Involved in the biosynthesis of lipid A, a phosphorylated glycolipid that in bacteria anchors the lipopolysaccharide to the outer membrane of the cell. Catalyzes the transfer of two 3-deoxy-D-manno-octulosonate (Kdo) residues from CMP-Kdo to lipid IV(A), the tetraacyldisaccharide-1,4'-bisphosphate precursor of lipid A. Lipid A-like molecules in plants may serve as structural components of the outer membranes of mitochondria and/or chloroplasts, or may be involved in signal transduction or plant defense responses. CMP-3-deoxy-beta-D-manno-octulosonate + lipid IVA (E. coli) = alpha-Kdo-(2->6)-lipid IVA + CMP + H(+) alpha-Kdo-(2->6)-lipid IVA + CMP-3-deoxy-beta-D-manno-octulosonate = alpha-Kdo-(2->4)-alpha-Kdo-(2->6)-lipid IVA + CMP + H(+) Glycolipid biosynthesis; KDO(2)-lipid A biosynthesis; KDO(2)-lipid A from CMP-3-deoxy-D-manno-octulosonate and lipid IV(A): step 1/4. Glycolipid biosynthesis; KDO(2)-lipid A biosynthesis; KDO(2)-lipid A from CMP-3-deoxy-D-manno-octulosonate and lipid IV(A): step 2/4. Expressed in leaves, stems and flowers. No visible phenotype under normal growth conditions, but plants lacking KDTA accumulate high levels of tetraacyldisaccharide 1,4'-bis-phosphate (lipid IVA). Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 30 subfamily.