Drought Stress Changes Microbes Living at Sorghum’s Roots

December 18, 2018

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Drought Stress Changes Microbes Living at Sorghum's Roots
Researchers analyzed the microbial communities that grow on the roots of sorghum. Here, confocal microscopy-based images of endophytic Streptomyces coelicolor (fluorescently tagged with mCherry) are shown growing on the surface of four-week-old roots of Sorghum bicolor. Researchers grew the sorghum (inset) at the Kearney Agricultural Research Extension Center in Parlier, California.

The Science

Droughts stress crops, but what if that wasn't the case? Answering that question involves looking at the bacteria and other microbes living on and around the plants' roots. Researchers examined microbes on sorghum roots, as the plant resists drought damage. They found that during a drought, sorghum shifts the balance of microbes in their root systems. The team's work suggests that drought plays a role in changing the development of the microbial communities around the roots. Further, the findings reveal evidence for a communication system between plants and nearby microbes.  

The Impact

While it's well known that soil moisture and other factors affect the composition of the microbes associated with plants, little is known about how the changes occur. This study offers insights into how plants trigger those changes. Specifically, it sheds new light on how plants communicate. Understanding the molecular mechanisms involved during drought stress may provide novel approaches to increase plant tolerance and, hence, productivity.

Summary

Drought stress can greatly reduce the health and productivity of plants, including candidate bioenergy feedstocks such as sorghum. Microbial communities associated with plant roots (root "microbiome") can have a significant influence on plant fitness, and the negative effects of drought stress on plant growth can be mitigated by the association of roots with certain bacteria. Host and environmental factors such as soil moisture affect the composition of the plant-associated microbiome, but little is known about the mechanisms by which this happens. Knowledge of this process could lead to the development of strategies to manipulate the root microbiome for enhanced plant resilience and productivity during drought stress. To gain a better understanding of the drought stress-plant development-plant microbiome interaction, researchers at the University of California, Berkeley and collaborating institutions investigated the root microbiome of a candidate bioenergy crop, sorghum. They found that root microbiome development was significantly delayed under drought conditions, while abundance and activity of a particular group of bacteria containing thick cell walls and lacking an outer cell membrane increased. Additionally, they observed enhanced expression of many bacterial genes associated with transport of specific amino acids and carbohydrates. They correlated this expression with increased production of the same compounds within the plant root. These results suggest the existence of a "communication" system between the root microbiome and host plant, whereby drought stress-induced metabolites are exuded by roots and may signal increased activity of bacterial transporters. This study highlights the importance of temporal sampling of plant-associated microbiomes. Also, the work suggests that strategies for manipulating the plant microbiome to develop crop plants with increased adaptation and higher productivity under conditions of stress could be feasible.

Contact

Program Manager
Cathy Ronning
Department of Energy, Office of Science, Biological and Environmental Research
catherine.ronning@science.doe.gov  

Principal Investigator
Peggy Lemaux
University of California, Berkeley
lemauxpg@berkeley.edu

Funding

The Department of Energy (DOE), Office of Science, Biological and Environmental Research (BER), Genomic Science Program, U.S. Department of Agriculture, and the DOE Office of Science BER Joint BioEnergy Institute funded this work. Research was performed using Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility sponsored by BER.

Publications

L. Xu, D. Naylor, Z. Dong, T. Simmons, G. Pierroz, K.K. Hixson, Y.M. Kim, E.M. Zink, K.M. Engbrecht, Y. Wang, C. Gao, S. DeGraaf, M.A. Madera, J.A. Sievert, J. Hollingsworth, D. Birdseye, H.V. Scheller, R. Hutmacher, J. Dahlberg, C. Jansson, J.W. Taylor, P.G. Lemaux, and D. Coleman-Derr, "Drought delays development of the sorghum root microbiome and enriches for monoderm bacteria." Proceedings of the National Academy of Sciences USA 115, E4284(2018). [DOI: 10.1073/pnas.1717308115]

Related Links

University of California, Berkeley press release: Drought treatment restructures plants' microbiomesExternal link

Highlight Categories

Program: BER, BSSD

Performer/Facility: University, DOE Laboratory, SC User Facilities, BER User Facilities, EMSL

Additional: Collaborations, Non-DOE Interagency Collaboration