Movements of transposable elements contribute to the genomic plasticity and species diversification in an asexually reproducing nematode pest

Abstract

Despite reproducing without sexual recombination, Meloidogyne incognita is an adaptive and versatile phytoparasitic nematode. This species displays a global distribution, can parasitize a large range of plants, and can overcome plant resistance in a few generations. The mechanisms underlying this adaptability remain poorly known. At the whole-genome level, only a few single nucleotide variations have been observed across different geographical isolates with distinct ranges of compatible hosts. Exploring other factors possibly involved in genomic plasticity is thus important. Transposable elements (TEs), by their repetitive nature and mobility, can passively and actively impact the genome dynamics. This is particularly expected in polyploid hybrid genomes such as the one of M. incognita. Here, we have annotated the TE content of M. incognita, analyzed the statistical properties of this TE landscape, and used whole-genome pool-seq data to estimate the mobility of these TEs across twelve geographical isolates, presenting variations in ranges of compatible host plants. DNA transposons are more abundant than retrotransposons, and the high similarity of TE copies to their consensus sequences suggests they have been at least recently active. We have identified loci in the genome where the frequencies of presence of a TE showed substantial variations across the different isolates. Overall, variations in TE frequencies across isolates followed their phylogenetic divergence, suggesting TEs participate in the species diversification. Compared with the M. incognita reference genome, we detected isolate and lineage-specific de novo insertion of some TEs, including within genic regions or in the upstream regulatory regions. We validated by PCR the insertion of some of these TEs inside genic regions, confirming TE movements have possible functional impacts. Overall, we show DNA transposons can drive genomic plasticity in M. incognita and their role in genome evolution of other parthenogenetic animal deserves further investigation.

Keywords: bioinformatics/phyloinformatics; contemporary evolution; evolution of sex; genomics/proteomics; host–parasite interactions; hybridization; transposons.