Regulation of High-Affinity Nitrate Transporter Genes and High-Affinity Nitrate Influx by Nitrogen Pools in Roots of Barley1
AUTOR(ES)
Vidmar, Joseph John
FONTE
American Society of Plant Physiologists
RESUMO
To investigate the regulation of HvNRT2, genes that encode high-affinity NO3− transporters in barley (Hordeum vulgare) roots, seedlings were treated with 10 mm NO3− in the presence or absence of amino acids (aspartate, asparagine, glutamate [Glu], and glutamine [Gln]), NH4+, and/or inhibitors of N assimilation. Although all amino acids decreased high-affinity 13NO3− influx and HvNRT2 transcript abundance, there was substantial interconversion of administered amino acids, making it impossible to determine which amino acid(s) were responsible for the observed effects. To clarify the role of individual amino acids, plants were separately treated with tungstate, methionine sulfoximine, or azaserine (inhibitors of nitrate reductase, Gln synthetase, and Glu synthase, respectively). Tungstate increased the HvNRT2 transcript by 20% to 30% and decreased NO3− influx by 50%, indicating that NO3− itself does not regulate transcript abundance, but may exert post-transcriptional effects. Experiments with methionine sulfoximine suggested that NH4+ may down-regulate HvNRT2 gene expression and high-affinity NO3− influx by effects operating at the transcriptional and post-transcriptional levels. Azaserine decreased HvNRT2 transcript levels and NO3− influx by 97% and 95%, respectively, while decreasing Glu and increasing Gln levels. This suggests that Gln (and not Glu) is responsible for down-regulating HvNRT2 expression, although it does not preclude a contributory effect of other amino acids.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=59004Documentos Relacionados
- Zinc Deficiency Up-Regulates Expression of High-Affinity Phosphate Transporter Genes in Both Phosphate-Sufficient and -Deficient Barley Roots1
- Isolation and Characterization of HvNRT2.3 and HvNRT2.4, cDNAs Encoding High-Affinity Nitrate Transporters from Roots of Barley1
- Rapid Up-Regulation of HKT1, a High-Affinity Potassium Transporter Gene, in Roots of Barley and Wheat following Withdrawal of Potassium1
- High-Affinity Potassium Transport in Barley Roots. Ammonium-Sensitive and -Insensitive Pathways1
- Feedback Regulation of Nitrate Influx in Barley Roots by Nitrate, Nitrite, and Ammonium.