Intensive herbicide use has selected for constitutively elevated levels of stress‐responsive mRNAs and proteins in multiple herbicide‐resistant Avena fatua L

BACKGROUND Intensive use of herbicides has led to the evolution of two multiple herbicide‐resistant (MHR) Avena fatua (wild oat) populations in Montana that are resistant to members of all selective herbicide families available for A. fatua control in US small grain crops. We used transcriptome and proteome surveys to compare constitutive changes in MHR and herbicide‐susceptible (HS) plants associated with non‐target site resistance. RESULTS Compared to HS plants, MHR plants contained constitutively elevated levels of differentially expressed genes (DEGs) with functions in xenobiotic catabolism, stress response, redox maintenance and transcriptional regulation that are similar to abiotic stress‐tolerant phenotypes. Proteome comparisons identified similarly elevated proteins including biosynthetic and multifunctional enzymes in MHR plants. Of 25 DEGs validated by RT‐qPCR assay, differential regulation of 21 co‐segregated with flucarbazone‐sodium herbicide resistance in F3 families, and a subset of 10 of these were induced or repressed in herbicide‐treated HS plants. CONCLUSION Although the individual and collective contributions of these DEGs and proteins to MHR remain to be determined, our results support the idea that intensive herbicide use has selected for MHR populations with altered, constitutively regulated patterns of gene expression that are similar to those in abiotic stress‐tolerant plants. © 2017 Society of Chemical Industry