Many higher plants can synthesize methyl chloride gas via a common metabolic route, also known as the biological chloride methylation. The reaction is catalyzed by an S-adenosyl-L- methionine (AdoMet) dependent halide/thiol methyltransferase (H/TMT). It is speculated that plants use chloride methylation to remove excess chloride via volatilization and hence maintain homeostatic levels of cytoplasmic chloride ion, suggesting a role of H/TMT in salt tolerance. In this project, the effect of engineering a Brassica oleracea thiol methyltransferase (BoTMT) into tomato was studied to determine the physiological relevance of this enzyme in conferring salt tolerance. Transgenic tomato plants acquired the ability to release methyl chloride in response to NaCl treatment, but exhibited no greater tolerance to NaCl, based on several morphological and physiological measurements, as compared to the wild-type plants. The results indicate that AdoMet dependent chloride methylation is unlikely to contribute to an increase in salt tolerance in higher plants.

Many higher plants can synthesize methyl chloride gas via a common metabolic route, also known as the biological chloride methylation. The reaction is catalyzed by an S-adenosyl-L- methionine (AdoMet) dependent halide/thiol methyltransferase (H/TMT). It is speculated that plants use chloride methylation to remove excess chloride via volatilization and hence maintain homeostatic levels of cytoplasmic chloride ion, suggesting a role of H/TMT in salt tolerance. In this project, the effect of engineering a Brassica oleracea thiol methyltransferase (BoTMT) into tomato was studied to determine the physiological relevance of this enzyme in conferring salt tolerance. Transgenic tomato plants acquired the ability to release methyl chloride in response to NaCl treatment, but exhibited no greater tolerance to NaCl, based on several morphological and physiological measurements, as compared to the wild-type plants. The results indicate that AdoMet dependent chloride methylation is unlikely to contribute to an increase in salt tolerance in higher plants.