Fig 1.
The DAF-7 signaling pathway is required for lifespan extension in response to dietary restriction.
A) Summary of the DAF-7/TGFβ pathway B-D) Representative lifespan curves of N2 (B), daf-7(e1372) (C), and daf-7(e1372);daf-3(e1376) (D) animals subjected to control (fed, solid lines) or bacterial deprivation (BD, dashed lines) diets. E) Summary of all alleles tested for BD response. * indicates BD lifespan was significantly different (p ≤ 0.001) than fed control group in all experiments, error bars reflect SEM. See S2 Table for individual experiment details.
Fig 2.
DAF-7 originating from chemosensory neurons acts on RIM/RIC interneurons to promote lifespan extension in response to DR.
A-C) Lifespan curves displaying rescue of BD defect of daf-7(ok3125) animals (A) by reintroducing wild-type daf-7 under the endogenous promoter (B), the ASI specific str-3 promoter, or the ASJ specific trx-1 promoter (C). D-E) Representative curves displaying rescue of BD defect of daf-1(m40) animals (D) by expressing wild-type daf-1 under its own promoter or the RIM/RIC/UV1 specific promoter, tdc-1 (E). F) Summary of all daf-1(m40) rescue experiments performed. * indicates BD lifespan was significantly different (p ≤ 0.05) than fed control group in all experiments, error bars reflect SEM. See S2 Table for individual experiment details.
Fig 3.
Dietary restriction acutely increases daf-7 expression in adult animals.
A) Quantification of GFP expression driven by ksIs2[daf-7p::GFP], normalized to exposure time in fed and BD conditions. Representative of 3 replicates performed with n>10 animals per condition. B,C) (i.) Quantification of fluorescence of FISH probes designed against daf-7 in ASI (identified by co-localization with str-3p::GFP) (B) and ASJ (identified by co-localization with trx-1p::GFP) (C) under fed and BD conditions. *** represents p < 0.001 by unpaired t-test. (ii.) Representative images of ASI or ASJ neurons corresponding to the quantifications presented in (i). All images taken with the same exposure time. D) Model of daf-7 expression change in response to dietary restriction.
Fig 4.
daf-7 is required for DAF-16/FoxO nuclear translocation in response to BD.
A) State of DAF-16a/b::GFP localization pattern in fed versus BD conditions. Representative of 2 replicates with total n = 116–154 animals per condition. B) Representative images of the zIs356[daf-16p::daf-16a/b::GFP] reporter in the intestine of wild-type or daf-7(e1372) animals in fed and BD conditions.
Fig 5.
daf-7 expression declines in aging animals.
A) Expression pattern of ksIs2[daf-7p::GFP] reporter in young (i,ii) and aged (iii,iv) animals. Solid triangles indicate ASI neurons, open triangles indicate ASJ neurons. B) Quantification of GFP expression driven by ksIs2[daf-7p::GFP], normalized to exposure time. Representative of 4 replicates with n>10 animals per day. *** represents p < 0.001 by one-way ANOVA C) Quantification of GFP expression driven by cuIs5[C183::myo-2p::GFP] in aging animals, normalized to exposure time. WT statistics indicated on graph, daf-7(e1372) statistics- Day 3 p = 0.0002; Day 5 p = 0.5225; Day 7 p = 0.0005; Day 9 p = 0.0445; all differences in daf-7(e1372) are a result of increased GFP fluorescence later in life. Representative of 4 replicates with n>10 animals per genotype per day. *** represents p < 0.001 by one-way ANOVA D) Summary of lifespan experiments initiating BD at various times in adulthood. * indicates BD lifespan was significantly different (p < 0.005) than fed control group in all experiments. See S4 Table for individual experiment details.
Fig 6.
A decline in neuronal daf-7 expression with advancing age alters sensitivity to effects of DR on lifespan.
Declines in daf-7 expression in ASI chemosensory neurons with age inhibit activity of daf-3 in RIM/RIC interneurons, the active form of which is able to interfere with the DR response in other tissues.