Biology subjects

Patterson, E.

Publications and source records attributed to Patterson, E..

15 recordsLinked to original sources

bioRxiv2026

Sex-specific bone marrow populations regulate skeletal phenotype and identify CD74-marked osteoclast precursor subsets

While there are clear differences in bone accrual and maintenance between men and women due to hormonal regulation, the potential cell-intrinsic factors governing this difference are poorly understood. To investigate this, we performed bone marrow transplantation assays using male or female bone marrow transplantation into male hosts. Micro-CT analyses of lethally irradiated 8-week-old male mice transplanted with female bone marrow exhibited increased vertebral body trabecular and cortical bone mass. To identify cell types mediating these effects, we performed comparative single cell sequencing analyses and identified several CD11B+CD74+ myeloid cell clusters. Male donor BM chimeric mice had a higher proportion of Cd74-expressing clusters compared to female donor BM chimeric mice. We confirmed that males have greater numbers of bone marrow-resident CD11B+CD74+ cells under physiological conditions. Elevated expression of X-linked genes Tlr7 and Kdm6a marked a population of CD11B+CD74+ cells. Lastly, we show that female CD11B+CD74+ cells exhibit diminished osteoclastogenesis. These findings demonstrate that male and female bone marrow-resident cells have cell-intrinsic differences that regulate bone mass and that CD74 marks a subset of osteoclast precursor-enriched myeloid populations.

cell biology↗

bioRxiv2026

Distribution of target-site resistance mechanisms to nicosulfuron and glyphosate in Amaranthus palmeri accessions from two different regions of Turkiye

Palmer amaranth (Amaranthus palmeri S. Watson) is a highly competitive weed that has evolved resistance to several modes of action and has recently become a significant problem in Turkiye. This study was designed to determine the distribution of common target-site resistance (TSR) mechanisms to the acetolactate synthase (ALS)-inhibiting herbicide, nicosulfuron, and the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS)-inhibiting herbicide, glyphosate, in A. palmeri accessions collected from two agricultural regions of Turkiye; the Cukurova Region and the Gediz Basin. A total of 96 accessions were analyzed for ALS gene mutations and relative EPSPS gene copy number variation. Whole-plant responses were also evaluated based on relative dry weight following treatment with nicosulfuron and glyphosate applied at twice the field rate. The ALS mutations Pro197Ser, Trp574Leu, and Ser653Asn were far more prevalent in plants from the Cukurova Region than those from the Gediz Basin. Elevated relative EPSPS gene copy numbers were more common and higher in the Gediz Basin. Single rate herbicide screening experiments confirmed that accessions from the Cukurova Region exhibited higher dry weight response to nicosulfuron, whereas those from the Gediz Basin had higher to glyphosate Multivariable regression analyses revealed that nicosulfuron response was primarily associated with the Pro197Ser and Trp574Leu mutations, while glyphosate response was correlated with EPSPS gene copy number. These findings reveal distinct regional patterns of TSR mechanisms in A. palmeri in Turkiye that are consistent with differences in herbicide use and/or introduction history, but the roles of local selection, demographic processes, and gene flow remain unclear.

plant biology↗

bioRxiv2026

Characterization of a novel R98Q mutation that confers resistance to sulfentrazone in common ragweed (Ambrosia artemisiifolia) populations from MichiganShort title: PPO resistance in common ragweed

BACKGROUNDIn 2023, soybean growers in Eaton County, Michigan, reported repeated failures to control common ragweed (Ambrosia artemisiifolia L.) with (PPO)-inhibiting herbicides, sulfentrazone and fomesafen, in non-genetically modified soybeans. This study aimed to investigate resistance levels and mechanisms of resistance in two suspected resistant populations (R1 and R2). RESULTSDose-response assays revealed resistance to sulfentrazone in both populations, with LD50 values 24 and 36-fold higher than the susceptible population and reduced sensitivity to fomesafen. Nanopore sequencing identified two PPO2 target-site substitutions at codon 98: Arg- 98-Leu (R98L) and a novel Arg-98-Gln (R98Q) mutation. Both substitutions were associated with reduced herbicide binding affinity in computational modelling simulations. R98Q substitution conferred strong and selective resistance in the PPO2 enzyme inhibition assays, supporting its role as a key resistance mechanism. CONCLUSIONThis study reports the first field occurrence of the R98Q substitution in PPO2 of A. artemisiifolia populations and demonstrates its association with to PPO inhibitor resistance. These findings highlight the rapid evolution of target-site resistance and the need for continued monitoring and rapid diagnostic tools to detect emerging mutations. Further research is needed to clarify the contribution of additional resistance mechanisms.

plant biology↗

bioRxiv2026

Investigating the mechanism of resistance to indaziflam in Poa annua

Indaziflam is an effective herbicide for controlling Poa annua, a weed, in turfgrass, orchards, and rangelands. An RNA-seq analysis was performed to identify differentially expressed genes associated with indaziflam-resistance in P. annua populations, with heterologous transformation performed for validation of candidate gene. Additionally, whole transcriptome variant calling was used to determine potential target site mutations. Transcriptome data were analyzed using weighted gene co-expression network analysis, Multiple modules were identified with high correlation to ED50 values of the resistant and susceptible populations. A cytochrome P450, CYP81A91_A, was identified that was homologous to CYP81A10 that confers resistance to five different herbicidal modes of action in Lolium rigidum. A single nucleotide polymorphism (SNP) causing an amino acid change (Thr432Arg) in coatomer subunit {gamma} was identified P. annua populations and several others originating from orchards. The up-regulated and positively correlated CYP81A91_A identified, when transformed to Arabidopsis thaliana, did not provide resistance to indaziflam; however, it did provide multifold resistance to simazine, another triazine class herbicide from a different MOA. A SNP in coatomer subunit {gamma} (Thr432Arg) was identified that may provide target site resistance given that coatomer proteins are involved in vesicle trafficking and in recycling of the cellulose synthase. HIGHLIGHTThis paper is a in-depth characterization of indaziflam resistance in Poa annua that identifies a novel mutation in coatomer subunit {gamma} as the potential root cause.

plant biology↗

bioRxiv2026

Changes in cuticle composition co-regulate drought and herbicide resistance in horseweed (Erigeron canadensis)

Horseweed (Erigeron canadensis) is a widely distributed annual weed that can cause significant yield losses if not properly controlled. Its phenotypic plasticity allows it to rapidly acclimate to new environmental conditions, such as drought and herbicides, such as glyphosate, with the potential for cross stress acclimatization. The objectives of this research were to uncover the physiological and genetic effects at the intersection of drought stress and glyphosate resistance. To this end, we performed greenhouse dose response experiments, RNAseq, 14C glyphosate absorption and translocation, and cuticular lipid profiling via GC/MS. Greenhouse dose-response experiments revealed that, after drought stress, there was a 2.5-3.7 fold reduction in glyphosate sensitivity via a significant reduction in glyphosate absorption, regardless if the starting population was resistant or susceptible to the field use rate already. Cuticular waxes were collected from each population with and without drought stress and were analyzed via GC/MS. When comparing total wax loads of plants grown under WW and DS conditions, we found that drought stress significantly increased total wax loads for all three populations. Additionally drought stress substantial increases the proportion of triterpenoids in the cuticle. By RNAseq, we found serval triterpenoid biosynthesis genes upregulated after drought, which likely drive the changes in cuticle composition and ultimately increased glyphosate resistance following drought. Ultimately, understanding how drought impacts glyphosate resistance is critical for maintaining optimal weed control in the changing climate. HighlightDrought stress induces changes to cuticle composition and gene expression that reduce glyphosate absorption, thereby increasing horseweeds ability to survive glyphosate application.

physiology↗

bioRxiv2025

Procrustean pseudo-landmark methods in Python to measure massive quantities of leaf shape data

PremiseWhen examining leaf shapes that are different from one another, it can be difficult to compare both the overall leaf shape and points along the leaf margin in biologically and statistically meaningful ways. MethodTo address this problem, we present a simple and user-friendly leaf shape analysis in Jupyter Notebook and Python that uses pseudo-landmarks and Generalized Procrustes Analysis to measure and compare the shape of any leaf. To demonstrate our analysis, we created a repository of real leaves gathered from eight experimental datasets. ResultsUsing our leaf repository, we explain how we can use pseudo-landmarks to compare all leaf shapes both within and between species using dimension reduction techniques like Principal Component Analysis and can predict leaf shapes using pseudo-landmarks through Linear Discriminant Analysis. Our leaf shape analysis also maps differences in shape as leaves grew around a rosette, showing the transition of shape across development (phyllotaxy). Finally, we showed how we can investigate the relationship between leaf shape variation and genetic diversity by combining shape with genetic data. DiscussionThrough the use of Generalized Procrustes Analysis and pseudo-landmarks, our leaf shape analysis presents a powerful tool for examining the shape of any leaf across multiple biological, ecological, evolutionary, and developmental scales.

plant biology↗

bioRxiv2024

Chromosome-level assemblies of Amaranthus palmeri, Amaranthus retroflexus, and Amaranthus hybridus allow for genomic comparisons and identification of a sex-determining region

Amaranthus palmeri (Palmer amaranth), A. retroflexus (redroot pigweed), and A. hybridus (smooth pigweed) are troublesome weeds that are economically damaging to several cropping systems. Collectively referred to as pigweeds, these species are incredibly adaptive and have become successful competitors in diverse agricultural settings. Development of genomic resources for these species promises to facilitate the elucidation of the genetic basis of traits such as biotic and abiotic stress tolerance (e.g., herbicide resistance) and sex determination. Here, we sequenced and assembled chromosome-level genomes of these three pigweed weed species. By combining the haplotype-resolved assembly of A. palmeri with existing restriction site-associated DNA sequencing data, we identified a [~]2.84 Mb region on chromosome 3 of Hap1 that is male-specific and contains 37 genes. Transcriptomic analysis revealed two genes within the male-specific region, RESTORER OF FERTILITY 1 (Rf1) and TLC DOMAIN-CONTAINING PROTEIN (TLC), were upregulated in male individuals across the shoot apical meristem, the floral meristem, and mature flowers, indicating their potential involvement in sex determination in A. palmeri. In addition, we rigorously classified cytochrome P450 genes in all three pigweeds due to their involvement in non-target site herbicide resistance. Finally, we identified contiguous extrachromosomal circular DNA (eccDNA) in A. palmeri, a critical component of glyphosate resistance in this species. The findings of this study advance our understanding of sex determination in A. palmeri and provide genomic resources for elucidating the genetic basis and evolutionary origins of adaptive traits within the genus.

genomics↗

bioRxiv2024

A transposable element insertion in IAA16 interrupts normal splicing and generates a novel dicamba resistance allele in Bassia scoparia

A dicamba-resistant population of kochia (Bassia scoparia) identified in Colorado, USA in 2012 was used to generate a synthetic mapping population that segregated for dicamba resistance. Linkage mapping associating dicamba injury with genotype derived from restriction-site-associated DNA sequencing identified a single locus in the kochia genome associated with resistance on chromosome 4. A mutant version of Auxin/Indole-3-Acetic Acid 16 (AUX/IAA16; a gene previously implicated in dicamba resistance in kochia) was found near the middle of this locus in resistant plants. Long read sequencing of dicamba-resistant plants identified a recently inserted Ty1/Copia retrotransposon near the beginning of the second exon of AUX/IAA16, leading to disruption of normal splicing. A molecular marker for this insertion allows for rapid detection of resistance. Stable transgenic lines of Arabidopsis thaliana ectopically expressing the mutant and wildtype alleles of AUX/IAA16 were developed. Arabidopsis thaliana plants expressing the mutant AUX/IAA16 allele grew shorter roots on control media. However, transgenic root growth was less inhibited on media containing either dicamba (5 M) or IAA (0.5 M) when compared to non-transgenic plants or those expressing the wildtype allele of AUX/IAA16. In vitro assays indicate reduced binding affinity and more rapid dissociation of the mutant AUX/IAA with TIR1 in the presence of several auxins, and protein modeling suggests the substitution of the glycine residue in the degron domain of AUX/IAA16 is especially important for resistance. A fitness cost associated with the mutant allele of AUX/IAA16 has implications for resistance evolution and management of kochia populations with this resistance mechanism. SignificanceAuxin mimics are amongst the most important herbicides in modern agriculture. Evolution of weeds that are resistant to these herbicides threatens sustainable crop production. Understanding the basis of auxin herbicide resistance informs the development of improved weed control technologies. Additionally, auxin-resistant mutations and their pleotropic effects help us understand auxin perception and signalling. We describe a transposable element insertion within an herbicide target site gene that alters splicing and reduces synthetic and natural auxin perception.

plant biology↗

bioRxiv2023

Enhanced metabolic detoxification is associated with fluroxypyr resistance in Bassia scoparia

Auxin-mimic herbicides chemically mimic the phytohormone indole-3-acetic-acid (IAA). Within the auxin-mimic herbicide class, the herbicide fluroxypyr has been extensively used to control an agronomically problematic Great Plains tumbleweed, kochia (Bassia scoparia). A 2014 field survey for herbicide resistance in kochia populations across Colorado identified a putative fluroxypyr resistant population that was assessed for response to five different herbicides representing four different herbicide modes of action. These included fluroxypyr and dicamba (auxin-mimics), atrazine (photosystem II inhibitor), glyphosate (EPSPS inhibitor), and chlorsulfuron (acetolactate synthase inhibitor). The greenhouse screen identified that this kochia population was resistant to fluroxypyr and chlorsulfuron, but sensitive to glyphosate, atrazine, and dicamba. This population was designated Flur-R. Subsequent dose response studies determined that 75% of the Flur-R population survived 628 g ae ha-1 of fluroxypyr (4X the label application rate in wheat fallow, which is 157 g ae ha-1 at 1X). Flur-R was 40 times more resistant to fluroxypyr than a susceptible population (J01-S) collected from the same field survey (LD50 720 and 20 g ae ha-1, respectively). Auxin-responsive gene expression increased following fluroxypyr treatment in Flur-R, J01-S, and in a dicamba-resistant, fluroxypyr-susceptible line 9425 in an RNA-sequencing experiment. In Flur-R, several transcripts with molecular functions for conjugation and transport were constitutively higher expressed, such as glutathione S-transferases (GSTs), UDP-glucosyl transferase (GT), and ATP binding cassette transporters (ABC transporters). After analyzing metabolic profiles over time, both Flur-R and J01-S rapidly converted [14C]-fluroxypyr ester, the herbicide formulation applied to plants, to [14C]-fluroxypyr acid, the biologically active form of the herbicide, and three unknown metabolites. Formation and flux of these metabolites was faster in Flur-R than J01-S, reducing the concentration of phytotoxic fluroxypyr acid. One unique metabolite was present in Flur-R that was not present in the J01-S metabolic profile. Gene sequence variant analysis specifically for auxin receptor and signaling proteins revealed the absence of non-synonymous mutations affecting auxin signaling and binding in candidate auxin target site genes, further supporting our hypothesis that non-target site metabolic degradation is contributing to fluroxypyr resistance in Flur-R. Significance StatementHerbicide resistance is an ever-present issue in weeds of cropping and rangeland systems. By understanding genetic mechanisms of resistance in individual cases of herbicide resistance, we can extrapolate important information such as how quickly resistance to a specific herbicide can spread. Every characterized herbicide resistance mechanism contributes to a working database used to address herbicide resistance in an agricultural or open-space setting. Knowing the exact mechanism of resistance helps researchers and industry members understand why herbicide applications are failing, and if resistant plants can still be controlled with other herbicide modes of action. In kochia line Flur-R, there is strong evidence to support a non-target site resistance mechanism, specifically herbicide degradation via increased enzymatic activity. Increased fluroxypyr degradation represents a novel resistance mechanism to fluroxypyr in the weed Bassia scoparia.

plant biology↗

bioRxiv2023

Defining cat mitogenome variation and accounting for numts via multiplex amplification and Nanopore sequencing

Hair shed by domestic cats is a potentially useful source of forensic evidence. Analysable hair DNA is predominantly mitochondrial, but the recent domestication history of cats means that mtDNA diversity is low. A 402-bp control region segment is usually sequenced, defining only a small number of distinct mitotypes in populations. Previously, we used a long-amplicon approach to sequence whole mitogenomes in a sample of blood DNAs from 119 UK cats, greatly increasing observed diversity and reducing random match probabilities. To exploit this variation for forensic analysis, we here describe a multiplex system that amplifies the cat mitogenome in 60 overlapping amplicons of mean length 360 bp, followed by Nanopore sequencing. Variants detected in multiplex sequence data from hair completely mirror those from long-amplicon data from blood from the same individuals. However, applying the multiplex to matched blood DNA reveals additional sequence variants which derive from the major feline nuclear mitochondrial insertion sequence (numt), which covers 7.9 kb of the 17-kb mitogenome and exists in multiple tandem copies. We use long-amplicon Nanopore sequencing to investigate numt variation in a set of cats, together with an analysis of published genome sequences, and show that numt arrays are variable in both structure and sequence, thus providing a potential source of uncertainty when nuclear DNA predominates in a sample. Forensic application of the test was demonstrated by matching hairs from a cat with skeletal remains from its putative mother, both of which shared a globally common mitotype at the control region. The random match probability (RMP) in this case with the CR 402-bp segment was 0.21 and this decreased to 0.03 when considering the whole mitogenome. The developed multiplex and sequencing approach, when applied to cat hair where nuclear DNA is scarce, can provide a reliable and highly discriminating source of forensic genetic evidence. The confounding effect of numt co-amplification in degraded samples where mixed sequences are observed can be mitigated by variant phasing, and by comparison with numt sequence diversity data, such as those presented here.

genetics↗

bioRxiv2023

FHY3/FAR1 transposable elements generate adaptive genetic variation in the Bassia scoparia genome

A near complete genome assembly consisting of 14 scaffolds, a total length of 969.6 Mb, and N50 scaffold length of 99.88 Mb, was generated to better understand how transposable element activity has led to adaptive evolution in Bassia scoparia (kochia), an agronomically important weed. The 9 largest scaffolds correspond to the 9 chromosomes of the close relative, Beta vulgaris. From this assembly, 54,387 protein-coding gene loci were annotated. We determined that genes containing Far-Red Elongated Hypocotyl 3 (FHY3) or Far-Red Impaired Response 1 (FAR1) functional domains have undergone a large, kochia-specific gene family expansion. We discovered that putative Mutator Don-Robertson (MuDR) transposable elements with detectable FHY3/FAR1 domains were tightly associated with segmental duplications of 5-enolpyruvylshikimate-3-phosphate synthase subsequently conferring resistance to the herbicide glyphosate. Further, we characterized a new MuDR subtype, named here as "Muntjac", which contributes to the evolution of herbicide resistance in kochia through the process of transduplication. Collectively, our study provides insights into the role of a FHY3/FAR1 gene as an active transposable element and contributes new perspectives on the interaction between transposons and herbicide resistance evolution. Significance StatementIn this work we discover that genes known as FHY3/FAR1, supposed "domesticated transposons", are still actively transposing in the weed Bassia scoparia rearranging the genome in new ways. One rearrangement they are involved in is the tandem duplication of the gene 5-enolpyruvylshikimate-3-phosphate synthase which is the gene that produces the target protein of glyphosate, one of the most important herbicides in the world. This work gives a specific example of the role that transposable elements play in making novel genetics and therefore the role that new genome rearrangements play in adaptative evolution, especially in response to external stress such as herbicides.

genomics↗

bioRxiv2023

On the cusp of adaptive change: the hierarchical radiation of phyllostomid bats

Adaptive radiations are bursts in biodiversity that lead to the origin of new evolutionary lineages and phenotypes. However, adaptive radiations typically occur over millions of years and it is unclear how the macroevolutionary dynamics that underpin them vary through time and among groups of organisms. Phyllostomid bats radiated extensively for diverse diets -from insects to vertebrates, fruit, nectar, and blood- and we use their molars as a model system to examine the dynamics of adaptive radiations. Three-dimensional shape analyses of lower molars of Noctilionoidea (Phyllostomidae and close relatives) indicate that different diet groups exhibit distinct morphotypes. Comparative analyses further reveal that phyllostomids are a striking example of a hierarchical radiation; their initial, higher-level diversification involved an early burst in molar morphological disparity as lineages invaded new diet-affiliated adaptive zones, followed by subsequent lower-level diversifications within adaptive zones involving less dramatic morphological changes. We posit that strong selective pressures related to initial shifts to derived diets may have freed molars from morpho-functional constraints associated with the ancestral molar morphotype. Then, lineages with derived diets (frugivores and nectarivores) diversified considerably within broad adaptive zones, likely reflecting finer-scale niche partitioning. The observed early burst pattern is only evident when examining molar traits that are strongly linked to diet, highlighting the importance of ecomorphological traits in comparative studies. Our results support the hypothesis that adaptive radiations are commonly hierarchical and involve different tempos and modes at different phylogenetic scales, with early bursts being more common at broader scales. SIGNIFICANCE STATEMENTMany groups of organisms are exceptionally diverse in their ecology, morphology, and number of species. But there is debate as to whether these groups commonly achieved this diversity through bursts in diversification early in their history. Phyllostomid bats are one of the most ecologically diverse mammalian families and a classic example of an adaptive radiation. We use their molar shapes, which correlate with diet, as a model for examining macroevolutionary patterns during diversifications. We find that phyllostomids experienced a two-step process of diversification; the first step involved a rapid burst, whereas the second involved finer-scale changes as lineages filled ecological niches. We posit that this is a common, yet underappreciated, pattern during the early histories of many diverse clades.

evolutionary biology↗

bioRxiv2021

Boundary domain genes were recruited to suppress bract growth and promote branching in maize

Grass inflorescence development is diverse and complex and involves sophisticated but poorly understood interactions of genes regulating branch determinacy and leaf growth. Here, we use a combination of transcript profiling, genetic and phylogenetic analyses to investigate tasselsheath1 (tsh1) and tsh4, two maize genes that simultaneously suppress inflorescence leaf growth and inhibit branching. We identify a regulatory network of inflorescence leaf suppression that involves the phase change gene tsh4 upstream of tsh1 and the ligule identity gene liguleless2 (lg2). We also find that a series of duplications in the tsh1 gene lineage facilitated its shift from boundary domain in non-grasses to suppressed inflorescence leaves of grasses. Collectively, these results suggest that the boundary domain genes tsh1 and lg2 were recruited to inflorescence leaves where they suppress growth and regulate a non-autonomous signaling center that promotes inflorescence branching, an important component of yield in cereal grasses.

plant biology↗

bioRxiv2020

Geminin is required for Hox gene regulation to pattern the developing limb

Development of the complex structure of the vertebrate limb requires carefully orchestrated interactions between multiple regulatory pathways and proteins. Among these, precise regulation of 5 Hox transcription factor expression is essential for proper limb bud patterning and elaboration of distinct limb skeletal elements. Here, we identified Geminin (Gmnn) as a novel regulator of this process. A conditional model of Gmnn deficiency resulted in loss or severe reduction of forelimb skeletal elements, while both the forelimb autopod and hindlimb were unaffected. 5 Hox gene expression expanded into more proximal and anterior regions of the embryonic forelimb buds in this Gmnn-deficient model. A second conditional model of Gmnn deficiency instead caused a similar but less severe reduction of hindlimb skeletal elements and hindlimb polydactyly, while not affecting the forelimb. An ectopic posterior SHH signaling center was evident in the anterior hindlimb bud of Gmnn-deficient embryos in this model. This center ectopically expressed Hoxd13, the HOXD13 target Shh, and the SHH target Ptch1, while these mutant hindlimb buds also had reduced levels of the cleaved, repressor form of GLI3, a SHH pathway antagonist. Together, this work delineates a new role for Gmnn in modulating Hox expression to pattern the vertebrate limb. SummaryThis work identifies a new role for Geminin in mouse limb development. Geminin is a nuclear protein that regulates gene expression to control several other aspects of vertebrate development.

developmental biology↗

bioRxiv2019

The Draft Genome of Kochia scoparia and the Mechanism of Glyphosate Resistance via Transposon-Mediated EPSPS Tandem Gene Duplication

Increased copy number of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene confers resistance to glyphosate, the worlds most-used herbicide. There are typically three to eight EPSPS copies arranged in tandem in glyphosate-resistant populations of the weed kochia (Kochia scoparia). Here, we report a draft genome assembly from a glyphosate-susceptible kochia individual. Additionally, we assembled the EPSPS locus from a glyphosate-resistant kochia plant by sequencing a kochia bacterial artificial chromosome library. These resources helped reconstruct the history of duplication in the structurally complex EPSPS locus and uncover the genes that are co-duplicated with EPSPS, several of which have a corresponding change in transcription. The comparison between the susceptible and resistant assemblies revealed two dominant repeat types. We discovered a FHY3/FAR1-like mobile genetic element that is associated with the duplicated EPSPS gene copies in the resistant line. We present a hypothetical model based on unequal crossing over that implicates this mobile element as responsible for the origin of the EPSPS gene duplication event and the evolution of herbicide resistance in this system. These findings add to our understanding of stress resistance evolution and provide an example of rapid resistance evolution to high levels of environmental stress.

genomics↗