Abstract
Recent studies have established that boron in plant cells occurs as the borate-rhamnogalacturonan II (RG-II) complex, but the physiological function of the complex has yet to be determined. 3-Deoxy-D-manno-oct-2-ulosonic acid (KDO) is a specific component monosaccharide of RG-II. Mutant plants lacking KDO should have altered RG-II structure and will be useful to study the function of B-RG-II complex. To obtain such a mutant we have been characterizing the KDO biosynthesis in Arabidopsis.
KDO cytidylyltransferase (CMP-KDO synthetase; CKS, EC 2.7.7.38) activates KDO prior to its incorporation into RG-II. Arabidopsis has one copy of CKS (At1g53000). With the three independent T-DNA insertion lines examined, no homozygous individuals were found and progeny from heterozygotes showed a 1:1 segregation ratio. When heterozygous males were crossed with wild-type females, cks mutation was not transmitted. These results indicate that cks mutation impairs pollen function and suggest that B-RG-II is essential for reproduction.
