The five lines selected for this study represent a broad spectrum of sexual phenotypes, including a male line, a recessive gynoecious line, a dominant gynoecious line, and two independent hermaphrodite lines. This diverse selection allows researchers to contrast the genetic signatures associated with different reproductive strategies. By mapping these sequences to the high-quality B10 reference genome, the team could identify specific single nucleotide variants and short insertions or deletions that distinguish each line. This approach moves beyond previous studies that often focused on single phenotypes or individual loci, offering a more integrative view of the genome.

Variant calling using the FreeBayes algorithm and functional annotation with VEP revealed a substantial number of genetic differences among the lines. Each line carried between 0.09 and 0.38 million single nucleotide variants, along with 0.03 to 0.08 million short indels. However, a striking finding was that only 1.3% of the filtered variants were shared across all genotypes. This low level of shared variation underscores the distinct breeding histories of these lines, suggesting that their unique sexual phenotypes are largely driven by lineage-specific genetic changes rather than a common set of mutations.

Among the identified coding consequences, approximately 5.4% were predicted to have a high impact on protein function. These high-impact variants defined a set of 270 genes that carry such mutations relative to the B10 reference in all lines. Additionally, the analysis identified over 500 genotype-restricted loci, which are variants unique to specific lines. For instance, 279 genes were found to be unique to the male line 859, while 48 were unique to the recessive gynoecious line 2gg. These unique loci represent potential candidates for further functional validation and may hold the key to understanding the specific mechanisms that drive each sexual phenotype.

Functional enrichment analysis revealed distinct molecular networks associated with each line. The male line 859 was dominated by a module involving brassinosteroid, gibberellin, and jasmonate signaling, along with DNA-repair factors. In contrast, the dominant gynoecious line was associated with S-adenosyl-methionine cycling and variants in the LEAFY transcription factor. The two hermaphroditic lines showed high-impact variants associated with distinct functional modules, including arginine and nitric oxide pathways in one line and secondary metabolism in the other. These findings suggest that different hormonal and metabolic pathways may be involved in determining floral sex, providing candidate routes for further investigation.

The study also identified hormone-biosynthetic genes and chromatin-remodeling subunits that co-localize with the classical F, M, and Gy loci known to control sex expression in cucumbers. Genes such as ACS1G, ACS11, CPS1, and BR6OX1, which are involved in ethylene and brassinosteroid biosynthesis, were found in proximity to these loci. Additionally, subunits of the SWI/SNF chromatin-remodeling complex were identified in these regions. This co-localization suggests that hormonal signaling and epigenetic regulation may work together to control the expression of sex-determining genes. These findings point to tractable candidates for functional validation and offer new insights into the regulatory mechanisms underlying floral fate.

The resulting variant atlas provides a valuable resource for marker development and future population-level validation. By identifying specific genetic variants associated with different sexual phenotypes, the study supports the development of molecular markers that can be used in breeding programs. These markers could help breeders select for desired sexual phenotypes more efficiently, improving the yield and hybrid-seed production of cucumber crops. The atlas also supports further multi-omics dissection of the hormonal, transcriptional, and epigenetic components associated with cucumber floral fate, offering a foundation for future research in this area.

This research highlights the importance of integrative genomic approaches in understanding complex traits like sex determination. By comparing multiple lines with contrasting phenotypes, the study reveals the line-specific molecular networks that contribute to sexual diversity in cucumbers. The findings not only advance our understanding of the genetic basis of floral sex but also provide practical tools for precision breeding. As the demand for efficient and high-yielding crops continues to grow, resources like this variant atlas will play a crucial role in developing new cucumber varieties with optimized sexual phenotypes.

The study was conducted by a team of researchers from the Department of Plant Genetics, Breeding, and Biotechnology at the Warsaw University of Life Sciences. The work was funded by the National Science Center, and the findings have been published in BMC Genomics. The open-access nature of the publication ensures that the data and methods are available to the broader scientific community, facilitating further research and collaboration. This study represents a significant step forward in the field of plant genomics and has the potential to impact cucumber breeding programs worldwide.

Subject of Research: Genomic analysis of sex determination in cucumber lines

Article Title: Genome-wide variant atlas of cucumber sex determination reveals line-specific molecular networks as a candidate resource for cucumber breeding

Article References: Turek, S., Głuchowska, A., Skarzyńska-Łyżwa, A., Sztenke, J., Pląder, W., & Pawełkowicz, M. (2026). Genome-wide variant atlas of cucumber sex determination reveals line-specific molecular networks as a candidate resource for cucumber breeding. BMC Genomics. https://doi.org/10.1186/s12864-026-13406-2

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13406-2

Keywords: cucumber, sex determination, genomics, plant breeding, variant atlas, molecular networks, hormonal regulation, chromatin remodeling, floral fate, precision breeding, Genome-wide, variant

The maxillary sinuses are air-filled cavities hollowed out of the cheekbones, one on each side of the nose. Because they sit within some of the densest bone of the midface, they frequently survive fires, explosions, and other events that destroy more fragile skeletal landmarks. Forensic scientists have long suspected that these cavities differ between men and women, since male skulls tend to be larger and more robust overall. Earlier studies using cone-beam computed tomography in Egyptian, Indian, Chinese, and Yemeni populations confirmed measurable differences in sinus volume and dimensions. What remained unclear was how reliably those differences could be combined into a single, defensible classification—and whether the nasal structures nearby could add discriminating power.

To find out, researchers led by Haidy M. Fakher of Benha University and Eman S. Shaltout of Assiut University assembled a comparative cross-sectional dataset of 195 adult Egyptians: 100 females and 95 males, drawn from two geographically distinct regions. One hundred four participants came from Assiut in Upper Egypt, and 91 from Benha in Lower Egypt. Each person had undergone a computed tomography scan of the paranasal sinuses, the standard CT protocol used to image this region. Written informed consent was obtained from all participants, and the study received approval from the Assiut University Committee on Research Ethics, in compliance with the Declaration of Helsinki.

From each scan, the team extracted six dimensions of the maxillary sinuses and three nasal measurements, including the nasofrontal angle and the distance from the nasion—the bridge of the nose where it meets the forehead—to the nasal tip. They also recorded age and engineered ten additional derived features, bringing the total to 20 variables for the machine learning analysis. This feature engineering step matters: raw anatomical distances often carry redundant or correlated information, and ratios or combined indices can reveal dimorphism that individual measurements miss. The researchers then faced a classic machine learning design question: in what order should feature selection and hyperparameter tuning be performed?

They answered it by building two competing analytical frameworks. Framework 1 and Framework 2 differed in the sequence in which feature selection and hyperparameter optimization were applied. Within each framework, the team tested six classifiers—among them Random Forest, Support Vector Machine, and gradient boosting methods such as XGBoost, LightGBM, and CatBoost—crossed with five feature-selection methods. Performance was evaluated with a battery of standard metrics: accuracy, the area under the receiver operating characteristic curve (AUC), precision, recall, F1-score, and specificity. This kind of systematic sweep is increasingly common in forensic anthropology, where researchers have moved from traditional discriminant function analysis toward algorithms capable of capturing nonlinear relationships among skeletal measurements.

The results showed statistically significant sex-related differences in several of the measurements, though with notable regional variation between Upper and Lower Egypt—a reminder that craniofacial morphology is shaped by both sex and population history. Framework 2, which applied feature selection and hyperparameter optimization in a different order, generally outperformed Framework 1. The best-performing models achieved AUCs of 0.771 and 0.768, and the highest accuracy reached 74.4 percent. Those numbers describe what statisticians call moderate discriminative power: far better than a coin flip, and genuinely useful as corroborative evidence, but not yet in the 90-plus percent range achieved when the full skull or pelvis is available.

Perhaps the most practically valuable finding was which features carried the most weight. The nasofrontal angle, the nasion-to-tip distance, and the mean anteroposterior maxillary dimension emerged as the most consistent predictors across models. In plain terms, the shape of the nose where it meets the brow and the front-to-back depth of the cheek sinus did much of the classification work. That nasal measurements proved robust is significant, because the external nose itself is cartilage and rarely survives, but its bony framework—the nasal aperture, the nasion, the underlying cavity architecture—is preserved in bone and easily captured on a CT scan of the head.

The study’s regional findings add an important caveat for practitioners. Because the strength of sexual dimorphism varied between the Assiut and Benha samples, models trained on one population may not transfer cleanly to another. This echoes a well-established principle in forensic anthropology: sex estimation standards are population-specific, and applying a formula derived from one ancestry group to remains from another can introduce systematic error. The Egyptian data suggest that even within a single country, north–south geographic variation is large enough to register in sinus and nasal metrics, which argues for building locally calibrated models rather than importing thresholds from other populations.

The methodological comparison embedded in the study also carries lessons for the growing field of machine learning in forensic anthropology. Recent reviews have catalogued a rapid expansion of AI applications in this discipline, from cranial data mining to deep learning on cephalometric images, but results vary widely depending on pipeline choices. By showing that the ordering of feature selection and hyperparameter optimization measurably affects performance, the Egyptian team highlights a decision point that many published studies leave unexamined. Their use of interpretable model-agnostic importance analysis, rather than treating the classifiers as black boxes, also aligns with a broader push for transparency in algorithms that may one day inform court testimony.

Where does this leave the sinuses in the forensic toolkit? The authors conclude that CT-based nasal and maxillary sinus anthropometry shows moderate utility for sex estimation in Egyptians, with machine learning improving classification by capturing complex morphometric relationships that simpler statistical methods miss. For identification teams working with incomplete remains, the message is that these protected midface structures can serve as a meaningful secondary indicator when primary skeletal landmarks are absent—best used alongside other evidence rather than in isolation. With no external funding and data available from the corresponding author upon reasonable request, the study stands as a careful, population-anchored step toward AI-assisted identification, and a demonstration that even the hidden air spaces of the face can testify when the rest of the skeleton cannot.

Subject of Research: Machine learning-based forensic sex estimation from CT-derived nasal and maxillary sinus measurements in an Egyptian population

Article Title: Machine learning-driven forensic sex prediction using CT-based nasal and maxillary sinus metrics

Article References: Machine learning-driven forensic sex prediction using CT-based nasal and maxillary sinus metrics. (n.d.). https://doi.org/10.1007/s00414-026-03951-6

Image Credits: AI Generated

DOI: 10.1007/s00414-026-03951-6

Keywords: forensic anthropology, sex determination, machine learning, computed tomography, maxillary sinus, nasal morphometry, sexual dimorphism, Egyptian population, feature selection, Random Forest, support vector machine, International Journal of Legal Medicine

The research, led by Zheng-Hang Liu and Fang-Yuan Xiong, with Zhong-Wei Wang as corresponding author, brought together teams from the Scientific Institute of Pearl River Water Resources Protection in Guangzhou and the State Key Laboratory of Breeding Biotechnology and Sustainable Aquaculture at the Institute of Hydrobiology, Chinese Academy of Sciences in Wuhan, along with conservation centers in Guigang dedicated to protecting rare Hongshui River fish. Their motivation was both scientific and practical. Without knowing how sex is determined in A. longipinnis, breeders cannot develop monosex production strategies, the gold standard for exploiting the growth advantage of females. And without a mapped sex chromosome system, the search for the master switch that sets off male or female development remains a needle-in-haystack problem.

The team’s method of choice was 2b-RAD sequencing, a streamlined genotyping approach that has become a favorite tool for fish geneticists working on species with little or no reference genomic information. The technique exploits a specific type of restriction enzyme to slice the genome at thousands of precisely defined positions, capturing short, uniform tags of DNA adjacent to each cut site. Sequencing these tags in a large panel of individuals generates a dense but manageable snapshot of genetic variation across the genome. Because the fragments are so consistent in length and composition, they can be compared across dozens or hundreds of animals to find sequences that appear in one sex and are completely absent in the other, which is precisely the signature expected of DNA residing on a Y chromosome.

Before any sex-linked screening could begin, however, the researchers needed a genomic scaffold on which to place their findings. They assembled a reference genome from a female individual, using k-mer depth distribution analysis to estimate genome size and assess heterozygosity, smudgeplot analysis to confirm ploidy, and BUSCO assessments to verify that the assembly captured a complete set of conserved single-copy genes. Quality and continuity metrics were visualized for two haplotypes, designated Hap-A and Hap-B, and predicted genes were functionally annotated against multiple databases, with circos plots providing global views of each haplotype’s landscape. The assembled female genome contained 50 chromosomes, consistent with the karyology of many cyprinids, and provided the coordinate system into which any male-specific sequence could ultimately be anchored.

The screen itself proved remarkably productive. Out of the many thousands of 2b-RAD tags compared between XY males and XX females, exactly three male-specific sequences emerged, designated ref65115, ref94872, and ref134458. In genomics, three hits might sound like a meager harvest, but in sex chromosome research it is precisely the kind of sparse, consistent signal that indicates a young or recently differentiated sex chromosome rather than a sprawling region of male-limited DNA. Each of the three sequences was detected only in males, never in females, and their joint presence pointed to a single shared origin on a male-specific segment of the genome.

The decisive step came when the researchers mapped these three sequences against the female reference genome using synteny and coverage depth analyses. All three aligned to a single contiguous window between positions 5,724,913 and 5,869,801 base pairs, a stretch of roughly 145 kilobases. Crucially, the alignment pattern indicated that the sequences did not correspond to an allele present in both sexes but instead represented a Y-specific insertion: a block of DNA that has been added to, or retained exclusively on, the Y chromosome and is entirely missing from the X. In other words, the male sex chromosome of A. longipinnis carries a discrete inserted segment at this genomic address, and that insertion is what separates males from females at the molecular level.

Confirmation followed through rigorous population-level validation. Using PCR primers designed from the flanking regions of the three markers, the team generated four diagnostic amplification assays, named ref65115-IN, ref94872-3, ref134458-1, and ref94872-5. On agarose gels, ref65115-IN produced a male-specific band of 217 base pairs, ref94872-3 a male-specific band of 335 base pairs, ref134458-1 a male-specific band of 265 base pairs, and ref94872-5 a shared band of 336 base pairs in both sexes together with a male-specific band of 211 base pairs. Each assay was then tested across 72 cultured individuals drawn from two geographically distinct populations, 18 males and 18 females each from Guangxi and Guizhou Provinces. The male-specific bands appeared in every male and in no female, providing strong evidence that the Y-specific insertion is shared across the species’ range rather than being a local variant confined to one river system.

Those results settle a question that has quietly constrained both the biology and the farming of this species. An XX/XY system means that sex is determined by which chromosome a sperm carries: females inherit two X chromosomes, males one X and one Y. In evolutionary terms, the finding is also intriguing. Many fish lineages show fluid, rapidly evolving sex determination, with different species even within the same genus employing XY, ZW, or environmental systems. Identifying a Y-specific insertion in A. longipinnis adds another data point to this comparative landscape, suggesting that a discrete, recent insertion event on the Y chromosome may have been the founding mutation of male determination in this lineage. That kind of simple origin story is increasingly common in fish genomics, where sex chromosomes are often young enough that the male-specific region is small and tractable.

For the aquaculture industry, the practical implications are immediate and considerable. Because females of A. longipinnis grow significantly faster than males, a monosex, all-female production system would raise yields, shorten production cycles, and reduce feed costs per kilogram of fish, much as all-female Nile tilapia and all-female grass carp culture have done in other systems. The newly validated PCR markers now give breeders a direct molecular test for genotypic sex: rather than waiting months for fish to reach a size at which gonads can be inspected, hatcheries can sex larvae or juveniles from a tiny tissue sample and identify XX females, XY males, and, in future work, potentially phenotypic sex-reversed individuals. Such marker-assisted selection is the foundation on which sex-control breeding programs are built, allowing the production of neomales, or XX individuals carrying testes, whose sperm carry only X chromosomes and who therefore sire all-female offspring when crossed with ordinary XX females.

The study’s authors are careful to frame their work as a beginning rather than an end. The three male-specific markers pin down the sex-determining region to a Y-specific insertion of about 145 kilobases on the female reference assembly, but the region still requires fine mapping against the male genome, and the identity of the master sex-determining gene within or near that insertion remains unknown. Future work will aim at chromosome-scale assignment of the sex chromosomes, high-resolution mapping of the sex-determining region, and ultimately the cloning of the master sex-determining gene, the single locus whose presence or absence tips embryonic development toward testis or ovary. Because the Y-specific region appears compact, that cloning effort is unusually feasible for a non-model fish, and the newly assembled, well-annotated female genome with its 50 chromosomal scaffolds provides exactly the platform such work requires. All experimental procedures were approved by the Animal Ethics Committee of the Institute of Hydrobiology, Chinese Academy of Sciences, and fish were anesthetized with MS-222 before tissue collection, reflecting the ethical standards applied throughout the study. Funded by the Scientific Institute of Pearl River Water Resources Protection, the research is open access under a Creative Commons license, ensuring that breeders, conservationists, and comparative genomics researchers across the field can build on these markers without restriction. For a species prized on dinner tables across southwestern China, and for the farmers who raise it, a 145-kilobase stretch of Y-chromosomal DNA has just become one of the most valuable sequences in the entire genome.

Subject of Research: Identification of male-specific DNA markers and an XX/XY sex determination system in Acrossocheilus longipinnis

Article Title: Identification of male-specific markers via 2b-RAD sequencing reveals an XX/XY sex determination system in Acrossocheilus longipinnis

Article References: Liu, Z.-H., Xiong, F.-Y., Zhou, Y.-L., E, Z.-C., Li, M., Dong, S.-H., Tian, J., Zhen, P., Gui, J.-F., & Wang, Z.-W. (2026). Identification of male-specific markers via 2b-RAD sequencing reveals an XX/XY sex determination system in Acrossocheilus longipinnis. BMC Genomics. https://doi.org/10.1186/s12864-026-13372-9

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13372-9

Keywords: Acrossocheilus longipinnis, sex determination, XX/XY system, 2b-RAD sequencing, male-specific markers, genome assembly, Y-specific insertion, sex-determining region, monosex breeding, aquaculture, marker-assisted selection, cyprinidae

The problem rsx tackles is deceptively simple to state but computationally brutal in practice. RAD-seq allows researchers to sample thousands of genomic positions scattered across the chromosomes of organisms whose genomes have never been sequenced in full, from fish and frogs to plants and fungi. By comparing how often each of these DNA fragments appears in males versus females, scientists can flag markers that show up almost exclusively in one sex, which are candidates for the sex-determining region. The standard analysis, implemented in the RADSex tool, builds an enormous table recording the sequencing depth of every marker in every individual, then tests each row for a statistically significant sex bias. As sequencing panels grow into the millions of distinct RAD tags, that table balloons, and the original C++ implementation becomes memory-hungry to the point of failure on ordinary workstations.

rsx attacks the memory bottleneck with a set of techniques drawn from modern systems programming and database engineering. DNA sequences are compressed into 2-bit packed keys, storing four nucleotides per byte with a one-byte header that preserves the exact sequence length. After the initial parallel reading of FASTQ files, every downstream command operates either on a memory-mapped marker table or on externally sorted, lz4-compressed chunks on disk, which means the tool never copies the whole dataset into RAM. The writable memory footprint is instead bounded by the number of individuals in the study, or by an explicit user-chosen buffer, and is completely independent of how many millions of markers the panel contains. This allows researchers to analyse tables with vast numbers of rare tags without discarding candidates, a down-sampling sacrifice the memory-hungry original sometimes forced.

Speed comes from a combination of parallelism and clever data structures. Group membership is encoded in bitsets built once from the population map, with one 64-bit machine word covering 64 individuals; intersecting a marker’s presence pattern with the male and female masks then costs 64 times fewer operations than scanning individuals one by one. Producer-consumer pipelines built on crossbeam channels stream parsed records from a parser thread to per-marker consumers, and external sorting with k-way merges handles order statistics and table merging without loading everything at once. Even the median depth, a routine quality-control statistic, is computed exactly from only the nonzero entries of each depth vector, exploiting the fact that a given RAD tag is absent in most individuals, which shrinks the sorting workload dramatically.

The most scientifically consequential addition, however, is statistical rather than computational. RADSex reported only frequentist significance calls, offering no measure of how strongly the evidence actually supports sex linkage. rsx augments every marker with conjugate Beta-Binomial Bayes factors and directional posterior probabilities, computed in closed form through log-gamma functions and log-sum-exp evaluation, so no sampling or numerical quadrature is needed. Each marker is then graded into one of three explicit tiers: a strict call meeting the conventional significance threshold, a hypothesis supported by posterior evidence, or a row supported only by its Bayes factor. A configurable prior probability that any given tag is sex-linked, along with adjustable Beta prior shapes on the group prevalence rates, lets researchers tailor the evidence model to their organism. Every output row also records the exact uncorrected p-value, the Bayes factor and the posterior, together with machine-readable provenance headers documenting the parameters used.

For dimensionality reduction, rsx streams a Gram matrix accumulation rather than ever materialising the full marker-by-individual matrix. By the fundamental theorem of the singular value decomposition, the eigenvectors of the n-individual by n-individual Gram matrix are exactly the principal component loadings that a full-matrix SVD would produce, so the result is identical up to sign and numerical tolerance while memory drops from scaling with both markers and individuals to scaling only with the square of the individual count. This identity, long used for out-of-core PCA on genotype matrices, is here derived and verified with SymPy scripts and a Lean model of the median selection rule, all shipped with the code. The authors also performed a forward-error analysis of the Yates-corrected chi-squared path, showing that 64-bit integer cross-products before floating-point conversion keep reported p-values accurate to a few units in the last place, and that p-values are clamped at ten to the minus sixteen to match the original reference and avoid spurious claims of exact zeros.

Validation was rigorous and, unusually for method papers, close to exhaustive. Across four published RAD-seq panels, rsx reproduced every call made by RADSex v1.2.0, recovering all Bonferroni-significant positive-control markers, and matched the original’s six-significant-digit output formatting exactly, including a small correction step for the decimal exponent that prevents off-by-one errors on powers of ten. Precision test suites check that the p-value evaluators track the complementary error function to one part in ten to the fifteenth and never leave the valid probability interval. The optional CUDA backend batches the per-marker arithmetic on the GPU, adding up to 29.86-fold acceleration on the p-value computation batch, while Python and C bindings expose the same core to notebooks and workflow engines, closing a long-standing gap since the original offered no programmatic interface.

The authors were careful to scope their comparisons honestly. Alternative tools such as SEX-DETector, which relies on RNA-seq segregation in controlled crosses, and findZX, which uses whole-genome coverage profiles, consume fundamentally different input data and cannot be benchmarked head-to-head on identical RAD-seq panels without manufacturing measurements that were never made. The team did execute both competitors on their authors’ own example datasets, confirming installation and end-to-end operation, but stopped short of claiming relative biological accuracy. What rsx offers instead is a drop-in replacement: the complete RADSex command set is preserved, command-line compatibility is maintained, and marker-table semantics are unchanged, so existing pipelines can adopt the new engine without modification while gaining the Bayesian evidence grades as a bonus.

Released under the GPL-3.0-or-later licence with a reproducibility archive covering every reported number, rsx arrives at a moment of surging interest in sex chromosome evolution across ecology and evolutionary biology. Researchers studying species with environmental or polygenic sex determination, or tracking the early stages of sex chromosome differentiation in recently diverged lineages, now have a tool that scales to contemporary sequencing volumes on laptops rather than clusters, and that reports not just a binary verdict but a graded, transparent accounting of the evidence for every marker. For a field long constrained by the computational ceiling of its standard workflow, the arrival of an allocation-bounded, statistically richer and GPU-accelerated successor marks a genuine widening of what non-model genomics can attempt.

Subject of Research: A high-performance Rust software toolkit for identifying sex-linked markers from RAD-seq data in non-model organisms

Article Title: rsx: a high-performance streaming toolkit for RAD-seq sex determination

Article References: Goswami, R., & Goswami, R. (2026). rsx: a high-performance streaming toolkit for RAD-seq sex determination. BMC Bioinformatics. https://doi.org/10.1186/s12859-026-06628-4

Image Credits: AI Generated

DOI: 10.1186/s12859-026-06628-4

Keywords: RAD-seq, sex determination, Rust, bioinformatics, streaming algorithms, Bayesian statistics, GPU computing, non-model organisms, sex-linked markers, BMC Bioinformatics, genomics, high-performance