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Genomics

Explore bioRxiv genomics preprints on sequencing, gene expression and genetic variation. Read source abstracts and verify methods in the manuscript; preprints are not peer reviewed.

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bioRxiv2025

Comparative genomics of Sympodiorosea identifies genome evolution mediated through selective pressure on the metabolic gene repertoire

Biological interactions involving host-associated fungi are manifestations of chemistry shaped over evolutionary time. For antagonistic fungi, specialization to host fungi is often facilitated through the acquisition of genes encoding novel secretions, including proteins and specialized metabolites that shape interactions with host defenses, as well the acquisition of nutrients. Alternatively, novel function may arise from diversifying selection eliciting evolutionary innovation in inert secretions. Through specialization, fungal metabolic capacity can serve as an imprint of the selective forces imposed on the antagonist and provide insights into its natural history and occupied niche. Here, we conduct a phylogenomic investigation of antagonistic ascomycetes in the genus Sympodiorosea, which are commonly found in basal fungus-growing ant gardens. Sympodiorosea and closely related genera of Escovopsis, Luteomyces, and Escovopsioides are canonically referenced as virulent mycoparasites, however, recent work has illuminated the possibility for diverse, non-virulent species to emerge within these attine-associated fungi. We explored genomic variation in Sympodiorosea to gain insight into the genomic potential for alternative lifestyles, focusing on diversity and evolution of metabolic genes. Our study revealed a constrained selective landscape across the Sympodiorosea genome. However, outcomes of in vitro interactions with host fungi are diverse and predictable based on the antagonists ant-species-of-origin, suggesting functional diversification. Phylogenomics reveals that gain/loss events of genes involved in secretions (secretome) are potential drivers of diversification. Additionally, we demonstrate that purifying selection acts more intensely on secretome-related genes relative to other genes. In contrast, few genes from the secretome experience diversifying selection, suggesting a mechanistic role for driving both functional differences between strains and host-specialization. Comparative genomics including other fungi within the family Hypocreales reveals that Sympodiorosea has experienced expansions and contractions in proteases genes that are discordant from expectations under a strictly mycoparasitic lifestyle, indicating either the potential for an alternative lifestyle within ant gardens, or that Sympodiorosea recently evolved from other niches. These results provide novel insight into genomic evolution of these fungi and inform future experimental studies of the ecology and chemistry of interactions within the complex fungus-growing ant symbiosis.

evolutionary biology↗

bioRxiv2018

GenoGAM 2.0: Scalable and efficient implementation of genome-wide generalized additive models for gigabase-scale genomes

GenoGAM (Genome-wide generalized additive models) is a powerful statistical modeling tool for the analysis of ChIP-Seq data with flexible factorial design experiments. However large runtime and memory requirements of its current implementation prohibit its application to gigabase-scale genomes such as mammalian genomes.\n\nHere we present GenoGAM 2.0 a scalable and efficient implementation that is 2-3 orders of magnitude faster than the previous version. This is achieved by exploiting the sparsity of the model using the SuperLU direct solver for parameter fitting, and sparse Cholesky factorization together with the sparse inverse subset algorithm for computing standard errors. Furthermore the HDF5 library is employed to store data efficiently on hard drive, reducing memory footprint while keeping I/O low. Whole-genome fits for human ChIP-seq datasets (ca. 300 million parameters) could be obtained in less than 9 hours on a standard 60-core server. GenoGAM 2.0 is implemented as an open source R package and currently available on GitHub. A Bioconductor release of the new version is in preparation.\n\nWe have vastly improved the performance of the GenoGAM framework, opening up its application to all types of organisms. Moreover, our algorithmic improvements for fitting large GAMs could be of interest to the statistical community beyond the genomics field.

bioinformatics↗

bioRxiv2018

The Genomic Geography and Evolution of Clusters of Tandemly Duplicated Genes in the Human and Mammal Genomes

Clusters of duplicated genes (CTDGs) are nearly ubiquitous in lifes genomes, and are associated with several well-known gene families, such as olfactory receptors, zinc fingers, and immunity-related genes, as well as with several highly variable traits, including olfaction, body plan architecture, and pathogen resistance. However, these observations are usually anecdotal, restricted to specific cases, and lacking evolutionary context. In this study, we use a robust statistical approach to characterize the CTDG repertoire and analyze the distribution of CTDGs across 18 mammal genomes, including human. We found that, on average, 18% of the genes in each species are parts of CTDGs. Although genes in CTDGs are enriched for several biological processes, these tend to be involved in the interactions between the organism and its environment. We further found that mammalian CTDGs are not uniformly distributed across chromosomes and that orthologs of the human chromosome 19 are among the most clustered chromosomes in nearly all mammalian genomes analyzed. We also found evidence that the human chromosome 19 was formed by a fusion event that occurred before the diversification of the rodent and primate lineages and maintained its high density of CTDGs during its subsequent evolution. Finally, using chromosome-level alignments across mammalian genomes, we show how the syntenic regions of the human chromosome 19 have been shrinking, increasing their gene density and possibly increasing the compactness of its CTDGs. These results suggest that CTDGs are a major feature of mammalian genomes and provide novel insights into the origin and evolution of regions with unusually high densities of CTDGs.

evolutionary biology↗

bioRxiv2019

Genome-wide DNA polymorphisms in four Actinidia arguta genotypes based on whole-genome re-sequencing

Among the genus Actinidia, Actinidia arguta possesses the strongest cold resistance and produces fresh fruit with an intense flavor. To investigate genomic variation that may contribute to variation in phenotypic traits, we performed whole-genome re-sequencing of four A. arguta genotypes originating from different regions in China and identified the polymorphisms using InDel markers. In total, 4,710,650, 4,787,750, 4,646,026, and 4,590,616 SNPs and 1,481,002, 1,534,198, 1,471,304, and 1,425,393 InDels were detected in the Ruby-3, Yongfeng male, Kuilv male, and Hongbei male genomes, respectively, compared with the reference genome sequence of Hongyang. A subset of 120 InDels were selected for re-sequencing validation. Additionally, genes related to non-synonymous SNPs and InDels in coding domain sequences were screened for functional analysis. The analysis of GO and KEGG showed that genes involved in cellular responses to water deprivation, sucrose transport, decreased oxygen levels and plant hormone signal transduction were significantly enriched in A. arguta. The results of this study provide insight into the genomic variation of kiwifruit and can inform future research on molecular breeding to improve cold resistance in kiwifruit.

plant biology↗

bioRxiv2019

Genome-wide association analyses of multiple traits in Duroc pigs using low-coverage whole-genome sequencing strategy

High-density markers discovered in large size samples are essential for mapping complex traits at the gene-level resolution for agricultural livestock and crops. However, the unavailability of large reference panels and array designs for a target population of agricultural species limits the improvement of array-based genotype imputation. Recent studies showed very low coverage sequencing (LCS) of a large number of individuals is a cost-effective approach to discover variations in much greater detail in association studies. Here, we performed cohort-wide whole-genome sequencing at an average depth of 0.73x and identified more than 11.3 M SNPs. We also evaluated the data set and performed genome-wide association analysis (GWAS) in 2885 Duroc boars. We compared two different pipelines and selected a proper method (BaseVar/STITCH) for LCS analyses and determined that sequencing of 1000 individuals with 0.2x depth is enough for identifying SNPs with high accuracy in this population. Of the seven association signals derived from the genome-wide association analysis of the LCS variants, which were associated with four economic traits, we found two QTLs with narrow intervals were possibly responsible for the teat number and back fat thickness traits and identified 7 missense variants in a single sequencing step. This strategy (BaseVar/STITCH) is generally applicable to any populations and any species which have no suitable reference panels. These findings show that the LCS strategy is a proper approach for the construction of new genetic resources to facilitate genome-wide association studies, fine mapping of QTLs, and genomic selection, and implicate that it can be widely used for agricultural animal breeding in the future.

genetics↗

bioRxiv2019

Massive gene presence/absence variation in the mussel genome as an adaptive strategy: first evidence of a pan-genome in Metazoa

Mussels are ecologically and economically relevant edible marine bivalves, highly invasive and resilient to biotic and abiotic stressors causing recurrent massive mortalities in other species. Here we show that the Mediterranean mussel Mytilus galloprovincialis has a complex pan-genomic architecture, which includes a core set of 45,000 genes shared by all individuals plus a surprisingly high number of dispensable genes ([~]15,000). The latter are subject to presence/absence variation (PAV), i.e., they may be entirely missing in a given individual and, when present, they are frequently found as a single copy. The enrichment of dispensable genes in survival functions suggests an adaptive value for PAV, which might be the key to explain the extraordinary capabilities of adaptation and invasiveness of this species. Our study underpins a unique metazoan pan-genome architecture only previously described in prokaryotes and in a few non-metazoan eukaryotes, but that might also characterize other marine invertebrates.\n\nSignificance statementIn animals, intraspecific genomic diversity is generally thought to derive from relatively small-scale variants, such as single nucleotide polymorphisms, small indels, duplications, inversions and translocations. On the other hand, large-scale structural variations which involve the loss of genomic regions encoding protein-coding genes in some individuals (i.e. presence/absence variation, PAV) have been so far only described in bacteria and, occasionally, in plants and fungi. Here we report the first evidence of a pan-genome in the animal kingdom, revealing that 25% of the genes of the Mediterranean mussel are subject to PAV. We show that this unique feature might have an adaptive value, due to the involvement of dispensable genes in functions related with defense and survival.

genetics↗

bioRxiv2026

Genome-wide Analysis Reveals High Genomic Diversity and Panmixia in Bay Pipefish (Syngnathus leptorhynchus) from Coos Bay, Oregon

The over 300 species of fishes in the charismatic family Syngnathidae (seahorses, pipefish, pipehorses, and seadragons) exhibit remarkable morphological and reproductive adaptations. Most syngnathid species inhabit shallow coastal regions where they are vulnerable to human activities, including habitat degradation and collection for use in traditional medicine and the aquarium trade. A gap remains in our understanding of within-species genetic diversity and population structure for most of the species in this family--information that is crucial for establishing baselines to detect future human-driven changes. Here, we investigate fine-scale population structure and genomic diversity in the bay pipefish (Syngnathus leptorhynchus), one of the relatively few temperate lineages within the Syngnathidae. Bay pipefish are habitat specialists that are closely associated with eelgrass (Zostera marina) along the Pacific coast of North America. Due to the patchy and changing nature of eelgrass habitat, bay pipefish provide an instructive case for using population genomics to explore patterns of connectivity in a dynamic coastal environment. We sampled 116 individuals from two locations separated by approximately 17 km in the Coos Bay estuary (Oregon, USA) and used restriction site-associated DNA sequencing (RAD-seq) to discover high and consistent genetic diversity at both sampling locations, with no indication of inbreeding. Genome-wide patterns of genetic variation showed minimal differentiation between the sampling sites, with levels of divergence indistinguishable from those expected under random sampling. Linkage disequilibrium was low and declined rapidly, and estimates of effective population size indicate a large, well-connected population within Coos Bay. These results establish a crucial genomic baseline for understanding how bay pipefish populations may respond to ongoing changes in their eelgrass habitat and offer a genomic framework for conservation and comparative studies across the Syngnathidae.

evolutionary biology↗

bioRxiv2026

Genomic footprints of historical introgression between ancient lineages of wild Oryza AA-genome species with widely separated contemporary distributions

Phylogenetic incongruence is increasingly recognized as pervasive, yet the extent to which reticulate evolution occurs between groups separated by substantial geographical distances and deep phylogenetic divergence remains poorly characterized. In the Oryza AA-genome group--a model for plant speciation and domestication--the traditional bifurcation model posits that Australian Oryza meridionalis and African Oryza longistaminata occupy basal branches, distinct from the more recently diversified monophyletic clade comprising Asian and other African lineages, including major cultivars. However, recent evidence from endogenous viral sequences has hinted at unexpected genetic relatedness between African O. longistaminata and Asian Oryza sativa, which are geographically and phylogenetically distant. Here, we conducted a genome-wide survey across 11 Oryza species to systematically identify genomic regions exhibiting phylogenetic incongruence. Widespread phylogenetic discordance was observed, notably involving genomic segments in which O. longistaminata showed phylogenetic proximity to Asian species, contradicting their established deep divergence. To distinguish between introgression and incomplete lineage sorting, we performed four-taxon ABBA-BABA tests, which provided statistical support for introgression. Furthermore, divergence time estimates for these incongruent regions were younger than the species divergence times, suggesting historical introgression between the ancestors of lineages that are currently separated by vast geographical distances. Systematic assessments indicated that potential analytical artifacts, such as compositional bias and substitution saturation, were unlikely to explain the observations. These convergent lines of evidence suggest that ancient introgression had occurred between currently geographically separated and evolutionarily divergent Oryza lineages, leaving detectable footprints across their modern genomes.

evolutionary biology↗

bioRxiv2026

JanusX: an integrated and high-performance platform for scalable genome-wide association studies and genomic selection

As genomic datasets expand in both sample size and marker density, genome-wide association studies (GWAS) and genomic selection (GS) require workflows that remain statistically rigorous, computationally efficient, and reproducible across the full analysis path, from genotype matrix to decision-relevant outputs. Here we present JanusX, an integrated high-performance framework that provides a streamlined, user-oriented workflow for GWAS and GS by unifying data handling, model execution, and visualization. Across simulated and real datasets, JanusX maintained high concordance with established baselines while substantially reducing runtime and memory usage. In GWAS, JanusX achieved up to a 19-fold speedup over GEMMA in linear mixed model (LMM) inference, and implemented additional LMM inference based on a sparse genomic relationship matrix with GRAMMAR-Gamma calibration, alleviating computational and memory bottlenecks in large-scale cohorts. JanusX also provides a FarmCPU implementation within its GWAS module, achieving a median 11.4-fold runtime improvement and reducing peak memory usage by 84.9% relative to rMVP. In GS, JanusX integrates an optimized best linear unbiased prediction (BLUP) backend that adaptively selects sample- and SNP-space solvers and incorporates a Preconditioned Conjugate Gradient (PCG) solver. This implementation efficiently completes five-fold cross-validation of 500k individuals x 500k single-nucleotide polymorphisms (SNPs) in 35.1 minutes with only 14.3 gibibyte (GiB) of peak memory. Beyond BLUP, JanusX integrates Bayesian and machine-learning predictors under a single interface with compact automatic tuning to ensure robust cross-model performance. JanusX therefore enables efficient locus discovery and genomic prediction under consistent analytical assumptions, even in large-scale cohorts.

bioinformatics↗

bioRxiv2026

Integrative Whole-Genome Analysis reveals Genomic Signatures of Innate Immunity in Indicine Cattle.

Indicine cattle (Bos indicus) are known for resilience to infectious diseases and environmental stress. However, the genomic basis underlying this advantage remains poorly understood. To characterize variations in immune-related genetic elements in four indicine breeds (Kangayam, Gir, Tharparkar, and Sahiwal), a taurine breed (Holstein Friesian), and a taurine-indicine crossbreed (Karan Fries), we performed integrative whole-genome analysis. Using whole-genome data representing 108 animals, we identified structural variants, copy number variants, single-nucleotide variations, and insertions/deletions. High-impact single-nucleotide variations in the key innate immune genes, CARD9 and NLRP8, shared across all indicine breeds, were absent in the other breeds. Genetic differentiation analysis identified several innate immune genes showing strong divergence between the indicine breeds and the taurine breed. Selective sweep detection analysis highlighted multiple breed-specific immune-related sweep regions. Functional enrichment analysis showed significant enrichment of immune pathways in indicine breeds. A comparison of the candidate genes with basal gene expression profiles of unchallenged peripheral blood mononuclear cells indicated that genomic variation influences the differential expression of several genes in indicine breeds. We synthesized the data from population genome structure analysis, nucleotide diversity, genetic differentiation, selective sweep analysis, and correlations with gene expression profiles. Indicine breeds exhibited a higher number of immune-related variants and stronger signals of selection in immune pathways. These findings provide a curated set of innate immune gene candidates in indicine breeds for future functional studies and breeding programs.

bioinformatics↗

bioRxiv2026

Whole-genome pre-amplification as a viable approach for genomic screening of FFPE-derived DNA samples

Whole-genome sequencing (WGS) enables comprehensive analysis of tumour genomes, but its use in formalin-fixed paraffin-embedded (FFPE) samples is limited by DNA fragmentation and low yields. Whole-genome amplification (WGA) methods such as multiple displacement amplification (MDA) can boost DNA availability but distort copy-number alteration (CNA) profiles. DNA ligation-mediated MDA (DLMDA) mitigates this bias by reconstituting fragmented templates, yet its performance in FFPE-derived DNA remains uncertain. We compared paired DLMDA pre-amplified (2h, 8h) and non-pre-amplified FFPE prostate tumour samples from 22 archival blocks (5, 15 and 20 years old). DLMDA increased DNA yield by 42- to 86-fold, with global CNA patterns largely preserved. However, DLMDA significantly reduced the number of detected CNA deletions and amplifications. These effects were independent of both block age and reaction time. CNA dropouts were randomly distributed across the genome, indicating that DLMDA does not introduce regional bias. Our results show that DLMDA enables robust DNA yield recovery and avoids false-positive CNA artefacts, but at the cost of reduced CNA sensitivity. While suitable for CNA screening pipelines through WGS, further improvements are required to minimise the false-negative risk and improve the techniques sensitivity for FFPE-based genomics.

molecular biology↗

bioRxiv2026

Genomic Foundation Models Reveal Chromatin-Domain-Scale Transposable Element Impacts on Rice Genome Architecture

Alignment-based detection of transposable element (TE) insertion polymorphisms suffers from reference bias and multi-mapping errors in repetitive genomic regions, creating a fundamental validation bottleneck for population-scale structural variant catalogs. Here, we demonstrate that the OneGenome-Rice (OGR) genomic foundation model (GFM)--a 1.25 billion parameter Mixtral architecture trained on 422 rice genomes without TE annotations--provides an entirely orthogonal, alignment-free approach that resolves TE-mediated structural divergence at chromatin-domain resolution. At the CTB4a cold-tolerance locus on chromosome 4, OGR embeddings revealed that the aus subpopulation (NONA_BOKRA) carries 2.2-fold higher structural divergence from indica than japonica, consistent with its 728 subpopulation-exclusive cold-protective TE insertions. Sliding-window analysis across 4.4 megabases identified a 25.6-fold divergence enhancement at TE clusters relative to the conserved CTB4a gene body. Critically, the minimal effective resolution was established at approximately 20 kilobases--corresponding to the median size of topologically associating domains (TADs) in the rice genome--while individual TE sites at 500 base pairs were undetectable (P = 0.94). Non-neural baselines confirmed the signal derives from learned representations of genomic context rather than simple nucleotide statistics. These findings establish GFMs as orthogonal validation tools for population-scale TE genotyping and provide computational evidence that TE functional effects are organized at the chromatin-domain level, with direct implications for prioritizing functional TE variants in crop breeding.

plant biology↗

bioRxiv2026

Pangenome-based human genome analysis improves trait association and genomic prediction

The Human Pangenome Reference Consortium has generated 462 open-access reference genomes and a variation graph that represents differences among them, providing a substrate for pangenome-based analysis methods that overcome the longstanding limitation of comparing all genomic data to a single linear reference. A key unresolved question is the extent to which these approaches can improve trait mapping. We investigate this using the genetics of gene expression variation as a model. We developed a graph-based method (EdgeDepth) for associating sequence variation with traits using short-read genome sequencing data, and show that it captures complex forms of genetic variation missed by other methods. We evaluated trait mapping performance using 430 samples with deep RNA-seq data, and found that pangenomic methods enable the detection of expression quantitative trait loci involving multiallelic indels and structural variants, leading to increased power at a subset of genes. These include 812 genes (7.9% of total) with [≥]20% improvement in statistical significance relative to the 1000 Genomes Project callset, and 185 (1.8%) with a 50% improvement, 10 of which are candidates to explain prior GWAS results. Notably, these analyses implicate GBAP1 pseudogene copy number as a causal factor in Crohns disease, likely via miRNA-mediated regulation of GBA1, which explains prior GWAS results based on flanking SNPs. The inclusion of pangenome-specific variation also improved the performance of gene expression prediction models, with median variance explained increasing from 10.1% to 12.5%, and 14.6% of genes showing significant improvement ({Delta}r2>0.05). Taken together, these results suggest that integration of pangenomic methods into human genetic studies will improve trait association and genomic prediction at a meaningful subset of genes.

genetics↗

bioRxiv2026

PGViS: Personal Genome Variant interpretation Score for lung cancer genomes

Inherited lung cancer risk arises from both protein-coding and non-coding germline variants, but the functional non-coding component is largely uncharacterized. Genome-wide association studies and polygenic risk scores identify tag variants, not causal ones. Neither resolves which regulatory element is perturbed. DNA foundation models such as DNABERT decode non-coding variant effects directly from sequence, without a large GWAS cohort. What is missing is a patient-level framework linking these predictions to population-level variant prevalence. We present PGViS (Personal Genome Variant interpretation Score), a statistical framework that quantifies individual non-coding germline regulatory risk in non-small cell lung cancer (NSCLC). PGViS integrates three variant-level signals: DNABERT-predicted disruption at transcription factor binding and splice sites, the cancer v/s reference alternate allele frequency shift, and a regulatory interaction term derived from cancer-to-reference allele frequency ratios. Each signal is weighted by cohort prevalence which are aggregated into a single ancestry-matched, reference-normalized score per patient. We applied PGViS to germline whole-genome sequencing from 1,102 TCGA and CPTAC patients, using the 1000 Genomes Project (n = 2,504 individuals) as the normal population reference. PGViS separated adenocarcinoma (AD) and squamous cell carcinoma from controls in European ancestry and East Asian AD. Genes at contributing loci were enriched for PI3K-Akt, Wnt, DNA damage response, and epithelial-mesenchymal transition programs. Smoking-stratified analysis concentrated this signal on canonical NSCLC driver pathways. PGViS is modular: it accommodates cohorts with broader ancestral representation and can adapt to other solid tumors, offering a cost-effective route to personal-genome risk assessment from germline variants alone.

bioinformatics↗

bioRxiv2026

CRISPR RNA-Guided Integrase Enables Targeted Genome Engineering and Prophage Functional Genomics in Plant-Pathogenic Pseudomonas

Pseudomonas species include important plant pathogens responsible for substantial agricultural losses. Although CRISPR-INTEGRATE has been applied for genome engineering in medically relevant Pseudomonas, its utility in plant-pathogenic Pseudomonas has not been established. Here, we demonstrate CRISPR-INTEGRATE, an RNA-guided Tn7-like transposition system that enables targeted chromosomal integration without double-strand breaks or host-dependent homologous recombination, across three plant-pathogenic Pseudomonas backgrounds. Targeted disruption of hrpJ, hrcC, and gacA was confirmed by PCR and Sanger sequencing and resulted in distinct phenotypes, including impaired type III secretion-associated virulence and hypersensitive response, altered colony morphology and biofilm formation, and reduced motility. We further coupled CRISPR-INTEGRATE with Cre-lox recombination to excise a ~40-kb prophage-associated region from the P. syringae pv. tomato DC3000 chromosome. Genomic characterization identified a 33.45-kb predicted prophage within this region, putative attL/attR sites sharing an identical 14-bp core sequence, an orthologous empty locus containing a candidate attB site, and conserved prophage-associated gene organization across P. syringae genomes. Deletion of the region altered bacterial growth and increased susceptibility to phage infection, with the strongest effect observed for phage Plaza, while having no detectable effect on the tested plant virulence phenotypes. Together, these findings establish CRISPR-INTEGRATE as a portable genome-engineering platform for plant-pathogenic Pseudomonas and demonstrate its utility for functional interrogation of individual genes and large accessory genomic elements.

pathology↗

bioRxiv2023

A comprehensive catalog of 3D genome organization in diverse human genomes facilitates understanding of the impact of structural variation on chromatin structure

The human genome is packaged into the three-dimensional (3D) nucleus and organized into functional units known as topologically associating domains (TADs) and chromatin loops. Recent studies show that the 3D genome can be modified by genome structural variants (SVs) through disrupting higher-order chromatin organizations such as TADs, which play an essential role in insulating genes from aberrant regulation by regulatory elements outside TADs. Here, we have developed an integrative Hi-C analysis pipeline to generate a comprehensive catalog of TADs, TAD boundaries, and loops in human genomes to fill the gap of limited resources. We identified 2,293 TADs and 6,810 sub-TADs missing in the previously released TADs of GM12878. We then quantified the impact of SVs overlapping with TAD boundaries and observed that two SVs could significantly alter chromatin architecture leading to abnormal expression and splicing of genes associated with human diseases.

genomics↗

bioRxiv2015

Genome of octoploid plant maca (Lepidium meyenii) illuminates genomic basis for high altitude adaptation in the central Andes

Maca (Lepidium meyenii Walp, 2n = 8x = 64) of Brassicaceae family is an Andean economic plant cultivated on the 4000-4500 meters central sierra in Peru. Considering the rapid uplift of central Andes occurred 5 to 10 million years ago (Mya), an evolutionary question arises on how plants like maca acquire high altitude adaptation within short geological period. Here, we report the high-quality genome assembly of maca, in which two close-spaced maca-specific whole genome duplications (WGDs, [~] 6.7 Mya) were identified. Comparative genomics between maca and close-related Brassicaceae species revealed expansions of maca genes and gene families involved in abiotic stress response, hormone signaling pathway and secondary metabolite biosynthesis via WGDs. Retention and subsequent evolution of many duplicated genes may account for the morphological and physiological changes (i.e. small leaf shape and loss of vernalization) in maca for high altitude environment. Additionally, some duplicated maca genes under positive selection were identified with functions in morphological adaptation (i.e. MYB59) and development (i.e. GDPD5 and HDA9). Collectively, the octoploid maca genome sheds light on the important roles of WGDs in plant high altitude adaptation in the Andes.

Genomics↗

bioRxiv2016

Improved genome assembly of American alligator genome reveals conserved architecture of estrogen signaling

The American alligator, Alligator mississippiensis, like all crocodilians, has temperature-dependent sex determination, in which the sex of an embryo is determined by the incubation temperature of the egg during a critical period of development. The lack of genetic differences between male and female alligators leaves open the question of how the genes responsible for sex determination and differentiation are regulated. One insight into this question comes from the fact that exposing an embryo incubated at male-producing temperature to estrogen causes it to develop ovaries. Because estrogen response elements are known to regulate genes over long distances, a contiguous genome assembly is crucial for predicting and understanding its impact.\n\nWe present an improved assembly of the American alligator genome, scaffolded with in vitro proximity ligation (Chicago) data. We use this assembly to scaffold two other crocodilian genomes based on synteny. We perform RNA sequencing of tissues from American alligator embryos to find genes that are differentially expressed between embryos incubated at male-versus female-producing temperature. Finally, we use the improved contiguity of our assembly along with the current model of CTCF-mediated chromatin looping to predict regions of the genome likely to contain estrogen-responsive genes. We find that these regions are significantly enriched for genes with female-biased expression in developing gonads after the critical period during which sex is determined by incubation temperature. We thus conclude that estrogen signaling is a major driver of female-biased gene expression in the post-temperature sensitive period gonads.

Genomics↗