Trans and cis factors regulating tissue and lactation specific gene expression in the tsetse fly (Glossina morsitans morsitans)

The tsetse Milk Gland Protein (GmmMGP1) is an essential component of nourishment during tsetse pregnancy. Transcription of gmmmgp1 is specific to the female accessory gland of the tsetse fly and correlates with intrauterine larval development. The regulatory sequence for this gene also drives gene expression in transgenic Drosophila female accessory gland tissues during reproduction. This work identifies and characterizes the regulatory sequence responsible for the unique pattern of gmmmgp expression. The minimal gmmmgp1 promoter was identified utilizing transgenic and in silico methodologies. Drosophila lacks a gmmmgp1 ortholog, suggesting that this promoter leverages a conserved regulatory system to drive gene expression. Transgenic analyses of the gmmmgp1 promoter using reporter/fusion constructs show that Drosophila lines carrying 2 kb, 500 bp and 236 bp of the gmmmgp1 promoter have tissue, stage and sex specific reporter expression. Expression is only observed in ovulating females suggesting regulation by undefined reproductive stimuli. Lines with 112 or 10 bp of the promoter lack significant reporter gene expression. The 124 bp region between the 236 and 112 bp constructs is critical for gmmmgp1 promoter function. In silico analysis of the critical region with regulatory regions from other tsetse milk protein genes predicts conservation of homeodomain transcription factor binding sites. Analysis of homeodomain protein expression patterns implicates the Ladybird Late homeodomain protein as a possible regulator of female accessory gland specific gene expression in response to reproductive stimuli.