[30]

Elucidating genes involved in early gravity signal transduction in Arabidopsis.  J. Bascom and S.E. Wyatt Dept. of Environmental and Plant Biology, Ohio University, Athens, OH.

   Few genes are known to function early in the gravity signal transduction pathway.  Cold treatments have been used previously to identify mutants in early gravity signal transduction (the gravity signal persistence (gps) mutants of Arabidopsis).  Therefore, a cold treatment, in conjunction with microarray analysis, was performed on wild-type Arabidopsis to identify additional genes involved in early signal transduction.  Wild-type Arabidopsis were gravistimulated at 4°C and this treatment was compared to a simple cold (4°C) treatment in which plants were kept vertical as a control.  The inflorescence stem tissue in the region of elongation was collected five minutes after the plants in each treatment were returned to vertical at room temperature.  RNA was extracted from these populations and used to make the target population for hybridization to Affymetrix ATH1 Arabidopsis gene chips.  Analysis of the microarray data was performed using GeneSpring software (Silicon Genetics, CA) and the Cross-Gene Error Model.  Differentially expressed genes were sorted based on function, fold change, and up- vs. down-regulation.  These include several transcription factors, as well as kinases and other signal transduction molecules.  Several auxin-responsive proteins were also strongly upregulated, as were a number of proteins whose function is unknown and several cytochrome p450 proteins.  Promising genes were confirmed with Quantitative RT-PCR over a time course of cold gravistimulation.  These results present many favorable gene candidates for further study as components of early gravity signal transduction in Arabidopsis.  (Partially supported by NASA: NAG2-1608 to SEW and the Honors Tutorial College at Ohio University).