Role of peptide transport in plant growth and development.
Peptide transport is a widespread phenomenon exemplified by the translocation of peptides 2-6 residues in length across the plasma membrane in an energy dependent and saturable manner. Peptide transport systems are distinct from amino acid uptake and play a variety of roles in bacteria to man. Although well studied in animals, bacteria and fungi, peptide transport has been poorly described in plants. Peptide transporters fall into three families; the ATP binding cassette family (ABC transporters), the peptide transporter (PTR) family (transporting di- and tripeptides) and the recently described oligopeptide transporter (OPT) family. The recent completion of the Arabidopsis genome sequence showed that this plant possesses 10-fold more peptide transporters than any other sequence organism. For example, the Arabidopsis genome is predicted to encode 52 PTR transporters and 9 OPT transporters.
Previous work from our laboratory demonstrated that antisense expression of AtPTR2, encoding a di-/tripeptide transporter, resulted in arrest of seed development (Song et al., 1997). These data clearly implicate peptide transport in important plant developmental processes.
Arabidopsis flower showing the expression of a AtOPT3-GUS (β-glucoronidase) fusion.
©Copyright, 2002.
More recently, we have focused our efforts on the OPT family members in Arabidopsis. For example, we recently cloned the cDNAs for these genes and showed that they could confer tetra-/ pentapeptide uptake ability when expressed in yeast (Koh et al., 2002). More recently, we have demonstrated that a T-DNA insertion in AtOPT3 resulted in an arrest of embryo development (Stacey et al., 2002). Again, these data argue for a very crucial role for peptide transport in plant growth and development. We are now continuing our investigation of AtOPT3 and the other eight OPT family members in Arabidopsis. This work will add to a growing realization of the importance of circulating peptides in plants, where they likely serve both a signaling (hormone) and nutritional role.
A portion of this work was
supported by the US Department of Agriculture, National Research Initiative
Competitive Grants Program under Grant No. 99-35304-8194. Any opinions,
findings, and conclusions or recommendations expressed in this material are
those of the author(s) and do not necessarily reflect the views of the US
Department of Agriculture.