Exhibits a fast rate of basal nucleotide exchange. Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. Together with GCR1, may regulate the cell cycle via a signaling cascade that uses phosphatidylinositol-specific phospholipase C (PI-PLC) as an effector and inositol 1,4,5-trisphosphate (IP(3)) as a second messenger. Promotes abscisic acid (ABA) responses in guard cells. Involved in the blue light (BL) signaling. Together with GCR1 and ADT3, required for BL-mediated synthesis of phenylpyruvate and subsequently of phenylalanine (Phe), in etiolated seedlings. Modulates root architecture (e.g. lateral root formation). Negatively regulated by RGS1. In collaboration with CAND2/PMTR1, regulates the melatonin-mediated stomatal closure involving H(2)O(2) and Ca(2+) signals (PubMed:29702752). G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site. Interacts with RGS1, THF1, the pirin protein PRN1, GTG1 and GTG2. Binds to GCR1. May interact with ADT3 (PubMed:12837948, PubMed:14500984, PubMed:15155892, PubMed:16415218, PubMed:16582010, PubMed:17158913, PubMed:17951432, PubMed:19135895, PubMed:21304159). No interactions with RACK1A, RACK1B or RACK1C (PubMed:25731164). Interacts with PLDALPHA1 (PubMed:14594812, PubMed:23913032). Interacts with CAND2/PMTR1 (PubMed:29702752). More abundant in roots and/or leaves. The helical domain (68-188) is required for self-activation. Hypersensitivity to ABA and glucose (Glc) during and after seed germination. Altered response to blue light (BL). Abnormal roots architecture; more auxin-induced lateral roots. Reduced H(2)O(2) concentration in melatonin-treated guard cells associated with impaired abscisic acid- (ABA) and melatonin-induced stomatal aperture (PubMed:29702752). Belongs to the G-alpha family. An article reported a role as negative regulator of ABA during seed germination; however, this paper was later retracted.