Abstract
In the last decades agricultural N-fertilization has led to a tremendous urea input into biosphere, accounting for over 50% of the world N-fertilizer consumption. Therefore urea, nitrate and ammonium are the three forms of N generally present in cultivated soils. Despite the great agricultural importance of urea for higher plants, the molecular and physiological bases of its transport have been investigated only in Arabidopsis and rice.In order to characterize a high-affinity urea transporter in maize, we isolated the ZmDUR3 ORF which is highly homologous (84% identity on nucleotide level) to the rice urea transporter OsDUR3. ZmDUR3encodes an integral membrane protein with 731 amino acid residues. By complementation assays, heterologous expression of ZmDUR3 could restore growth of a yeast dur3 mutant on urea medium.The identification and characterization of urea transporters in higher plants is important not only for understanding the urea-related plant N-nutrition processes, but also for exploring potential strategies to improve urea-based N-fertilizer use efficiency in agricultural crop production.