Extrachromosomal circular DNA mediated spread of herbicide resistance in interspecific hybrids of pigweed

Extrachromosomal circular DNA (eccDNA) is a type of double-stranded circular DNA that is derived from chromosomes. High copy number and expression level of eccDNA encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) have been linked with glyphosate resistance in pigweed (Amaranthus spp). Previous studies have reported the apparent transfer of glyphosate resistance across related species of pigweed and have linked this with the possibility of a pollen-mediated eccDNA transfer. Here, Koo et al. used fluorescent in situ hybridization to confirm this hypothesis. They found that two pigweed species (Amarathus spinosus and Amarathus palmeri) carry similar eccDNA which conferred their glyphosate resistance that was likely acquired through interspecific hybridization by pollen transfer. Further experiments confirmed the ability of A. palmeri’s eccDNA to be transferred across species. Ultimately, the authors showed that eccDNA enables copy number variation in non-reproductive cells which, under strong selection pressure, may drive rapid adaptive evolution and acquisition of glyphosate resistance. (Summary by Abdulkabir Omeiza Abdulmalik  @Omeiza_PlantDoc) Plant Physiol. 10.1093/plphys/kiad281