|Willis, Patti - DEPT BIOCHEM, NDSU|
Submitted to: Abstracts 2000 Annual Meeting of Entomological Society Of America
Publication Type: Abstract Only
Publication Acceptance Date: August 4, 2000
Publication Date: N/A
Technical Abstract: Spacer regions in the nuclear ribosomal RNA gene cluster have been extensively used as a source of genetic diversity among subspecies and closely related species. The nucleotide sequence of spacers ITS1 and ITS2 have most often been examined. These two spacers are separated by the very small 5.8S rRNA gene. A third non-coding segment, the intergenic spacer (IGS), is situated between the 28S and 18S rRNA genes. It is typically larger than either ITS1 or ITS2 and has been underutilized as a source of genetic diversity. Primers in the conserved part of the 18S and 28S rRNA genes allowed amplification of the entire IGS and the ITS1-ITS2 regions from the boll weevil (Anthonomus grandis) and thurberia weevil. The IGS amplicon is >8 kb. In these insects the rRNA gene cluster alternates with the histone gene cluster. Primers in the histone genes were used to break the region into smaller pieces for sequencing. There may be as much as 5% sequence divergence in the non-histone IGS spacer between boll weevil and thurberia weevil. ITS1 is 762 bp and ITS2 is 578 bp and there appears to be <2% divergence. IGS has also been amplified from western and Mexican corn rootworms (Diabrotica virgifera v. and D. v. zeae). The corn rootworm IGS region is about 1200 bp. Some RFLP's have been observed among individual insects. Sequencing is in progress.