title: Analysis of CMP-sialic acid transporter-like proteins in plants.
abstract: It is commonly accepted that sialic acids do not exist in plants. However, putative gene homologs of animal sialyltransferases and CMP-sialic acid transporters have been detected in the genomes of some plants. To elucidate the physiological functions of these genes, we cloned 2 cDNAs from Oryza sativa (Japanese rice), each of which encodes a CMP-sialic acid transporter-like protein designated as OsCSTLP1 and OsCSTLP2. To examine the CMP-sialic acid transporter activity of OsCSTLP1 and OsCSTLP2, we introduced their expression vectors into CMP-sialic acid transporter activity-deficient Lec2 cells. Transfection with OsCSTLP1 resulted in recovery of the deficit phenotype of Lec2 cells, but transfection with OsCSTLP2 did not. We also performed an in vitro nucleotide sugar transport assay using a yeast expression system. Among the nucleotide sugars examined, the OsCSTLP1-containing yeast microsomal membrane vesicles specifically incorporated CMP-sialic acid, indicating that OsCSTLP1 has CMP-sialic acid transporter activity. On the other hand, OsCSTLP2 did not exhibit any nucleotide sugar transporter activity. T-DNA insertion lines of Arabidopsis thaliana targeting the homologs of the OsCSTLP1 and OsCSTLP2 genes exhibited a lethal phenotype, suggesting that these proteins play important roles in plant development and may transport important nucleotide sugars such as CMP-Kdo in physiological conditions.
authors.affiliation: Glyco-chain Functions Laboratory, RIKEN-FRS, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. staka@noguchi.or.jp
authors.forename: Shou
authors.initials: S
authors.lastname: Takashima
authors.forename: Junichi
authors.initials: J
authors.lastname: Seino
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Fujiyama
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tsujimoto
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Ishida
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hashimoto
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D001692:Biological Transport; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid / Q000378:metabolism; D004269:DNA, Bacterial; D018076:DNA, Complementary; D017343:Genes, Plant; D008861:Microsomes; D009711:Nucleotides / Q000378:metabolism; D027361:Organic Anion Transporters / Q000235:genetics / Q000378:metabolism; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013400:Sugar Acids / Q000378:metabolism; D027981:Symporters; D014157:Transcription Factors; D014162:Transfection
chemical_list: D004269:DNA, Bacterial; D018076:DNA, Complementary; D009711:Nucleotides; D027361:Organic Anion Transporters; D010940:Plant Proteins; D013400:Sugar Acids; D027981:Symporters; C036483:T-DNA; D014157:Transcription Factors; C421224:sialic acid transport proteins; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid