transfer experiments showed how resistance levels vary with seedling age.A clinostat was used in conjunctioni•:with a series of aperture experiments to examine the geotropic responses of both mutant and wild-type roots grown in light and in darkness.Mutant and wild-type root growth rates were compared both in the presence and absence of 2,4-D.Mutant, wild-type and F2 seed stocks were examined for seed size variation. Mutant seed was found to be bigger in addition to having a reduced post-harvest dormancy requirement and faster germination.Microscopy was used in an attempt to discover any changes in root tip ultrastructure which might account for the altered geotropic response and increased growth rate of the mutant.The many characteristics examined appear to be the pleiotropic effects of the single recessive gene aux-1.The value of the genetic approach as a tool for the investigation of physiological processes in plants has been illustrated.