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

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

Agadir

Congreso; 13th International Congress of orthopterology; 2019

Orthopterist´s Society

rasshoppers genus Dichroplus Stål are dominantin South American grasslands, and compriserepresentatives considered major pests ofseveralcrops, i.e., barley, rye, oats, wheat, flax orlucerne,as well as forages on natural pasturesin Argentina. Additionally, in Cytogenetics, thisgenus has received special attention due to itschromosomal diversity. While standardkaryotypesin most Acrididae species consists of 2n=23/24acro-telocentric chromosomes (with FN=23/24)and X0/XX sex chromosome determinationsystem (SCDS), Dichroplus species showextensivevariation in chromosome number, morphologyand derived neo-SCDS. This extreme neo-SCDS diversity is explained by theoccurrence ofchromosomal rearrangements, mostly centricfusions betweenthe X chromosome and anautosome, generating a neo-X, and the nonfusedautosome partner becoming a neo-Y. Thesederived sex chromosomes frequently evolvethrough additional chromosomalrearrangements(e.g. inversions) and the accumulation of repetitiveelements, mainly satellite DNA (satDNA) andTransposable Elements (TEs). However, currentknowledge aboutrepetitive DNA organization inDichroplus chromosomes is scarce and absent inthe maculipennis species group. For thisreason,wehave performed a genomic study inspecies withdifferent SCDS: D. robustulus (2n=23♂/24♀;X0/XX), D. maculipennis (2n=22♂/ 22♀;neo-XY/neo-XX),D. vitattus(2n=20♂/20♀; neo-XY/neo-XX), D.obscurus (2n=18♂/18♀; neo -XY/neo-XX)and D.silveiraguidoi (2n=8♂/8♀;neo-XY/neo-XX), thelatter species showing the most dramatic case ofchromosomal reduction inOrthoptera.During last years, massive sequencing has provenas very resolutive to find large collections ofsatDNA families within a same genome (i.e. thesatellitome). Here, we performed a low coveragesequencing of genomic DNA from males in theIllumina HiSeq X platform, yielding about 5 Gb dataof 2×150 nt paired-end reads per individual, i.e.,~1x coverage. To analyze this data, we performed abioinformatic analysis using the satMiner protocol,a toolkit for mining and analyzing satDNA.Comparison ofsatDNA content between maleswith different sex determination systems revealedvariable numbers of satDNA families, with highvalues in species with neo-sex chromosomes(Fig.1). Although preliminary, these resultssuggest a differential accumulation of satDNA asa process involved in the degeneration processtypical of sex chromosome evolution. The presentstudy of satDNA is the first high-throughputcharacterization of repetitive elements inDichroplus, thus contributing to the knowledgeof the origin, structure and evolutionof neo-sexchromosomes.Figure 1. Repeat landscapes showing abundance anddivergence values. Satellite DNA of D. robustulus (left) and D.silveiraguidoi (right) males are shown.Key Words: Dichroplus, neo-sex chromosome,Satellite DNA, satMiner, degeneration process, sexchromosome evolution