Related Experiment Video
Updated: Aug 9, 2026

Measuring Fluxes of Mineral Nutrients and Toxicants in Plants with Radioactive Tracers
Published on: August 22, 2014
Urea transport by nitrogen-regulated tonoplast intrinsic proteins in Arabidopsis
Lai-Hua Liu1, Uwe Ludewig, Brigitte Gassert
1Institut für Pflanzenernährung, Universität Hohenheim, D-70593 Stuttgart, Germany.
Abstract:
Urea is the major nitrogen (N) form supplied as fertilizer in agricultural plant production and also an important N metabolite in plants. Because urea transport in plants is not well understood, the aim of the present study was to isolate urea transporter genes from the model plant Arabidopsis. Using heterologous complementation of a urea uptake-defective yeast (Saccharomyces cerevisiae) mutant allowed to isolate AtTIP1;1, AtTIP1;2, AtTIP2;1, and AtTIP4;1 from a cDNA library of Arabidopsis. These cDNAs encode channel-like tonoplast intrinsic proteins (TIPs) that belong to the superfamily of major intrinsic proteins (or aquaporins). All four genes conferred growth of a urea uptake-defective yeast mutant on 2 mm urea in a phloretin-sensitive and pH-independent manner. Uptake studies using 14C-labeled urea into AtTIP2;1-expressing Xenopus laevis oocytes demonstrated that AtTIP2;1 facilitated urea transport also in a pH-independent manner and with linear concentration dependency. Expression studies showed that AtTIP1;2, AtTIP2;1, and AtTIP4;1 genes were up-regulated during early germination and under N deficiency in roots but constitutively expressed in shoots. Subcellular localization of green fluorescent protein-fused AtTIPs indicated that AtTIP1;2, AtTIP2;1, and AtTIP4;1 were targeted mainly to the tonoplast and other endomembranes. Thus, in addition to their role as water channels, TIP transporters may play a role in equilibrating urea concentrations between different cellular compartments.
More Related Videos
Related Concept Videos
Short-distance Transport of Resources
Protein Transport to the Outer Chloroplast Membrane
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Overview of Nitrogen Metabolism
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
Protein Transport to the Thylakoids
Protein Transport to the Inner Chloroplast Membrane
Inorganic Nitrogen Assimilation

