Cheatgrass (Bromus tectorum) is an invasive plant species widely distributed throughout the Western United States that threatens grassland biodiversity and poses a significant wildfire risk to Department of Defense (DoD) managed lands. This annual grass spreads rapidly and outcompetes native grass species after burn events, producing large quantities of dry biomass that can fuel subsequent fires. Increasing frequency and severity of drought may alter the distribution and abundance of cheatgrass in the future, underscoring the need to understand how this invasive grass responds to water limitation in order to predict the impacts of climate change on cheatgrass population dynamics and to assess the risk of wildfire to DoD lands. This project will use a chemoproteomic approach to characterize redox changes in cheatgrass roots under drought conditions and in response to treatment with phenazine‐1‐carboxylic acid (PCA), a microbially produced small molecule that has demonstrated cheatgrass biocontrol properties and is known to perturb redox homeostasis. The project will advance the scientific understanding of cheatgrass biology by identifying key proteins and molecular mechanisms involved in cheatgrass drought response and under PCA biocontrol treatment. This work will also clarify the genetic factors that may promote sensitivity or resistance toward these stressors, which will contribute to a predictive understanding of cheatgrass population dynamics under climate change.

Three different cheatgrass accessions and the related model grass species, Brachypodium distachyon, will be grown in a laboratory setting under water‐replete and drought conditions to characterize how distinct genetic backgrounds may influence plant redox response to water limitation and PCA treatment. To accomplish this, the project team will identify and measure the abundances of redox‐sensitive proteins under various treatment conditions and then identify pathways and functions affected by an imbalance of redox homeostasis. The project team will also evaluate changes to the cheatgrass‐associated root microbiomes with and without drought and PCA exposure using 16S sequencing.  

While previous research on cheatgrass populations has yielded some insight into genetic variation and markers, there is still limited data linking specific cheatgrass genes to defined functions, and no studies have examined cheatgrass phenotypic response to environmental stressors at the molecular level. Gene‐to‐function characterization is necessary to identify the mechanisms responsible for plant resilience or susceptibility to drought and predict how different populations may respond to stress events. The approaches described in this project can also be readily applied to other invasive plant species and to other biotic and abiotic stress conditions. This work will contribute important molecular‐level insight into cheatgrass drought response, including identification of specific redox changes to the root proteome and characterization of perturbations to the cheatgrass microbiome, which will inform future efforts to develop targeted cheatgrass biocontrol measures.