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R Turgeon

Publications and source records attributed to R Turgeon.

24 records · Page 2Linked to original sources
PubMed1986

Expression of a foreign gene linked to either a plant-virus or a Drosophila promoter, after electroporation of protoplasts of rice, wheat, and sorghum.

The bacterial chloramphenicol acetyltransferase (CAT) gene was expressed in protoplasts of three important graminaceous plant species after introduction of the gene by electroporation. Gene transfer occurred when high-voltage electric pulses were applied either directly or indirectly (without anode contact) to a solution containing plasmid DNA and protoplasts of rice, wheat, or sorghum. The indirect method was more rapid, resulted in higher protoplast viability, and was less subject to contamination than the direct-contact method. Gene expression of approximately equal magnitude resulted when the CAT gene was fused to either the 35S promoter of cauliflower mosaic virus or the copia long terminal repeat promoter of Drosophila. Together with recent advances in regeneration of callus and whole plants from protoplasts, this system makes it possible to study inheritance and expression of genes introduced into graminaceous monocotyledonous plants.

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PubMed1984

Termination of nutrient import and development of vein loading capacity in albino tobacco leaves.

The sink-source conversion in developing leaves of tobacco (Nicotiana tabacum L.) was studied to determine whether import termination is caused by the onset of export or is related to achievement of positive carbon balance. Albino shoots were grown in vitro and grafted to detopped stems of green tobacco plants. Termination of import was studied by providing mature leaves of the stock plant with (14)CO(2) and detecting the presence of labeled nutrient in developing albino leaves by whole-leaf autoradiography. In albino leaves, import terminated progressively in the basipetal direction at the same stage of development as in leaves of green shoots. Starch was not present in the plastids of mesophyll cells of mature albino leaves but starch was synthesized when discs were cut from these leaves and incubated on 3 millimolar sucrose. Import ceased progressively in developing green leaves even when photosynthesis was prevented by darkening. It was concluded that cessation of import does not require achievement of positive carbon balance and is not the direct result of export initiation.To determine whether vein loading capacity develops in albino leaves, discs were cut from mature leaves and floated on [(14)C]sucrose solution. Uptake of label into the veins was detected by autoradiography and this uptake was sensitive to the phloem loading inhibitor p-chloromercuribenzenesulfonic acid. However, the amount of label taken up by veins in albino leaves was less than that taken up by veins of mature green leaves.

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PubMed1982

Cytokinesis, cell expansion, and the potential for cytokinin-autonomous growth in tobacco pith.

Pith tissue from Nicotiana tabacum L. cv ;Maryland Mammoth' or ;Wisconsin 38' was isolated, free of vascular tissue, and cultured on a medium containing auxin but no cytokinin. Explants from the apical 1 cm of stem, within the pith rib meristem, initiated callus growth with 100% efficiency. Macroscopically visible callus was evident 5 days after the tissue was isolated, and the cultures grew persistently in the absence of cytokinin. Heat treatment, sometimes used to initiate cytokinin habituation, was not required. Explants from tissue basipetal to the pith rib meristem declined in the frequency of habituation with increasing distance from the shoot apex. Although pith tissue which was growing, in vivo, was more prone than mature tissue to establish cytokinin-habituated callus, the basipetal decline in habituation frequency extended well beyond the zone of cell expansion. Explants from mature pith 40 centimeters or more from the shoot apex grew in the absence of cytokinin with 18% frequency, although the response required at least 2 weeks of culture. Further analysis demonstrated that tissue near the periphery of mature pith was more prone to cytokinin-habituation than tissue from the pith center.

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PubMed1976

Studies on the recovery of crown gall tumor cells.

Our previous studies have shown that, while a persistent but potentially reversible suppression of the tumorous state appears to be a characteristic feature of the vegetative phase of teratoma shoot growth in the crown gall disease of plants, a recovery from that state occurs during the reproductive phase. An analysis has now been made of the reproductive process in an attempt to define the precise stage at which recovery occurs. The results of this analysis have shown that diploid somatic cells of teratoma-derived flower parts such as those found in petals and filaments are inherently neoplastic. On the other hand, haploid cells of plants grown from anthers of the same flowers and diploid cells of F(1) generation plants grown from teratoma-derived seed have, by generally accepted criteria, recovered from the tumorous state. These findings have been interpreted to mean that the loss of neoplastic properties occurs in crown gall teratoma cells during meiosis rather than during fertilization or later stages of the reproductive process.An analysis of more than 2000 teratoma-derived tumor shoots has shown, moreover, that a recovery from the tumorous state may also occur, although apparently as a very rare event, during the vegetative phase of teratoma shoot growth.

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