Ammonium influence on nitrogen assimilating enzymes and protein accumulation in suspension cultures of Paul's Scarlet rose

Abstract

The influence of NH4"^ on protein accumulation was examined by growing suspension cuhures of Rosa cv. Paul's Scarlet on two defined media. Both contained 1920 |xmol of NO," but only one contained 72,8 \imo\ of NH4"^. At the conclusion of a 14-day growth period, cultures grown with NH4''' possessed twice as much protein as cultures grown without NH^"^. The influence of NH4"^ did not appear to be a substrate effect, since the amount of NH4* provided accounted for only 10% of the nitrogen recovered in protein.The provision of NH4'^ in the starting medium increased the activity (nmol substrate • h"' • g~' fr wt) of glutamate dehydrogenase and glutamate synthase, and reduced the activity of glutamine synthetase. A comparison of the total activity per culture for each of these enzymes with the rate of nitrogen incorporation into protein showed that the enzymatic potential of glutamine synthetase and glutamate dehydrogenase greatly exceeded the actual in vivo rate of nitrogen assimilation through the respective pathways. Thus it was concluded that the availability of either of these enzymes does not limit nitrogen assimilation in rose cells and the fluctuations in their level brought about by NH4"*^ was of no physiological importance.The activity of glutamate synthase per culture approximated the rate of nitrogen incorporation into protein during early stages of growth, and for that reason may have limited nitrogen assimilation or caused a diversion of nitrogen through the alternative pathway to glutamate catalyzed by glutamate dehydrogenase.' Permanent address; Bibekananda Mohanty, CSRS Program,

Quantification of organelle changes in plant suspension cultures during growth

“…The ER is associated with polypeptide formation, plastids are the site for the synthesis of several amino acids including the aspartate family (Wallsgrove et al 1983), and mitochondria have been shown in rose cultures to contribute as much as one-fourth of their metabolized carbon to amino acid skeletons (Hunt & Fletcher 1976). Recognizing the involvement of these cell components with protein synthesis, it is of interest to compare the observed structural changes noted in the study with previous protein and respiration data collected on cultures of Paul's Scarlet rose (Hunt & Fletcher 1976;Mohanty & Fletcher 1980). In earlier studies it was shown that the maximum rate of protein synthesis (110 mg protein/g frwt) (Hunt & Fletcher 1976) was on day 5 and thereafter declined rapidly until day 10, where it remained at a fairly constant and low level until culture death.…”

“…Each period lasts several days and is similar to one of the developmental stages characteristic of cells present in meristematic regions of intact plants. With rose cultures it has been shown that as the cells progress through the various growth periods, a number of important physiological processes, organic acid metabolism (Fletcher & Beevers 1970), amino acid synthesis (Hunt & Fletcher 1976;Nesius & Fletcher 1975), respiration (Hunt & Fletcher 1976), and protein synthesis (Hunt & Fletcher 1976;Mohanty & Fletcher 1980) change dramatically. It has also been established with various cell lines that during culture growth cells experience numerous ultrastructural changes (Fowke 1986;Sutton-Jones & Street 1968).…”

Hydroponic culturing upregulates sucrose and glutamine metabolism by enhancing their utilization via intermediates of aerobic pathway in wheat

“…Seed from each genotype were sprouted in a controlled en- The nitrate reductase activity was estimated by the method described by Jaworski (1971). Glutamine synthatase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) activity were extracted by the method of Mohanty and Fletcher (1980). The GS activity was assayed by Kanamori and Matsumoto (1974).…”

Apical stem culturing to enhance cell sap assimilates towards grain sucrose and glutamine metabolism in wheat

“…Glutamate synthase (GOGAT) activity was extracted by the method of Mohanty and Fletcher (1980). Developing grains (1 g) was homogenized in liquid nitrogen with 5 ml of extraction medium containing 100 mM Tris-HCl (pH 7.5), 0.2 M sucrose, 10 mM KCl, 10 mM MgCl 2 , 10 mM EDTA and 10 mM b-mercaptoethanol was added.…”