Poster: Oxidative stress
Abs #
68: Evidence of a key role of ascorbate oxidase in oxygen management in plants
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Presenter: |
De Tullio, Mario C., detullio@botanica.uniba.it |
Authors | De Tullio, Mario C. (A) Ciraci, Samantha (A) Liso, Rosalia (A) Arrigoni, Oreste (A) | | Affiliations: |
(A): Dept. Plant Biology and Pathology, University of Bari, Italy
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Molecular oxygen is the friend and foe of all aerobic organisms. The rate of oxygen generation could be too high and potentially dangerous during photosynthetic activity. On the other hand, oxygen availability could be too low under specific environmental conditions (e. g. seed germination under hypoxic conditions). Therefore, a general mechanism regulating oxygen availability in plants would be highly desirable [Raven et al. 1994, Biol Rev. 69: 61-94].
Ascorbate oxidase (AAO, EC 1.10.3.3) is a multi-copper oxidase well-characterized at molecular level, but of still uncertain function [Arrigoni et al. 2003, Rend. Acc. Naz. Lincei 14: 127-134; De Tullio et al. 2004, Biol. Plant, in press]. We investigated the possible involvement of AAO in oxygen management in plants. AAO activity is up-regulated by light in leaves performing dioxygenic photosynthesis (effect prevented by DCMU) and also increases in dark upon hyperoxic conditions. Enzyme activity increases in the facultative CAM plant Kalanchoe blossfeldiana under conditions inducing the CAM cycle, i.e. when dioxygen produced during photosynthesis cannot be dispersed via the stomata. AAO activity is unevenly distributed in leaves of C4 plants and located almost exclusively in the cell walls of bundle sheath cells. In addition, AAO activity decreases in ripening fruits and in wounded tissues, possibly in connection with the increased rate of oxygen consumption occurring in the climacteric and in wound respiration. Such dynamics in AAO activity strongly suggest that, beside other previously discussed roles [Jiang et al. 2003, Development 130: 1429-1438; Pignocchi et al. 2003, Plant Physiol. 132: 1631-1641], AAO could contribute in regulating oxygen availability during plant development.
