Hydrogen peroxide scavenging mechanisms are components of Medicago truncatula partial resistance to Aphanomyces euteiches |
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| Authors: | Naceur Djébali Haythem Mhadhbi Claude Lafitte Bernard Dumas Marie-Thérèse Esquerré-Tugayé Mohamed Elarbi Aouani and Christophe Jacquet |
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| Institution: | (1) Centre of Biotechnology of Borj Cedria, Laboratory of Legumes, BP 901, Hammam-Lif, 2050, Tunisia;(2) Universit? de Toulouse, Surfaces Cellulaires et Signalisation chez les V?g?taux, BP 42617, Auzeville, 31326 Castanet-Tolosan, France;(3) NEPAD/North Africa Biosciences Network, National Research Center, El Buhouth St, Cairo, 12311, Egypt;(4) Present address: Centre of Biotechnology of Borj Cedria, Laboratory of Molecular Physiology of Plants, BP 901, Hammam-Lif, 2050, Tunisia |
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| Abstract: | The biochemical processes underlying the expression of resistance in the roots of Medicago truncatula against Aphanomyces euteiches infection was investigated, with emphasis on oxidative stress. The levels of H2O2, superoxide dismutase, peroxidase, ascorbate peroxidase, catalase, soluble phenolics and lignin were measured in the roots
of two lines, A17 partially resistant and F83005.5 susceptible to A. euteiches at three infection stages; penetration of the epidermis (1 dpi), colonization of the cortex (3 dpi) and invasion of the root
stele (6 dpi). A rapid and large decrease of the H2O2 levels in A17 roots occurred. However, in F83005.5 roots, the decrease in H2O2 levels was delayed until 3 dpi. In A17 roots, the activities of ascorbate peroxidase, peroxidase and catalase were induced
as early as 1 dpi, whereas a general decrease in the activity of the four antioxidant enzymes was observed in F83005.5 roots.
The levels of soluble phenolics and lignin were increased in A17 roots at 3 and 6 dpi, respectively. The H2O2 levels were negatively correlated to ascorbate peroxidase, catalase and lignin production at 1, 3 and 6 dpi, respectively
in A17 roots. Physiological concentrations of H2O2 found in M. truncatula infected roots had no detrimental effect on the in vitro growth of this oomycete. Our data suggest that H2O2 does not have a direct antimicrobial effect on M. truncatula resistance to A. euteiches, but is involved in cell wall strengthening around the root stele, preventing pathogen invasion of the vascular tissues. |
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