Mating induces shrinking and death in Caenorhabditis mothers

Abstract

Interactions between the germ line and the soma help optimize reproductive success. We discovered a phenomenon linking reproductive status to longevity: In both hermaphroditic and gonochoristic Caenorhabditis, mating leads to female shrinking and death, compressing postreproductive life span. Male sperm induces germline- and DAF-9/DAF-12-dependent shrinking, osmotic stress susceptibility, and subsequent life-span decrease, whereas seminal fluid induces DAF-16-dependent life-span decrease and fat loss. Our study provides insight into the communication between males and the female germ line and soma to regulate reproduction and longevity, revealing a high-reproduction, low-life-span state induced by mating. Postmating somatic collapse may be an example of the sexually antagonistic influence that males in many species exert on female behavior to maximize their own reproductive success.

Fig. 1.. Postmating somatic collapse: Hermaphrodites shrink and die after mating.

Statistical analysis: survival curves, log-rank test, body size, and others. t test, *P < 0.05, **P < 0.01, ***P < 0.001 for all graphs. Error bars represent SEM unless noted. n.s., not significant. (A) Length of unmated and mated N2 worms. (Inset) Representative pictures of unmated and mated N2 on day 7. Scale bar, 1 mm. (B) Life spans of unmated and mated N2 worms. Unmated N2:16.0 ± 1.0 days, n = 30 worms; mated N2:9.6 ± 0.2 days, n = 36, P < 0.05. (C) Length of unmated fog-2(q71) hermaphrodites (n = 35), and fog-2(q71) mated with N2 (n = 42), fer-6(hc6) (n = 24), and gon-2(q362) males (n = 29). (D) Mean life spans of unmated and mated fog-2. Unmated: 19.0 ± 0.6 days (n = 94); fog-2 × N2:12.0 ± 0.8 days (n = 83); fog-2 × fer-6: 15.0± 0.9 days (n = 28); fog-2 x gon-2:19.2 ± 0.6 days (n = 73).

Fig. 2.. Postmating shrinking is mediated by the germline pathway.

(A) Mated daf-2(e1370) worms shrink up to 25% compared with unmated daf-2, g whereas germline pathway mutants [glp-1(e2141), daf-12(rh61rh411), and daf-9(rh50)] do not shrink after mating. (B) Mated daf-2 (19.4 ± 2.2 days, n = 60) live 45% shorter than unmated daf-2 (37.0 ± 1.9 days, n = 47), P < 0.001. Mated glp-1 (11.6 ± 0.5 days, n = 60) live 55% shorter than unmated glp-1 (24.1 ± 1.3 days, n = 48), P < 0.001. Mated daf-12 (12.1 ± 1.0 days, n = 26) live 20% shorter than unmated daf-12 (16.0 ± 1.4 days, n = 20), P < 0.05; mated daf-9 (11.3 ± 0.4 days, n = 45) live 16% shorter than unmated daf-9 (13.4 ± 0.5 days, n = 36), P < 0.01. (C) Pdaf-9::daf-9::gfp expression in the spermatheca is decreased after mating with N2 males, but not with fer-6 males, and is not affected by FUdR. Error bars denote SD. a.u., arbitrary units. (D) 50 μM FUdR treatment dynamically prevents shrinking in mated N2s. (E) Mated daf-16 (10.83 ± 0.6 days, n = 53) live 15% shorter than unmated (12.62 ± 0.5 days, n = 40), P < 0.05. Adult treatment with FUdR eliminates the difference between mated and unmated daf-16(mu86) life span [unmated, 13.2 ± 0.6 days (n = 36); mated, 13.8 ± 0.5 days (n = 48), P = 0.385]. By contrast, FUdR does not prevent postmating life-span decrease in the wild type. Unmated, 21.0 ± 0.9 days (n = 41); mated, 15.3 ± 0.7 days (n = 43); P < 0.001. (F) Mated daf- 16(mu86) worms shrink by 15%. *P < 0.05, **P < 0.01, ***P < 0.001 for all graphs. Error bars represent SEM unless noted. n.s., not significant.

Fig. 3.. Postmating life-span decrease is mediated by DAF-16, and shrinking correlates with osmotic stress sensitivity.

(A) DAF-16::GFP in glp-1 translocates from the nucleus to the cytoplasm after mating. GFP channel images of glp-1 unmated (left) and mated worms (middle); red arrows point to dark nuclei. Scale bar, 100 μm. (Right) Quantification of GFP localization. (B) Pins-7::gfp expression [maximum ± SD (error bars)] increases significantly in the intestine postmating. a.u., arbitrary units. (C)Survival curves under osmotic stress (400 mM NaCl): Day 1 mated N2 and daf-16(mu86) died faster than the unmated controls put under osmotic stress starting on day 4. Unmated N2: 40.3 ± 6.0 hours, n = 31; mated N2:18.5 ± 1.8 hours, n = 35, P <0.001. Unmated daf-16:19.2 ± 1.9 hours, n = 35; mated daf-16:11.8 ± 1.1 hours, n = 35, P < 0.001. Mated daf-9(rh50) and daf-12(rh61rh411) survived as long as the unmated controls under osmotic stress. Unmated daf-9: 31.2 ± 4.3 hours, n = 30; mated daf-9: 25.7 ± 3.8 hours, n = 23, P = 0.3242. Unmated daf-12: 25.6 ± 2.5 hours, n = 38; mated daf-12: 26.2 ± 2.3 hours, n = 33, P = 0.9714. glp-1 and daf-2 mated worms survive longer than wild type on NaCl, but still die prematurely. glp-1 unmated (n = 35): 131.7 ± 10.4 hours; glp-1 mated (n = 29): 23.2 ± 3.8 hours; P < 0.0001. daf-2 unmated (n = 33): 250.5 ± 30.0; daf-2 mated (n = 34): 17.7 ± 1.8 hours; P < 0.0001. *P < 0.05, **P < 0.01, ***P < 0.001 for all graphs.

Fig. 4.. Evolutionary conservation of mating-induced shrinking and death.

(A) Sperm decreases DAF-9 activity and induces germline proliferation, which in turn emits a DAF-12-dependent signal that results in shrinking and subsequent life-span shortening, probably due to reduced osmotic stress resistance. Seminal fluid induces a germline-independent signal that causes both fat loss and DAF-16 cytoplasmic translocation (possibly amplified by INS-7), further reducing life span (LS). (B to D) Mated C. remanei and C. sp.9 shrink (B) and die prematurely (C). C. remanei: unmated: 26.9 ± 2.8 days, n = 48; mated:15.1 ± 0.8 days, n = 48, P < 0.001. C sp.9: unmated: 17.3 ± 1.2 days, n = 42; mated: 11.9 ± 0.8 days, n = 41, P < 0.01. An interspecies cross between C. remanei (C.r) males and C. elegans (C.e) hermaphrodites does not reduce life span (C) or induce shrinking (D). C.e unmated: 19.4 ± 0.6 days, n = 33; C.e × C.e:8.2 ± 0.4 days, n = 36; C.e × C.r. 18.8 ± 0.9 days; n = 27. (E) Postreproductive life span is significantly reduced in mated worms. Unmated N2 worms (n = 60): mean LS = 11.2 ± 0.5 days; reproductive span (RS) = 3.1 ± 0.1 days; postreproductive LS = ~8.1 days. Mated N2 worms (n = 62): LS = 8.7 ± 0.3 days; P = 0.131 (compared with unmated LS); RS = 7.7 ± 0.1 days, P < 0.001 (compared with unmated RS); postreproductive LS = ~1.0 day. *P < 0.05, **P < 0.01, ***P < 0.001 for all graphs. Error bars represent SEM unless noted. n.s., not significant.