Abstract
The active regulation of extracellular pH is critical for the virulence of fungal pathogens. Penicillium expansum is the causal agent of green-blue mold on stored pome fruits and during its infection process acidifies the host tissues by secreting organic acids. P. expansum is also the main producer of patulin (PAT), a mycotoxin found in pome fruit-based products and that represents a serious health hazard for its potential carcinogenicity. While it is known that PAT biosynthesis in P. expansum is regulated by nutritional factors such as carbon and nitrogen and by the pH, the mechanistic effects of biocontrol on PAT production by P. expansum are not known. In this work, we assessed how optimal and suboptimal concentrations of the biocontrol agent (BCA) Papiliotrema terrestris LS28 affect both extracellular pH and PAT biosynthesis in P. expansum . In wounded apples, the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from P. expansum infection, respectively, and reduced PAT contamination in both cases. However, the suboptimal concentration of the BCA increased the specific mycotoxigenic activity by P. expansum . In vitro , the rate of PAT biosynthesis was strictly related to the extracellular pH, with the highest amount of PAT detected in the pH range 4–7, whereas only traces were detectable at pH 3. Moreover, both in vitro and in apple wounds the BCA counteracted the extracellular P. expansum -driven acidification maintaining extracellular pH around 4, which is within the pH range that is optimal for PAT biosynthesis. Conversely, in the absence of LS28 the pathogen-driven acidification led to rapidly achieving acidic pH values (<3) that lie outside of the optimal pH range for PAT biosynthesis. Taken together, these results suggest that pH modulation by LS28 is important to counteract the host tissue acidification and, therefore, the virulence of P. expansum . On the other hand, the buffering of P. expansum -driven acidification provided by the BCA increases the specific rate of PAT biosynthesis through the extension of the time interval at which the pH value lies within the optimal range for PAT biosynthesis. Nevertheless, the antagonistic effect provided by the BCA greatly reduced the total amount of PAT.
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Claims 13
Claim · model-written summary
Optimal BCA concentration gave almost complete protection of wounded apples from P. expansum infection.
- Taxon
- apples
Malus domesticae1 - Treatment
- optimale2
- Interactor
- P. expansum
Penicillium expansume2pathogen - Second interactor
- Papiliotrema terrestris LS28Papiliotrema terrestrise3biocontrol_agent
- Outcome
- protection from P. expansum infectione2
- Direction
- almost completee2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e2“the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from P. expansum infection, respectively, and reduced PAT contamination in both cases”
e3“biocontrol agent (BCA) Papiliotrema terrestris LS28”
Claim · model-written summary
Suboptimal BCA concentration gave partial protection of wounded apples from P. expansum infection.
- Taxon
- applesMalus domesticae1
- Treatment
- suboptimale2
- Interactor
- P. expansumPenicillium expansume2pathogen
- Second interactor
- Papiliotrema terrestris LS28Papiliotrema terrestrise3biocontrol_agent
- Outcome
- protection from P. expansum infectione2
- Direction
- partiale2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e2“the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from P. expansum infection, respectively, and reduced PAT contamination in both cases”
e3“biocontrol agent (BCA) Papiliotrema terrestris LS28”
Claim · model-written summary
Optimal BCA concentration reduced PAT contamination in wounded apples.
- Taxon
- applesMalus domesticae1
- Treatment
- optimale2
- Interactor
- P. expansumPenicillium expansume2pathogen
- Second interactor
- Papiliotrema terrestris LS28Papiliotrema terrestrise3biocontrol_agent
- Outcome
- PAT contaminatione2
- Direction
- reducede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e2“the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from P. expansum infection, respectively, and reduced PAT contamination in both cases”
e3“biocontrol agent (BCA) Papiliotrema terrestris LS28”
Claim · model-written summary
Suboptimal BCA concentration reduced PAT contamination in wounded apples.
- Taxon
- applesMalus domesticae1
- Treatment
- suboptimale2
- Interactor
- P. expansumPenicillium expansume2pathogen
- Second interactor
- Papiliotrema terrestris LS28Papiliotrema terrestrise3biocontrol_agent
- Outcome
- PAT contaminatione2
- Direction
- reducede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e2“the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from P. expansum infection, respectively, and reduced PAT contamination in both cases”
e3“biocontrol agent (BCA) Papiliotrema terrestris LS28”
Claim · model-written summary
Suboptimal BCA concentration increased the specific mycotoxigenic activity of P. expansum.
- Taxon
- applesMalus domesticae1
- Treatment
- suboptimale4
- Interactor
- P. expansumPenicillium expansume4pathogen
- Second interactor
- Papiliotrema terrestris LS28Papiliotrema terrestrise3biocontrol_agent
- Outcome
- specific mycotoxigenic activitye4
- Direction
- increasede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e4“the suboptimal concentration of the BCA increased the specific mycotoxigenic activity by P. expansum”
e3“biocontrol agent (BCA) Papiliotrema terrestris LS28”
Claim · model-written summary
In vitro, the rate of PAT biosynthesis was strictly related to extracellular pH.
- Taxon
- applesMalus domesticae1
- Treatment
- extracellular pHe5
- Outcome
- rate of PAT biosynthesise5
- Setting
- In vitroe5
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e5“In vitro , the rate of PAT biosynthesis was strictly related to the extracellular pH”
Claim · model-written summary
The highest amount of PAT was detected at extracellular pH in the range 4–7.
- Taxon
- applesMalus domesticae1
- Treatment
- pH range 4–7e6
- Outcome
- amount of PAT detectede6
- Direction
- higheste6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e6“the highest amount of PAT detected in the pH range 4–7”
Claim · model-written summary
Only traces of PAT were detectable at pH 3.
- Taxon
- applesMalus domesticae1
- Outcome
- only traces were detectablee7
- Qualifier
- at pH 3e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e7“only traces were detectable at pH 3”
Claim · model-written summary
The BCA maintained extracellular pH around 4 against P. expansum-driven acidification in vitro and in apple wounds.
- Taxon
- applesMalus domesticae1
- Treatment
- the BCAe4
- Interactor
- P. expansumPenicillium expansume4pathogen
- Second interactor
- Papiliotrema terrestris LS28Papiliotrema terrestrise3biocontrol_agent
- Outcome
- extracellular pHe4
- Direction
- maintaininge4
- Value
- around 4e4
- Setting
- in vitroe4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e4“both in vitro and in apple wounds the BCA counteracted the extracellular P. expansum -driven acidification maintaining extracellular pH around 4”
e3“biocontrol agent (BCA) Papiliotrema terrestris LS28”
Claim · model-written summary
In the absence of LS28, pathogen-driven acidification rapidly led to acidic pH values below 3.
- Taxon
- applesMalus domesticae1
- Outcome
- rapidly achieving acidic pH valuese4
- Value
- <3e4
- Qualifier
- in the absence of LS28e4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e4“in the absence of LS28 the pathogen-driven acidification led to rapidly achieving acidic pH values (<3)”
Claim · model-written summary
pH modulation by LS28 appears important to counteract host tissue acidification and the virulence of P. expansum.
- Taxon
- applesMalus domesticae1
- Treatment
- pH modulation by LS28e4
- Interactor
- P. expansumPenicillium expansume4pathogen
- Second interactor
- LS28e4biocontrol_agent
- Outcome
- virulence of P. expansume4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e4“pH modulation by LS28 is important to counteract the host tissue acidification and, therefore, the virulence of P. expansum”
Claim · model-written summary
The buffering of P. expansum-driven acidification by the BCA increased the specific rate of PAT biosynthesis.
- Taxon
- applesMalus domesticae1
- Treatment
- buffering of P. expansum -driven acidification provided by the BCAe4
- Interactor
- P. expansumPenicillium expansume4pathogen
- Outcome
- specific rate of PAT biosynthesise4
- Direction
- increasese4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e4“the buffering of P. expansum -driven acidification provided by the BCA increases the specific rate of PAT biosynthesis”
Claim · model-written summary
The antagonistic effect of the BCA greatly reduced the total amount of PAT in apples.
- Taxon
- applesMalus domesticae1
- Treatment
- the antagonistic effect provided by the BCAe4
- Outcome
- total amount of PATe4
- Direction
- greatly reducede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In wounded apples”
e4“the antagonistic effect provided by the BCA greatly reduced the total amount of PAT”
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