Kruppel homologue 1 acts as a repressor and an activator in the transcriptional response to juvenile hormone in adult mosquitoes

Kruppel homologue 1 (Kr-h1) is a zinc finger transcription factor that is upregulated in insects by juvenile hormone (JH) in metamorphosis and adult reproduction. The molecular function of Kr-h1 in reproduction remains largely unknown. Here we report that AaKr-h1 functions as an important transcription regulator in adult female Aedes aegypti mosquitoes. The amount of AaKr-h1 protein increases with rising JH levels after adult emergence, reaches its peak at 48 h after eclosion, then decreases gradually and disappears after blood feeding. RNA interference (RNAi)-mediated depletion of AaKr-h1 substantially reduced egg production after blood feeding. Using a chromatin immunoprecipitation cloning approach, we identified in vivo AaKr-h1 binding sites in previtellogenic female mosquitoes. Binding of AaKr-h1 to the target genes correlated with its protein abundance. Interestingly, RNAi experiments indicated that AaKr-h1 played distinct roles when it bound to individual target genes. For example, depletion of AaKr-h1 led to substantial upregulation of AAEL005545 and AAEL004444, but also significantly decreased the expression of AAEL005957 and AAEL013177 when compared with the control mosquitoes. In summary, AaKr-h1 directly binds to the regulatory regions of its target genes and acts as a transcriptional activator or a repressor in a promoter-specific manner.