Heterotrimeric G proteins are known to be important components of regulatory pathways in animals and fungi and the elucidation of G protein signaling in plants is an emerging area of investigation. The study of signaling and regulatory control of plants responses to environmental stress at the molecular level is an area of wide interest and the plant growth regulator abscisic acid is known to play a major role in the plant response to environmental stress.  This work reports on the characterization of the stress induced caleosin gene RD20/CLO3.  Here the interaction of the caleosin protein Responsive to Dehydration 20, RD20/CLO3 with the alpha subunit (GPA1) of the heterotrimeric G protein complex in Arabidopsis was investigated at protein level and the N-terminal domain of RD20 protein was found to interact with GPA1.
 Characterization of the effect of RD20/Clo3 on plant stomatal density and index indicate that the gene is necessary for the ABA mediated reduction of stomatal proliferation.   In addition, methods to improve the level of protein expression in E. coli and the subsequent purification of RD20 and GPA1 were developed.  The purified protein will be used in future studies to investigate the role of RD20 as a potential GTPase Accelerating Protein for GPA1.