Glutamine and glutamate levels and related metabolizing enzymes in tomato fruits with different shelf-life

Free amino acids composition and glutamate dehydrogenase (GDH) and glutamine synthetase (GS) levels were evaluated in fruits of Lycopersicon esculentum var. esculentum genotypes having standard (cv. Caimanta) and altered (nor and rin mutants) ripening characteristics. Two accessions of the wild L. esculentum var. cerasiforme (LA1385 and LA1673) were also assayed. Shelf-life (SL) of these fruits ranged from 12 (cv. Caimanta) to 36 (nor mutant) days. The relative glutamate content (as percentage of total free amino acid content) of ripe mature fruits differed considerably among lines, having cv. Caimanta and the nor mutant the highest and the lowest values, respectively. A negative correlation between the relative glutamate content and fruit SL was also found. In the standard ripening cv. Caimanta, GS was principally present in green mature fruits while GDH was found in ripe mature fruits. In the other lines, GS and GDH were detected at both maturation stages. Summarizing, standard SL correlates with higher relative glutamate content and reciprocal induction pattern of GS and GDH, while long SL is associated with lower relative glutamate content and simultaneous presence of both enzymes in the pericarp of tomato fruits. These data suggest that the regulation of the level of glutamate, GS and GDH during fruit ripening is related to the final SL of fruits.