Abstract
The oxidative burst, the generation of reactive oxygen species (ROS) in response to microbial pathogen attack, is a ubiquitous early part of the resistance mechanisms of plant cells. It has also become apparent from the study of a number of plant–pathogen interactions and those modelled by elicitor treatment of cultured cells that there may be more than one mechanism operating. However, one mechanism may be dominant in any given species. NADPH oxidases have been implicated in a number of systems and have been cloned and characterized. However, the enzyme system which is the major source of ROS in French bean ( Phaseolus vulgaris ) cells treated with a cell wall elicitor from Colletotrichum lindemuthianum , appears to be dependent on an exocellular peroxidase. The second component, the extracellular alkalinization, occurs as a result of the Ca 2+ and proton influxes and the K + efflux common to most elicitation systems as one of the earliest responses. The third component, the actual reductant/substrate, has remained elusive. The low molecular weight compound composition of apoplastic fluid was compared before and after elicitation. The substrate only becomes available some min after elicitation and can be extracted, so that by comparing the profiles by LC‐MS it has been possible to identify possible substrates. The mechanism has proved to be complex and may involve a number of low molecular weight components. Stimulation of H 2 O 2 production was observed with saturated fatty acids such as palmitate and stearate without concomitant oxylipin production. This biochemical evidence is supported by immunolocalization studies on papillae forming at bacterial infection sites that show the peroxidase isoform present at sites of H 2 O 2 production revealed by cerium chloride staining together with the cross‐linked wall proteins and callose and callose synthase. The peroxidase has been cloned and expressed in Pichia pastoris and has been shown to catalyse the oxidation reaction with the same kinetics as the purified enzyme. Furthermore, Arabidopsis plants transformed heterologously using the French bean peroxidase in antisense orientation have proved to be highly susceptible to bacterial and fungal pathogens. Thus it is possible that Arabidopsis is another species with the potential to mount an apoplastic oxidative burst and these transformed plant lines may be useful to identify the peroxidase that is responsible.
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Claims 4
Claim · model-written summary
Saturated fatty acids such as palmitate and stearate stimulated H2O2 production in French bean cells without oxylipin production.
- Taxon
- French bean
Phaseolus vulgarise1 - Treatment
- saturated fatty acids such as palmitate and stearatee2
- Outcome
- H 2 O 2 productione2
- Direction
- Stimulatione2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“French bean ( Phaseolus vulgaris ) cells treated with a cell wall elicitor from Colletotrichum lindemuthianum”
e2“Stimulation of H 2 O 2 production was observed with saturated fatty acids such as palmitate and stearate without concomitant oxylipin production”
Claim · model-written summary
Arabidopsis plants transformed with the French bean peroxidase in antisense orientation were highly susceptible to bacterial and fungal pathogens.
- Taxon
- Arabidopsis
Arabidopsise3 - Treatment
- transformed heterologously using the French bean peroxidase in antisense orientatione3
- Interactor
- bacterial and fungal pathogense3pathogen
- Gene
- French bean peroxidasee3
- Outcome
- susceptible to bacterial and fungal pathogense3
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Arabidopsis plants transformed heterologously using the French bean peroxidase in antisense orientation have proved to be highly susceptible to bacterial and fungal pathogens”
Claim · model-written summary
The French bean peroxidase cloned and expressed in Pichia pastoris catalysed the oxidation reaction with the same kinetics as the purified enzyme.
- Taxon
- French beanPhaseolus vulgarise1
- Gene
- peroxidasee4
- Outcome
- catalyse the oxidation reaction with the same kineticse4
- Comparator
- purified enzymee4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“French bean ( Phaseolus vulgaris ) cells treated with a cell wall elicitor from Colletotrichum lindemuthianum”
e4“The peroxidase has been cloned and expressed in Pichia pastoris and has been shown to catalyse the oxidation reaction with the same kinetics as the purified enzyme”
Claim · model-written summary
The peroxidase isoform was present at sites of H2O2 production in papillae at bacterial infection sites.
- Taxon
- French beanPhaseolus vulgarise1
- Organ / stage
- papillaee5
- Outcome
- peroxidase isoform present at sites of H 2 O 2 productione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“French bean ( Phaseolus vulgaris ) cells treated with a cell wall elicitor from Colletotrichum lindemuthianum”
e5“immunolocalization studies on papillae forming at bacterial infection sites that show the peroxidase isoform present at sites of H 2 O 2 production revealed by cerium chloride staining”
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