PROLINE METABOLIC PATHWAYS IN CALLI FROM LYCOPERSICON-ESCULENTUM AND L-PENNELLII UNDER SALT STRESS

The enzyme activities of the proline metabolic pathways were determined in control and salt-treated (140 M NaCl) calli derived from cotyledons of the domestic salt-sensitive tomato Lycopersicon esculentum and the wild salt-tolerant L. pennellii. Glutamate, glutamine, asparagine, and aspartate levels increased in both genotypes under salt stress, while proline accumulation increased markedly only in the salt sensitive tomato. Activity of glutamine synthetase (GS) decreased in the salt-treated calli of the domestic species, whereas both NADH- and NADPH-glutamate synthase (GOGAT) activities increased; GS and NADPH-GOGAT decreased together in the salinized calli of the wild species. Decreasing ornithine levels were found due to NaCl in both tomato populations, while ornithine transaminase (OT) decreased in the wild type only. Increasing NADPH-A-pyrroline-5-carboxylate reductase (P5CR) and decreasing proline oxidase (Pro oxi) occurred in the salinized calli of the wild type. Conversely, Pro oxi and proline dehydrogenase (Pro dH) decreased highly in the salinized calli of the domestic population, while no significant changes in P5CR were found.