Poster: Tropisms
Abs #
405: Cloning and complementation of the gps3 mutant
The gravity persistent signal (gps) mutants are defective in one or more steps of the gravity signal transduction pathway and have altered response after gravistimulation at 4°C. gps3 over-responds, curving to a greater angle than the wildtype, when gravistimulated at 4°C and returned to vertical at room temperature. Thermal asymmetric interlaced polymerase chain reaction (TAIL PCR) was used to clone the GPS3 gene. TAIL PCR results indicated the T-DNA tag to be inserted 3` of At1g43950, an Auxin Response Factor (ARF) 9 like gene. The protein predicted by At1g43950 corresponds to the DNA binding domain homologous to ARF9. However, the protein lacks the carboxy terminal binding region which is essential in ARF9 for dimerization that regulates the auxin responsive genes. Analysis using the Protein Localization program (PLOC) has indicated the At1g43950 protein to be a nuclear localizing protein, as would be appropriate for a transcription factor. A series of constructs involving the ARF9 like gene, endogenous promoter, 35S promoter and GFP fusion have been made to assess the tissue specificity and sub-cellular localization of this protein. The implication of a defect in an ARF9-like gene producing the gps3 mutant phenotype is intriguing. Studies on ARF9 suggest that it could be involved in tissue-specific transcriptional activation and repression of the auxin response genes. This creates a possibility for a mechanism of auxin tissue specificity that is defective in the gps3 and could result in auxin activity across an extended region of inflorescence stem, resulting in the over-response phenotype as seen in gps3. (Supported by NAG2-1608 from National Aeronautics and Space Administration.)
