Biology subjects

Meiners, I.

Publications and source records attributed to Meiners, I..

4 recordsLinked to original sources

bioRxiv2026

Fendioxypyracil Exhibits Potent Inhibition of PPO-Resistant Mutant Enzymes and Robust Activity Against PPO-Resistant Amaranthus

Background: Resistance to protoporphyrinogen oxidase (PPO) inhibiting herbicides is mainly driven by diverse target-site mutations, reducing the effectiveness of this site of action in row crop systems. Fendioxypyracil is a newly developed PPO inhibitor with high intrinsic grass and broadleaf activity, but its performance against resistant populations and target-site enzyme variants remains insufficiently characterized. Results: Enzyme assays using PPO2 from Amaranthus palmeri and Setaria viridis demonstrated that fendioxypyracil maintained low IC50 values across a broad range of resistance associated mutations, including dG210 deletion and G210, R128, and G399 substitutions, whereas oxadiazon, tiafenacil, and saflufenacil showed substantial loss of potency. Greenhouse dose response experiments confirmed strong fendioxypyracil efficacy, with susceptible and G399A populations controlled at <3 g ai/ha, while dG210 and R128G populations showed only moderate shifts in sensitivity but remained effectively controlled at the recommended rate. Transgenic Arabidopsis thaliana expressing resistant PPX2 alleles exhibited faster and more severe injury with fendioxypyracil compared to saflufenacil. Field trials conducted in a PPO resistant Amaranthus palmeri population demonstrated that fendioxypyracil provided consistent weed control and density reduction, matching the performance of trifludimoxazin and saflufenacil while exceeding that of fomesafen. Conclusion: Fendioxypyracil provides robust and broad-spectrum activity against PPO resistant Amaranthus populations and target mutant enzymes, maintaining efficacy across diverse mutation backgrounds. These results demonstrate its potential as an effective tool for managing PPO inhibitor resistance and sustaining weed control in row-crop production systems.

molecular biology↗

bioRxiv2026

Novel Protoporphyrinogen oxidase 1 mutations endow resistance to PPO-inhibiting herbicides in Bassia scoparia

PPO-inhibiting herbicides are widely used to manage weeds in different cropping systems, yet resistance evolution threatens their long-term efficacy. Here, we investigated the molecular basis of resistance to PPO-inhibiting herbicides in Bassia scoparia biotypes collected from four locations in North Dakota, USA. Greenhouse dose-response assays revealed high levels of resistance to saflufenacil and carfentrazone-ethyl, while fomesafen retained full efficacy across all biotypes. Resistant plants did not show increased copy number or elevated expression of PPO1 or PPO2. Sequencing of survivor plants revealed conserved PPO2 sequences, but consistent target-site substitutions at position F454 in PPO1, including F454I, F454L, and F454V. In vitro enzyme assays demonstrated that these substitutions impair PPO1 sensitivity to saflufenacil and carfentrazone-ethyl, but not to fomesafen. Ectopic expression of B. scoparia PPO1 F454 mutant variants in Arabidopsis thaliana conferred tolerance to saflufenacil and carfentrazone-ethyl, but not to fomesafen, supporting greenhouse and in vitro results. Molecular modeling indicated that the conformational flexibility and interaction profile of fomesafen enables it to maintain binding to mutated PPO1 variants, in contrast to the more rigid structures of saflufenacil and carfentrazone-ethyl. A yeast-based complementation system further confirmed that F454 substitutions decrease herbicide sensitivity. In addition, developmental profiling showed distinct expression patterns of PPO1 and PPO2 during early growth stages in B. scoparia and Amaranthus spp., highlighting isoform-specific roles. Together, these findings represent the first reported PPO1 target-site mutations in a broadleaf weed species as a key mechanism of resistance and highlight that fomesafen is effective to control resistant B. scoparia populations.

biochemistry↗

bioRxiv2024

Extrachromosomal DNA-mediated glutamine synthetase 2 (GS2) amplification enables glufosinate resistance in Amaranthus palmeri

BackgroundPalmer amaranth achieves resistance to glufosinate by overproducing the chloroplastic glutamine synthetase (GS2) protein, a result of the amplification and overexpression of its nuclear coding gene. This study examined how amplified GS2 copies are inherited, identified their physical location in the cell, and investigated the mechanism of GS2 amplification. ResultsSegregation analysis revealed that inheritance of amplified GS2 copies deviates from classical Mendelian patterns, with poor correlation between plant level resistance and GS2 amplification. Fluorescence in situ hybridization revealed chromosomal insertions of GS2 and potential extrachromosomal circular DNA (eccDNA), and variability in GS2 amplification both among individual plants and within cells (not all cells in plants with high GS2 copy number showed GS2 amplification). The unpredictable inheritance patterns and distribution of GS2 copies across multiple chromosomes suggest a role for eccDNA in GS2 amplification. This was confirmed through eccDNA sequencing, which also identified multiple isoforms of GS2. ConclusionThis is the second documented case of herbicide resistance conferred by eccDNA-mediated target-site gene amplification in Palmer amaranth.

genomics↗

bioRxiv2024

A Novel Genomic Rearrangement in the Amaranthus palmeri Extrachromosomal Circular DNA Provides Dual Herbicide Resistance to Glyphosate and Glufosinate

Amplification of chloroplastic glutamine synthetase (GS2) has been characterized as one of the resistance mechanisms in glufosinate-resistant Amaranthus palmeri accession (MSR2). Previously, the overamplification of the glyphosate-resistance gene, 5-enolpyruvylshikimate-3-phosphate (EPSPS), in A. palmeri was determined to be driven by an extrachromosomal circular DNA (eccDNA). Here, a novel eccDNA is described that carries both glyphosate and glufosinate-ammonium target site due to co-duplication of their chromosomic native region, conferring resistance. Besides EPSPS, the novel replicon has a region replaced by a fragment carrying the GS2 isoforms (GS2.1 and GS2.2) and other genes. The co-existence of eccDNA carrying only EPSPS was confirmed in MSR2 samples harboring dual targeting eccDNA. The genomic structure of GS2 and EPSPS amplification was also assessed in a different glufosinate-resistant A. palmeri accession (MSR1) along with MSR2. The accessions showed distinct GS2.1 and GS2.2 amplification patterns suggesting the existence of diverse replicons that were not assembled here. The EPSPS was amplified in both accessions, and a correlation was observed with the GS2 isoforms in MSR2, further supporting the co-existence of these genes in the same replicon. These findings shed light on the complexity of eccDNA formation in plant systems, with the collection and accumulation of extra pieces of DNA.

genomics↗