Plants and the art of microbial maintenance

It is known for centuries that seedlings produce a diverse array of medically-valuable chemicals in their roots.

The benefits for human health are clear, but it's been less apparent how and why plants expend 20 percent of their energy building these exotic chemicals. Is it for defense? Is it waste? What is it for?

A joint study of the John Innes Center and the Chinese Academy of Sciences has shed light on this fundamental question of plant specialized metabolism.

Appearing in the newspaper Science, the study reveals that plants use their root-derived chemicals to muster and maintain communities of microbes. It suggests that a variety of plant nutrients be provided for the production of microbial communities that are adapted to the specific needs of the farmer.

The findings provide researchers with a gateway to the plant root microbiota in a range of major crops.

"This question has fascinated people and we have found that this is the case," says Professor Anne Osbourn of the John Innes Center, co-author of the study.

"We assume that the plant is a microbiota root for its own benefit." "We can understand what plant is doing and what kind of microbes are we? "adds Professor Osbourn.

In this study the team uncovered a metabolic network expressed in the roots of the well-known model plant Arabidopsis thaliana. This network, organized primarily around gene clusters, can be triterpenes.

Yang Bai of the Chinese Academy of Sciences grew up in Beijing.

The results showed clear differences in the types of microbial communities that these plants compared with the wild plants.

In further experiments the group synthesized many of these newly-discovered chemicals and their effects on communities of microbial cultures in a laboratory re-enactment of plant-microbial interactions in the soil.

"Using this approach, we can see that very small differences in chemical structures can have profound effects on a molecule. this cocktail of chemicals, "says Dr. Ancheng Huang.

Comparisons with root bacterial profiles in rice and wheat Arabidopsis triterpenes demonstrated that these genetic networks were modulating bacteria towards the assembly of an Arabidopsis-specific root microbiota.

The next steps for the researchers is to explore further the benefits of this nutrient limitation and pathogen challenge.

The full study "A specialized metabolic network selectively modulates Arabidopsis root microbiota, "appears in Science.