Detection of genetic variation and base modifications at base-pair resolution on both DNA and RNA.

Accurate decoding of nucleic acid variation is critical to understand the complexity and regulation of genome function. Here we use a single-molecule magnetic tweezer (MT) platform to identify sequence variation and map a range of important epigenetic base modifications with high sensitivity, specificity, and precision in the same single molecules of DNA or RNA. We have also developed a highly specific amplification-free CRISPR-Cas enrichment strategy to isolate genomic regions from native DNA.

Comparison of library preparation methods reveals their impact on interpretation of metatranscriptomic data.

Background: Metatranscriptomics is rapidly expanding our knowledge of gene expression patterns and pathway dynamics in natural microbial communities. However, to cope with the challenges of environmental sampling, various rRNA removal and cDNA synthesis methods have been applied in published microbial metatranscriptomic studies, making comparisons arduous. Whereas efficiency and biases introduced by rRNA removal methods have been relatively well explored, the impact of cDNA synthesis and library preparation on transcript abundance remains poorly characterized.

Contrasted patterns of crossover and non-crossover at Arabidopsis thaliana meiotic recombination hotspots.

The vast majority of meiotic recombination events (crossovers (COs) and non-crossovers (NCOs)) cluster in narrow hotspots surrounded by large regions devoid of recombinational activity. Here, using a new molecular approach in plants, called "pollen-typing", we detected and characterized hundreds of CO and NCO molecules in two different hotspot regions in Arabidopsis thaliana. This analysis revealed that COs are concentrated in regions of a few kilobases where their rates reach up to 50 times the genome average.

Hot regions of noninterfering crossovers coexist with a nonuniformly interfering pathway in Arabidopsis thaliana.

In most organisms that have been studied, crossovers formed during meiosis exhibit interference: nearby crossovers are rare. Here we provide an in-depth study of crossover interference in Arabidopsis thaliana, examining crossovers genome-wide in >1500 backcrosses for both male and female meiosis. This unique data set allows us to take a two-pathway modeling approach based on superposing a fraction p of noninterfering crossovers and a fraction (1 - p) of interfering crossovers generated using the gamma model characterized by its interference strength nu.

Characterization of meiotic non-crossover molecules from Arabidopsis thaliana pollen.

Meiotic recombination is essential for proper segregation of homologous chromosomes and thus for formation of viable gametes. Recombination generates either crossovers (COs), which are reciprocal exchanges between chromosome segments, or gene conversion not associated with crossovers (NCOs). Both kinds of events occur in narrow regions (less than 10 kb) called hotspots, which are distributed along chromosomes.

Integrative epigenomic mapping defines four main chromatin states in Arabidopsis.

Post-translational modification of histones and DNA methylation are important components of chromatin-level control of genome activity in eukaryotes. However, principles governing the combinatorial association of chromatin marks along the genome remain poorly understood. Here, we have generated epigenomic maps for eight histone modifications (H3K4me2 and 3, H3K27me1 and 2, H3K36me3, H3K56ac, H4K20me1 and H2Bub) in the model plant Arabidopsis and we have combined these maps with others, produced under identical conditions, for H3K9me2, H3K9me3, H3K27me3 and DNA methylation.