The number of genetic technologies available for the study of the silkworm, Bombyx mori, is second only to those available for Drosophila melanogaster.
Germ-line transformation, enhancer-trapping, genome editing/modification using CRISPRs, TALENS, ZFNs are all established technologies in B. mori.
But, surprisingly, there is still no promoter available to strongly drive transgene expression ubiquitously in larvae, pupae and adults. Until now.
Tsubota et al. (2014) describe their identification of just such a ubiquitously expressed gene while performing an enhancer-trap screen in B. mori. Fortunately, their enhancer-trap element landed in the 5’UTR of the ubiquitously expressed gene, allowing them to tentatively connect the observed gene expression pattern to a particular gene regulatory region.
The gene they ‘hit’ was hsp90, which is a housekeeping gene abundantly expressed throughout Bombyx (as well as most other organisms). Hsp90 has a number of roles including assisting protein-folding, preventing protein-aggregation, and facilitating protein-transport.
Tsubota et al. (2014) isolated 2.9 kb upstream of the putative transcription start site, attach it to a GFP reporter-gene and then reintroduced the construct back into the genome of B. mori using what are now standard silkmoth transformation technologies. They found the 2.9 kb fragment they isolated to be sufficient for strong ubiquitous expression in all life stages. They attempted to minimize the fragment size required for ‘full’ activity and found that a 2.0 kb fragment was equally good while a 1.6 kb fragment had significantly lower activity.
The authors also present some data suggesting that this promoter will have excellent activity in other Lepidoptera but may be less effective than other available promoters for use in insects other than Lepidoptera.
If you are working with Lepidoptera or Lepidoptera cell-lines and need a strong promoter , the work of Tsubota et al (2014) could be of some interest..
Tsubota T, Uchino K, Suzuki TK, Tanaka H, Kayukawa T, Shinoda T, Sezutsu H (2014) Identification of a Novel Strong and Ubiquitous Promoter/Enhancer in the Silkworm Bombyx mori. G3: Genes|Genomes|Genetics 4: 1347-1357
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