Research: Plants defend against insects by inducing ‘leaky-gut syndrome’


Damaging the gut lining of insects is one way plants try to avoid being eaten


Few supposed ailments are as cringe-worthy to the medical community (or as lucrative to natural-health peddlers) as the notion of “leaky-gut syndrome.” Despite the fact that unbiased sources continuously state that there is no quality research to support its existence, leaky-gut syndrome in humans gets a lot of attention — especially when people feel they can to point fingers at glyphosate as a cause.

But before you walk away too dismissive, some new research out of Penn State and published in the July 22 issue of Proceedings of the National Academy of Sciences dive deeper into the effects of leaky-gut syndrome — on insects.

The researchers found that plants may induce leaky gut syndrome — more accurately referenced as permeability of the gut lining — in insects as part of a multipronged strategy for protecting themselves from being eaten. By improving our understanding of plant defenses, the findings could contribute to the development of new pest control methods.

“We found that a combination of physical and chemical defenses in corn plants can disrupt the protective gut barriers of fall armyworms, creating opportunities for gut microbes to invade their body cavities,” said Charles Mason, postdoctoral scholar in entomology. “This can cause septicemia, which can kill the insect, or simply trigger an immune response, which can weaken the insect.”

The researchers reared fall armyworms in the laboratory and inoculated them with one of three types of naturally occurring gut bacteria. They fed the insects on one of three types of maize — one that is known to express enzymes that produce perforations in insect gut linings; one that is characterized by numerous elongated trichomes, or fine hairs that occur on the surface of the plant and help defend against herbivores; and one that has just a few short trichomes. The team used scanning electron microscopy to evaluate the impacts of the various bacteria and maize types on the integrity of the fall armyworms’ gut linings.

The scientists found that the presence of all three types of gut bacteria decreased the ability of fall armyworm larvae to damage maize plants, especially when other defenses — such as elongated trichomes and enzymes, both of which can perforate gut linings — were present. However, the species of gut bacteria varied in the extent to which they weakened the insects.

“Our results reveal a mechanism by which some plants use insects’ gut microbiota against them in collaboration with their own defenses,” said Mason.

Gary Felton, professor and head of the Department of Entomology, noted that the results should have broad significance towards understanding the ecological function of plant defenses.

“In the context of our study, disparate plant defenses, such as leaf trichomes and plant enzymes, all require certain gut microbes for their optimal defense against herbivores,” he said. “Our results predict that the variation in the effectiveness of plant defenses in nature may be, in significant part, due to the variability observed in the microbial communities of insect guts.”

The team said the results could help to inform the development of insect-resistant crops.

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