The nitrate reductase gene (niaD) is the most frequently utilized as a selectable marker for homologous integration at the niaD locus of Aspergillus oryzae. In this study we developed a method for curing of the niaD-based plasmid integrated on the A. oryzae genome. Positive selection using a modified chlorate medium containing leucine as a nitrogen source enabled efficient isolation of the stra...

Using the inhibitor of RNA synthesis, 4,5',8-trimethylpsoralen plus near ultraviolet light, the half-life of the rate-limiting RNA species required for the induction of nitrate reductase in XD cells of tobacco was estimated to be 4 hours. Amino acids, the end product of nitrate assimilation, reduced the half-life to 1 hour. It is suggested that amino acids exert a posttranscriptional control on...

Nitrate is an important nitrogen source used by plants. Despite of the considerable variation in the amount of soil nitrate, plants keep cytosolic nitrate at a homeostatic controlled level. Here we describe a set of homeostatic controller motifs and their interaction that can maintain robust cytosolic nitrate homeostasis at fluctuating external nitrate concentrations and nitrate assimilation le...

When tobacco is provided with a high nitrate supply, only a small amount of the nitrate taken up by the roots is immediately assimilated inside the roots, while the majority is transported to the leaves where it is reduced to ammonium. To elucidate the importance of root nitrate assimilation, tobacco plants have been engineered that showed no detectable nitrate reductase activity in the roots. ...

A PCR approach was used to construct a database of nasA genes (called narB genes in cyanobacteria) and to detect the genetic potential for heterotrophic bacterial nitrate utilization in marine environments. A nasA-specific PCR primer set that could be used to selectively amplify the nasA gene from heterotrophic bacteria was designed. Using seawater DNA extracts obtained from microbial communiti...

Plants adopt various strategies to fulfill their nitrogen nutrition requirement, the most important being the uptake of nitrate from the soil and its subsequent assimilation in to amino acids. The uptake of nitrate is energy dependent and is an active process involving high affinity and low affinity transport systems. The net uptake of the anion depends upon both influx as well as on its passiv...

We determined the quantum requirements for growth (1/ϕμ ) and fatty acid (FA) biosynthesis (1/ϕFA ) in the marine diatom, Phaeodactylum tricornutum, grown in nutrient replete conditions with nitrate or ammonium as nitrogen sources, and under nitrogen limitation, achieved by transferring cells into nitrogen free medium or by inhibiting nitrate assimilation with tungstate. A treatment in which tu...

Nitrate reductase (NR) is the key enzyme of nitrate assimilation subjected to inhibition by heavy metal treatment .In general, the inhibitory effect of heavy metals may be attributed to either blocking the supply of reducing equivalents of nitrate reduction, formation of mercurial derivatives of thiol(–SH) groups of nitrate reductase or synthesis of phytochelatins (PC).The effect of mercury(Hg)...

Nitrate reductase inhibitor is usually found in the roots of rice plants (Oryza sativa L. cv MR7), but it was also produced in the shoots of aging plants. The inhibitor was inducible in the shoot of rice seedlings by dark, minus-nitrate or plus-ammonium treatments. There appears to be a general involvement of the inhibitor in the control of nitrate assimilation in the plant.