Characterization of cotton superoxide dismutases during the incompatible interaction with Xanthomonas campestris pv. malvacearum [S21-69]

The total enzymatic activity of superoxide dismutase (SOD) of cotton (Gossypium hirsutum L.) and the transcriptional activities of SOD genes were studied during the interaction of cotton cotyledons with the incompatible bacterium Xanthomonas campestris pv. malvacearum race 18 (Xcm18). Enzymatic activity measurements resulted in a peak of SOD activity observed at 4 hrs postinfiltration. This early increase in SOD activity is thought to contribute to the oxidative burst observed in hypersensitive reactions (HR). cDNA fragments encoding cotton SOD genes were isolated by RT-PCR using a cDNA library constructed from bacterially-infiltrated cotton cotyledons. The fragments were sequenced and their similarities to known cytoplasmic Cu/ZnSOD (Cu/ZnSODcyt), chloroplastic Cu/ZnSOD (Cu/ZnSODchl), MnSOD and FeSOD were established based on amino acid sequence analysis. A time course study on the transcript accumulation of the cotton SOD genes, during cotton HR to Xcm18, was performed using a semiquantitative RT-PCR analysis. It was shown that steady state mRNA levels of Cu/ZnSODcyt and Cu/ZnSODchl were similar in the compatible and the incompatible interactions. In contrast, MnSOD and FeSOD were induced in the incompatible interaction at 2 and 10 hrs postinfiltration. Importantly, catalase gene expression studies showed that catalase is transcriptionally stable over the same time period, with a slight increased level in the incompatible interaction, as compared to the compatible interaction. The later results could suggest that the mitochondrialy localized MnSOD may contribute to the SOD enzymatic activity peak observed 4 hrs postinfiltration. Electron micrographs of cotton cells interacting with the incompatible Xcm18 indicated that mitochondria were concentrated in the vicinity of the cytoplasmic membrane, an observation that could suggest an involvement of the mitochodria in the apoptotic events of the HR in cotton. (Texte intégral)

Bibliographic Details

Main Authors:	Voloudakis, Andreas, Marmey, Philippe, Delannoy, Etienne, Jalloul, Aida, Daniel, Jean-François, Nicole, Michel
Format:	conference_item biblioteca
Language:	eng
Published:	ISPMB Office
Subjects:	H20 - Maladies des plantes, Gossypium hirsutum, superoxyde dismutase, relation hôte pathogène, Xanthomonas campestris malvacearum, http://aims.fao.org/aos/agrovoc/c_3339, http://aims.fao.org/aos/agrovoc/c_24091, http://aims.fao.org/aos/agrovoc/c_34017, http://aims.fao.org/aos/agrovoc/c_36123,
Online Access:	http://agritrop.cirad.fr/514057/
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