Metabolism in orange fruits is driven by photooxidative stress in the leaves

Florine Poiroux-Gonord (1) , Jérémie Santini (2) , Anne-Laure Fanciullino (3) , Félicie Lopez-Lauri (4) , Jean Giannettini (2) , Huguette Sallanon (4) , Liliane Berti (2) , Laurent Urban (4)

1 GEQA - Génétique et Ecophysiologie de la qualité des agrumes
2 Laboratoire de Biochimie et Biologie Moléculaire Végétales - UMR6134
3 PSH - Unité de recherche Plantes et Systèmes de Culture Horticoles
4 EA 4279 Laboratoire Physiologie des Fruits et Légumes

In plants, stress signals propagate to trigger distant responses and thus stress acclimation in nonexposed organs. We tested here the hypothesis that leaves submitted to photooxidative stress may influence the metabolism of nearby fruits and thus quality criteria. Leaves of orange trees (Citrus sinensis (L.) Osbeck cv. 'Navelate') were acclimated to shade for one week and then submitted to full and medium light conditions. As expected, photoinhibition was detected in leaves of both full and medium light treatments as revealed by stress indicators (Fv/Fm, Performance Index) for at least 99 hours after treatments. In the fruits near the stressed leaves, we then determined the activities of enzymes related to oxidative stress, superoxide dismutase, catalase and the enzymes of the ascorbate/glutathione cycle, as well as the contents in sugars, organic acids and carotenoids. Ascorbate peroxidase and monodehydroascorbate reductase activities in the pulp of fruits were dramatically higher in both treatments when compared to the control. Ascorbate and total sugars were not affected by the photooxidative stress. However, the full light treatment resulted in a 16% increase in total organic acids, with succinic acid being the major contributor, a shift towards less glucose+fructose and more sucrose, and a 15% increase in total carotenoids, with cis-violaxanthin being the major contributor. Our observations strongly suggest the existence of a signal generated in leaves in consequence of photooxidative stress, transmitted to nearby fruits. Exploiting such a signal by agronomic means promises exciting perspectives in managing quality criteria in fruits accumulating carotenoids.

Mots clés: genes

Domaines: Biochimie [q-bio.BM]

Florine Poiroux-Gonord, Jérémie Santini, Anne-Laure Fanciullino, Félicie Lopez-Lauri, Jean Giannettini, et al.. Metabolism in orange fruits is driven by photooxidative stress in the leaves. Physiologia Plantarum, 2013, 149 (2), pp.175-187. ⟨10.1111/ppl.12023⟩. ⟨hal-00789965⟩