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1. Genomic determination of breeding systems and trans-specific evolution of HD MAT genes in suilloid fungi

   https://doi.org/10.1093/genetics/iyad069  

   Ke, Yi-Hong; Branco, Sara; Bazzicalupo, Anna L; Nguyen, Nhu H; Liao, Hui-Ling; Kennedy, Peter; Bruns, Thomas D; Kuo, Alan; LaButti, Kurt; Barry, Kerrie; et al (April 2023, GENETICS)

   Stajich, J (Ed.)

   Abstract Studying the signatures of evolution can help to understand genetic processes. Here, we demonstrate how the existence of balancing selection can be used to identify the breeding systems of fungi from genomic data. The breeding systems of fungi are controlled by self-incompatibility loci that determine mating types between potential mating partners, resulting in strong balancing selection at the loci. Within the fungal phylum Basidiomycota, two such self-incompatibility loci, namely HD MAT locus and P/R MAT locus, control mating types of gametes. Loss of function at one or both MAT loci results in different breeding systems and relaxes the MAT locus from balancing selection. By investigating the signatures of balancing selection at MAT loci, one can infer a species’ breeding system without culture-based studies. Nevertheless, the extreme sequence divergence among MAT alleles imposes challenges for retrieving full variants from both alleles when using the conventional read-mapping method. Therefore, we employed a combination of read-mapping and local de novo assembly to construct haplotypes of HD MAT alleles from genomes in suilloid fungi (genera Suillus and Rhizopogon). Genealogy and pairwise divergence of HD MAT alleles showed that the origins of mating types predate the split between these two closely related genera. High sequence divergence, trans-specific polymorphism, and the deeply diverging genealogy confirm the long-term functionality and multiallelic status of HD MAT locus in suilloid fungi. This work highlights a genomics approach to studying breeding systems regardless of the culturability of organisms based on the interplay between evolution and genetics. 

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2. The quantitative genetics of gene expression in Mimulus guttatus

   https://doi.org/10.1371/journal.pgen.1011072  

   Veltsos, Paris; Kelly, John K. (April 2024, PLOS Genetics)

   Lasky, Jesse R. (Ed.)

   Gene expression can be influenced by genetic variants that are closely linked to the expressed gene (cis eQTLs) and variants in other parts of the genome (trans eQTLs). We created a multiparental mapping population by sampling genotypes from a single natural population ofMimulus guttatusand scored gene expression in the leaves of 1,588 plants. We find that nearly every measured gene exhibits cis regulatory variation (91% have FDR < 0.05). cis eQTLs are usually allelic series with three or more functionally distinct alleles. The cis locus explains about two thirds of the standing genetic variance (on average) but varies among genes and tends to be greatest when there is high indel variation in the upstream regulatory region and high nucleotide diversity in the coding sequence. Despite mapping over 10,000 trans eQTL / affected gene pairs, most of the genetic variance generated by trans acting loci remains unexplained. This implies a large reservoir of trans acting genes with subtle or diffuse effects. Mapped trans eQTLs show lower allelic diversity but much higher genetic dominance than cis eQTLs. Several analyses also indicate that trans eQTLs make a substantial contribution to the genetic correlations in expression among different genes. They may thus be essential determinants of “gene expression modules,” which has important implications for the evolution of gene expression and how it is studied by geneticists. 

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3. The Evolution of Locally Adaptive Chromosome Inversions in Mimulus guttatus

   https://doi.org/10.1111/mec.17708  

   Kollar, Leslie M; Stanley, Lauren E; Kenchanmane_Raju, Sunil K; Lowry, David B; Niederhuth, Chad E (March 2025, Molecular Ecology)

   ABSTRACT Chromosomal inversion polymorphisms are ubiquitous across the diversity of diploid organisms and play a significant role in the evolution of adaptations in those species. Inversions are thought to operate as supergenes by trapping adaptive alleles at multiple linked loci through the suppression of recombination. While there is now considerable support for the supergene mechanism of inversion evolution, the extent to which inversions trap pre‐existing adaptive genetic variation versus accumulate new adaptive variants over time remains unclear. In this study, we report new insights into the evolution of a locally adaptive chromosomal inversion polymorphism (inv_chr8A), which contributes to the adaptive divergence between coastal perennial and inland annual ecotypes of the yellow monkeyflower,Mimulus guttatus. This research was enabled by the sequencing, assembly and annotation of new annual and perennial genomes ofM. guttatususing Oxford Nanopore long‐read sequencing technology. In addition to the adaptive inv_chr8A inversion, we identified three other large inversion polymorphisms, including a previously unknown large inversion (inv_chr8B) nested within inv_chr8A. Through population genomic analyses, we determined that the nested inv_chr8B inversion is significantly older than the larger chromosomal inversion in which it resides. We also evaluated the potential role of key candidate genes underlying the phenotypic effects of inv_chr8A. These genes are involved in gibberellin biosynthesis and anthocyanin regulation. Although little evidence was found to suggest that inversion breakpoint mutations drive adaptive phenotypic effects, our findings do support the supergene mechanism of adaptation and suggest it may sometimes involve nested inversions that evolve at different times. 

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4. P ool P arty 2: An integrated pipeline for analysing pooled or indexed low‐coverage whole‐genome sequencing data to discover the genetic basis of diversity

   https://doi.org/10.1111/1755-0998.13888  

   Willis, Stuart; Micheletti, Steven; Andrews, Kimberly R.; Narum, Shawn (November 2023, Molecular Ecology Resources)

   Abstract Whole‐genome sequencing data allow survey of variation from across the genome, reducing the constraint of balancing genome sub‐sampling with estimating recombination rates and linkage between sampled markers and target loci. As sequencing costs decrease, low‐coverage whole‐genome sequencing of pooled or indexed‐individual samples is commonly utilized to identify loci associated with phenotypes or environmental axes in non‐model organisms. There are, however, relatively few publicly available bioinformatic pipelines designed explicitly to analyse these types of data, and fewer still that process the raw sequencing data, provide useful metrics of quality control and then execute analyses. Here, we present an updated version of a bioinformatics pipeline calledPoolParty2that can effectively handle either pooled or indexed DNA samples and includes new features to improve computational efficiency. Using simulated data, we demonstrate the ability of our pipeline to recover segregating variants, estimate their allele frequencies accurately, and identify genomic regions harbouring loci under selection. Based on the simulated data set, we benchmark the efficacy of our pipeline with another bioinformatic suite,angsd, and illustrate the compatibility and complementarity of these suites usingangsdto generate genotype likelihoods as input for identifying linkage outlier regions using alignment files and variants provided byPoolParty2. Finally, we apply our updated pipeline to an empirical dataset of low‐coverage whole genomic data from population samples of Columbia River steelhead trout (Oncorhynchus mykiss), results from which demonstrate the genomic impacts of decades of artificial selection in a prominent hatchery stock. Thus, we not only demonstrate the utility ofPoolParty2for genomic studies that combine sequencing data from multiple individuals, but also illustrate how it compliments other bioinformatics resources such asangsd. 

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5. Genetic variation at transcription factor binding sites largely explains phenotypic heritability in maize

   https://doi.org/10.1038/s41588-025-02246-7  

   Engelhorn, Julia; Snodgrass, Samantha J; Kok, Amelie; Seetharam, Arun S; Schneider, Michael; Kiwit, Tatjana; Singh, Ayush; Banf, Michael; Doan, Duong_Thi Hai; Khaipho-Burch, Merritt; et al (September 2025, Nature Genetics)

   Abstract Comprehensive maps of functional variation at transcription factor (TF) binding sites (cis-elements) are crucial for elucidating how genotype shapes phenotype. Here, we report the construction of a pan-cistrome of the maize leaf under well-watered and drought conditions. We quantified haplotype-specific TF footprints across a pan-genome of 25 maize hybrids and mapped over 200,000 variants, genetic, epigenetic, or both (termed binding quantitative trait loci (bQTL)), linked tocis-element occupancy. Three lines of evidence support the functional significance of bQTL: (1) coincidence with causative loci that regulate traits, includingvgt1,ZmTRE1and the MITE transposon nearZmNAC111under drought; (2) bQTL allelic bias is shared between inbred parents and matches chromatin immunoprecipitation sequencing results; and (3) partitioning genetic variation across genomic regions demonstrates that bQTL capture the majority of heritable trait variation across ~72% of 143 phenotypes. Our study provides an auspicious approach to make functionalcis-variation accessible at scale for genetic studies and targeted engineering of complex traits. 

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