G3: Genes|Genomes|Genetics最新文献

Flavonoids are secondary metabolites associated with plant seed coat and flower color. These compounds provide health benefits to humans as anti-inflammatory and antioxidant compounds. The expression of the late biosynthetic genes in the flavonoid pathway is controlled by a ternary MBW protein complex consisting of interfacing MYB, beta-helix-loop-helix (bHLH), and WD40 Repeat (WDR) proteins. P, the master regulator gene of the flavonoid expression in common bean (Phaseolus vulgaris L.), was recently determined to encode a bHLH protein. The T and Z genes control the distribution of color in bean seeds and flowers and have historically been considered regulators of the flavonoid gene expression. T and Z candidates were identified using reverse genetics based on genetic mapping, phylogenetic analysis, and mutant analysis. Domain and AlphaFold2 structure analyses determined that T encodes a seven-bladed β-propeller WDR protein, while Z encodes a R2R3 MYB protein. Deletions and SNPs in T and Z mutants, respectively, altered the 3D structure of these proteins. Modeling of the Z MYB/P bHLH/T WDR MBW complex identified interfacing sequence domains and motifs in all three genes that are conserved in dicots. One Z MYB motif is a possible beta-molecular recognition feature (β-MoRF) that only appears in a structured state when Z MYB is modeled as a component of a MBW complex. Complexes containing mutant T and Z proteins changed the interaction of members of the complex in ways that would alter their role in regulating the expression of genes in the flavonoid pathway.

Island species are highly vulnerable due to habitat destruction and their often small population sizes with reduced genetic diversity. The Hawaiian Islands constitute the most isolated archipelago on the planet, harboring many endemic species. Kokia is an endangered flowering plant genus endemic to these islands, encompassing 3 extant and 1 extinct species. Recent studies provided evidence of unexpected genetic diversity within Kokia. Here, we provide high-quality genome assemblies for all 3 extant Kokia species, including an improved genome for Kokia drynarioides. All 3 Kokia genomes contain 12 chromosomes exhibiting high synteny within and between Kokia and the sister taxon Gossypioides kirkii. Gene content analysis revealed a net loss of genes in K. cookei compared to other species, whereas the gene complement in K. drynarioides remains stable and that of Kokia kauaiensis displays a net gain. A dated phylogeny estimates the divergence time from the last common ancestor for the 3 Kokia species at ∼1.2 million years ago (mya), with the sister taxa (K. cookei + K. drynarioides) diverging ∼0.8 mya. Kokia appears to have followed a stepping-stone pattern of colonization and diversification of the Hawaiian archipelago, likely starting on low or now submerged older islands. The genetic resources provided may benefit conservation efforts of this endangered endemic genus.

The aye-aye (Daubentonia madagascariensis) is the only extant member of the Daubentoniidae primate family. Although several reference genomes exist for this endangered strepsirrhine primate, the predominant usage of short-read sequencing has resulted in limited assembly contiguity and completeness, and no protein-coding gene annotations have yet been released. Here, we present a novel, fully annotated, chromosome-level hybrid de novo assembly for the species based on a combination of Oxford Nanopore Technologies long reads and Illumina short reads and scaffolded using genome-wide chromatin interaction data-a community resource that will improve future conservation efforts as well as primate comparative analyses.

Caenorhabditis elegans is one of the most popular model organisms used to genetically dissect complex biological phenomena. One common technique used routinely in the C. elegans laboratory is the generation of strains carrying combinations of genetic mutations via classical genetic crosses. Here, we have developed a simple and convenient application to quickly identify useful genetic markers (phenotypical and fluorescent) and their chromosomal positions to aid in the development of genetic cross strategies. The user-friendly software identifies and prioritizes markers with the least genetic distance to a gene of interest, as well as displays the strain name, ease of scoring, nature of the marker (fluorescent transgene or phenotypic information), mating efficiency, and number of available alleles. In addition, recombination frequencies between the gene of interest and each genetic marker are calculated automatically. The application, called "SoMarker," is designed for both MacOS and Windows environments and is available to freely download and modify through open-source software.

The Mexican fruit fly, Anastrepha ludens, is a polyphagous true fruit fly (Diptera: Tephritidae) considered one of the most serious insect pests in Central and North America to various economically relevant fruits. Despite its agricultural relevance, a high-quality genome assembly has not been reported. Here, we described the generation of a chromosome-level genome for the A. ludens using a combination of PacBio high fidelity long-reads and chromatin conformation capture sequencing data. The final assembly consisted of 140 scaffolds (821 Mb, N50 = 131 Mb), containing 99.27% complete conserved orthologs (BUSCO) for Diptera. We identified the sex chromosomes using three strategies: 1) visual inspection of Hi-C contact map and coverage analysis using the HiFi reads, 2) synteny with Drosophila melanogaster, and 3) the difference in the average read depth of autosomal versus sex chromosomal scaffolds. The X chromosome was found in one major scaffold (100 Mb) and eight smaller contigs (1.8 Mb), and the Y chromosome was recovered in one large scaffold (6.1 Mb) and 35 smaller contigs (4.3 Mb). Sex chromosomes and autosomes showed considerable differences of transposable elements and gene content. Moreover, evolutionary rates of orthologs of A. ludens and Anastrepha obliqua revealed a faster evolution of X-linked, compared to autosome-linked, genes, consistent with the faster-X effect, leading us to new insights on the evolution of sex chromosomes in this diverse group of flies. This genome assembly provides a valuable resource for future evolutionary, genetic, and genomic translational research supporting the management of this important agricultural pest.

Retinoblastoma tumor suppressor proteins (Rb) are highly conserved metazoan transcriptional corepressors involved in regulating the expression of thousands of genes. The vertebrate lineage and the Drosophila genus independently experienced an Rb gene duplication event, leading to the expression of several Rb paralogs whose unique and redundant roles in gene regulation remain to be fully explored. Here, we used a novel CRISPRi system in Drosophila to identify the significance of paralogy in the Rb family. We engineered dCas9 fusions to the fly Rbf1 and Rbf2 paralogs and deployed them to gene promoters in vivo, studying them in their native chromatin context. By directly querying the in vivo response of dozens of genes to Rbf1 and Rbf2 targeting, using both transcriptional as well as sensitive developmental readouts, we find that Rb paralogs function as "soft repressors" and have highly context-specific activities. Our comparison of targeting endogenous genes to reporter genes in cell culture identified striking differences in activity, underlining the importance of using CRISPRi effectors in a physiologically relevant context to identify paralog-specific activities. Our study uncovers the complexity of Rb-mediated transcriptional regulation in a living organism, and serves as a stepping stone for future CRISPRi development in Drosophila.

Exploring genomic regions linked with drought tolerance and photosynthesis in cowpea could accelerate breeding of climate-resilient cowpea varieties A Genome-wide association study (GWAS) was conducted to identify marker-trait associations for agronomic and photosynthetic traits measured under well-watered and water-stressed conditions. One hundred and twelve cowpea accessions from IITA were phenotyped for agronomic and photosynthetic traits across three locations in two years: Ibadan, Ikenne (2020 and 2021) and Kano (2021 and 2022). The accessions were genotyped using 19,000 DArT-Seq SNP markers from which 9,210 markers were utilized for GWAS analysis using BLINK and mixed linear model (MLM) in GAPIT. Results revealed significant accession × environment interactions for measured traits while ΦPSII, ΦNO and ΦNPQ had significant and consistent correlations with grain yield across conditions. GWAS identified five SNP markers having consistent associations with grain yield under well-watered and water-stressed conditions and three markers associated with ΦNPQ and ΦNO. Gene annotations revealed Vigun04g169000 and Vigun08g168900 genes linked with grain yield and highly expressed under water-stressed conditions have functional roles in regulating plant development and adaptive response to environmental stress. Vigun07g133400, Vigun07g132700 and Vigun07g258000 genes linked with ΦNPQ and ΦNO are involved in activities controlling photoprotection and stress-induced damage in plants. This study identified natural genetic variation in cowpea and correlations between photosynthetic traits and grain yield under real-field drought conditions. The identified SNP markers upon validation would be valuable in marker-assisted selection and useful for cowpea breeders to harness the role of photosynthesis in genetic enhancement of cowpea tolerance to drought.

In C. elegans, the germline is specified via a preformation mechanism that relies on the PIE-1 protein's ability to globally silence mRNA transcription in germline precursor cells, also known as the P lineage. Recent work from our group has identified additional genome silencing events in C. elegans during oogenesis and in starved L1 larvae, and these require the condensin II complex, topoisomerase II (TOP-2), and components of the H3K9me/heterochromatin pathway. Interestingly, silencing in oocytes also requires PIE-1, but this is not the case in starved L1s. Here, we ask if additional genome silencing components besides PIE-1 are required to repress gene expression in the P lineage of early embryos, and we find that condensin II and TOP-2 are required and the H3K9me/heterochromatin pathway is not. We show that depletion of TOP-2/condensin II activates the normally suppressed RNA polymerase II to inappropriately transcribe somatic genes in the P lineage. We also present evidence that while both PIE-1 and TOP-2/condensin II are required for genome silencing in the P lineage, PIE-1 can silence transcription independently of TOP-2/condensin II when misexpressed in somatic cells. Thus, in oocytes, all three genome silencing systems (TOP-2/condensin II, H3K9me, and PIE-1) are operational while in both early embryos and starved L1s two of the three are active. Our data show that multiple, redundantly acting genome silencing mechanisms act in a mix and match manner to repress transcription at different developmental stages in the C. elegans germline.

Rhipicephalus (Boophilus) microplus is globally one of the most economically important ectoparasites of cattle costing the agriculture industry billions of dollars annually. Resistance to chemical control measures has prompted the development of novel methods of control. Recent advancements in genetic control measures for human and other animal vectors have utilized sex determination research to manipulate sex ratios, which have shown promising results in mosquitoes namely Aedes aegypti and Anopheles stephensi. Here, we use R. (B.) microplus as a model to provide foundational research to allow similar avenues of investigation in ticks using R. (B.) microplus as a model. Karyotypes for R. (B.) microplus show an XX:XO sex determining system with the largest chromosome being the sex chromosome. Using flow cytometric methods, the size of the sex chromosome was estimated at 526.91 Mb. All measures to identify the sex chromosome within the cattle tick genome assembly associated sex chromosomal characteristics to two chromosomes. This discrepancy between the assembly and karyotypes of the tick led to generating a new genome assembly with a single adult male specimen. The two chromosomes in question aligned with a single scaffold within the new genome that had a length of 513.29 Mb and was the first time the sex chromosome was identified in an Ixodid genome assembly.

The Florida Scrub-Jay (Aphelocoma coerulescens), a Federally Threatened, cooperatively-breeding bird, is an emerging model system in evolutionary biology and ecology. Extensive individual-based monitoring and genetic sampling for decades has yielded a wealth of data, allowing for the detailed study of social behavior, demography, and population genetics of this natural population. Here, we report a linkage map and a chromosome-level genome assembly and annotation for a female Florida Scrub-Jay made with long-read sequencing technology, chromatin conformation data, and the linkage map. We constructed a linkage map comprising 4,468 SNPs that had 34 linkage groups and a total sex-averaged autosomal genetic map length of 2446.78 cM. The new genome assembly is 1.33 Gb in length, consisting of 33 complete or near-complete autosomes and the sex chromosomes (ZW). This highly contiguous assembly has an NG50 of 68 Mb and a Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness score of 97.1% with respect to the Aves database. The annotated gene set has a BUSCO transcriptome completeness score of 95.5% and 17,964 identified protein-coding genes, 92.5% of which have associated functional annotations. This new, high-quality genome assembly and linkage map of the Florida Scrub-Jay provides valuable tools for future research into the evolutionary dynamics of small, natural populations of conservation concern.