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. The heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi probably by modulating cell wall-related genes expression (e.g. lower xylose content in cell walls); involved in resistance to fungal pathogens such as Alternaria brassicicola and Fusarium oxysporum. Modulates root architecture (e.g. lateral root formation). Acts with XGL3 in the positive regulation of root waving and root skewing. Involved in the asymmetric division of zygote and specification of apical and basal cell lineages (PubMed:27014878). G proteins are composed of 3 units, alpha, beta and gamma. Interacts with the gamma subunits GG1 and GG2. The dimers GB1-GG1 and GB1-GG2 interact with NDL1, NDL2 and NDL3. Interacts with WNK8. Interacts with XLG2 (PubMed:11121078, PubMed:11513956, PubMed:17158913, PubMed:17468261, PubMed:19825634, PubMed:19948787, PubMed:22940907). Interacts with RACK1A, RACK1B and RACK1C (PubMed:25731164). Interacts with ZAR1 (via GBeta-binding domain) (PubMed:27014878). Localized to the cell membrane when attached to gamma subunits as GG1 and GG2 or to both the plasma membrane and the nucleus when interacting with ZAR1. A number of isoforms are produced. According to EST sequences. Expressed in seedlings (especially at the hypocotyl/root junction), roots, leaves (restricted to veins and guard cells), and flowers (PubMed:17468261, PubMed:18441222). Also present in hydathods (PubMed:17468261). Expressed in guard cells, mesophyll tissue of cotyledons, trichomes and whole siliques, but not in seeds (PubMed:17492287). In flowers, mostly expressed in stigma and pollen, and moderately present in sepals and stamen filaments. In siliques, observed at both ends, gradually disappearing toward the center. Induced locally by Alternaria brassicicola but systemically by Fusarium oxysporum. The DWD box is required for interaction with DDB1A. Shorter hypocotyls and abnormal roots architecture; more auxin-induced lateral roots. Enhanced susceptibility to necrotrophic and vascular pathogenic fungi, such as Alternaria brassicicola, Plectosphaerella cucumerina and Fusarium oxysporum associated with a disturbed expression of genes involved in cell wall metabolism. Longer and wider primary roots with faster growth. Severely compromised root waving and abnormal root skewing response. Hypersensitivity to ethylene (ACC). Belongs to the WD repeat G protein beta family. An article reported a role as negative regulator of ABA during seed germination; however, this paper was later retracted.