Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction. Involved in the abscisic acid (ABA) and ethylene signaling pathways. Regulates basipetal transport of auxin (IAA) in roots and hypocotyls, and thus modulates root architecture (e.g. lateral root formation). The heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi probably by modulating cell wall-related genes expression; involved in resistance to Plectosphaerella cucumerina. G proteins are composed of 3 units, alpha, beta and gamma. GPG1 interacts with the beta subunit GB1. The dimer GB1-GG2 interacts with NDL1, NDL2 and NDL3. Binds to NUDT7. Localized to the cell membrane when attached to beta subunit GB1. Additional isoforms seem to exist. Mostly expressed in roots (excluded from the stele), seedlings (especially at the hypocotyl/root junction), floral stems, floral buds, flowers and siliques, and, to a lower extent, in leaves (restricted to guard cells). Also present in hydathods. In seedlings, first observed at the hypocotyl/root junction but later confined to the root, including root hairs. In flowers, expressed in the apex of stamen filaments at a very early developmental stage and disappeared before the flower opened. Not present in siliques. Hypersensitive to auxin-mediated induction of lateral roots, within the epidermis and/or cortex, attenuating basipetally transported auxin and graviresponsiveness. Enhanced sensitivity to glucose. Abnormal roots architecture. Enhanced susceptibility to necrotrophic and vascular pathogenic fungi, such as Plectosphaerella cucumerina associated with a disturbed expression of genes involved in cell wall metabolism (e.g. lower xylose content in cell walls).