A step to the gigantic genome of the desert locust: chromosome sizes and repeated DNAs

Abstract

The desert locust (Schistocerca gregaria) has been used as material for numerous cytogenetic studies. Its genome size is estimated to be 8.55 Gb of DNA comprised in 11 autosomes and the X chromosome. Its X0/XX sex chromosome determinism therefore results in females having 24 chromosomes whereas males have 23. Surprisingly, little is known about the DNA content of this locust's huge chromosomes. Here, we use the Feulgen Image Analysis Densitometry and C-banding techniques to respectively estimate the DNA quantity and heterochromatin content of each chromosome. We also identify three satellite DNAs using both restriction endonucleases and next-generation sequencing. We then use fluorescent in situ hybridization to determine the chromosomal location of these satellite DNAs as well as that of six tandem repeat DNA gene families. The combination of the results obtained in this work allows distinguishing between the different chromosomes not only by size, but also by the kind of repetitive DNAs that they contain. The recent publication of the draft genome of the migratory locust (Locusta migratoria), the largest animal genome hitherto sequenced, invites for sequencing even larger genomes. S. gregaria is a pest that causes high economic losses. It is thus among the primary candidates for genome sequencing. But this species genome is about 50 % larger than that of L. migratoria, and although next-generation sequencing currently allows sequencing large genomes, sequencing it would mean a greater challenge. The chromosome sizes and markers provided here should not only help planning the sequencing project and guide the assembly but would also facilitate assigning assembled linkage groups to actual chromosomes.

Repetitive DNAs in Melipona scutellaris (Hymenoptera: Apidae: Meliponidae): chromosomal distribution and test of multiple heterochromatin amplification in the genus

“…This is the first effort to locate this sequence in Hymenoptera. The presence of a unique chromosomal cluster of U2 snDNA was also observed in true bugs (Bardella et al 2016) and the grasshoppers Abracris flavolineata and Schistocerca gregaria (Bueno et al 2013;Camacho et al 2015), although multiple clusters were also noticed in other species, like grasshoppers (Palacios-Gimenez et al 2013;Castilho et al 2017). The use of this probe in other Melipona and Hymenoptera will elucidate the organization and evolution patterns of this sequence, which could be a good tool for understanding chromosome evolution.…”

Standardization of multivariate regression models for estimation of the gregariousness level of the main pest locust

“…Examples include Locusta migratoria (L.) in Africa and Asia (Uvarov, ), Chortoicetes terminifera (Walker) in Australia (Key, ), Melanoplus species in North America (Dingle et al., ), Schistocerca cancellata paranensis (Burmeister) in South America (Waloff & Pedgley, ), Dociostaurus maroccanus (Thunberg) in southern Europe and northern Africa (Latchininsky, ), and Schistocerca gregaria (Forskål) in Africa, Middle East, and South‐West Asia (Waloff, ; Pedgley, ). Locusta migratoria and S. gregaria are the paradigm pest locust species, given their notoriously devastating effects as well as their usefulness for research ranging from cytogenetics to molecular and neurophysiological works (e.g., Camacho et al., ).…”

TAREAN: a computational tool for identification and characterization of satellite DNA from unassembled short reads

“…The number of reads in each cluster is proportional to the genomic abundance of the corresponding repeat, thus enabling its quantification. This repeat clustering analysis is at the core of the RepeatExplorer pipeline (20), which was originally designed and used for repeat characterization in plants (reviewed in (21)), but also proved to be efficient in repeat identification in other organisms, including bats (22), fish (23) and insects (24). …”