Intact DNA purified from flow-sorted nuclei unlocks the potential of next-generation genome mapping and assembly in Solanum species

Flow Sorting-Assisted Optical Mapping

Optical mapping-a technique that visualizes short sequence motives along DNA molecules of hundred kilobases to megabase in size-has found an important place in genome research. It is widely used to facilitate genome sequence assemblies and analyses of genome structural variations. Application of the technique is conditional on availability of highly pure ultra-long high-molecular-weight DNA (uHMW DNA), which is challenging to achieve in plants due to the presence of the cell wall, chloroplasts, and secondary metabolites, just as a high content of polysaccharides and DNA nucleases in some species. These obstacles can be overcome by employment of flow cytometry, enabling a fast and highly efficient purification of cell nuclei or metaphase chromosomes, which are afterward embedded in agarose plugs and used to isolate the uHMW DNA in situ. Here, we provide a detailed protocol for the flow sorting-assisted uHMW DNA preparation that has been successfully used to construct whole-genome as well as chromosomal optical maps for 20 plant species from several plant families.

Spatially resolved transcriptomics reveals plant host responses to pathogens

BACKGROUND

Thorough understanding of complex model systems requires the characterisation of processes in different cell types of an organism. This can be achieved with high-throughput spatial transcriptomics at a large scale. However, for plant model systems this is still challenging as suitable transcriptomics methods are sparsely available. Here we present GaST-seq (Grid-assisted, Spatial Transcriptome sequencing), an easy to adopt, micro-scale spatial-transcriptomics workflow that allows to study expression profiles across small areas of plant tissue at a fraction of the cost of existing sequencing-based methods.

RESULTS

We compare the GaST-seq method with widely used library preparation methods (Illumina TruSeq). In spatial experiments we show that the GaST-seq method is sensitive enough to identify expression differences across a plant organ. We further assess the spatial transcriptome response of Arabidopsis thaliana leaves exposed to the bacterial molecule flagellin-22, and show that with eukaryotic (Albugo laibachii) infection both host and pathogen spatial transcriptomes are obtained.

CONCLUSION

We show that our method can be used to identify known, rapidly flagellin-22 elicited genes, plant immune response pathways to bacterial attack and spatial expression patterns of genes associated with these pathways.