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 8
Claim · model-written summary
NADPH oxidases have been implicated in oxidative burst systems and characterized.
Not reportedTaxon
Verbatim
e0“NADPH oxidases have been implicated in a number of systems and have been cloned and characterized.”
Claim · model-written summary
An exocellular peroxidase appears to be the main ROS source in elicited French bean cells.
- Taxon
- French bean
Phaseolus vulgarise0 - Treatment
- cell wall elicitore0
- Interactor
- Colletotrichum lindemuthianum
Colletotrichum lindemuthianume0pathogen - Gene
- exocellular peroxidasee0
- Outcome
- major source of ROSe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
Claim · model-written summary
Extracellular alkalinization follows calcium and proton influx and potassium efflux in elicitation systems.
- Taxon
- plantsViridiplantaet0
- Outcome
- extracellular alkalinizatione0
- Qualifier
- Ca(2+) and proton influxes and the K(+) effluxe0
Verbatim
e0“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”
t0“in plants”
Claim · model-written summary
The candidate substrate becomes available minutes after elicitation and is extractable.
- Taxon
- plantsViridiplantaet0
- Outcome
- substrate only becomes availablee0
- Qualifier
- some min after elicitatione0
Verbatim
e0“The substrate only becomes available some min after elicitation and can be extracted”
t0“in plants”
Claim · model-written summary
Palmitate and stearate stimulated hydrogen peroxide production without oxylipin production.
- Taxon
- plantsViridiplantaet0
- Treatment
- saturated fatty acids such as palmitate and stearatee0
- Outcome
- H(2)O(2) productione0
- Direction
- Stimulatione0
Not reportedComparator
Verbatim
e0“Stimulation of H(2)O(2) production was observed with saturated fatty acids such as palmitate and stearate without concomitant oxylipin production.”
t0“in plants”
Claim · model-written summary
The peroxidase isoform occurs at hydrogen peroxide production sites in infection papillae alongside cross-linked wall proteins, callose and callose synthase.
- Taxon
- plantsViridiplantaet0
- Organ / stage
- papillaee0
- Gene
- peroxidase isoforme0
- Outcome
- present at sites of H(2)O(2) productione0
Verbatim
e0“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”
t0“in plants”
Claim · model-written summary
Cloned French bean peroxidase expressed in Pichia catalysed oxidation with the kinetics of the purified enzyme.
- Taxon
- French beanPhaseolus vulgarist0
- Gene
- peroxidasee0
- Outcome
- catalyse the oxidation reactione0
- Qualifier
- same kineticse0
- Comparator
- purified enzymee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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.”
t0“French bean (Phaseolus vulgaris)”
Claim · model-written summary
Arabidopsis transformed with French bean peroxidase in antisense orientation became highly susceptible to bacterial and fungal pathogens.
- Taxon
- Arabidopsis
Arabidopsise0 - Treatment
- transformed heterologously using the French bean peroxidase in antisense orientatione0
- Gene
- French bean peroxidasee0
- Outcome
- susceptible to bacterial and fungal pathogense0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis plants transformed heterologously using the French bean peroxidase in antisense orientation have proved to be highly susceptible to bacterial and fungal pathogens”
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