Inheritance of Chloramphenicol Resistance, a Trait Selected in Cell Cultures of Nicotiana sylvestris. Speg. and Comes.

Three cell lines with improved resistance to growth inhibition by chloramphenicol were selected from cell cultures of Nicotiana sylvestris. Resistance was retained in callus cultures of two out of three plants regenerated from one of the lines, but not in cultures of plants regenerated from the other two lines. Sexual progeny of the two resistant plants were either sensitive or showed slow segregation for chloramphenicol resistance. In callus from only two of the seedlings was inheritance of chloramphenicol resistance clearly demonstrated

Cell Culture Manipulations as a potential breeding tool.

Protagonists of plant tissue and cell culture methods are now commonplace. Applications of these techniques can be found in nearly every field of plant science and they have resulted in many valuable contributions to· our knowledge of primary and secondary metabolism, the cell cycle, the regulation of growth and differentiation, and plant/micro-organism interactions. From the agricultural point of view the obvious attractions of tissue culture methods for virus eradication and rapid clonal propagation of commercial varieties have continued to draw a great deal of attention and the number of species for which the basic culture criteria have either been met, or are under intensive study, is now quite extensive (43). Interest in genetic manipulations of plant cell cultures has continued to increase, despite the many obstacles in the way of wide application of these methods. It is therefore expected that those interested in overcoming low temperature stress would also direct some attention to these genetic manipulations. This review will consider the different methods for genome modification in cell cultures and the problems encountered in the application of these methods. The extent to which these problems have been and can be overcome will be evaluated with particular reference to experiments performed with crop species, and having a potential for crop improvement. In addition the limited progress which has been made in breeding for chilling resistance using tissue cultures will be considered

Environmental stress resistance: Selection in plant cell cultures.

The selection of variant lines in plant cell cultures has expanded to such an extent that it is no longer easy to review the subject in its entirety. The most recent and comprehensive review1 covers the variant cell lines which had been described by the beginning of 1979. The purpose of this report is to look at the progress in the selection of cell lines resistant to various environmental stresses. The rationale behind the selection of this kind of variant is generally practical, the objective bei11g to obtain cultivars of crop plants with a greater tolerance to adverse climatic o~ soil conditions. A further potential value of resistant cell lines for studies on the nature of stress sensitivity and resistance will also be emphasise-d here. Cell lines resistant to several different stresses have been described and these are considered in the following sections

Inheritance of Chloramphenicol Resistance, a Trait Selected in Cell Cultures of Nicotiana sylvestris. Speg. and Comes.

Three cell lines with improved resistance to growth inhibition by chloramphenicol were selected from cell cultures of Nicotiana sylvestris. Resistance was retained in callus cultures of two out of three plants regenerated from one of the lines, but not in cultures of plants regenerated from the other two lines. Sexual progeny of the two resistant plants were either sensitive or showed slow segregation for chloramphenicol resistance. In callus from only two of the seedlings was inheritance of chloramphenicol resistance clearly demonstrated

Cross-resistance in Cell Lines of Nicotians sylvestris Selected for Resistance to Individual Antibiotics.

Cell lines initially selected for resistance to the antibiotics Icanamycin, streptomycin and chloramphenicol, were each tested for resistance to several different antibiotics. Only the kanamycin resistant lines showed any cross-resistance to other antibiotics. The three lines tested were resistant to streptomycin and neomycin, while one of them, KR103, was also resistant to chloramphenicol early in its history, although this resistance was subsequently lost. None of the lines showed any resistance to cycloheximide

Microarray analysis of spring barley cultivars displaying differing sensitivity to physiological leaf spot (PLS)

peer-reviewedPhysiological leaf spot (PLS) is a disorder of spring barley (Hordeum vulgare L.), which has become more pronounced in recent years. The initial symptoms are small chlorotic/brown spots on the upper four leaves, which may develop into necrotic lesions with an irregular shape. As PLS occurs on leaves that are directly exposed to sunlight, it is thought that high light stress could be a trigger for the condition. This study concentrates on two cultivars, Cooper and Crusader, which display differential sensitivity to PLS. Biochemical measurements and enzyme assays revealed substantial difference in levels of ascorbate, type III peroxidases, and superoxide dismutase between the chosen cultivars during the 2003 growing season. A global gene expression study, using these field samples, was performed by microarray analysis. This supported the biochemical findings and highlighted additional sets of genes differentially expressed between the cultivars. Transcripts of particular interest, which appeared, included calcium signalling genes, cold-responsive genes and those involved in the assembly of Photosystem I. We conclude that susceptibility to PLS is related to levels of expression of genes with a role in countering the effects of oxidative stress.Teagasc Walsh Fellowship Programm

Mutagenesis and Triazine Herbicide Effects in Strawberry Shoot Cultures.

The effects of simazine on shoot culture of two varieties of strawberry were investigated with a view to establishing a system for in vitro selection of resistant mutants. In single shoots some chlorophyll loss occurred at herbicide levels producing little growth inhibition, but efficient bleaching was associated with severe suppression of growth. Varying simazine and sucrose levels, in both single and multiple shoot cultures did not reveal any conditions where chlorophyll destruction and growth inhibition could be separated. A protective effect, against bleaching, of high sucrose levels was not linked to suppression of photosynthesis, as assessed by CO2-fixation measurements. Mutagenesis with nitrosomethyl urea resulted in chlorophyll deficiencies in about 10% of shoots arising from axillary buds, but no resistant sectors emerged from 8000 and 400 mutagenized explants placed on medium containing inhibitory levels of simazine and streptomycin sulphate, respectively

Selection of Plant Cell Lines with Enhanced Chilling Resistance.

Cell cultures of Nicotiana sybestris and Capsicum annuum, both without and following exposure to the mutagen, EMS, have been submitted to chilling for 21 days at —3 CC and +5 °C respectively and the cell lines derived from the surviving cells tested for their subsequent resistance to the chilling treatment. Some of the cell lines when again submitted to the chilling stress showed no enhanced survival, others retained their resistance after an extended period of growth at 24 °C. The application of the mutagen promoted the isolation of such stable resistant cell lines. Studies of the response of the respiratory activity of isolated mitochondria to temperature from a resistant and from a sensitive cell line of C. annuum revealed a difference similar to that previously reported from studies on isolated mitochondria from chilling-sensitive and chilling-resistant plants of various species

Growth and peroxidase production in cultures of horseradish (Armoraciu mticunu).

Peroxidase, an enzyme of commercial importance to the diagnostic industry, is currently extracted and purified from the roots of field-grown horseradish plants (Armoracia rusticana) by conventional methods. It is, however, known that plant peroxidases occur in undifferentiated cells maintained in culture at a specific and total activity which may surpass that of the root (Shinshi & Noguchi, 1976). In this report we have examined cell cultures of the horseradish plant as a source of the enzyme

Production of artificial seeds of Daucus Carota.

Production of artificial seeds (somatic embryogenesis) was first observed in the 1950s and is a tissue multi plication process which can produce thousands of embryos, each with the potential to form a plant from a few grams of callus