Submitted to: Chromosome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2023
Publication Date: 1/24/2023
Citation: Crane, Y.M., Crane, C.F., Cambron, S.E., Springmeyer, L.J., Schemerhorn, B.J. 2023. Molecular characterization of eliminated chromosomes in Hessian Fly (Mayetiola destructor (Say)). Chromosome Research (2023). 31(1). Article 3. https://doi.org/10.1007/s10577-023-09718-8
Interpretive Summary: Eliminated (E) chromosomes have been known to exist in several insect species for over a hundred years, but their reason for existence, as well as what they are comprised of has remained a mystery. These chromosomes are only found in the cells of ovaries and testes of some insect species and previous research has shown that removal of them from the germ line cells creates sterile insects indicating they serve a necessary function. Our group set out to determine what distinguishes E chromosomes and causes them to them to be specifically removed during cellular division. Utilizing a variety of techniques, from chromosome banding, DNA library construction, and other mechanisms, we closely examined the E chromosomes to identify similarities between them and the stable chromosomes sets. We found that the E chromosomes are nearly identical copies of the S chromosomes, but that they contain some specific sequences that are different than the stable chromosomes. This information will be useful to other insect and pest researchers.
Technical Abstract: Like other cecidomyiid Diptera, Hessian fly has stable S chromosomes and dispensable E chromosomes that are retained only in the germline. Amplified fragment length polymorphisms (AFLP), suppressive subtractive hybridization (SSH), fluorescent in-situ hybridization (FISH), and sequencing were used to investigate similarities and differences between S and E chromosomes. More than 99.9% of AFLP bands were identical between separated ovary and somatic tissue, but one band was unique to ovary and resembled Worf, a non-LTR retrotransposon. Arrayed clones, derived by SSH of somatic from ovarian DNA, showed no clones that were unique to ovary. FISH with BAC clones revealed a diagnostic banding pattern of BAC positions on both autosomes and both sex chromosomes, and each E chromosome shared a pattern with one of the S chromosomes. Sequencing analysis showed that E chromosomes are nearly identical to S chromosomes, since no sequence could be confirmed to belong only to E-chromosomes. There were a few questionably E-specific sequences that are candidates for further investigation. Thus the E chromosomes appear to be derived from S chromosomes by the acquisition or conversion of sequences that produce the negatively heteropycnotic region around the centromere.