alpha-L-arabinofuranosidase activity during development and ripening of normal and ACC synthase antisense tomato fruit
2002
Sozzi, G.O. | Fraschina, A.A. | Navarro, A.A. | Cascone, O. | Greve, L.C. | Labavitch, J.M.
Alpha-L-Arabinofuranosidases (alpha-Af) are plant enzymes that have the capacity to release terminal arabinofuranosyl residues from a wide variety of pectic and hemicellulosic polymers, as well as different glycoconjugates. Our interest in alpha-Af is related to its potential role in ripening-related loss of arabinose from tomato fruit cell walls. Using both control (cv. VF 36) and ACC synthase antisense (A11.1) tomatoes (Lycopersicon esculentum Mill.), we demonstrate that tomato alpha-Af activity is present during the entire ontogeny of the fruit. Immature 10-day-old fruit displayed 6-fold more alpha-Af activity on a per gram fresh weight basis, than mature green fruit. In VF 36 fruit, alpha-Af activity increased 45% from mature green 4 (48 days post anthesis) to light red stages (55 days) when fruit ripened on the vine. In contrast, no similar increase was detected in ACC synthase antisense fruit that do not ripen in the same time frame. However, when A11.1 fruit were detached at 48 days after anthesis and treated continuously with 100 mL(.)L-1 ethylene the fruit ripened and alpha-Af increased, as in ripening normal fruit. The alpha-Af activity pattern is similar to that reported for tomato beta-galactosidases. The increasing alpha-Af activity during ripening and the decreased activity in antisense ACC synthase fruit after reaching the mature green stage suggest a role for ethylene in the ripening-related synthesis or activation of this enzyme.
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