High-throughput satellitome analysis in grasshoppers genus Dichroplus (Acrididae, Melanoplinae) with multiple neo-XY sex chromosome systems

ELIO CASTILLO; CONFALONIERI V. A.; CAMACHO, JUAN PEDRO; CIGLIANO, MARÍA MARTA; MARONNA, MAXIMILIANO; RUIZ-RUANO, F; MARTÍ, DARDO

AGADIR

Congreso; 13th International Congress of Orthopterology; 2019

Orthopterist´s Society

Grasshoppers genus Dichroplus Stål are dominant in South American grasslands, and comprise representatives considered major pests of several crops, i.e., barley, rye, oats, wheat, flax or lucerne, as well as forages on natural pastures in Argentina. Additionally, in Cytogenetics, this genus has received special attention due to its chromosomal diversity. While standard karyotypes in most Acrididae species consists of 2n= 23/24 acro-telocentric chromosomes (with FN=23/24) and X0/XX sex chromosome determination system (SCDS), Dichroplus species show extensive variation in chromosome number, morphology and derived neo-SCDS. This extreme neo-SCDS diversity is explained by the occurrence of chromosomal rearrangements, mostly centric fusions between the X chromosome and an autosome, generating a neo-X, and the non-fused autosome partner becoming a neo-Y. These derived sex chromosomes frequently evolve through additional chromosomal rearrangements (e.g. inversions) and the accumulation of repetitive elements, mainly satellite DNA (satDNA) and Transposable Elements (TEs). However, current knowledge about repetitive DNA organization in Dichroplus chromosomes is scarce and absent in the maculipennis species group. For this reason, we have performed a genomic study in species with different SCDS: D. robustulus (2n=23♂/24♀; X0/XX), D. maculipennis 2n=22♂/22♀; neoXY/neoXX), D. vitattus (2n=20♂/20♀; neo-XY/neo-XX), D. obscurus (2n=18♂/18♀; neo-XY/neo-XX) and D. silveiraguidoi (2n=8♂/8♀; neoXY/neoXX), the latter species showing the most dramatic case of chromosomal reduction in Orthoptera.During last years, massive sequencing has proven as very resolutive to find large collections of satDNA families within a same genome (i.e. the satellitome). Here, we performed a low coverage sequencing of genomic DNA from males using the Illumina HiSeq X platform, yielding about 5 Gb data of 2×150 nt paired-end reads per individual, i.e., ~1x coverage. To analyze this data, we applied a bioinformatic analysis using the satMiner protocol, a toolkit for mining and analyzing satDNA.Comparison of satDNA content between males with different sex determination systems revealed variation in abundance and number of satDNA families, with high values in species with neo-sex chromosomes (Fig. 1). Although preliminary, these results suggest a differential accumulation of satDNA as a process involved in the degeneration process typical of sex chromosome evolution. The present study of satDNA is the first high-throughput characterization of repetitive elements in Dichroplus, thus contributing to the knowledge of the origin, structure and evolution of neo-sex chromosomes.