title: The cloning and characterization of two ammonium transporters in the salt-resistant green alga, Dunaliella viridis.
abstract: Ammonium (NH(4) (+)) transport is a key process in nitrogen metabolism. To elucidate the role of ammonium transporters in the nitrogen consumption of the salt-resistant green alga, Dunaliella viridis, two ammonium transporter genes, DvAMT1;1 and DvAMT1;2, were isolated from cDNA libraries of D. viridis. DvAMT1;1 and DvAMT1;2 share only 40% amino acid identity, indicating that they have highly divergent coding sequences. Functional complementation in a yeast mutant defective in ammonium uptake indicated that both DvAMT1;1 and DvAMT1;2 were functional ammonium transporters. Quantitative RT-PCR showed similar expression patterns, but different transcript abundance levels, for DvAMT1;1 and DvAMT1;2 under different nitrogen conditions. Both were induced at low nitrogen and inhibited at high nitrogen concentrations, especially when NH(4) (+) was the nitrogen source. At the transcriptional level, DvAMT1;1 was diurnally regulated, while DvAMT1;2 was not. In addition, under NaCl concentrations that ranged from 0.5 to 3 M, DvAMT1;1 was down-regulated at the higher salt conditions; conversely, DvAMT1;2 maintained a relatively low, but stable, transcript abundance. The observed differences in transcriptional regulation of DvAMT1;1 and DvAMT1;2 are indicative of their diverse physiological functions in D. viridis.
authors.affiliation: Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Song
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gao
authors.forename: Zhengkai
authors.initials: Z
authors.lastname: Xu
authors.forename: Rentao
authors.initials: R
authors.lastname: Song
mesh_terms: D015139:Blotting, Southern; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D000460:Chlorophyta / Q000187:drug effects / Q000235:genetics*; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009584:Nitrogen / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D055049:Salt Tolerance / Q000187:drug effects / Q000235:genetics*; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D018076:DNA, Complementary; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; C088952:ammonium transporters, plant; D012965:Sodium Chloride; D009584:Nitrogen