high-NaCl Medium Research Articles

Salt-tolerance in Brassica juncea L. I. In vitro selection, agronomic evaluation and genetic stability

In vitro selection of salt tolerant plants of Brassica juncea L. (Indian mustard) cv. Prakash has been accomplished by screening highly morphogenic cotyledon explant cultures on high NaCl media. Out of a total of 2,620 cotyledons cultured on high salt medium, 3 survived, showed sustained growth and regenerated shoots. They were multiplied by axillary bud culture on NaCl free medium. The salt-selected shoots retained salt tolerance following 3 month of growth and multiplication on control medium. While two of these somaclones flowered and set seeds, third one grew slowly, had abnormal leaf morphology and was sterile. The seed of the two fertile plants were sown in the field to raise R1 segregating generation. Data were recorded for field, other agronomic components and oil content. The somaclonal lines, both selected salt-tolerant and non-selected, showed tremendous amount of variation for all the characters studied. One of the two tolerant somaclones invariably showed reduced height, longer reproductive phase and higher 1000 seed weight. Based on the agronomic performance of R1 plants of these somaclones, some plants were selected and their progeny were evaluated for agronomic performance under standard field conditions and salt-tolerance in the greenhouse using sand pot culture method. Most of the lines bred true for their specific characteristics. In the greenhouse, selected salt-tolerant somaclones (SR-2 and SR-3) performed better for plant growth, yield and other agronomic traits at higher salt treatments, indicating thereby that salt-tolerance trait selected in vitro was expressed in the whole plants and is genetically stable and transmitted onto the progeny. The two tolerant lines, however, differed in their salt-tolerance during vegetative and reproductive phases as indicated by their salt-tolerance and stress susceptibility indices. The mechanism of salt-tolerance is not clear and needs to be further investigated.

Multiple tropomyosin polypeptides in chicken embryo fibroblasts: differential repression of transcription by Rous sarcoma virus transformation.

We have found that cytoskeletal extracts of cultured chicken embryo fibroblasts contain at least seven distinct polypeptides (two major and five minor) which cross-react with antiserum to chicken smooth muscle tropomyosin. These polypeptides range in apparent molecular weight from 31,000 to 47,000, and each is encoded by mRNAs which specifically hybridize to cloned muscle tropomyosin cDNAs. These nonmuscle tropomyosin species and their respective mRNAs are electrophoretically distinct from those of chicken skeletal muscle and appear by genomic DNA blotting to comprise a part of a multigene tropomyosin family. In Rous sarcoma virus-transformed chicken embryo fibroblasts, synthesis of the tropomyosins is differentially repressed such that the synthesis of the major species (cp35 and cp33, cytoskeletal proteins of molecular weight 35,000 and 33,000, respectively) and three minor species is drastically reduced, whereas the synthesis of two of the minor species (cp32 and cp31) remains essentially unchanged. Analysis of cellular mRNA and runoff nuclear transcription experiments indicate that the repression of tropomyosin synthesis by Rous sarcoma virus transformation occurs at the level of transcription. This repression of tropomyosin synthesis is partially mimicked in normal chicken embryo fibroblasts during incubation in high-NaCl medium, a condition in which chicken embryo fibroblasts acquire many characteristics of transformed cells.

Multiple tropomyosin polypeptides in chicken embryo fibroblasts: differential repression of transcription by Rous sarcoma virus transformation.

We have found that cytoskeletal extracts of cultured chicken embryo fibroblasts contain at least seven distinct polypeptides (two major and five minor) which cross-react with antiserum to chicken smooth muscle tropomyosin. These polypeptides range in apparent molecular weight from 31,000 to 47,000, and each is encoded by mRNAs which specifically hybridize to cloned muscle tropomyosin cDNAs. These nonmuscle tropomyosin species and their respective mRNAs are electrophoretically distinct from those of chicken skeletal muscle and appear by genomic DNA blotting to comprise a part of a multigene tropomyosin family. In Rous sarcoma virus-transformed chicken embryo fibroblasts, synthesis of the tropomyosins is differentially repressed such that the synthesis of the major species (cp35 and cp33, cytoskeletal proteins of molecular weight 35,000 and 33,000, respectively) and three minor species is drastically reduced, whereas the synthesis of two of the minor species (cp32 and cp31) remains essentially unchanged. Analysis of cellular mRNA and runoff nuclear transcription experiments indicate that the repression of tropomyosin synthesis by Rous sarcoma virus transformation occurs at the level of transcription. This repression of tropomyosin synthesis is partially mimicked in normal chicken embryo fibroblasts during incubation in high-NaCl medium, a condition in which chicken embryo fibroblasts acquire many characteristics of transformed cells.

Transformation parameters induced in chick cells by incubation in media of altered NaCl concentration

Lowering the NaCl concentration of the medium in which normal chick cell cultures are incubated causes them to enlarge, vaculate, and appear morphologically similar to cells transformed by the Bryan strain of Rous sarcoma virus (RSV). Raising the NaCl concentration of the medium causes cells to become round or spindle shaped and to appear morphologically similar to cells transformed by the Schmidt-Ruppin strain of RSV. Uninfected chick cell cultures incubated in either low or high NaCl medium also express many characteristics of transformed cells. They lose contact inhibition of growth and movement, grow to higher saturation densities, synthesize reduced amounts of fibronectin, exhibit increased lectin agglutinability, transport increased amounts of hexoses, have reduced levels of succinic dehydrogenase activity, produce increased amounts of lactate and pyruvate, and can be serially passaged in culture significantly longer than normal chick fibroblasts. We were not able to induce normal chick cells to exhibit all transformation parameters by incubation an altered NaCl media: the cells did not grow in soft agar or in low serum medium. Cells transformed by the Bryan and Schmidt-Ruppin strains of RSV exhibit strain-specific changes in their intracellular Na + and K + concentrations. Cells incubated in altered NaCl media exhibit altered intracellular monovalent cation concentrations similar to those seen in the cells they resemble morphologically. Results presented in this publication identify a possible new transformation parameter, alteration of the intracellular Na + and K + concentrations, and suggest that many, but not all transformation parameters may be consequences of the altered intracellular monovalent cation concentrations.

Alteration of the phospholipid composition of Staphylo-coccus aureus cultured in medium containing NaCl

1. 1. Cardiolipin of Staphylococcus aureus 209 P markedly increases and phosphatidylglycerol and lysylphosphatidylglycerol diminish as the NaCl concentration of the culture medium increases. 2. 2. The major change in fatty acid composition lies in the proportion of branched acids, resulting in an increase of the branched fatty acids in cardiolipin when cultured in high NaCl medium.

The effect of tonicity, d-mannitol, d-sorbitol, and choline chloride on the water content of mouse brain slices, and on the compartmentation of the space indicated by ‘extracellular space markers’

(1) Mouse cerebrum slices were incubated with ‘extracellular space markers’ in either HEPES-( N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid) buffered media with various concentrations of NaCl, or standard HEPES-buffered medium with 400 mM choline chloride, 800 mM d-mannitol, or 800 mM d-sorbitol added. Nominal tonicities of the media ranged from 170 to 1100 mosM. (2) Tissue swells extensively in media ranging from hypotonic to hypertonic containing various salt concentrations. Swelling is less in the choline chloride medium, and is slight in the d-mannitol or d-sorbitol medium. (3) In media with various salt concentrations, the penetration of inulin, sucrose, d-mannitol, d-sorbitol, and sulfate into tissue is greater at 37°C than at 0°C, showing the presence of a second marker (inulin) space for these substances; i.e., a tissue compartment which is accessible to the marker substance at 37°C but not at 0dgC (Cohen et al. 6). At both temperatures, the smaller the marker molecule, the larger the indicated ‘extracellular space’; and the greater the NaCl concentration, the greater the marker penetration. The size of the second space is only slightly dependent on the marker, or on the salt concentration. For some markers, the second space is reduced or absent in the sugar alcohol or choline chloride medium. (4) Several ‘extracellular space markers’ may enter some cellular compartment. The 800 mM sugar alcohols increase the permeability of cells to markers. Choline chloride, d-mannitol, and d-sorbitol, in high concentrations, enter most tissue water but are not actively concentrated. (5) The entry of thiocyanate is anomalous, being consistently greater at 0°C than 37°C. (6) In high NaCl medium, d-glutamate at 0°C penetrates tissue to the same extent as inulin at 37°C thus indicating the continuing existence at 0°C of a tissue compartment corresponding to the 37°C inulin space. Several other amino acids give larger tissue spaces at 0°C, with concentrative uptake of l-histidine and l-leucine occurring by 20 min incubation, and glycine by 60 min incubation. (7) It has been suggested that the second marker space may consist of a ramifying system of microtubules extending throughout a cell body and communicating with the extracellular space through a micropore. The effects of the incubation medium on the second space and on the total tissue water may be due in part to changes in the size of these tubules.

THE ADAPTATION OF TETRAHYMENA TO A HIGHNaClENVIRONMENT

1. A culture of Tetrahymena pyriformis adapted to a high NaCl medium, containing 220 mM NaCl, was investigated. The concentration of NaCl in the medium of the normal (unadapted) animals was about 35 mM.2. Upon direct transfer to the high NaCl medium, only 2% of the normal cells were sufficiently tolerant of the stress to survive and divide. Data were presented indicating that stress tolerance is a heritable character, and that this character was selected for upon transfer to the high NaCl medium.3. The cell volume of the adapted cells was 45% less than that of the normal animals. The adapted cells were more nearly spherical than normal cells. Despite the smaller size of the adapted cells, the amount of non-volatile material per cell was the same in normal and adapted cells.4. The main feature of the adaptation was a greatly increased ability of adapted cells to maintain a low cellular salt concentration. Sodium concentration in normal cells in normal medium was 13 meq./l. of cells. Sodium concentration in...