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. 2018 Jan 18;7:e32018. doi: 10.7554/eLife.32018

Figure 6. Expression of SOD2 in single neuron subtype fully rescues olfactory degeneration.

(A) Box plots show PIs of 1 week old (orange boxes) and 7 weeks old (grey boxes) transgenic flies overexpressing SOD2 exclusively in projection neurons (PNs) (GH146-Gal4;UAS-SOD2) and their genetic controls in response to attractive (2,3-butanedione) and aversive (3-octanol) odors. Note that expression of SOD2 exclusively in PNs fully rescues olfactory performance in 7 weeks old flies indicating that sensitivity to oxidative stress of PNs represents a key player in the aging-associated decline of the olfactory system. (B) Box plots show PIs of 1 week old (orange) and 7 weeks old (grey) transgenic flies overexpressing SOD2 under the control of ORCO-Gal4 in OSNs (ORCO-Gal4;UAS-SOD2) and their genetic controls in response to attractive (2,3-butanedione) and aversive (3-octanol) odors. Importantly, overexpression of SOD2 under the control of ORCO-Gal4 in OSNs had no effect on the behavior of old flies. (C) Box plots show preference of 1 week old and 7 weeks old flies raised on standard fly food (first two boxes) and 7 weeks old flies raised on standard fly food mixed with Resveratrol (third grey box) in response to attractive (2,3-butanedione) and aversive (3-octanol) odors. All p-values were calculated via t-test (ns >0.05, *p≤0.05, **p≤0.01, ***p≤0.001). In all figures, asterisks above a single bar refer to p-values of comparison to the control (7 weeks old flies in second bar). (D) Box plots show untreated and treated (flies were inoculated with the indicated bacterial strain after being pretreated to become germfree) 1 week old (light (treated) and dark orange (not germfree, standard conditions as in all other experiments before) and 7 weeks old (dark and light grey) flies. Treated flies were inoculated with Lactobacillus plantarum NI202877, L. plantarum WJL, Acetobacter pomorum (A.p.), while control flies were just raised on standard fly food. P.I.s of flies to the attractive odor 2,3-butanedione is shown. All p-values were calculated via two-way ANOVA with the Bonferroni multiple comparison posthoc test (ns >0.05, *p≤0.05, **p≤0.01, ***p≤0.001). Asterisks above a single box refer to p-values of comparison to the control (7 weeks old treated control). Box plot show median and upper/lower quartiles (n = 8, 60 flies/trial 30 ♀ and 30 ♂). (E) Summary and model of presented results. SOD2, the mitochondrial form of SOD, protects projection neurons (PN) from oxidative stress. Their vulnerability to oxidative stress and reactive oxygen species (ROS) appears to be the weak point of the olfactory system of Drosophila. The decline in function of PNs ultimately results in strongly reduced sensitivity to odors and accordingly diminishes behavioural responses.

Figure 6—source data 1. Source data for Figure 6 and Figure 6—figure supplement 1.
elife-32018-fig6-data1.xlsx (71.6KB, xlsx)
DOI: 10.7554/eLife.32018.021

Figure 6.

Figure 6—figure supplement 1. SOD2 and antioxidants slow down aging-associated olfactory decline.

Figure 6—figure supplement 1.

(A) Box plots show P.I.s of 1 week old (orange bars) and 7 weeks old (grey bars) transgenic flies overexpressing SOD2 exclusively in projection neurons (PNs) (GH146-Gal4;UAS-SOD2) and their genetic controls in response to attractive (putrescine) and aversive (benzaldehyde) odors. (B) Box plots show P.I.s of 1 week old (orange bars) and 7 weeks old (grey bars) transgenic flies overexpressing SOD2 under the control of ORCO-Gal4 in OSNs (ORCO-Gal4;UAS-SOD) and their genetic controls in response to attractive (putrescine) and aversive (3-octanol) odors. (C) Box plots show preference of 1 week old and 7 weeks old flies raised on standard fly food (first two bars) and 7 weeks old flies raised on standard fly food mixed with Resveratrol (third grey bar) in response to attractive (putrescine) and aversive (benzaldehyde) odors. All p-values were calculated via t-test (ns >0.05, *p≤0.05, **p≤0.01, ***p≤0.001). In all figures, asterisks above a single bar refer to p-values of comparison to the control (7 weeks old flies in second bar). (D) Box plots show 1–2 weeks old flies raised on standard food with solvent or on standard fly food supplemented with Resveratrol for 1 week. There is no significant difference between the treated and control flies (n = 8). (E) Box plots show untreated and treated (flies were inoculated with the indicated bacterial strain after being pretreated to become germfree) 1 week old (light (treated) and dark orange (not germfree, standard conditions as in all other experiments before) and 7 weeks old (dark and light grey) flies. Treated flies were inoculated with Lactobacillus plantarum NI202877, L. plantarum WJL, Acetobacter pomorum (A.p.), while control flies were just raised on standard fly food. P.I.s of flies to attractive (putrescine) and aversive (benzaldehyde, 3-octanol) odors is shown. All p-values were calculated via two-way ANOVA with the Bonferroni multiple comparison posthoc test (ns >0.05, *p≤0.05, **p≤0.01, ***p≤0.001). Asterisks above a single bar refer to p-values of comparison to the control (7 weeks old treated control). Box plot show median and upper/lower quartiles (n = 8, 60 flies/trial 30 ♀ and 30 ♂).