Transcriptional regulator that specifically binds 5'-GATA-3' or 5'-GAT-3' motifs within gene promoters (PubMed:22102866, PubMed:25077795). Involved in the modulation of chloroplast development, growth and division in a cytokinin-dependent manner (PubMed:22102866, PubMed:22811435). Repressor of the gibberellic acid (GA) signaling pathway that regulates flowering and modulates greening, in a SOC1-dependent manner (PubMed:20844019, PubMed:23739688, PubMed:25077795). Prevents the accumulation of SOC1 during flowering (PubMed:23739688). Promotes chlorophyll biosynthesis throughout the plant, by regulating chlorophyll biosynthetic genes (e.g. HEMA1 and GUN4) and chloroplast localized glutamate synthase (e.g. GLU1) (PubMed:18417639, PubMed:20844019, PubMed:21453984, PubMed:22102866, PubMed:23878229, PubMed:25077795). Involved in the regulation of sugar-sensing genes (e.g. HXK1, HXK2, STP13 and PLT6) (PubMed:18417639). Regulator of germination, senescence, elongation growth and flowering time (PubMed:20844019, PubMed:22102866, PubMed:23878229). Influences also leaf starch content (PubMed:22102866). Forms heterodimers with GATA18. Expressed predominantly in leaves, and barely in stems, flowers and siliques. First observed in the inflorescence meristem (IM) and young flower buds (PubMed:23335616). Detected throughout the floral bud. In young flowers, restricted to the inner whorls, specifically the petals, stamens, and carpels (PubMed:18417639, PubMed:23335616). In older flowers, accumulates more in the stamens than in the petals and carpels (PubMed:18417639). Observed in anther locules, vascular strands, and ovules (PubMed:23335616). During imbibition, expressed in the endosperm, especially at the time of testa rupture. Later restricted to the cotyledons (PubMed:20844019). In mature embryos, restricted to the cotyledons. In young seedlings, mostly expressed in shoot tissues, including the tip, circumference, and vasculature of the cotyledons, the emerging leaves, the meristematic region, and the basal part of the hypocotyl, and, at low levels, in the primary roots. In older seedlings, accumulates in the green shoot tissues (PubMed:22811435). By light (including both red and white lights) (PubMed:17208962, PubMed:17587690). Levels follow a circadian and diurnal rhythm, with a peak at 20 hours, thus preempting dawn (PubMed:17208962). Activated by gibberellic acid (GA) (PubMed:20844019). Induced by cytokinin and derivatives (e.g. benzyladenine, t-Zeatin and 6-benzylaminopurine) in light conditions (PubMed:16212609, PubMed:17587690, PubMed:21453984, PubMed:22811435). Triggered by nitrate (PubMed:16262716). Negatively regulated by AP3/PI (PubMed:18417639). Strong accumulation during cold imbibition of nondormant seeds, but not at warm temperatures. Regulated by PIF transcription factors (PubMed:20844019). Repressed by HAN (PubMed:23335616). Inhibited by SOC1 (PubMed:23739688). Down-regulated by auxin (2,4D) and auxin response factors (e.g. ARF2 and ARF7) (PubMed:23878229). Pale green leaves and reduced chlorophyll levels associated with altered regulation of sugar-sensing genes (e.g. HXK1, HXK2, STP13 and PLT6) (PubMed:18417639, PubMed:21453984, PubMed:22102866, PubMed:22811435). Reduced chloroplast size (PubMed:22811435). Faster seed germination. Early flowering. Increased leaves size (PubMed:20844019, PubMed:22102866). Reduced gibberellic acid (GA) levels due to increased GA turnover and associated with reduced expression of GA-anabolizing enzymes (e.g. GA3OX1) but increased expression of GA-catabolizing enzymes (e.g. GA2OX2) (PubMed:20844019). Small seeds with deformed seed coats (PubMed:22102866). The double mutant gnc cga1, lacking both GATA22 and GATA21, exhibits reduced sensitivity to cytokinin (e.g. benzyladenine) toward chloroplasts growth (PubMed:22811435). Belongs to the type IV zinc-finger family. Class B subfamily.