Carrot, resistant cell lines

Speck, P., F. Escher, and J. Solms. Effect of salt pretreatment on quality and storage stability of air-dried carrots. Lebensm Wiss Technol 1977 10 308. Widholm, J. Selection and characterization of a Daucus carota cell line resistant to four amino acid analogs. J Exp Bot 1978 29 1111. 

It is difficult to explain why toxic hydrocarbons can be made selective to carrots by the addition of a nontoxic oil but not by the addition of water. Green (7) found some correlation between the toxicity of oils and their ability to emulsify. It is commonly found that high aromatic oils are easier to emulsify than are oils with low aromatic content. It is possible that some action between the aromatic hydrocarbons and the emulsifying agent results in increased toxicity. There is some evidence that the permeability of the protoplasmic membrane is the key to carrot resistance. If this is true, the presence of the emul er or the physical properties of the emulsion might increase the cell penetration of the hydrocarbons. Work is being continued along these lines and on the fundamental reasons for differential plant resistance to oils. 

Berlin and Widholm (31) selected carrot and tobacco cells resistant to PFP. In contrast with the Ccirrot line, which showed the expected increases in free Phe, the PFP-resistant cells (TX4) had almost normal levels of Phe, but did show dramatic increases in phenolics apparently due to a 10- to 20-fold rise in phenylalanine ammonia lyase (PAL) activity as compared to control cells (TXl). It was suggested that this cell line was resistant to PFP due to the higher PAL activity, which could detoxify PFP by conversion to p-fluorocinnamic acid. If this method could be generally applied, it would allow for the positive selection of cell strains overproducing a specific class of secondary compounds. 

Borkird and Sung [1] isolated seven ABA-insensitive cell lines in a somatic embryo culture of carrot in which ABA failed to arrest the development of torpedo-stage embryos into plantlets, as occurs in wild type when ABA is added. All lines also showed reduced auxin sensitivity. Characterization of three lines showed lower levels of ABA uptake as a possible cause of ABA insensitivity. However, the uptake of 2,4-D was higher than in wild-type embryos. In tobacco, cell-lines resistant to inhibition of growth by ABA were also isolated [25], and cell proliferation continued in the presence of what would be growth-inhibiting ABA concentrations for normal cell lines. 

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