Phosphorylates the second messenger diacylglycerol (DAG) to generate phosphatidic acid (PA), another important signaling molecule (PubMed:14665624). PA is required for plant development and responses to abiotic stress and pathogen attack (Probable). May be involved in the accumulation of PA during cold stress (Probable). Involved in response to freezing stress by modulating the accumulation of PA (PubMed:29853600). Exhibits high specificity for the unsaturated DAG analogs 1-stearoyl-2-arachidonoyl-sn-glycerol (1,2-SAG) and 1,2-dioleoyl-sn-glycerol (1,2-DOG) (PubMed:14665624, PubMed:16081412). Exhibits high specificity for 1-palmitoyl, 2-oleoyl-sn-glycerol (1,2 POG), 1-stearoyl, 2-linoleoyl-sn-glycerol (1,2-SLG) and 1-oleoyl, 2-palmitoyl-sn-glycerol (1,2-OPG) (PubMed:16081412). Has almost no activity toward 1,2-dioctanoyl-sn-glycerol (1,2-DOCG), 1,2-dipalmitoyl-sn-glycerol (1,2-DPG), 1,2-dimyristoyl-sn-glycerol (1,2-DMG) and 1-oleoyl-2-acetyl-sn-glycerol (1,2-OAG) (PubMed:16081412). Functions together with DGK4 in male gametophyte development and biosynthesis of phosphatidylglycerol and phosphatidylinositol in the endoplasmic reticulum (ER) (PubMed:32471859). Involved in PA production for pollen grain growth, as well as leaf and root growth (PubMed:32471859). a 1,2-diacyl-sn-glycerol + ATP = a 1,2-diacyl-sn-glycero-3-phosphate + ADP + H(+) 1-octadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycerol + ATP = 1-octadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + ADP + H(+) 1,2-di-(9Z-octadecenoyl)-sn-glycerol + ATP = 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphate + ADP + H(+) Optimum pH is 7.2. Monomer. A number of isoforms are produced. According to EST sequences. Expressed in rosette and cauline leaves, flowers, siliques and roots. Highly expressed in young leaves and at lower levels in older leaves. In young seedlings, expressed at the root-shoot junction zone and vascular bundles of the cotyledons. In older plants, expressed in root tip, central cylinder, root hair, leaf mesophyll cells and guard cells, sepals, filaments of the anthers, stigma, valves of young and early adult siliques and hilum of seeds. Induced by cold stress (PubMed:14665624). Induced by wounding (PubMed:16081412). No visible phenotype under normal growth conditions, but the double mutants dgk2 and dgk4 exhibit defective pollen growth and seed development because of non-viable male gametophyte. Belongs to the eukaryotic diacylglycerol kinase family.