Uptake, Metabolism, and Storage of Phosphate and Nitrogen in Plant Cells; an NMR Perspective

1995

Appl Environ Microbiol

The metabolism of glucose and xylose was studied as a function of oxygenation in suspensions of Candida tropicalis by 31 P and 13 C nuclear magnetic resonance spectroscopy. Both the rate of carbohydrate metabolism and the cytoplasmic pH were independent of the rate of oxygenation in cells metabolizing glucose. However, these two parameters were markedly dependent on the rate of oxygenation in C. tropicalis cells metabolizing xylose. For example, the cytoplasmic pH in fully oxygenated xylose-metabolizing cells was 7.8 but decreased to 6.3 in anoxic cells. In general, suspensions of cells consuming xylose had a lower rate of sugar uptake, a more acidic cytoplasmic pH, lower levels of sugarphosphomonoesters (SP) and ATP, higher levels of intracellular P i , a more alkaline vacuolar pH, and a lower rate of extracellular P i assimilation and polyphosphate synthesis than cells consuming glucose. These observations indicate that C. tropicalis metabolizing xylose is less energized than glucose-metabolizing cells. On both carbon sources, however, an inverse correlation between intracellular levels of SP and P i was observed. Also, uptake of extracellular P i correlated with the synthesis of polyphosphates within the cells. During anoxia, P i was not taken up, and polyphosphates were hydrolyzed instead to fulfill the cells' requirements for phosphate.

Section: Resultsmentioning

confidence: 99%

Phosphorus-31 and carbon-13 nuclear magnetic resonance studies of glucose and xylose metabolism in Candida tropicalis cell suspensions

Lohmeier-Vogel

Hahn‐Hägerdal

1995

Appl Environ Microbiol

“…In fact, it completely depletes the medium from Pi (4), and while it is sequestered in the vacuoles, the cytoplasmic Pi level is very strictly regulated (unpublished observations, 4). Vacuolar Pi concentrations of higher than 100 mM have been reported for Catharanthus roseus (24,47). Also the pH in both the cytoplasm and the vacuole are strictly regulated during this rapid Pi uptake (4,45).…”

Section: Resultsmentioning

confidence: 97%

“…For example, the relatively narrow linewidth, but comparatively short relaxation time allow the rapid collection of quantitative data (3,21,42). However, all other resonances, such as those for amino acids, are broad in '4N NMR spectra and hence they are studied more advantageously by "~N NMR (25,42,47). The latter nucleus gives better resolved spectra because it does not have the quadrupole moment which is inherent in 14N, but isotopic labeling with l~N isotopically labeled precursors is required (47).…”

Section: Resultsmentioning

confidence: 98%

“…The culture media for tissue-cultured plant cells generally contain NH4NO 3 and hence both NH4 + and NOz-can potentially be taken up and assimilated into amino acids. Two NMR nuclei can in principle be used to study the nitrogen metabolism in plants, 14N and 15N NMR (47). Particularly for the study of NO 3-and NH4 ÷, the 14N NMR nucleus provides certain advantages.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Noninvasive NMR studies of metabolism in cultured Catharanthus roseus cells

In Vitro Cell.Dev.Biol.-Plant

Lundberg

Bagh

1999

Self Cite

Nuclear magnetic resonance (NMR) spectroscopy provides a unique modality for the study of tissue-cultured plant cells. One of its major attractions is that it allows noninvasive studies of plant material. In addition, it can provide insight into the pH in the vacuole and cytoplasm, and into the compartmentalization of certain metabolites. In this review we show how phosphorus-31 NMR is used to study intracellular pH, phosphate uptake and storage, and energy metabolism in suspension ceils of Catharanthus roseus. In addition, multinuclear NMR studies of the uptake of ammonium and the gradients of K + over the membrane are discussed as well. The use of two-dimensional NMR for the study of whole cell extracts is also described. Finally, we show how nitrogen-14 and nitrogen-15 NMR are used to obtain information about the assimilation of inorganic sources in developing carrot somatic embryos. These NMR studies provide a unique insight into the metabolism of tissue-cultured plant cells.

“…One-dimensional NMR spectra acquisition conditions ('••N and ' *N NMR spectra) were obtained by the methods of Thorpe et al, (1989), Chemical shifts were referenced to NO3 with resonance assignments based on previous work (Thorpe et al, 1989, Vogel and Ltmdberg 1989, Lundberg et al, 1990 as well as addition of standards to cell extracts.…”

Section: Nmr Spectroscopymentioning

confidence: 99%

Stage‐specific nitrogen metabolism in developing carrot somatic embryos

Joy

McLntyre

et al. 1996

Physiologia Plantarum

Self Cite

The physiology of individual somatic embryo developmental stages otDaucus carota L. was examined by in vivo nuclear magnetic resonance (NMR) spectroscopy, amino acid analysis and 14C‐labeling. 15N NMR spectroscopy was used to examine the uptake and incorporation of 15N isotopically labeled inorganic nitrogen sources. NMR spectra of proembryogenic masses (PEMs) contained resonances for histidine, amino sugars, glutamine, arginine, urea, alanine. α‐amino nitrogen, serine, aliphatic amines and several unknowns. Similar resonances were found in various embryo developmental stages. However, resonances for arginine and aliphatic amines peaked during globular and torpedo stages and substantially decreased in germinating stage embryos. The dominant resonances observed in non‐embryogenic cells and germinating embryos were glutamine and α‐amino nitrogen. Amino acid analysis of the various embryo stages showed that glutamate, glutamine and arginine were the major contributors to the soluble amino acid profiles. During development, glutamate and glutamine continued to increase in concentration whereas arginine and its related metabolites (i.e. ornithine and y‐aminobutyric acid [GABA]) were biphasic; increasing in globular and torpedo stage embryos and decreasing in germinating embryos. Carbon‐14 labeling indicated that labeled glutamine pools in non‐embryogenic and germinating embryos were greatest compared to other embryo stages, whereas labeled GABA pools were greatest in globular and torpedo stage embryos. Taken together, these data indicate that the physiology of each embryo developmental stage is distinct. They also suggest that during somatic embryo development, a switch takes place in metabolism whereby the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway is predominant in non‐embryogenic cells and germinating stage embryos. Furthermore, during early to mid‐embryo development (PEMs, globular and torpedo stage embryos), metabolism utilizing the omithine cycle is enhanced and predominant.