Poster: Tropisms
Abs #
672: Auxin transport in gps mutants of arabidopsis:insights into gravitropic signal transduction
The gps (gravity persistent signal) mutants of Arabidopsis have an abnormal response when gravistimulated at 4ºC and returned to vertical at room temperature. gps1 doesn’t respond, gps2 bends in the opposite direction to wildtype and gps3 over-responds curving to an angle greater than the wildtype. At 4ºC, starch-containing statoliths sedimented normally in wildtype but auxin transport was abolished indicating that the mutants are affected in an aspect of signal transduction that occurs after statolith sedimentation. Assessment of statolith reorientation in the mutants indicated that statoliths sedimented normally in the gps mutants when they were gravistimulated at 4ºC. Pulse- chase studies done using [3H]-IAA indicated that there was increased polar auxin transport in gps1 after gravistimulation at 4ºC and returned to room temperature, although the mutant showed no gravitropic bending under these conditions. These results nullified the hypothesis that auxin transport was disrupted in gps1. gps3 also showed an increased polar auxin transport, which could provide a mechanism for the exaggerated response to gravistimulation in the cold. gps2 showed normal polar auxin transport. Improper redistribution of auxin during or after the cold treatment could be the basis for phenotypes of gps1 and gps2. Experiments are being conducted to examine asymmetric auxin redistribution in the mutants using immunostaining and expression of an auxin responsive promoter: GUS gene fusion in the inflorescence to determine if the mutations alter lateral distribution of auxin after cold gravistimulation. (Supported in part by the grants from The American Society of Gravitational Space Biology, the NSCORT in Plant Biology at NC State University and the United States Department of Agriculture)
