A two-component high-affinity nitrate uptake system in barley

A - Papers appearing in refereed journals

Tong, Y., Zhou, J-J., Li, Z. and Miller, A. J. 2005. A two-component high-affinity nitrate uptake system in barley. The Plant Journal. 41 (3), pp. 442-450.

AuthorsTong, Y., Zhou, J-J., Li, Z. and Miller, A. J.

The analysis of genome databases for many different plants has identified a group of genes that are related to one part of a two-component nitrate transport system found in algae. Earlier work using mutants and heterologous expression has shown that a high-affinity nitrate transport system from the unicellular green algae, Chlamydomonas reinhardtii required two gene products for function. One gene encoded a typical carrier-type structure with 12 putative trans-membrane (TM) domains and the other gene, nar2 encoded a much smaller protein that had only one TM domain. As both gene families occur in plants we investigated whether this transport model has more general relevance among plants. The screening for nitrate transporter activity was greatly helped by a novel assay using (15)N-enriched nitrate uptake into Xenopus oocytes expressing the proteins. This assay enables many oocytes to be rapidly screened for nitrate transport activity. The functional activity of a barley nitrate transporter, HvNRT2.1, in oocytes required co-injection of a second mRNA. Although three very closely related nar2-like genes were cloned from barley, only one of these was able to give functional nitrate transport when co-injected into oocytes. The nitrate transport performed by this two-gene system was inhibited at more acidic external pH and by acidification of the cytoplasm. This specific requirement for two-gene products to give nitrate transport function has important implications for attempts to genetically manipulate this fundamental process in plants.

KeywordsPlant Sciences
Year of Publication2005
JournalThe Plant Journal
Journal citation41 (3), pp. 442-450
Digital Object Identifier (DOI)doi:10.1111/j.1365-313X.2004.02310.x
PubMed ID15659102
Open accessPublished as non-open access
Funder project or code502
The cell biology of nitrogen acquisition and allocation
Project: 4503

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