Chromosomal mapping of two Mariner-like elements in the grasshopper Abracris flavolineata (Orthoptera: Acrididae) reveals enrichment in euchromatin

Abstract

The occurrence of transposable elements (TEs) is a ubiquitous characteristic of eukaryotic genomes, and these sequences are highly abundant in some species. Due to their large genomes, grasshoppers (Orthoptera) appear to be potentially good candidates in terms of having genomes that harbour considerable numbers of TEs. In the present study, we have investigated the occurrence of two Mariner-like elements (MLEs) within the genome of the grasshopper, Abracris flavolineata (De Geer, 1773), describing their distribution in both the A (i.e. standard or normal) complement and B chromosomes. PCR amplification followed by cloning and sequencing revealed two Mariner-like elements, which were named Afmar1 and Afmar2. Moreover, subsequent fluorescence in situ hybridization (FISH) assays indicated an abundance of these elements in the euchromatic regions of all the standard complement chromosomes and an absence of such sequences in heterochromatic regions. These sequences were also abundant in the euchromatic B chromosome: Afmar1 was distributed along the entire length of the chromosome, whereas Afmar2 was restricted to the proximal/interstitial regions of the chromosomal long arm. The general aspects of the distribution patterns of the two MLEs are discussed as well as their possible involvement in the origin and diversification of the B chromosome in A. flavolineata.