Abstract
BACKGROUND: While it is known that arbuscular mycorrhizal fungi (AMF) can improve nutrient acquisition and herbivore resistance in crops, the mechanisms by which AMF influence plant defense remain unknown. Plants respond to herbivory with a cascade of gene expression and phytochemical biosynthesis. Given that the production of defensive phytochemicals requires nutrients, a commonly invoked hypothesis is that the improvement to plant defense when grown with AMF is simply due to an increased availability of nutrients. An alternative hypothesis is that the AMF effect on herbivory is due to changes in plant defense gene expression that are not simply due to nutrient availability. In this study, we tested whether changes in plant defenses are regulated by nutritional provisioning alone or the response of plant to AMF associations. Maize plants grown with or without AMF and with one of three fertilizer treatments (standard, 2 × nitrogen, or 2 × phosphorous) were infested with fall armyworm (Spodoptera frugiperda; FAW) for 72 h. We measured general plant characteristics (e.g. height, number of leaves), relative gene expression (rtPCR) of three defensive genes (lox3, mpi, and pr5), total plant N and P nutrient content, and change in FAW mass per plant. RESULTS: We found that AMF drove the defense response of maize by increasing the expression of mpi and pr5. Furthermore, while AMF increased the total phosphorous content of maize it had no impact on maize nitrogen. Fertilization alone did not alter upregulation of any of the 3 induced defense genes tested, suggesting the mechanism through which AMF upregulate defenses is not solely via increased N or P plant nutrition. CONCLUSION: This work supports that maize defense may be optimized by AMF associations alone, reducing the need for artificial inputs when managing FAW.
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Claims 5
Claim · model-written summary
AMF increased maize mpi expression.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We found that AMF drove the defense response of maize by increasing the expression of mpi and pr5.”
Claim · model-written summary
AMF increased maize pr5 expression.
- Treatment
- AMFe0
- Interactor
- AMFe0symbiont
- Gene
- pr5e0
- Outcome
- expression of mpi and pr5e0
- Direction
- increasinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We found that AMF drove the defense response of maize by increasing the expression of mpi and pr5.”
Claim · model-written summary
AMF increased total maize phosphorous content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while AMF increased the total phosphorous content of maize it had no impact on maize nitrogen.”
Claim · model-written summary
AMF had no impact on maize nitrogen.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while AMF increased the total phosphorous content of maize it had no impact on maize nitrogen.”
Claim · model-written summary
Fertilization alone did not alter defense gene upregulation.
- Taxon
- plantt0
- Treatment
- Fertilization alonee0
- Outcome
- upregulation of any of the 3 induced defense genese0
- Direction
- did not altere0
Not reportedComparator
Verbatim
e0“Fertilization alone did not alter upregulation of any of the 3 induced defense genes tested”
t0“plant defenses”
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