Comparative Studies on Nitrate Reductase in Agrostemma githago Induced by Nitrate and Benzyladenine

Abstract

The characteristics of nitrate-nitrate reductase and benzyladenine-nitrate reductase were compared by four methods but no differences could be detected: (a) Both enzymes sedimented with the same velocity during sucrose density gradient centrifugation. (b) Their distribution among fractions obtained by differential precipitation with (NH4)2SO4 was identical. (c) The elution profile of nitrate-nitrate reductase and benzyladenine-nitrate reductase after chromatography on diethylaminoethyl Sephadex A-25 columns showed no significant difference. (d) On polyacrylamide gel, the electrophoretic migration of the two enzymes was also identical.NR' in excised embryos of Agrostemma githago can be induced by incubating them in media containing either nitrate or a cytokinin (1-3). The physiological significance of the hormonal induction of NR, as opposed to substrate induction, is not known at this point. Accumulating evidence indicates, however, that cytokinins are acting in a manner different from nitrate in inducing NR. BA loses its effectiveness as an inducer of NR after 64 hr of seed germination, whereas the effect of nitrate is not time-limited (4). The level of NR decreases upon

Posttranscriptional Regulation of the Sesbania rostrata Early Nodulin Gene SrEnod2 by Cytokinin

“…It remains to be determined whether this oscillation in SrEnod2 mRNA is regulated in a circadian manner. In a study by Pilgrim et al (1993) on nitrate reductase mRNA, expression of which is known to be induced by cytokinin (Dilworth and Kende, 1974;Lu et al, 1990), it was found that nitrate reductase mRNA accumulation also oscillates in a circadian fashion. These oscillations in mRNA accumulation were shown by nuclear run-on assays to occur at a posttranscriptional level; therefore, the involvement of posttranscriptional mechanisms for the oscillation in SrEnod2 mRNA accumulation may also be plausible.…”

“…mRNA accumulation is enhanced by cytokinins, including those encoded by a wheat protein kinase gene (Sano and Youssefian, 1994), the gene for the small subunit of Rubisco (RbcS) (Flores and Tobin, 1988), the chlorophyll a / b binding protein gene (Cab) (Flores and Tobin, 1988), defense-related genes (Memelink et al, 1987), the PEP carboxylase gene (PepC) (Suzuki et al, 1994), nitrate reductase genes (Lips and Roth-Bejerano, 1969;Dilworth and Kende, 1974;Lu et al, 1990), the pollen allergen gene (Ciml) (Crowell, 1994), the multiple stimulus response gene cDNA (pLS216) (Dominov et al, 1992), genes of the anthocyanin biosynthetic pathway (Deikman and Hammer, 1995), cyclin D homologs (Soni et al, 1995), and genes for a number of unidentified cDNAs (Crowell et al, 1990). It was shown by nuclear run-on assays that the expression of genes encoding PEP carboxylase (Suzuki et al, 1994), nitrate reductase (Lu et al, 1990), chalcone synthase, and dihydrofolate reductase (Deikman and Hammer, 1995) are enhanced primarily at the transcriptional level by cytokinin.…”

Cytokinin regulation of a soybean pollen allergen gene

“…Among the mRNAs that have been shown to accumulate in response to cytokinin are those encoding the light-harvesting chlorophyll a/b-binding protein [ 14,15,23,40], the small subunit of ribulose-l,5-bisphosphate carboxylase (Rubisco) [13,14,21,24], nitrate reductase [10,11,19,22,25], an early nodulin…”

Polyribosome Formation in Relation to Cytokinin-induced Cell Division in Suspension Cultures of Glycine max [L.] Merr.

“…Numerous studies have shown that the cytokinins also stimulate protein and/or RNA synthesis in various plant tissues (8,25,32,34,45,47,50 (9,16,20) and could initiate qualitative changes in protein synthesis which would result in the synthesis of the specific cell division proteins which are necessary for a cell to progress through its division cycle (14,15).…”