Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/7/2006
Publication Date: 7/7/2006
Citation: Vasconcelos, M.W., Lubkowitz, M., Grusak, M.A. 2006. Oligopeptide transporters and their role in fe(ii)- and fe(iii)-nicotianamine transport in rice (oryza sativa l.). In: Proceedings of the Thirteenth International Symposium on Iron Nutrition and Interactions in Plants, July 3-7, 2006, Montpellier, France. p.99. Interpretive Summary:
Technical Abstract: The ability of organisms to transport small peptides (two to five amino acids) is wide-ranging, and is present in humans, bacteria, fungi, archaea, and plants. There are three major groups of peptide transporters, divided by their substrate specificity: the ATP binding cassette (ABC), the peptide transporters (PTRs), and the oligopeptide transporters (OPTs). Whereas the ABC and PTR transporters seem to have a diverse range of substrates, the OPTs specifically transport peptides of three to five residues. The role of the OPTs, especially in plants, is still not a well documented process, although some progress is being made in Arabidopsis thaliana. In rice (Oryza sativa L.), this OPT family of transporters has not been characterized. Recently, we identified and characterized nine putative rice oligopeptide transporter orthologs (OsOPT1 to OsOPT9). These are localized to chromosomes 1, 2, 3, 4, 6 and 10 in the rice genome. The predicted protein sequences show a high similarity to the nine Arabidopsis thaliana (AtOPTs), Candida albicans (CaOpt1), Schizosaccharomyces pombe (Isp4p) and Saccharomyces cereviseae (Opt1p and Opt2p) OPTs, amongst others. Sequence similarity comparisons showed that the plant OPTs form a distinct subfamily when compared to the fungal and bacterial OPTs. Hydrophilicity plots of the rice OPTs suggest that they are integral membrane proteins with 12 to 18 transmembrane domains. The two highly conserved motifs (NP6 and KIPPR) were found among all OsOPT members, and the predicted OsOPT proteins shared 51 to 91% homology amongst each other. The expression pattern of the OsOPTs also was analyzed in different rice tissues (green leaves, senescing leaves, pedicels, hulls, roots, immature endosperms and isolated embryos) by RT-PCR. While some of the OsOPTs seem to be constitutively expressed, others seem to be more tissue specific. To study transport capacity, the cDNAs encoding 5 of the 9 OsOPTs were cloned into the fet3fet4 yeast mutant (defective in iron uptake); the transformed yeast lines were used to assess the transport of Fe(III)NA or Fe(II) NA. Two of the 9 OsOPTs were able to grow in synthetic defined media supplemented with different concentrations of Fe(II)NA or Fe(III) NA. This study provides new data describing a novel gene family with iron uptake capacity in plants. This work was supported in part by funds from USDA-ARS under Agreement No. 58-6250-6-001 and from the Harvest Plus Project under Agreement No. 58-6250-4-F029 to MAG.