Figure 3. srl is required, but not sufficient, for exercise-induced improvement to endurance capacity.

(A) Time to exhaustion assays conducted on y¹w^67c23, UAS-srl;mef2-Gal4, and srl¹ flies. Flies overexpressing srl in the muscle increase time to exhaustion as compared to y¹w^67c23 control flies (t-test: p = 0.0031). (B) Change in time to exhaustion in exercised flies as compared to unexercised flies of the same genotype. Wild-type and srl overexpressing flies increase time to exhaustion as a result of exercise (t-test, exercised and unexercised flies: p = 0.0001 and 0.0004, respectively for each genotype) to the same extent, while srl¹ mutant flies in fact decrease time to exhaustion after exercise training (t-test, exercised and unexercised srl¹: p = 0.0044, exercised y¹w^67c23 and exercised srl¹: p = 0.0005). (C) Endurance climbing assays conducted on 25 day-old y¹w^67c23, UAS-srl;mef2-Gal4, and srl¹ flies. Unexercised srl¹ display a decrease in climbing speed compared to unexercised y¹w^67c23 (multivariate regression, genotype effect: p = 0.0011), while unexercised srl overexpressers do not statistically differ from unexercised y¹w^67c23 flies. (D) After training, both exercised y¹w^67c23 and exercised UAS-srl;mef2-Gal4 flies show increased climbing speed when compared to unexercised control flies (multivariate regression, genotype effect: p = 0.0002 and p<0.0001, respectively), though srl¹ flies show no significant improvement (multivariate regression, genotype effect: p = 0.817). Survival rates during treatment of (E) unexercised and (F) exercised y¹w^67c23, UAS-srl;mef2-Gal4, and srl¹ flies. Unexercised flies were placed on the training machine but not allowed to run. Survival during treatment is statistically improved by exercise in all three genotypes (multivariate regression; treatment-by-age, all p values<0.012). Exercised UAS-srl;mef2-Gal4 flies also show increased survival compared to exercised y¹w^67c23 flies (multivariate regression, genotype effect, p = 0.0027).