Poster: Membrane transport

Abs # 166: The OPT family of peptide transporters in Arabidopsis thaliana

Presenter:	Stacey, Minviluz G., staceym@missouri.edu
Authors	Stacey, Minviluz G. (A)   Patel, Ami  (A)   Osawa, Hiroki  (A)   Gassmann, Walter  (A)   Stacey, Gary  (A)
Affiliations:	(A): University of Missouri

Peptide transport, a cellular process involving the transport of small peptides across the cell membrane in a carrier-mediated, energy-dependent manner, is a widely observed phenomenon in eukaryotes and prokaryotes. The OPT (OligoPeptide Tansport) family of peptide transporters was first identified in yeast. OPT proteins have 12-14 transmembrane domains, predominantly transport tetra- and pentapetides and likely use proton motive force to drive transport. Database searches for homology with the Candida albicans CaOPT1 revealed nine putative Arabidopsis OPT orthologs (AtOPT1-AtOPT9) that form a distinct subfamily compared with fungal OPTs. We are currently employing three approaches to elucidate the functional role of AtOPTs in plant growth and development. First, we are isolating T-DNA lines for each of the AtOPTs. As published previously, AtOPT3 mutant plants exhibited an embryo-lethal phenotype. We now have T-DNA mutant lines for eight of the nine AtOPTs and are continuing to characterize these lines phenotypically. Secondly, we have constructed promoter-GUS fusions for seven of the AtOPTs. Transgenic plants were stained for GUS to characterize gene expression at various stages of development, as well as under different growth conditions. Each of the AtOPT fusions exhibited differential tissue-specific expression, although all were preferentially expressed in vascular tissues of vegetative and reproductive organs. Moreover, AtOPT expression levels responded differently to limiting metal conditions in the growth medium. Thirdly, cDNAs for the AtOPTs are being expressed in Xenopus oocytes to characterize their transport properties.