Poster: Late and Moved Abstracts

Abs # 1369: Enzymes of amino acid metabolism in leaves of Spartina alterniflora

Presenter:	Ireland, Robert J., rireland@mta.ca
Authors	Ireland, Robert J. (A)   Kelly, Heather L. (A)   Buckingham, Katherine M. (A)   McIntyre, Laurel  (A)
Affiliations:	(A): Mount Allison University, Biology Dept.

Spartina alterniflora is a perennial coastal grass that often dominates the intertidal zone of salt marshes of Eastern North America. It has extensive root and rhizome systems that help stabilize the hypoxic mud flats in which they grow. S. alterniflora is a facultative halophyte that uses C4 photosynthesis as part of its strategy to compete in this environment. We have previously shown that roots, rhizomes, and leaves have high concentrations of free amino acids in the spring and fall, with much lower levels during the summer. Glutamine and asparagine comprise over half of the amino acid pool, serving as the major nitrogenous transport compounds. In the roots, glutamine synthetase (GS) and NADH-glutamate synthase showed similar seasonal patterns, peaking in the early spring and showing another rise in the Fall. GS levels were much higher than glutamate synthase, presumably providing the glutamine for export or synthesis of asparagine. In rhizomes, GS peaked later in the spring, but NADH-glutamate synthase showed a less pronounced seasonal pattern. Low levels of Fd-glutamate synthase were detectable in roots but not in rhizomes. Two GS isoforms were separated from leaf extracts: the activity of both decreased throughout the growing season, but the activity of one form decreased more quickly and was absent by the end of the summer. Immunolocalization using antibodies raised against GS1 and GS2 revealed a complex pattern of changes in cellular distribution of the two forms across the season.