Expression Patterns of Arabidopsis DRG Genes: Promoter-GUS Fusions, Quantitative RT-PCR and Patterns of Protein Accumulation in Response to Environmental Stresses
Stafstrom, Joel P.
MetadataShow full item record
DRGs are very highly conserved GTP-binding proteins. All eukaryotes contain DRG1 and DRG2 orthologs. Arabidopsis has three DRGs: AtDRG1 (At4g39520), AtDRG2 (At1g17470), and AtDRG3 (At1g72660). DRG2 and DRG3 encode proteins that are 95% identical; identity between DRG1 and DRG2/3 is 55%. The focus of this article is expression of Arabidopsis DRGs. DRG1 and DRG2 promoter-GUS constructs showed similar spatial expression in seedlings and mature organs, but gene-specific differences were noted. Quantitative real-time PCR experiments indicated similar levels of DRG1 and DRG2 mRNA accumulation in most tissues. DRG3 transcripts were very low in all tissues. Heat stress at 37 C led to a 10-fold increase in DRG1 transcripts and a 1000-fold increase in DRG3 transcripts. DRG1 antibodies recognized a 43-kD protein, and DRG2 antibodies recognized bands at 30, 43, and 45 kD. Plants were exposed to stresses (salt, heat, cold, UV light, osmotic, and other stresses) and examined by Western blotting. Only heat stress caused detectable changes. Heat did not affect DRG1, but DRG2 and a 72-kD protein recognized by DRG2 antibodies both increased. The modest changes in DRG mRNA and protein levels seen here suggest that other types of regulation, such as altered subcellular localization, may be important for their cellular functions.