Project description:<p><strong>BACKGROUND:</strong> Manchurian walnut (Juglans mandshurica Maxim.) is a tree with multiple industrial uses and medicinal properties in the Juglandaceae family (walnuts and hickories). J. mandshurica produces juglone, which is a toxic allelopathic agent and has potential utilization value. Furthermore, the seed of J. mandshurica is rich in various unsaturated fatty acids and has high nutritive value.</p><p><strong>FINDINGS:</strong> Here, we present a high-quality chromosome-scale reference genome assembly and annotation for J. mandshurica (n = 16) with a contig N50 of 21.4 Mb by combining PacBio high-fidelity reads with high-throughput chromosome conformation capture data. The assembled genome has an estimated sequence size of 548.7 Mb and consists of 657 contigs, 623 scaffolds and 40,453 protein-coding genes. In total, 60.99% of the assembled genome consists of repetitive sequences. Sixteen super-scaffolds corresponding to the 16 chromosomes were assembled, with a scaffold N50 length of 33.7 Mb and a BUSCO complete gene percentage of 98.3%. J. mandshurica displays a close sequence relationship with Juglans cathayensis, with a divergence time of 13.8 million years ago. Combining the high-quality genome, transcriptome and metabolomics data, we constructed a gene-to-metabolite network and identified 566 core and conserved differentially expressed genes, which may be involved in juglone biosynthesis. Five CYP450 genes were found that may contribute to juglone accumulation. NAC, bZip, NF-YA and NF-YC are positively correlated with the juglone content. Some candidate regulators (e.g., FUS3, ABI3, LEC2 and WRI1 transcription factors) involved in the regulation of lipid biosynthesis were also identified.</p><p><strong>CONCLUSIONS:</strong> Our genomic data provide new insights into the evolution of the walnut genome and create a new platform for accelerating molecular breeding and improving the comprehensive utilization of these economically important tree species.</p>
Project description:We performed RNA-Seq across multiple time points of development (stages 13, 19, 21, 23) in Parhyale hawaiensis and generated an improved genome annotation.
Project description:Maintaining transcriptional fidelity is essential for precise gene regulation and genome stability. Despite this, cryptic antisense transcription, occurring opposite to canonical coding sequences, is a pervasive feature across all domains of life. How such potentially harmful cryptic sites are regulated remains incompletely understood. Here, we show that nucleosome arrays within gene bodies play a key role in suppressing cryptic transcription. Using the fission yeast Schizosaccharomyces pombe as a model, we demonstrate that CHD1-family chromatin remodelers coordinate with the transcription elongation machinery, specifically the PAF complex, to position nucleosomes at sites of cryptic transcription initiation within gene bodies. In the absence of CHD1, AT-rich sequences within gene bodies lose nucleosome occupancy, exposing promoter-like sequences that drive cryptic initiation. While cryptic transcription is generally detrimental, we identify a subset of antisense transcripts that encode critical meiotic genes, suggesting that cryptic transcription can also serve as a source of regulatory innovation. These findings underscore the essential role of nucleosome remodelers in maintaining transcriptional fidelity and reveal their broader contributions to cellular homeostasis and evolutionary adaptability.
Project description:Maintaining transcriptional fidelity is essential for precise gene regulation and genome stability. Despite this, cryptic antisense transcription, occurring opposite to canonical coding sequences, is a pervasive feature across all domains of life. How such potentially harmful cryptic sites are regulated remains incompletely understood. Here, we show that nucleosome arrays within gene bodies play a key role in suppressing cryptic transcription. Using the fission yeast Schizosaccharomyces pombe as a model, we demonstrate that CHD1-family chromatin remodelers coordinate with the transcription elongation machinery, specifically the PAF complex, to position nucleosomes at sites of cryptic transcription initiation within gene bodies. In the absence of CHD1, AT-rich sequences within gene bodies lose nucleosome occupancy, exposing promoter-like sequences that drive cryptic initiation. While cryptic transcription is generally detrimental, we identify a subset of antisense transcripts that encode critical meiotic genes, suggesting that cryptic transcription can also serve as a source of regulatory innovation. These findings underscore the essential role of nucleosome remodelers in maintaining transcriptional fidelity and reveal their broader contributions to cellular homeostasis and evolutionary adaptability.
Project description:Genome/chromosome organization is highly ordered and controls nuclear events. Here, we show that the TATA box-binding protein (TBP) interacts with the Cnd2 kleisin subunit of condensin to mediate interphase and mitotic chromosome organization in fission yeast. TBP recruits condensin onto RNA polymerase III-transcribed (Pol III) genes and highly transcribed Pol II genes; condensin in turn associates these genes with centromeres. Inhibition of the Cnd2-TBP interaction disrupts condensin localization across the genome and the proper assembly of mitotic chromosomes, leading to severe defects in chromosome segregation and eventually causing cellular lethality. We propose that the Cnd2-TBP interaction coordinates transcription with chromosomal architecture by linking dispersed gene loci with centromeres. This chromosome arrangement can contribute to the efficient transmission of physical force at the kinetochore to chromosomal arms, thereby supporting the fidelity of chromosome segregation. Genome-wide distributions of condensin and Pol III factors in fission yeast.
Project description:Centromeres are chromosomal regions that serve as platforms for kinetochore assembly and spindle attachments, ensuring accurate chromosome segregation during cell division. Despite functional conservation, centromeric sequences are diverse and usually repetitive across species, making them challenging to assemble and identify. Here, we describe centromeres in the model oomycete Phytophthora sojae by combining long-read sequencing-based genome assembly and chromatin immunoprecipitation for the centromeric histone CENP-A followed by high-throughput sequencing (ChIP-seq). P. sojae centromeres cluster at a single focus in the nucleus at different life stages and during nuclear division. We report a highly contiguous genome assembly of the P. sojae reference strain, which enabled identification of 15 highly enriched CENP-A binding regions as putative centromeres. By focusing on 10 intact regions, we demonstrate that centromeres in P. sojae are regional, spanning 211 to 356 kb. Most of these regions are transposon-rich, poorly transcribed, and lack the euchromatin mark H3K4me2 but are embedded within regions with the heterochromatin marks H3K9me3 and H3K27me3.