Increase in IAA levels by EPSPS copy number variation relates to fitness advantage in Eleusine indica.

BACKGROUND

Long-term use of chemical weed control has led to some weedy species evolving herbicide resistance traits with fitness advantage. Our previous studies revealed glyphosate resistance in an Eleusine indica population due to copy number variation of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) comes with fitness advantage under non-competitive conditions. Here, transcriptomics and targeted metabolomics were used to investigate physiological basis associated with the fitness advantage.

RESULTS

Relative copy number of EPSPS gene and plant dry weight of the glyphosate-resistant (R) population was 88.3- and 1.2- times, respectively, higher than that in the wild type (WT) plants that were isolated from within the R population. Seven genes were screened to be relevant to fitness growth trait by RNA-seq. The level of aromatic amino acids Tryptophan (Trp), Phenylalanine (Phe) and Tyrosine (Tyr), products in the shikimate pathway catalyzed by EPSPS, was 1.2-times higher in R compared to the WT plants. The metabolites associated with Trp metabolism indole-3-acetic acid (IAA), 3-indolepropionic acid (IPA), indole-3-acetamide (IAM) in the R plants were 2.0-, 1.8- and 1.4- times higher than that in the WT plants, respectively.

CONCLUSION

All the results indicate that fitness advantage in the studied R E. indica population may be caused by higher IAA production due to over-expression of the EPSPS gene and pleiotropically by elevated carbon metabolism. The findings in this research can provide reference information for control strategies to the glyphosate-resistant E. indica. © 2025 Society of Chemical Industry.