Abstract
3-Deoxy-D-manno-oct-2-ulosonate (KDO) is a specific component monosaccharide of rhamnogalacturonan II. KDO cytidylyltransferase (CMP-KDO synthetase; CKS) converts KDO into CMP-KDO, which is the immediate precursor of KDO residues in RG-II. Mutant plants lacking CKS activity will be useful to study the physiological role of RG-II and KDO in higher plants. We therefore started this study to isolate and characterize Arabidopsis CKS.
A BLAST search using bacterial or maize CKS sequences as a probe identified an Arabidopsis ortholog, At1g53000. The protein had a putative chloroplast transit peptide and the targeting was confirmed by expressing an GFP fusion protein in protoplasts.
The recombinant protein expressed in bacteria had the CKS activity with a pH optimum of 9.5. Uridine 5'-triphosphate also served as a substrate at an efficiency of 40% to that of CTP. Phenotypic analyses of T-DNA insertion lines and RNAi plants for CKS are now being undertaken.
