The Drosophila wing makes an excellent model system for many developmental processes. From growth control and proliferation through patterning and signal transduction to eventually cell fate establishment and differentiation, the wing magically presents something for everyone. We have used this system in an undergraduate course in Genetics and Development to identify genes responsible for proper wing development.
The fluted (fl1) mutation was discovered by Helen Redfield in 1921 and over 90 years later we have molecularly mapped that mutation to the genome and further characterized its phenotype. After reviewing the historical mapping data, students in the Bio414L course designed deficiency and transposon insertion complementation tests and identified insertions in CG5873 that failed to complement fl1. Whole genome sequencing revealed that the lesion in fl1 is an approximately 1 kb deletion that removes most of exon 1 and the start of translation—not surprising since fl1 behaves as a genetic null. What is surprising is that fl1 is temperature sensitive. At 25° the wings have longitudinal creases between L3 and L4 and between L4 and L5. At 18°, these creases are much more severe, and at 29° the wings are almost wild-type. We used time-lapse imaging to identify when the creases present and found that after inflation, the wings were perfectly flat, but during the drying stage the wings creased and withered. These wings then slowly disintegrated over time where after a week, much of the intervein tissue had broken away.
The CG5873/cysu gene encodes for a Heme Peroxidase and has been linked to the Duox gene in wing development (Hurd et al, 2015 PLoS Genetics 11(11): e1005625) where it functions to remove the reactive oxygen species (ROS) created by Duox. It is possible that in fluted wings, an excess of ROSs are created that causes the deterioration of the wing. Increasing the temperature could alleviate this by causing the ROSs to volatilize at a higher rate.