Phytochrome-Mediated Light Regulation of Nitrate Reductase Expression in Squash Cotyledons

Abstract

In etiolated squash (Cucurbita maxima L.) cotyledons, nitrate-inducible NADH:nitrate reductase activity and protein were increased in darkness by red light pulses with red/far-red photoreversibility. Continuous far-red light also led to increased levels of nitrate reductase activity and protein. Poly(A)+ RNA, which hybridizes to squash nitrate reductase cDNA, was also increased by light treatments. Thus, we found that after nitrate triggering, nitrate reductase expression appears to be regulated by light via phytochrome.

5[prime] Proximal Regions of Arabidopsis Nitrate Reductase Genes Direct Nitrate-Induced Transcription in Transgenic Tobacco

“…In addition to the two determining factors nitrate and carbohydrates, other factors also regulate NR gene expression. Light signals at red/far-red (Rajasekhar et al, 1988;Melzer et al, 1989) and at blue (Melzer et al, 1989) regions of the spectrum both increase the NR mRNA levels of etiolated seedlings. Cytokinin enhances, whereas ABA suppresses, the light induction of NR transcription in etiolated barley leaves (Lu et al, 1990(Lu et al, , 1992.…”

cDNA Clones for Corn Leaf NADH:Nitrate Reductase and Chloroplast NAD(P)+:Glyceraldehyde-3-Phosphate Dehydrogenase

“…RNA blots were baked in vacuo for 2 h at 80'C and prehybridized, hybridized, and washed as for DNA blots. Autoradiography was at -70'C for varying lengths of time (15 (3,4,(6)(7)(8). The DNA sequence of Zmnrl is presented in Figure Figure 1 Figure 2.…”

“…Pulses of red and continuous far-red light, which induce the phytochrome system, enhanced NR, and it appeared that phytochrome mediated light enhancement of NR expression, but only in the presence of nitrate (15). We have isolated a cDNA clone for corn leaf NR and used it to study NR regulation by nitrate in the dark and light.…”

Phylogenetic analysis and photoregulation of siroheme biosynthesis genes: uroporphyrinogen III methyltransferase and sirohydrochlorin ferrochelatase of Arabidopsis thaliana

“…The primary step of nitrogen assimilation from soil is the reduction of nitrate to nitrite catalysed by nitrate reductase, a well known enzyme that is light regulated and under the circadian control (de Cires et al 1993;Deng et al 1990;Huber et al 1992;Raghuram et al 1999). The light response and regulation of nitrate reductase is mediated by phytochromes (Rajasekhar et al 1988). Light also stimulates the activity of nitrite reductase of mustard, tomato and maize leaves via the phytochrome mediated signaling pathway (Becker et al 1992;Rajasekhar and Mohr 1986).…”