Profile of the mosaic element BTMR1 in the genome of the bumble bee Bombus terrestris (Hymenoptera: Apidae).

Co-evolution involving a mariner transposon, Botmar1 and the other repeats contained in the Bombus terrestris genome was investigated. We found that the 5'-region of Botmar1 forms one of the components of a mosaic element, known as B. terrestris mosaic repeat 1 (BTMR1), which is also composed of inner segments originating from two different retrotransposons and a pseudogene corresponding to an RNA methyltransferase cDNA. The fact that BTMR1 is interspersed within chromosomes and the differences in its abundance in different species indicate that it is very probably a mobile element. Nevertheless, the absences of direct or inverted repeats at its ends and of target site duplication indicate that its mobility is not ensured by a cardinal transposable element, but putatively by a Crypton-like element.

DNA modifications and genome rearrangements during the development and sex differentiation of the bumble bee Bombus terrestris.

Bombus terrestris is a bumble bee that, like most hymenopteran species, exhibits ploidy-specific sex determination controlled by a single sex gene. Depending on their ploidy and the queen pheromone repression, the imagoes differentiate into three castes: males, workers and queens. Here, we focus on the differences of genome organization that occur during development and sex differentiation. We found that cytosine methylation is a significant epigenetic factor with profiles that can be correlated with both processes. We also showed that two kinds of genomic rearrangement occur. The first consists of important DNA amplifications that have sequence profiles that differ in the different developmental instars and sexes. In the second kind, DNA losses also occur, at least involving the mosaic transposable element B. terrestris mosaic repeat 1 (BTMR1).