Active oxygen species production in tobacco cells elicited by cryptogein

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Active oxygen species production in tobacco cells elicited by cryptogein

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Lipoxygenase-mediated production of fatty acid hydroperoxides is a specific signature of the hypersensitive reaction in plants

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Resistance of Cotton Towards Xanthomonas campestris pv. malvacearum

International audienceInteractions between Gossypium spp. and the bacterial pathogen Xanthomonas campestris pv. malvacearum are understood in the context of the gene-for-gene concept. Reviewed here are the genetic basis for cotton resistance, with reference to resistance genes, resistance gene analogs, and bacterial avirulence genes, together with the physiological mechanisms involved in the hypersensitive response to the pathogen, including production of signaling hormones, synthesis of antimicrobial molecules and alteration of host cell structures. This host-pathogen interaction represents the most complex resistance gene/avr gene system yet known and is one of the few in which phytoalexins are known to be specifically localized in HR cells at anti-microbial concentrations

Apoplastic peroxidase generates superoxide anions in cells of cotton cotyledons undergoing the hypersensitive reaction to Xanthomonas campestris pv. malvacearum race 18

Cotton cotyledons displayed a hypersensitive reaction (HR) in the resistant cultivar Reba B50 after infiltration with the avirulent race 18 of #Xanthomonas campestris pv. #malvacearum (Xcm). Generation of active oxygen species during the HR was studied biochemically and cytochemically. O2(-) was detected in cotyledon disks by the cytochrome c reduction assay 3 h after inoculation. This activity was inhibited by superoxide dismutase (SOD) and by the peroxidase inhibitors salicylhydroxamic acid (SHAM) and KCN but not by the NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI). Strong NADH oxidation activity also was found 3 h after inoculation in crude extracts or in apoplastic washing fluid and was dramatically decreased after treatment with SHAM or KCN. NADH oxidation was activated by 2,4-dichlorophenol and MnCl2, indicating the involvement of a peroxidase. Activity of cationic peroxidase isoforms (pI 9 to 9.5) constitutively expressed in cotyledons was found to be enhanced 3 h after inoculation in the resistant cultivar. Activities of apoplastic peroxidase(s) and H2O2 accumulation were observed cytochemically, 3 and 4 h post inoculation, respectively. When digitonin, a O2(-) elicitor, was infiltrated into cotyledons of resistant and susceptible cultivars, generation of O2(-) radicals was shown to be reduced by SOD and inhibited by SHAM and KCN as observed after infection, and also by DPI. Our results strongly suggest that cotton cotyledons contain two O2(-) generating systems and that cells undergoing the HR in response to an avirulent race of Xcm produce O2(-) through the activation of an apoplastic peroxidase. (Résumé d'auteur

Are elicitins cryptograms in plant-oomycete communications?

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