For decades, it has been clear that soil microbes strongly affect plant health. For this reason, plant microbiomes?which mostly come from soil?have great potential to help improve agricultural productivity and restore damaged ecosystems. Because microbiomes are so complex, it is unclear how and why they affect plants. Part of the answer may lie in the evolutionary histories of plants and their microbiomes, which share a habitat and therefore must adapt to the same environmental stresses, such as drought. The research funded by this award will test the hypotheses that (1) drought-adapted soil microbiomes help plants tolerate drought, and (2) drought-adapted plants help soil microbes survive drought. DNA sequencing will be used to identify differences in drought-adapted versus non-adapted soil microbiomes. Then, physiological and biochemical techniques, such as CT-scanning of root structures, will reveal the effects of those drought-adapted and non-adapted microbiomes on plant health. These experiments will be done using both corn and Eastern Gamagrass, a native species. This research has the potential to improve current methods for predicting the effects of soil microbes on plant health, and thus impact agriculture and conservation practices. This award will also grow the American scientific workforce by supporting the training of one post-doctoral researcher, one Ph.D. student researcher, and two undergraduate student researchers. Finally, this award supports a portable museum exhibit that brings scientific content to hundreds of people in rural communities across Kansas.
This project is motivated by the lack of knowledge of how adaptation to a shared environmental stressor affects plant-microbiome interactions. Because root microbiomes are derived from soil, the constituent microbial lineages encounter environmental stressors both with and without a host. Whether the same microbial genes and traits contribute to stress tolerance and survival in both situations, or whether there is a fitness tradeoff between host-associated vs. free-living stages is not clear. Similarly, it is unknown whether microbiome adaptation to a given environmental challenge impacts the ability of a plant host to withstand the same challenge. To address these questions, drought will be used as a model stressor. First, shotgun metagenome sequencing of soils from across two natural precipitation gradients will characterize how historical water limitation shapes community-wide gene content, after controlling for variation in soil structure and chemical content measured using 3D X-ray CT and ICP-MS, respectively. Second, repeated metagenome and metatranscriptome sequencing will test for changes in the frequency and expression of microbial genes in natural soils after six months of experimentally induced drought. This experiment will be replicated in mesocosms both with and without plant hosts. Finally, the effects of drought-adapted and non-adapted soil microbiomes on plant physiology and drought tolerance will be measured using growth assays, RNA-seq, ionomics, and laser ablation tomography. This research may disentangle the genetic, physiological, and ecological interdependencies that shape the evolution of plant microbiomes.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
