Disease relevance of GPA1

• Biochemical characteristics of a rice (Oryza sativa L., IR36) G-protein alpha-subunit expressed in Escherichia coli [1].

High impact information on GPA1

• Surprisingly, S1P regulates stomatal apertures and guard cell ion channel activities in wild-type plants, but not in knockout lines of the sole prototypical heterotrimeric G-protein alpha-subunit gene, GPA1 (refs 5, 6, 7-8) [2].
• We found that Arabidopsis thaliana plants harboring transferred DNA insertional mutations in the sole prototypical heterotrimeric GTP-binding (G) protein alpha subunit gene, GPA1, lack both ABA inhibition of guard cell inward K(+) channels and pH-independent ABA activation of anion channels [3].
• Results from loss of function and ectopic expression and activation of GPA1 indicate that this subunit is a positive modulator of cell division in plants [4].
• Inducible overexpression of GPA1 in Arabidopsis confers inducible ectopic cell division [4].
• The alpha subunit of a prototypical heterotrimeric GTP-binding protein (G protein), which is encoded by a single gene (GPA1) in Arabidopsis, is a modulator of plant cell proliferation. gpa1 null mutants have reduced cell division in aerial tissues throughout development [4].

Biological context of GPA1

• The interaction between THF1 and GPA1 has been confirmed by in vitro and in vivo coimmunoprecipitation, FRET analysis, and genetic epistasis and provides evidence of a sugar-signaling mechanism between plastids and the plasma membrane [5].
• Contact between root plastidic THF1 and GPA1 at the plasma membrane occurs at sites where the plastid membrane abuts the plasma membrane, as demonstrated by Förster resonance energy transfer (FRET) [5].
• The sequences of genomic and cDNA clones indicate that GPA1 has 14 exons, and the deduced amino acid sequence shows that the GPA1 gene product (GP alpha 1) has 383 amino acid residues (44,582 Da) [6].
• Restriction fragment length polymorphism mapping experiments show that GPA1 is approximately 1.2 centimorgans from the visible marker er on chromosome 2 [6].
• Insertion mutagenesis confirms that GPA1 and the sole canonical G-protein-coupled receptor (GCR1) in Arabidopsis also have a role in this blue light-mediated event [7].

Anatomical context of GPA1

• The Plastid Protein THYLAKOID FORMATION1 and the Plasma Membrane G-Protein GPA1 Interact in a Novel Sugar-Signaling Mechanism in Arabidopsis [5].
• Use of an oligopeptide corresponding to the fifteen C-terminal residues of the Arabidopsis G alpha-subunit (GP alpha 1), as an affinity ligand, led to the resolution of a tightly binding 37 kDa membrane polypeptide from detergent solubilised Zea microsomal fraction membranes [8].

Associations of GPA1 with chemical compounds

• Our data show that GPA1, AGB1, and GCR1 each negatively regulates ABA signaling in seed germination and early seedling development [9].
• The Arabidopsis putative G protein-coupled receptor GCR1 interacts with the G protein alpha subunit GPA1 and regulates abscisic acid signaling [10].
• The GP alpha 1 protein exhibits similarity to all known G protein alpha subunits--36% of its amino acids are identical and 73% are similar (identical and conservative changes) to mammalian inhibitory guanine nucleotide-binding regulatory factor alpha subunits and transducins [6].

Physical interactions of GPA1

• However, whether GCR1 actually interacts with GPA1 was unknown [10].
• One of the identified GPA1-interacting proteins is the cupin-domain protein AtPirin1 [11].

Other interactions of GPA1

• We demonstrate by in vitro pull-down assays, by yeast split-ubiquitin assays, and by coimmunoprecipitation from plant tissue that GCR1 and GPA1 are indeed physically coupled [10].
• These data indicate that AtPirin1 likely functions immediately downstream of GPA1 in regulating seed germination and early seedling development [11].
• Single- and double-null mutants for the GPA1, AGB1 genes encoding the alpha and beta subunit of the heterotrimeric G protein, respectively, have wild-type sensitivity to R and FR [12].
• The amino acid sequence of RGA1 was 77% and 86% identical to the sequences of alpha subunits from Arabidopsis thaliana and tomato (products of GPA1 and TGA1), respectively, and 42% to 69% identical to sequences of mammalian alpha subunits [13].
• Using seeds that carry a null mutation in the genes encoding RGS protein (AtRGS1) and the alpha-subunit (AtGPA1) of the G protein in Arabidopsis (named rgs1-2 and gpa1-3, respectively), our genetic evidence proved the involvement of the AtRGS1 protein in the modulation of seed germination [14].

Analytical, diagnostic and therapeutic context of GPA1

• This gene, named GPA1, was isolated by using a DNA probe generated by polymerase chain reaction based on protein sequences from mammalian and yeast G protein alpha subunits [6].
• Molecular cloning and characterization of GPA1, a G protein alpha subunit gene from Arabidopsis thaliana [6].

References