Drosophila life span and physiology are modulated by sexual perception and reward

Abstract

Sensory perception can modulate aging and physiology across taxa. We found that perception of female sexual pheromones through a specific gustatory receptor expressed in a subset of foreleg neurons in male fruit flies, Drosophila melanogaster, rapidly and reversibly decreases fat stores, reduces resistance to starvation, and limits life span. Neurons that express the reward-mediating neuropeptide F are also required for pheromone effects. High-throughput whole-genome RNA sequencing experiments revealed a set of molecular processes that were affected by the activity of the longevity circuit, thereby identifying new candidate cell-nonautonomous aging mechanisms. Mating reversed the effects of pheromone perception; therefore, life span may be modulated through the integrated action of sensory and reward circuits, and healthy aging may be compromised when the expectations defined by sensory perception are discordant with ensuing experience.

Fig. 1. Exposure to sex-specific pheromones significantly affects physiology, stress resistance, and lifespan in Drosophila

(A) The protocol used to expose male flies to masculine or feminine pheromones. Five experimental males were housed with either 25 control (donor pheromone = male) or feminized (donor pheromone = female) males. (B) Male flies exposed to male donor pheromone exhibit higher TAG amounts than flies exposed to female donor pheromone (N = 40 for each treatment). Box plots represent the medians and standard error of the mean (box boundaries) for each experimental group. Lines adjacent to the box represent mean values. P-value is by t-test. (C) Male experimental flies exposed to male donor pheromones exhibit greater starvation resistance relative to genetically identical males exposed to female donor pheromones (N=88 and 82, respectively; P-value is by log-rank test). (D) Male experimental flies exposed to male donor pheromones exhibit a longer lifespan relative to flies that are exposed to female donor pheromones (N=184 and 195, respectively; P-value is by log-rank test). (E) TAG amounts are progressively restored after removal (at T=0) of female donor pheromones (N = 50 for each time point). *** = p ≤ 0.001, ** = p ≤ 0.01, no stars= p ≥ 0.05 by t-test. (F) Differences in age-specific mortality caused by pheromone exposure were reversed within days after feminized males were replaced with control males.

Fig. 2. The effects of pheromone exposure are mediated by taste perception involving gustatory receptor ppk23

(A–C) The Poxn^ΔXB strain lacks taste neurons in the labellum, the legs, and the wing margins, while the Poxn^Full1 strain lacks taste neurons in the labellum only. (A) Starvation resistance. N = 46–48 experimental flies for all treatments. Significance values are as follows: P ≤ 0.0001 for Poxn^Full1 (exposed to control vs. feminized donor flies); P = 0.56 for Poxn^ΔXB. (B) TAG amounts. Box plots are presented as in Fig 1. (C) Lifespan. N=100–103 experimental flies for all treatments. Significance values are P = 0.001 for Poxn^Full1 exposed to control vs. feminized donor flies and P = 0.30 for Poxn^ΔXB exposed to control vs. feminized donor flies. (D–F) The gustatory receptor ppk23 is required for pheromone effects. (D) Starvation resistance. N = 40 and 39 for control flies exposed to feminized or control donor males, respectively (P ≤ 0.0001). N = 43 and 46 for ppk23 mutant flies exposed to female or male donor pheromones, respectively (P=0.92). (E) TAG amounts. Box plots are presented as in Fig. 1. (F) Lifespan. N = 98 and 99 for control flies exposed to male or female donor pheromones, respectively. N = 89 and 86 for ppk23 mutant flies exposed to male or female donor pheromones, respectively. P-values were obtained for lifespan and starvation resistance by log-rank test and for TAG amounts by t-test.

Fig. 3. Activation of ppk23-positive pheromone-sensing neurons in the foreleg of male flies is necessary and sufficient for changes in physiology and lifespan

(A) Targeted inhibition of ppk23-expressing neurons abrogates differences in starvation caused by pheromone exposure. N = 48 and 39 for control (ppk23-GAL4;w¹¹¹⁸) flies exposed to male or female donor pheromones, respectively (P ≤ 0.0001). N=38 and 50 for treatment (ppk23-GAL4; UAS-shi^ts) flies exposed to male or female donor pheromones, respectively (P = 0.96). (B) Targeted inhibition of fruitless-expressing neurons abrogates the effect of pheromone exposure on starvation resistance. N = 47 and 49 for control (fru-GAL4 X w¹¹¹⁸) flies exposed to male or female donor pheromones, respectively (P ≤ 0.0001). N = 46 and 47 for treatment (fru-GAL4; UAS-shi^ts) flies exposed to male or female donor pheromones, respectively (P=0.65). (C) Surgical removal of the forelegs abrogates the effects of pheromone exposure on starvation resistance. N = 50 for each genotype/treatment. P=0.0008 for unmanipulated and P=0.66 for amputee flies exposed to either male or female donor pheromones. See also Fig. S9. (D–F) Activation of ppk23-expressing neurons via heat-activated TRPA1 phenocopies the effects of pheromone exposure. (D) Starvation resistance. N = 50 for control (ppk23-GAL4;w¹¹¹⁸), N=45 for flies with activated neurons (ppk23-GAL4;UAS-TRPA1) (P ≤ 0.0001). (E) TAG amounts. Box plots are presented as in Fig 1. (F) Lifespan. N=193 (ppk23-GAL4;w¹¹¹⁸) and N=191 (ppk23-GAL4;UAS-TRPA1). P-values were obtained for lifespan and starvation resistance by log-rank test and for TAG amounts by t-test.

Fig. 4. Aging and physiology are modulated by neural mechanisms of expectation and reward

(A) Inhibition of npf-expressing neurons abrogates differences in starvation caused by pheromone exposure. N = 43 and 45 for control (npf-GAL4;w¹¹¹⁸) flies exposed to male or female donor pheromones, respectively (P = 0.005 by log-rank test). N = 48 and 47 for treatment (npf-GAL4; UAS-shi^ts) flies exposed to male or female donor pheromones, respectively (P = 0.50 by log-rank test). (B) Activation of npf-expressing neurons causes decreased longevity in the absence of pheromone exposure. UAS-dTrpA1/+; npf-GAL4/+ males (N=239) exhibit significantly shorter lifespan compared to UAS-dTrpA1/+ (N=235; p≤0.001 by log-rank test) and npf-GAL4/+ (N=179; p≤0.001 by log-rank test) male transgene controls. (C) Mortality rates are reduced when males exposed to female donor pheromone (dashed black line) are given access to excess females (dashed red line; P=0.02 through 20 days of age by Aalen regression). Cohorts consisted of five experimental males together with either (i) 30 control donor males (solid black), (ii) 30 feminized donor males (dashed black), (iii) 5 feminized donor males + 25 females (dashed red), or (iv) 5 control donor males + 25 females (solid red). 20 replicate cohorts, totaling 100 experimental flies, were measured for each treatment. (D) Significantly enriched Gene Ontology pathways and functions whose genes are differentially regulated following pheromone exposure. A complete list of genes with significant changes in expression is provided in Table S1.