The level of sophistication with which one can genetically manipulate insects is very much determined by how well transgene expression can be regulated.
Xu et al (2014) in Insect Molecular Biology describe their successful efforts to isolate promoters from two genes with male Bombyx mori germ-line specific expression patterns.
One gene, β-tubulin, is known to play a role in spermatogenesis and the promoters from various orthologous genes from Drosophila, Aedes and Anopheles have been isolated and used to regulate gene expression in testis. Bombyx mori has four isoforms of β-tubulin with Bmβ4 with the most similarity to Dmβ2 from D. melanogaster. Xu et al. isolated a 1900 bp DNA fragment 5’ of the first ATG of Bmβ4 and tested it for promoter activity.
The second gene, radial spoke head protein (RSHP), encodes a protein which in some non-insects is involved in meiosis, sperm flagellum formation and cilia function, but in insects has an unknown function. In B. mori RSHP1 (BmR1), is expressed specifically in the testis. Xu et al isolated a 1600 bp DNA fragment 5’ of the first ATG of BmR1 and tested it for promoter activity.
Both promoters resulted in very similar patterns of EGFP expression that were limited to the testis beginning during the 5th larval instar and were continuous through the adult stage.
Germ-line-specific promoters can be useful for a number of applications such as manipulating sex and sex ratios for population control (e.g. Sterile Insect Technique).
If the promoters isolated by Xu et al are similarly functional in other species of Lepidoptera besides B. mori, their utility will be greatly increased and if not then the structure/function relationships elucidated by Xu et al will be useful for cloning the promoters of orthologous genes.
Xu J, Bi H, Chen R, Aslam AFM, Li Z, Ling L, Zeng B, Huang Y, Tan A (2014) Transgenic characterization of two testis-specific promoters in the silkworm, Bombyx mori. Insect Mol Biol: n/a-n/a 10.1111/imb.12144