Validation of a heat-inducibleIxodes scapularisHSP70 promoter and developing a tick-specific 3xP3 promoter sequence in ISE6 cells

Abstract

ABSTRACTIxodes scapularisis an important vector of many pathogens, including the causative agent of Lyme disease, tick-borne encephalitis, and anaplasmosis. The study of gene function inI. scapularisand other ticks has been hampered by the lack of genetic tools, such as an inducible promoter to permit temporal control over transgenes encoding protein or double-stranded RNA expression. Studies of vector-pathogen relationships would also benefit from the capability to activate anti-pathogen genes at different times during pathogen infection and dissemination. We have characterized an intergenic sequence upstream of the heat shock protein 70 (HSP70) gene that can driveRenillaluciferase expression and mCherry fluorescence in theI. scapulariscell line ISE6. In another construct, we replaced theDrosophila melanogasterminimal HSP70 promoter in the synthetic 3xP3 promoter with a minimal portion of theI. scapularisHSP70 promoter and generated anI. scapularisspecific 3xP3 (Is3xP3) promoter. Both promoter constructs, IsHSP70 and Is3xP3, allow for heat-inducible expression of mCherry fluorescence in ISE6 cells with an approximately 10-fold increase in the percentage of fluorescent positive cells upon exposure to a 2 h heat shock. These promoters described here will be valuable tools for gene function studies and temporal control of gene expression, including anti-pathogen genes.Graphical abstract