Loss ofOsARF18confers glufosinate ammonium herbicide resistance in rice

Abstract

ABSTRACTWeed is one of the major biotic stresses that causes severe loss of crop yield. Herbicide is one of the most cost-effective ways to control weeds. Thus, the development of herbicide-resistant crops is critical for the application of herbicides. To isolate new glufosinate ammonium resistance loci, we screened a rice ethyl methyl sulfonate-mutagenized library and obtained theglufosinateammonium-resistant mutantgar1-1.GAR1encodes auxin response factor 18 (OsARF18). A G-to-A substitution in the coding region ofOsARF18results in loss of function ofOsARF18and thereby enhances glufosinate ammonium resistance ofgar1-1, which was confirmed by three additional CRISPR/Cas9-editedgar1alleles.GLUTAMINE SYNTHETASE 1;1(OsGS1;1) andGLUTAMINE SYNTHETASE 1;2(OsGS1;2) were upregulated ingar1-1upon glufosinate ammonium treatment, directly contributing to increased GS activity that enhances glufosinate ammonium herbicide resistance. We further show that OsARF18 suppressesOsGS1;1andOsGS1;2expression.Comparative transcriptomic analyses reveal a huge shift in the gene expression profile involved in stress tolerance and growth. A large number of detoxification-related genes are enriched ingar1-1, which may also contribute to enhanced herbicide resistance. Moreover, stress tolerance-related genes are upregulated and growth-related genes are downregulated ingar1-1, consistent with the improved tolerance to salt and osmotic stress ofgar1mutants. Taken together, our study demonstrates thatOsARF18is a negative regulator of glufosinate ammonium resistance as well as salt and osmotic stress tolerance, suggesting a role in balancing the stress response and growth.