Assessment of Crop Motility and Regulation of lwf¹ and takeout genes in Drosophila melanogaster

Elizabeth Bacon
Marquette University
Mentor: Dr. Edward Blumenthal

The Drosophila mutation lot’s wife (lwf¹) mutation adversely affects the digestive system and flies die a few days after eclosing as adults. It appears that this mutation results in an inability to move food from the crop (the food storage organ) into the midgut.  It is possible the problem lies in altered crop motility.  This project investigated the effects of the lwf¹ mutation on crop motility as well as its effect on regulation of the takeout (to) gene.  The to gene is a circadian clock-regulated gene whose expression is induced under starvation conditions in the organs related to feeding (antennae, head, cardia, and crop) (Sarov-Blat, et al., Cell 2000). It appears that lwf¹ mutants starve to death, so measuring the levels of to could provide more information about the role of the lwf gene. 

Crop motility was measured by exposing the crop and observing the contractions of the duct and lobes.  The lwf¹ homozygotes had twice the rate of duct contractions and three times the rate of lobe contractions as lwf¹ heterozygotes.  Homozygotes also had ratios of total lobe to total duct contractions and average lobe to average duct contractions that were 1.7 times higher than heterozygotes.  Crop duct contractions of heterozygous and homozygous lwf¹ were also observed in intact flies and showed the same pattern as the exposed crops.  Crops from heterozygous starved and fed flies were observed and compared at 24 and 48 hours, and the data indicated that there was no difference in crop motility due to starvation.  It appears that crop motility is affected by the lwf¹ mutation, but not directly affected by starvation.

The levels of to and lwf expression were measured using Real-Time RT-PCR.  Whole fly cDNA and crop and cardia cDNA from fed heterozygous females was compared and showed that the crop and cardia have higher levels of to, but that lwf expression was not enriched in these tissues.  Fed and starved crop and cardia cDNA were compared and showed that the starved flies had lower levels of to, in contrast to the published data, and also higher levels of lwf.  It appears that lwf is regulated by starvation and is responsible for regulating crop motility, but the link between these findings is not yet clear.

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