A pathogen's toxin-busting trick can backfire and help its rivals
Mauri M, Unger K, Gershenzon J, Allen RJ, Agler MT
Plant Microbiome
The mustard-family plants in many vegetable gardens, including arugula and broccoli relatives, make their own natural pesticides, and this research shows those chemicals shape hidden battles among leaf bacteria that can tip the scales toward a healthier plant.
Plant leaves are covered in bacteria, some helpful and some troublemakers, and the troublemakers often carry an enzyme that breaks down the plant's chemical defenses so they can feed and multiply. But this study found that breaking down the toxin also helps the harmless bacteria nearby survive, and once revived, those helpful bacteria compete so hard for food that they can actually hold the troublemaker back. It's a reminder that a bacterium's 'weapon' can sometimes work against it once the whole neighborhood gets involved.
Key Findings
The pathogen Pseudomonas viridiflava uses an enzyme called SaxA to break down the Arabidopsis defense chemical 4MSOB-ITC, a toxin most commensal bacteria can't resist.
Detoxifying the toxin rescues nearby commensal bacteria, and their subsequent nutrient competition can limit the pathogen's own growth, a trade-off confirmed with a mathematical consumer-resource model.
Whether SaxA acts as a virulence factor or a plant-beneficial trait depends on context, including how sensitive the commensals are and how fast the pathogen degrades the toxin.
chevron_right Technical Summary
Scientists found that a toxin-busting enzyme used by an opportunistic plant pathogen doesn't always help it win. By breaking down a plant's chemical defenses, the pathogen also rescues friendly bacteria nearby, and those revived neighbors then compete for food so fiercely that they can stunt the pathogen's own growth.
Abstract Preview
Original paper
Bacterial degradation of a plant toxin and nutrient competition with commensals trade off to constrain pathogen growth.
Healthy plant leaves potentially host both commensal bacteria and opportunistic pathogens, which, under some circumstances, may cause disease. The interactions between commensals and opportunistic ...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed.