African Journal of Biotechnology Vol. 6 (17), pp. 1982-1986, 5 September 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Water stress induces overexpression of superoxide dismutases that contribute to the protection of cowpea plants against oxidative stress

Yao Casimir Brou¹*, Adolphe Zézé¹, Omar Diouf² and Murielle Eyletters³

¹Institut National Polytechnique Félix Houphouët-Boigny, département A.R.A., B.P. 1313 Yamoussoukro, Côte d'Ivoire.

²CERAAS : Centre d’Etude Régional pour l’Amélioration de l’Adaptation à la Sécheresse – BP 3320 Thiès-Escale – Sénégal.

³Université Libre de Bruxelles, Laboratoire de Physiologie et d’Agrotechnologies végétales, Avenue F.D. Roosevelt, 50 (CP 169) B-1050 Brussels, Belgique.

*Corresponding author. E-mail: ycasimir_brou@yahoo.fr. Tél.: +225-07-58-79-05. Fax: +225-30-64-25-30.

Abbreviations: Cu/ZnSOD, Copper/Zinc-SOD; FeSOD, iron-SOD; MnSOD, manganese-SOD; mRNA, messenger ribonuc-leic acid; PS II, photosystem II; RNA, ribonucleic acid; SDS, sodium dodecyl sulphate; SOD, superoxide dismutase.

Accepted 18 June, 2007

Water stress is known to induce active oxygen species in plants. The accumulation of these harmful species must be prevented by plants as rapidly as possible to maintain growth and productivity. The aim of this study was to determine the effect of water stress on superoxide dismutase isozymes (SOD, EC 1.15.1.1.) in two cowpea cultivars [Vigna unguiculata L. Walp., cv. Bambey 21 (B21) and cv. TN88-63]. Plants were submitted to water stress by withholding water supply and the expression of SOD was characterized during stress induction. In the same time, photosynthesis characteristics were deter-mined through the measurement of the quantum yield of PS II photochemistry and the energy absorp-tion rate per reaction centre. Results show how water stress regulates the synthesis and the activity of superoxide dismutase isoforms and how these enzymes contribute to protect photosynthesis against the damageable effects of superoxide radicals in cowpea. Increased MnSOD and FeSOD activity and concentration were shown to be induced by water stress and associated with protection of photosystem II photochemistry and whole plant growth against oxidative stress in these plants. On the contrary, plants unable to express high MnSOD and/or FeSOD isoforms showed more sensitivity to water stress.

Key words: Oxidative stress, superoxide dismutase, photochemistry, Vigna unguiculata, water stress.