Disease relevance of RGA1

• A cDNA encoding the alpha-subunit of the heterotrimeric G-protein in rice (RGA1) was overexpressed in Escherichia coli and then isolated by Ni2+-nitrilotriacetic acid affinity chromatography [1].
• The RGA1 protein contains all the consensus regions of G protein alpha subunits except the cysteine residue near the C-terminus for ADP-ribosylation by pertussis toxin [2].

High impact information on RGA1

• We also show that auxin is necessary for GA-mediated control of root growth, and that attenuation of auxin transport or signalling delays the GA-induced disappearance of RGA from root cell nuclei [3].
• Here, we show that RGL2 regulates seed germination in response to GA, and that RGL1, GAI, and RGA do not [4].
• Here we report the molecular cloning of GAI and a closely related gene GRS [5].
• The DELLA protein REPRESSOR OF ga1-3 (RGA) accumulated in the triple mutant, whose phenotype could be partially rescued by loss of RGA function [6].
• The rga and gai null mutations additively suppressed the recessive sly1 mutant phenotype, further supporting the model that SCFSLY1 targets both RGA and GAI for degradation [7].

Biological context of RGA1

• The DELLA domain protein RGA (repressor of ga1-3) is a repressor of GA response that appears to undergo GA-stimulated protein degradation [8].
• The rate of guanine nucleotide binding of RGA1 (kon,GTP[S]=0.0141+/-0.0014 min-1) and, at steady state, the kcat value for GTP hydrolysis (0.0075+/-0.0001 min-1) were very low even at 2 mM MgCl2 [1].
• Southern analysis indicates that there are no other genes similar to the RGA1 gene in the rice genome [2].
• Sequence analysis of genomic clone reveals that the RGA1 gene has 14 exons and 13 introns, and encodes a polypeptide of 380 amino acid residues with a calculated molecular weight of 44.5 kDa [2].
• A cDNA clone, RGA1, was isolated by using a GPA1 cDNA clone of Arabidopsis thaliana G protein alpha subunit as a probe from a rice (Oryza sativa L. IR-36) seedling cDNA library from roots and leaves [2].

Associations of RGA1 with chemical compounds

• Photoaffinity labelling with [alpha-32P]GTP and a GTP[S]-binding assay revealed that RGA1 incorporated 32P and showed specific binding to a guanine nucleotide [1].
• Guanidine binding of RGA1 was affected by the concentration of MgCl2 (maximum at 2 mM) [1].
• The presence of several structural features, including homopolymeric serine and threonine residues, a putative nuclear localization signal, leucine heptad repeats, and an LXXLL motif, indicates that the RGA protein may be a transcriptional regulator that represses the GA response [9].

Regulatory relationships of RGA1

• The DELLA family members AtRGA or (Repressor of ga1-3) and OsSLR1 (SLENDER RICE1) proteins both appear to be subject to GA-induced proteolysis [10].

Other interactions of RGA1

• GAI and RGA are known to be negative regulators of gibberellin (GA) responses [11].
• As with RGA, green fluorescent protein (GFP)-tagged RGL1 protein was localized to the nucleus, but unlike GFP-RGA, there was no degradation after GA treatment [11].
• In Arabidopsis thaliana, GA derepresses its signaling pathway by inducing proteolysis of the DELLA protein REPRESSOR OF ga1-3 (RGA) [7].
• GA thus promotes Arabidopsis petal, stamen and anther development by opposing the function of the DELLA proteins RGA, RGL1 and RGL2 [12].
• However, the C-terminal amino acid sequence, which has been proposed to be a receptor-binding region, of RGA1 was different not only from the analogous sequences of mammalian alpha subunits but also from those of the products of GPA1 and TGA1 [13].

Analytical, diagnostic and therapeutic context of RGA1

• Molecular cloning and characterization of RGA1 encoding a G protein alpha subunit from rice (Oryza sativa L. IR-36) [2].
• Confocal microscopy and immunoblot analyses demonstrated that the levels of both the GFP-RGA fusion protein and endogenous RGA were reduced rapidly by GA treatment [14].

References