May be involved in the synthesis of minor phospholipids and in modulation of IP3-mediated signal transduction. a 1,2-diacyl-sn-glycero-3-phosphate + CTP + H(+) = a CDP-1,2-diacyl-sn-glycerol + diphosphate Requires a divalent cation for activity. Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP-diacylglycerol from sn-glycerol 3-phosphate: step 3/3. Roots and sink leaves. Belongs to the CDS family.