Identification, Characterization, and Functional Analysis of Nematode-Inducible Amino Acid and Peptide Transporters in Arabidopsis

Donald Danforth Plant Science Center, Saint Louis MO

Investigators

Abstract

Identification, characterization, and functional analysis of nematode-inducible amino acid and peptide transporters in Arabidopsis Chris Taylor (PI), Erik Nielsen (co-PI), Daniel Schachtman (co-PI) Donald Danforth Plant Science Center Plant parasitic nematodes are some of the most destructive plant pathogens, causing worldwide losses exceeding $77 billion annually to 21 agronomic crops. Of these, root-knot nematodes (Meloidogyne spp.) are capable of reproducing on over 2,000 species of plants and are responsible for approximately 50% of overall nematode damage. Symptoms of plant infection by root-knot nematodes include knot- or gall-like formations on the roots. These knots, or galls, inhibit the root's ability to take up and transport nutrients and water. The root-knot nematodes induce the formation of highly specialized plant cells, called giant cells. Giant cells exhibit many of the hallmarks of transfer cells, which are known for their high metabolic and solute transport activity. They contain dense cytoplasm and numerous mitochondria, are multinucleated, and contain thickened cell walls and a highly invaginated plasma membrane with large surface area. Giant cells also contain few plasmodesmata, which indicates that they are symplastically isolated from cells in the rest of the root. The lack of plasmodesmatal connections and the large increase in plasma membrane surface area suggest that solute transport into and out of giant cells occurs via an apoplastic route. Using microarrays and quantitative real time PCR, it was observed by us that nearly 130 different genes encoding transporters exhibit significant changes in expression levels during nematode infestation. These transporters are members of gene families whose function is to transport amino acids, peptides, sugars, water, anions, or auxin. Of the nematode-induced transporters, nine belong to the amino acid transporter superfamily and five belong to the peptide transporter family. These results highlight the importance of amino acid and peptide transport during nematode parasitism. However, little is known about the tissue-specific expression, sub-cellular localization, and function of these transporters during nematode infestation. Therefore a project has been initiated to examine the role amino acid and peptide transporters play during nematode infestation. The expression characteristics of nematode-induced transporters will be examined using promoter fusions and their subcellular location will be assessed using histo-tagged proteins. The transporters will also be examined in yeast and Xenopus oocytes to determine their substrate specificity and kinetics. Knockout plants for each of the transporter genes will be examined for their ability to support nematode growth. Broader Impacts: The analysis of transporter genes during nematode infestation will provide an opportunity to examine an important facet of the basic biology of parasitism in plants. The results of this research might also lead to the development of strategies to improve the resistance of plants to nematode infection. Other "Broader Impacts" include the training of graduate students and postdoctoral fellows. In addition, the participating labs are involved in outreach programs to undergraduates at Washington University and to St. Louis area high school science teachers.