Characterization of Resistance to the Proline Analog Azetidine Carboxylic Acid in a Nicotiana sylvestris Cell Line

Abstract

A Nicotiana sylvestris cell line resistant to the proline analog, azetidine carboxylic acid (Ns AR -l) was selected from mutagenized cells. Uptake, incorporation and internal pools of amino acids in the resistant cells were compared to those of non-selected sensitive N. sylvestris cells (Ns). Rates of AzCA and proline uptake by Ns AR -l cells were ¼ of those of Ns cells while valine and leucine were efficiently transported into both types of cells. Incorporation of AzCA and proline into the TCA insoluble fraction by Ns AR -l cells occurred at very low rates as compared to those of Ns cells. The endogenous pool of soluble proline was similar in both cell lines, but the total intracellular soluble amino acids pool was 2–3 fold higher in the sensitive cells. The experimental results suggest that resistance to AzCA in Ns AR -l cells is due to alterations in the transport system of proline and AzCA.