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 acropetal 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 fungal pathogens such as Alternaria brassicicola, Plectosphaerella cucumerina and Fusarium oxysporum. G proteins are composed of 3 units, alpha, beta and gamma. Interacts with the beta subunit GB1. The dimer GB1-GG1 interacts with NDL1, NDL2 and NDL3. Binds to NUDT7. Localized to the cell membrane when attached to beta subunit GB1 (Probable) (PubMed:17158913). Present in the cytoplasm when associated with NUDT7 (PubMed:22068106). Mostly expressed in seedlings (especially at the hypocotyl/root junction), young cauline leaves, open flowers, and floral stems, and, to a lower extent, in roots (restricted to the stele), rosette leaves (restricted to veins), siliques, and unopened floral buds. Also present in hydathods. In seedlings, first observed at the hypocotyl/root junction but later confined to the hypocotyl. In flowers, restricted to the stigma of mature flowers. In siliques, confined to the abscission zone. Induced locally by Alternaria brassicicola but systemically by Fusarium oxysporum. Enhanced susceptibility to Alternaria brassicicola, Plectosphaerella cucumerina and Fusarium oxysporum associated with a disturbed expression of genes involved in cell wall metabolism (e.g. lower xylose content in cell walls). Reduced induction of the plant defensin gene PDF1.2, and decreased sensitivity to methyl jasmonate (MeJA). Hypersensitive to auxin-mediated induction of lateral roots, within the central cylinder, attenuating acropetally transported auxin signaling. Enhanced sensitivity to glucose and mannitol during seed germination. Abnormal roots architecture.