CONICET | Buscador de Institutos y Recursos Humanos

GABA accumulates in immature tomato fruits and rapidly in response to a variety of abiotic stresses in other plants. It is probably due to activation of glutamate decarboxilase (GAD), one of the three enzymes of the GABA shunt together with GABA transaminase (GABAT) and succinic semialdehyde dehydrogenase (SSADH). Arabidopsis was the only plant specie where this pathway was studied. Under physiological conditions, GABA is catabolized via GABAT to SSA, a highly reactive molecule, and further to succinate via SSADH. The activity of SSADH could be restricted under stressful conditions, although SSA did not accumulate suggesting that an alternative pathway for SSA catabolism may be active such as SSA reductase (SSR). In this work we investigated the levels of SSA and transcripts of SSADH and SSR as well as their activities in different organs of tomato plant. Firstly, we analyzed tomato fruits during ripening process, as a continuous transition. We observed a decrease in the activities of both enzymes and in SSA content. However, the transcript level of SSADH increased during the ripening process. The activity of these enzymes and the levels of SSA were also studied in other organs of the plant. In spite of SSA toxicity, we observed that SSA accumulated at a certain level under physiological conditions, suggesting complementary roles for SSADH and SSR in keeping low SSA levels in tomato organs.