Biology subjects

Rosling, A.

Publications and source records attributed to Rosling, A..

3 recordsLinked to original sources

bioRxiv2023

Purifying Selection and Persistent Polymorphism among Nuclei in the Multinucleate Arbuscular Mycorrhizal (AM) Fungi

Arbuscular mycorrhizal (AM) fungi form obligate symbiosis with the roots of the majority of land plants and are found in all terrestrial ecosystems. The source and structure of genetic variation in AM fungi has remained an enigma due to difficulties in the axenic cultivation and generation of high-quality genome assemblies from most species. Furthermore, how AM fungi survives long-term without a single nuclear stage per cell life history is puzzling, prompting hypotheses on selection at the nuclear level which functions to purge deleterious mutations. In this study, we aimed to characterize both intra- and inter-organismal genetic variation in AM fungi by analyzing genomic information from individual nuclei of three strains from two species of the genus Claroideoglomus. We observed overall low levels of genetic variation within the strains, most of which represent rare variants likely kept at low frequency by purifying selection. We also observed variants that have been maintained as polymorphic across both strains and species. The results in this study affirm our conceptual understanding that nuclei in AM fungal strains function as populations of asexually reproducing units. Further, we propose that selection acts on different levels within the organism, with strong signals of purifying selection on nuclei within strain.

evolutionary biology↗

bioRxiv2021

In-depth phylogenomic analysis of arbuscular mycorrhizal fungi based on a comprehensive set of de novo genome assemblies

O_LIMorphological characters and nuclear ribosomal DNA (rDNA) phylogenies have so far been the basis of the current classifications of arbuscular mycorrhizal (AM) fungi. Improved understanding of the phylogeny and evolutionary history of AM fungi requires extensive ortholog sampling and analyses of genome and transcriptome data from a wide range of taxa. C_LIO_LITo circumvent the need for axenic culturing of AM fungi we gathered and combined genomic data from single nuclei to generate de novo genome assemblies covering seven families of AM fungi. Comparative analysis of the previously published Rhizophagus irregularis DAOM197198 assembly confirm that our novel workflow generates high-quality genome assemblies suitable for phylogenomic analysis. Predicted genes of our assemblies, together with published protein sequences of AM fungi and their sister clades, were used for phylogenomic analyses. C_LIO_LIBased on analyses of sets of orthologous genes, we highlight three alternative topologies among families of AM fungi. In the main topology, Glomerales is polyphyletic and Claroideoglomeraceae, is the basal sister group to Glomeraceae and Diversisporales. C_LIO_LIOur results support family level classification from previous phylogenetic studies. New evolutionary relationships among families where highlighted with phylogenomic analysis using the hitherto most extensive taxon sampling for AM fungi. C_LI

genomics↗

bioRxiv2019

From single nuclei to whole genome assembly

A large proportion of Earth's biodiversity constitutes organisms that cannot be cultured, have cryptic life-cycles and/or live submerged within their substrates1-4. Genomic data are key to unravel both their identity and function5. The development of metagenomic methods6,7 and the advent of single cell sequencing8-10 have revolutionized the study of life and function of cryptic organisms by upending the need for large and pure biological material, and allowing generation of genomic data from complex or limited environmental samples. Genome assemblies from metagenomic data have so far been restricted to organisms with small genomes, such as bacteria11, archaea12 and certain eukaryotes13. On the other hand, single cell technologies have allowed the targeting of unicellular organisms, attaining a better resolution than metagenomics8,9,14-16, moreover, it has allowed the genomic study of cells from complex organisms one cell at a time17,18. However, single cell genomics are not easily applied to multicellular organisms formed by consortia of diverse taxa, and the generation of specific workflows for sequencing and data analysis is needed to expand genomic research to the entire tree of life, including sponges19, lichens3,20, intracellular parasites21,22, and plant endophytes23,24. Among the most important plant endophytes are the obligate mutualistic symbionts, arbuscular mycorrhizal (AM) fungi, that pose an additional challenge with their multinucleate coenocytic mycelia25. Here, the development of a novel single nuclei sequencing and assembly workflow is reported. This workflow allows, for the first time, the generation of reference genome assemblies from large scale, unbiased sorted, and sequenced AM fungal nuclei circumventing tedious, and often impossible, culturing efforts. This method opens infinite possibilities for studies of evolution and adaptation in these important plant symbionts and demonstrates that reference genomes can be generated from complex non-model organisms by isolating only a handful of their nuclei.

genomics↗