CONICET | Buscador de Institutos y Recursos Humanos

Glutamate dehydrogenase (GDH) catalyses a reversible reaction for the reductive amination of α-ketoglutarate to glutamate. Although GDH is ubiquitous in plant tissues, its physiological role is a subject of controversy. GDH is a hexamer comprised of two subunit polypeptides α and β, that differ slightly in mass and charge. The association of both subunits yields seven possible GDH isoenzymes. In several plant species these subunits are encoded by at least two distinct genes, however in tomato (Solanum lycopersicum) only one gene, coding for the β subunit (SlgdhB), was isolated. Looking for others functional gdh genes in tomato, we searched in the transcript and genomic sequences available at Sol Genomic Network database (www.sgn.cornell.edu). We found a complete cDNA of 1604 bp, with a 56.9 % of identity to SlgdhB. This clone was highly similar to the genes encoding the α subunit of N. plumbaginifolia (87%) and N. tabacum (88%). We isolated the corresponding SlgdhA putative promoter and analyzed the predictive cis-acting elements. The expression of gdhB and gdhA was studied by real time PCR and western blot analysis using antibodies that recognizes both subunits or only the α subunit. We found that the expression of both gdh genes and the isoenzyme profile were diverse in the different tomato tissues. These data suggest that gdhB and gdhA are independently regulated in tomato plants.