Malate in tomato: novel biochemical for unrevealed functions?

TRONCONI, M.; MARINATTO, A; ANDREO, CARLOS S; MARIA FABIANA DRINCOVICH

San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

The C4 acid malate is present at high levels in leaves and fruits of tomato plants being implicated in numerous physiological processes. However, the current understanding of malate metabolism in tomato is still limited. Tomato genome contains seven genes encoding NAD(P)-malic enzymes (NAD(P)-ME); three are supposed to be cytosolic (NADP-ME1 to 3), two are predicted to be mitochondrial (NAD-MEm1 and -2) and two plastidic (NADP-MEpl1 and 2). This ME composition implies that tomato possesses an additional plastidic isoform in comparison to all C3 species characterized so far. Expression analysis based on qRT-PCR reveled that all ME are expressed with different pattern of expression in organs as well as during fruit development. In this regard, whilst both NAD-MEm transcripts are more abundant in green fruit stages, NADP-ME1 and NADP-MEpl2 are highly expressed during green-red transition. Enzymatic activity determination and western blot assays confirm these differences in the ME expression during fruit maturation. On another hand, NADP-MEpl1, but mostly -2, transcripts are present at high levels in cells surrounding vascular tissue of leaves. Moreover, their abundance in leaf is increased with the fruit development. Finally, the kinetics and regulatory properties showed by recombinant forms of these proteins suggest divergent functions of the two plastidic NADP-MEs in tomato