G6PDH EXPRESSION AND ACTIVITY CORRELATES WITH DROUGHT TOLERANCE IN A LONG SHELF LIFE TOMATO LANDRACE

Tolerance to water deficit as well as extended fruit shelf life are sought-after traits in tomato breeding, very appreciated both by farmers and consumers. Both these features characterize several Mediterranean landraces, including many genotypes adapted to the dry growth seasons typical of Southern Italy. Glucose 6 phosphate dehydrogenase (G6PDH) is the rate-limiting enzyme of the Oxidative Pentose Phosphate Pathway, inducing the oxidation of glucose-6-phosphate and the corresponding reduction of moieties of NADP+ to NADPH. A functional role has been suggested for this enzyme in ROS detoxification, highlighting its contribution in abiotic stress response. Furthermore, G6PDH activity and the corresponding NAPDH availability have been recently associated with red color and ripening of tomato fruits. In order to clarify the G6PDH roles in tomato drought tolerance and fruit ripening, we pursued an integrated approach where biochemical and molecular parameters were evaluated together in the Italian landrace Giallo Beneventano grown under different conditions. This landrace showed interesting yields upon drought and an unusually long shelf life (LSL) of fruits, up to 5-6 months. LSL trait has been related with a mutation in the nor allele Solyc10g006880, suggesting that a change in the ethylene signalling pathway regulating the ripening processes occurs in this particular landrace. Enzyme activity assays as well as gene expression quantifications indicated that G6PDH - and the related ascorbate peroxidase -showed significant changes in Giallo Beneventano compared to commercial varieties under drought stress in leaf tissues and during fruit ripening (from green to fully mature). Based on these data, we suggest that a constitutively high level of specific activities involved in ROS detoxification can play a key role in the enhanced drought tolerance and longer fruit shelf life exhibited by Mediterranean tomato landraces. Acknowledgments - The authors thank the Department of Agriculture (IPA Sector) of Regione Campania for providing seeds of the tomato landrace Giallo Beneventano.