A set of experiments was conducted in which flies were fed food with blue food c

Question

A set of experiments was conducted in which flies were fed food with blue food coloring. Healthy flies looked normal, while unhealthy flies would take on a blue color throughout their bodies (the “Smurf” phenotype). A hypothesis is that this was due to defects in one type of protein.

a) In the “Smurf” flies, what kind of tissue does the blue food coloring first cross to get into the body?

b) Which type of protein in this tissue do you think is affected in “Smurf” flies, and how could a mutation change its molecular & cellular function to cause the “Smurf” phenotype?

c)  How could the mutation in Part B lead to overall poorer health of the organism?

Explanation / Answer

Aging is caused by gradual damage to the body’s organs and tissues, but the specifics of the kinds of damage that result in death is still unknown. Walker and his colleagues at the UCLA suspected that the intestines might be involved. They tested intestinal integrity by giving the flies food tinted with blue dye. Although they found no effect of the dye on total food intake, they noticed that the older flies turned blue just a week prior to their death. Researchers named this the “Smurf” phenotype. a) They discovered that the “Smurf” phenotype, resulted from the breakage of the intestinal barrier and the leakage of the dye into the hemolymph during digestion. b) In Drosophila mutations in subunits of mitochondrial cx II result in elevated oxidative stress resulting in reduced lifespan. To find out the potential role of mitochondrial dysfunction in the age-related loss of intestinal integrity, the researchers examined flies carrying a defect in sdhB, which displayed reduced longevity. Surprisingly, after just 12 days about 35% of sdhB mutants showed intestinal barrier defects. They also examined the relationship between intestinal barrier dysfunction and IIS ( insulin/insulin-like growth factor signaling) activity in aging flies. Expression levels of Thor (4E-BP), Insulin-like receptor (InR), and ImpL2 was measured. Smurf flies showed significantly higher levels of all three genes compared with age-matched non-Smurfs, which was consistent with increased dFOXO activity and reduced IIS. c) Intestines from aged flies were found to have higher counts of indigenous bacteria than their young ones which have been reported to influence epithelium renewal during aging. Thus, there might be a role of the gut microbiome in the intestinal barrier dysfunction/AMP/IIS axis of aging.

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