Submitted to: Insect Molecular Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2010
Publication Date: 8/1/2010
Publication URL: ddr.nal.usda.gov/bitstream/10113/44249/1/IND44393428.pdf
Citation: Roehrdanz, R.L., Heilmann, L., Senechal, P., Sears, S., Evenson, P.L. 2010. Histone and Ribosomal RNA Repetitive Gene Clusters of the Boll Weevil are Linked in a Tandem Array. Insect Molecular Biology. 19(4):463-471. Interpretive Summary: The histone and ribosomal RNA gene families are critically important for all animals. Both the rRNA and the histone gene clusters are known to be highly repeated and located in different parts of the total genome. We found that in the boll weevil these two families have merged. A close relative of the boll weevil also has this gene array. This alternating arrangement of the two repeat units is novel and has not been reported in any other insect groups. Gene arrangements have proven to have phylogenetic utility. The histone-rRNA repeat could help to clarify ancestral relationships of the boll weevil in the genus Anthonomus. If this genome organization is found in other insect groups, it could be a very valuable marker defining deeper levels of insect evolution.
Technical Abstract: Histones are the major protein component of chromatin structure. The histone family is made up of a quintet of proteins, four core histones (H2A, H2B, H3 & H4) and the linker histones (H1). Spacers are found between the coding regions. Among insects this quintet of genes is usually clustered and the clusters are tandemly repeated. Ribosomal DNA contains a cluster of the rRNA sequences 18S, 5.8S, and 28S. The rRNA genes are separated by the spacers ITS1, ITS2 and IGS. This cluster is also tandemly repeated. We have found that the ribosomal RNA repeat unit of at least two species of Anthonomine weevils, Anthonomus grandis and A. texanus (Coleoptera: Curculionidae), is interspersed with a block containing the histone gene quintet. The histone genes are situated between the rRNA 18S and 28S genes in what known as the intergeneic spacer region (IGS). The complete reiterated Anthonomus grandis histone-ribosomal sequence is 16,248 bp.