Polyamines as short-term salt tolerance traits in tomato

Abstract In leaves of a salt-sensitive tomato species ( Lycopersicon esculentum Mill.) and its wild salt-tolerant relative species Lycopersicon pennellii (Correll) D’Arcy, changes induced by NaCl stress in carbon compounds (sugars and organic acids), amino acids related to synthesis of polyamines (glutamate, arginine and proline) and polyamines (putrescine, spermidine and spermine) were compared in light and dark after short-term exposure (24 h). The levels of sugars increased more in the salt-sensitive cultivar upon salt stress, especially under light. The changes in the carbon compounds and amino acids were different under light and dark conditions. Thus, in the 200 mM NaCl treated leaves of L. esculentum , the high sugar accumulation found in light was parallel to the no accumulation of both organic acids and amino acids (glutamate and arginine). The opposite response was observed in the treated leaves of L. pennellii with the same stress level in dark. Putrescine increases with salinity were greater in L. pennellii than in L. esculentum either in dark or in light. The higher total polyamine levels in light as opposed to the dark found in both species were rather more due to spermidine and spermine than to putrescine. With regard to the ratio between the diamine putrescine and polyamines, spermidine and spermine, this was always higher in L. pennellii than in L. esculentum. Moreover, the different response between species was clearly observed from the 100 mM NaCl treatment. A higher deviation of glutamate compared to proline seems to be also related to the salt tolerance during the night, as the proline/polyamine ratio increases were higher in the salt-tolerant species.