No abstract

Summary• Plant population genomics informs evolutionary biology, breeding, conservation and bioenergy feedstock development. For example, the detection of reliable phenotype-genotype associations and molecular signatures of selection requires a detailed knowledge about genome-wide patterns of allele frequency variation, linkage disequilibrium and recombination.• We resequenced 16 genomes of the model tree Populus trichocarpa and genotyped 120 trees from 10 subpopulations using 29 213 single-nucleotide polymorphisms.• Significant geographic differentiation was present at multiple spatial scales, and range-wide latitudinal allele frequency gradients were strikingly common across the genome. The decay of linkage disequilibrium with physical distance was slower than expected from previous studies in Populus, with r 2 dropping below 0.2 within 3-6 kb. Consistent with this, estimates of recent effective population size from linkage disequilibrium (N e 4000-6000) were remarkably low relative to the large census sizes of P. trichocarpa stands. Fine-scale rates of recombination varied widely across the genome, but were largely predictable on the basis of DNA sequence and methylation features.• Our results suggest that genetic drift has played a significant role in the recent evolutionary history of P. trichocarpa. Most importantly, the extensive linkage disequilibrium detected suggests that genome-wide association studies and genomic selection in undomesticated populations may be more feasible in Populus than previously assumed.

SUMMARYThe genusTrichodermacontains fungi with high relevance for humans, with applications in enzyme production for plant cell wall degradation and use in biocontrol. Here, we provide a broad, comprehensive overview of the genomic content of these species for “hot topic” research aspects, including CAZymes, transport, transcription factors, and development, along with a detailed analysis and annotation of less-studied topics, such as signal transduction, genome integrity, chromatin, photobiology, or lipid, sulfur, and nitrogen metabolism inT. reesei,T. atroviride, andT. virens, and we open up new perspectives to those topics discussed previously. In total, we covered more than 2,000 of the predicted 9,000 to 11,000 genes of eachTrichodermaspecies discussed, which is >20% of the respective gene content. Additionally, we considered available transcriptome data for the annotated genes. Highlights of our analyses include overall carbohydrate cleavage preferences due to the different genomic contents and regulation of the respective genes. We found light regulation of many sulfur metabolic genes. Additionally, a new Golgi 1,2-mannosidase likely involved inN-linked glycosylation was detected, as were indications for the ability ofTrichodermaspp. to generate hybrid galactose-containingN-linked glycans. The genomic inventory of effector proteins revealed numerous compounds unique toTrichoderma, and these warrant further investigation. We found interesting expansions in theTrichodermagenus in several signaling pathways, such as G-protein-coupled receptors, RAS GTPases, and casein kinases. A particularly interesting feature absolutely unique toT. atrovirideis the duplication of the alternative sulfur amino acid synthesis pathway.

Centromeres serve as platforms for the assembly of kinetochores and are essential for nuclear division. Here we identified Neurospora crassa centromeric DNA by chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) of DNA associated with tagged versions of the centromere foundation proteins CenH3 (CENP-A) and CEN-C (CENP-C) and the kinetochore protein CEN-T (CENP-T). On each chromosome we found an ϳ150-to 300-kbp region of enrichment for all three proteins. These regions correspond to intervals predicted to be centromeric DNA by genetic mapping and DNA sequence analyses. By ChIP-seq we found extensive colocalization of CenH3, CEN-C, CEN-T, and histone H3K9 trimethylation (H3K9me3). In contrast, H3K4me2, which has been found at the cores of plant, fission yeast, Drosophila, and mammalian centromeres, was not enriched in Neurospora centromeric DNA. DNA methylation was most pronounced at the periphery of centromeric DNA. Mutation of dim-5, which encodes an H3K9 methyltransferase responsible for nearly all H3K9me3, resulted in altered distribution of CenH3-green fluorescent protein (GFP). Similarly, CenH3-GFP distribution was altered in the absence of HP1, the chromodomain protein that binds to H3K9me3. We conclude that eukaryotes with regional centromeres make use of different strategies for maintenance of CenH3 at centromeres, and we suggest a model in which centromere proteins nucleate at the core but require DIM-5 and HP1 for spreading.Centromeres serve critical functions in genome stability and replication, yet their assembly, maintenance, and roles throughout some phases of the cell cycle (e.g., interphase) are still poorly understood. A major impediment to the study of centromeres in many organisms is their identification. In general, centromeric DNA sequences are AT rich and repetitive, making them difficult to sequence and assemble. While critical for survival, they are also rapidly evolving, perhaps driven by a proposed mechanism for centromere-mediated meiotic drive suppression (22,41,57,58). Therefore, centromeric DNA sequences may be highly divergent even between closely related organisms and must be identified biochemically in each species. A functional definition for centromeric regions is the presence of a centromere-specific histone H3 variant, CenH3 (CENP-A), in place of H3.Among fungi, centromere sequences have been functionally or biochemically identified in the yeasts Saccharomyces cerevisiae (reviewed in reference 38) and Schizosaccharomyces pombe (87) and the dimorphic fungus Candida albicans (65, 76). The centromeres of filamentous fungi have been difficult to assemble and are absent or not easily recognizable by bioinformatic tools in the almost completely sequenced and assembled genomes of Fusarium graminearum (teleomorph: Gibberella zeae) (20), Aspergillus fumigatus (26), Nectria haematococca (18), and even the one filamentous fungus for which there is a predicted "telomere-to-telomere" assembly, Mycosphaerella graminicola (http://genome.jgi-psf.org/Mycgr3/Mycgr3.i...

Yarrowia lipolytica is a promising microbial cell factory for the production of lipids to be used as fuels and chemicals, but there are few studies on regulation of its metabolism. Here we performed the first integrated data analysis of Y. lipolytica grown in carbon and nitrogen limited chemostat cultures. We first reconstructed a genome-scale metabolic model and used this for integrative analysis of multilevel omics data. Metabolite profiling and lipidomics was used to quantify the cellular physiology, while regulatory changes were measured using RNAseq. Analysis of the data showed that lipid accumulation in Y. lipolytica does not involve transcriptional regulation of lipid metabolism but is associated with regulation of amino-acid biosynthesis, resulting in redirection of carbon flux during nitrogen limitation from amino acids to lipids. Lipid accumulation in Y. lipolytica at nitrogen limitation is similar to the overflow metabolism observed in many other microorganisms, e.g. ethanol production by Sacchromyces cerevisiae at nitrogen limitation.