Alteration of the Wound-Induced Suberization by Catalase Inhibition in the Potato (Solanum

WOUND-HEALING OF THE POTATO (Solanum tuberosum l.) tuber IN RESPONSE TO CATALASE INHIBITION

Bajji M, Colson M, Delaplace P, Gastiny F, du Jardin P

Plant Biology Unit, Gembloux Agricultural University, 2, Passage des Déportés, B-5030 Gembloux, Belgium

Introduction: Wound-healing results in the production of a suberized periderm that effectively protects underlying tissues from desiccation and invasion by pathogens. Wounding of potato tubers triggers a massive production of reactive oxygen species probably via a plasma membrane-associated NADPH-dependent oxidase (Razem and Bernards, 2003). The resulting hydrogen peroxide (H2O2) was found to be required for polyphenolic domain formation during wound-induced suberization (Razem and Bernards, 2002). In the present work, we investigated the wound-healing of potato tubers in response to catalase (CAT) inhibition, a treatment expected to favour H2O2 accumulation.

Materials and Methods: Three different experiments were performed. First, potato tubers (cv. Mérit) were halved longitudinally, immediately treated with either water (Control) or with a CAT inhibitor (CI, Aminotriazole) at 5 mM during 2 h, and allowed to wound heal in the dark at 20 °C and 80 % RH for 7 d. The healed tuber halves were then subjected to a forced desiccation treatment at 64 °C for 2 h to evaluate their resistance to water loss. Second, the effect of CI treatment was assessed on tuber halves (cv. Mérit) after different healing periods using, as parameters, water loss and pathogen attack symptoms. Third, the first experiment was extended to other potato cultivars and other treatments favouring H2O2 accumulation.

Results and Conclusions: The rate of desiccation-induced water loss in wounded tuber halves previously treated with 5 mM CI was significantly higher than in the Control. A healing period of 1 d before CI treatment was sufficient to avoid pathogen attack and a period of 3 d prevented both infection and water loss of the treated tubers. The use of an additional CAT inhibitor (thiourea) and exogenous H2O2 on 3 potato cultivars (Mérit, Désirée, and Gasoré) indicated that wound-healing failure of the treated tubers was common to both CAT inhibitors and exogenous H2O2 and not due to any specific effects of the different compounds. We suggest that H2O2 metabolism must be under strict regulatory control during the early events of potato tuber wound-healing.

References: Razem FM, Bernards MA. 2002. Hydrogen peroxide is required for poly(phenolic) domain formation during wound-induced suberization. J Agric Food Chem 50; 1009-1015. Razem FM, Bernards MA. 2003. Reactive oxygen species production in association with suberization: evidence for an NADPH-dependent oxidase. J Exp Bot 54; 935-941.