Salicylic Acid Shapes Plant Root Microbiome

Plants grow in microbially rich environments, but only some of those microbes end up as part of the plant root microbiome. Jeffery L. Dangl of the University of North Carolina, Chapel Hill; Sarah L. Lebeis, now at the University of Tennessee, Knoxville; and coworkers figured out that salicylic acid, a plant defense hormone found in leaves, also plays a role in determining who’s in and who’s out of the root microbial community (Science 2015, DOI: 10.1126/science.aaa8764). The team profiled the root microbes of Arabidopsis thaliana mutants with altered immune systems. In normal plants, it’s common for some root bacterial families to be enriched and others to be depleted relative to the diverse microbial community in the soil. In Arabidopsis mutants with altered salicylic acid production or signaling, some of the bacterial families are even further enriched or depleted, suggesting that salicylic acid helps control the assembly of a normal root microbiome. The researchers don’t know whether this control is a result of salicylic acid’s normal immune function or currently unknown effects on microbes and plant roots. The work “could open new avenues for modulating the root microbiome to enhance crop production and sustainability,” the researchers write.