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Sept. 24, 2018

MSU scientists get to the root of plant stress response

Michigan State University microbiologist Ashley Shade and plant biologist Sheng Yang He have been awarded a three-year, $500,000 grant from the National Science Foundation to investigate how the microbiome interacts with, and may mediate, plant responses during environmental stress and how plants may recruit different—and potentially beneficial—root microbes during such periods.

Scientists know that plants associate closely with some soil microorganisms and engage with them in beneficial relationships near the root surface. It is likewise anticipated that beneficial microbes support plant resilience to environmental stresses. However, it is not well understood how microbes are recruited to the root during stress or which members of the diverse soil microbial community are most responsive during stress. This research will investigate how microorganisms respond to plant hormones that signal stress. 

“Like the human microbiome project, which has revealed the critical role of the gut microbiome in human health, this project will provide major advancements of how plants recruit and benefit from close association with microbes,” said Robin Buell, MSU Foundation Professor of plant biology and director of MSU’s Plant Resilience Institute, which generated the preliminary data for the NSF proposal. “With this information, we will be poised to improve agriculture in a sustainable manner.”

Working with soils collected from the Kellogg Biological Station agricultural cropping systems, Shade and He will use controlled-environment chambers and greenhouses to grow plants to assess how they recruit microbes when they are stressed and exposed to particular phytohormones that they make in response. 

“The controlled environment will allow us to control and impose the stresses as well as observe direct changes in the root microbial communities that result,” said Shade, an assistant professor in the Department of Microbiology and Molecular Genetics and the Department of Plant, Soil and Microbial Sciences

The research team will collect chemicals, including phytohormones, that plants exude from their roots during stress to examine how those chemicals alter the behavior of microbial communities and particular species of root-associated bacteria in the laboratory.

“This response is expected to be more complex because the plants will exude many chemicals from their roots in addition to any possible phytohormones, such as sugars and amino acids that bacteria may want to eat,” Shade said. “By comparing the responses across experiments, we hope to identify those microbes that are particularly recruited to plants for their benefit during stress, and not just those bacteria that are looking for a free meal.”

Shade and He will assemble synthetic communities of bacteria that are highly responsive to plant stress signals. Through the creation of a simple community containing the most responsive bacteria, a model community will be made to demonstrate how the system works collectively. 

Understanding the dynamic relationships between soil microbes and plants during stress is important for anticipating and potentially managing expected changes in plant performance — given environmental and land-use changes, specifically as mediated by phytohormones and other plant signals released from the roots during stress. 

“Because some plant hormones used in this study are involved in biotic interactions, this research has the potential to discover interplays between microbial communities that mediate biotic and abiotic stress responses,” said He, a University Distinguished Professor in the Departments of Plant Biology; Plant, Soil and Microbial Sciences; and Microbiology and Molecular Genetics. 

By: Val Osowski