Light regulation nitrate reductase

Melzer, J.M., Kleinhofs, A. Warner, R.L. (1989). Nitrate reductase regulation effects of nitrate and light on nitrate reductase mRNA accumulation. Molecular and General Genetics 217, 341-6. 

Rajasekhar, V.K., Gowri, G. Campbell, W.H. (1988). Phytochrome-mediated light regulation of nitrate reductase expression in squash cotyledons. Plant Physiology 88, 242 1. 

In barley, upon addition of nitrate, NR mRNA accumulated rapidly in both leaf and root tissue. After 2 hr of exposure to nitrate, NR mRNA reached peak levels in the roots and nearly 80% of peak levels in the leaves. Low levels of NR mRNA were detected in roots in the absence of nitrate, but the possibility of trace levels of nitrate contamination could not be ruled out (Melzer et al, 1989). The rapid increase in NR mRNA in the leaves is somewhat surprising in that appreciable nitrate was not detected in leaf tissue for several hours after exposure of the roots to nitrate. After induction for 4 hr in the roots and 12 hr in the leaves, the levels of NR mRNA declined and stabilized at 50-70% of peak levels. Nitrate reductase activity and nitrate content in the leaves continued to increase while NR mRNA declined, indicating that regulation of NR is not entirely a function of NR mRNA or nitrate concentration. After the initial 24-hr induction period, NR activity and NR mRNA remained stable for several days in barley seedlings grown under continuous light and nitrate (Melzer et al, 1989). 

Nitrite reductase is regulated by nitrate and light in a manner similar to NR. Nitrite reductase activity increases in response to nitrate or nitrite (Ingle et al. 

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