Ershov, N. I. | bioRxiv Science

bioRxiv2023

Unravelling genome organization of neopolyploid flatworm Macrostomum lignano

Whole genome duplication (WGD) is an evolutionary event resulting in a redundancy of genetic material. Different mechanisms of genome doubling through allo- or autopolyploidization could lead to distinct evolutionary trajectories of newly formed polyploids. Genome studies on such species are undoubtedly important for understanding one of the crucial stages of genome evolution. However, assembling neopolyploid appears to be a challenging task because its genome consists of two homologous (or homeologous) chromosome sets and therefore contains the extended paralogous regions with a high homology level. Post-WGD evolution of polyploids includes rediploidization, first part of which is cytogenetic diploidization led to the formation of species, whose polyploid origin might be hidden by disomic inheritance and diploid-like meiosis. Earlier we uncovered the hidden polyploid origin of free-living flatworms of the genus Macrostomum (Macrostomum lignano, M. janickei, and M. mirumnovem). Despite the different mechanisms for their genome doubling, cytogenetic diploidization in these species accompanied by intensive chromosomal rearrangements including chromosomes fusions. In this study, we reported unusual subgenomic organization of M. lignano through generation and sequencing of two new laboratory sublines of DV1 that differ only by a copy number of the large chromosome MLI1. Using non-trivial assembly-free comparative analysis of their genomes, including adapted multivariate k-mer analysis, and self-homology within the published genome assembly of M. lignano, we deciphered DNA sequences belonging to MLI1 and validated them by sequencing the pool of microdissected MLI1. Here we presented the uncommon mechanism of genome rediplodization of M. lignano, which consists in (1) presence of three subgenomes, emerged via formation of large fused chromosome and its variants, and (2) sustaining their heterozygosity through inter- and intrachromosomal rearrangements.

genomics↗

bioRxiv2022

A new microbiological weapon against lepidopteran pests

Nowadays researchers provide more and more evidence that it is necessary to develop an ecologically friendly approach to pest control. This is reflected in a sharp increase in the value of the biological insecticide market in recent decades. In our study, we found a virus strain belonging to the genus Cypovirus (Reoviridae); the strain was isolated from Dendrolimus sibiricus: that possesses attractive features as a candidate for mass production of biological agents for lepidopteran-pest control. We describe morphological, molecular, and ecological features of the new Cypovirus strain. This strain was found to be highly virulent to D. sibiricus (half-lethal dose is 68 occlusion bodies per second-instar larva) and to have a relatively wide host range (infects representatives of five families of Lepidoptera: Erebidae, Sphingidae, Pieridae, Noctuidae, and Lasiocampidae). The virus strain showed a strong interaction with a nontoxic adjuvant (optical brightener), which decreased the lethal dose for both main and alternative hosts, decreased lethal time, and may expand the host range. Moreover, we demonstrated that the insecticidal features were preserved after passaging through the most economically suitable host. By providing strong arguments for possible usefulness of this strain in pest control, we call on virologists, pest control specialists and molecular biologists to give more attention to the Cypovirus genus, which may lead to new insights in the field of pest control research and may provide significant advantages to compare with baculoviruses and Bacillus thuringiensis products which are nowadays main source of bioinsecticides. Significance statementWithin this article we are describing unique set of features of newly discovered cypovirus strain which possess by significant premises for modern biological insecticides requirements: high potency, universality, true regulating effect, flexible production (possibility to choose host species for production), interaction with enhancing adjuvants, ecologically friendly. Basing on genome alignment we suggest that increasing of host range of new strain is the sequence of evolutionary event which was occurred after coinfection of different CPV species within same host. This finding open new perspective to consider CPVs as perspective agent of biocontrol products.

microbiology↗