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Heterotrophic tobacco cell cultures during greening (1981)

Brangeon, Judy ; Nato, Aimé

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 53 (1981), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Structural changes in cells and plastids are described that occur during the greening of an initially dark-grown cell suspension of tobacco (Nicotiana tabacum L. cv. Xanthi). The pattern of cell growth during greening, expressed in dry weight or cell number, showed a classical sigmoid curve with a lag phase (T0–T2), an exponential phase (T3–T9) and a stationary phase (T10–T21). Achlorophyllous vacuolated cells (T0), obtained after 3 culture cycles in the dark, contained amyloplasts devoid of lamellae. Exposure to light brought about an enrichment in cytoplasm and an amyloplast to proplastid transformation (starch loss) accompanied by chlorophyll synthesis. By T3, many cells appeared meristematic and contained dividing proplastids with rudimentary single lamellae typical of those in intact meristematic leaf cells. As cell division occurred (T3 to T9), plastids replicated and their internal membrane system developed progressively into defined grana-intergrana thylakoids. By the stationary phase of cell growth (T14), the lamellar system had reached a highly structured grana-intergrana network typical of higher plant chloroplasts. We have emphasized the analogies between the sequence of events (proplastid to chloroplast transition) during the greening of tobacco cells and that in developing intact leaves; in this respect the cell cultures provide a useful material for studies dealing with the biogenesis of structural or physiological events.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1981.tb04508.x

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Glutamine synthetase in ribulose 1,5-bisphosphate carboxylase/oxygenase deficient tobacco mutants in cell suspension culture (1984)

Hirel, Bertrand ; Nato, Aimé ; Martin, Francis

Springer

Plant cell reports 3 (1984), S. 106-108

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ISSN: 1432-203X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract In two tobacco mutants lacking ribulose, 1,5-bisphosphate carboxylase/oxygenase the amount of glutamine synthetase and its activity were determined and compared with the wild type green cells. It was shown that in these two mutants glutamine synthetase protein content was six times lower than in the wild type. This situation was comparable to that found in etiolated cells where ribulose 1,5-bisphosphate carboxylase/oxygenase was absent. These observations suggest that a common regulatory mechanism might control the dual light dependent biosynthesis of both enzymes. The results have also implications concerning the efficiency of the reassimilation of ammonia by chloroplastic glutamine synthetase during the photorespiratory process.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02441011

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Carbon metabolism in in vitro cultures of date palm: the role of carboxylases (PEPC and RubisCO) (1999)

Masmoudi, Raja ; Rival, Alain ; Nato, Aimé ; [et al.]

Springer

Plant cell, tissue and organ culture 57 (1999), S. 139-143

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ISSN: 1573-5044

Keywords: carbon metabolism ; carboxylases ; CO2 fixation ; Phoenix dactylifera L. ; somatic embryogenesis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm (Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic (NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO2 h−1 mg−1 TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7 to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased from 5.3 to 1.2 μmol CO2 h−1 mg−1 TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO2 h−1 mg−1 TSP ) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006308529895

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