HOW TOMATO PLANTS ARE GETTING RID OF SSA

BURDISSO, PAULA; SORREQUIETA, AUGUSTO; BOGGIO, SILVANA B.; VALLE, ESTELA M.

Carlos Paz

Congreso; XLIV Reuniòn Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

SAIB

GABA accumulates in immature tomato fruits and 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. 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.