Tomato root-associated Sphingobium harbors genes for neutralizing toxic compound

Kyoto, Japan — Regardless of how one says ‘tomato’, they all contain tomatine, a toxin in the plant’s green fruit, leaves, and roots. Tomatoes produce the bitter-tasting compound — a major plant-specialized metabolite secreted from the roots — to defend against pathogens and foragers.

Such metabolites function as nutrients and chemical signals, affecting the formation of microbial communities that greatly influence plant growth.

Previous studies have found that plant-based organic toxins — saponins, such as tomatine — alter the microbial community around tomato roots by increasing the bacterium Sphingobium. Yet, what remained unknown was how the microbe’s colonies in the tomato rhizosphere — the soil surrounding the roots — dealt with tomatine.

Now, a research group led by Kyoto University has revealed that Sphingobium possesses a series of enzymes that hydrolyze tomatine, detoxifying it.

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