(A) A model for the role of self-sperm in mating-induced demise resistance. The absence of self-sperm (right panel) activates the CEH-18 and VAB-1 sensing pathway in the somatic gonad. (B-C) Young, feminized (fog-2[q71]) worms (B, day 4 of life) were sensitive to a brief interaction with males when young (B, p=0.0001 vs. no males) but when the sperm-sensing pathway was blocked by loss of CEH-18 and VAB-1 (fog-2[q71]; ceh-18[mg57] grown on vab-1 targeting RNAi bacteria), these worms (C) were resistant to a brief, 2 hr interaction with males and had a normal lifespan (n.s. vs. no males). (D-E) Middle-aged, self-sperm depleted hermaphrodites (D, day 7 of life) were sensitive to a brief mating with males (D, p<0.0001 vs. no males) but when the sperm-sensing pathway was blocked by loss of CEH-18 and VAB-1 (ceh-18[mg57] grown on vab-1 targeting RNAi bacteria), these middle-aged worms (E) were resistant to a brief, 2 hr interaction with males and had a normal lifespan (E, n.s. vs. no males). For all experiments, worms that received male sperm (dashed lines) were selected by hand-picking based on the presence of fluorescent male sperm in their uterus or spermatheca following a two-hour interaction with him-5(e1467) males. Images above the lifespan curves in panels B-E show the state of the germline with oocytes in pink and the blocking of sperm-sensing pathway by a blue line. Lifespans were performed with 86–115 animals per condition. Lifespan assays were performed at 20°C. Lifespan data are plotted as Kaplan-Meier survival curves and p-values were determined using Mantel-Cox log ranking. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, n.s. = not significant. See also Supplementary file 2 for extended statistics and replicates. (F) The CEH-18 interaction network calculated by GeneMANIA (Warde-Farley et al., 2010). Lines indicate genetic interactions (green), co-expression (purple), physical interactions (orange), and ‘other’ (gray). The differential expression of the genes in the network is shown with a blue-red gradient. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, no stars = not significant. Network members not detected by the RNA-seq are in gray with dotted outlines. The number of differentially expressed genes in this network was statistically enriched (p=0.0043) as measured using the hypergeometric distribution test. See Figure 2—source data 1 for exact differential expression values. (G) Selected, enriched GO terms from the genes that are differentially expressed between young hermaphrodite versus young feminized that never interacted with a male and contain a CEH-18 binding site as defined by CEH-18 ChIP-seq (Kudron et al., 2018), see Material and methods. GO terms that were enriched in the genes expressed more highly in young hermaphrodites are shown in green and GO terms enriched in the genes more highly expressed in young feminized individuals are in pink. P-values were calculated with the Fisher’s exact test and were corrected for multiple hypothesis testing with Benjamini-Hochberg. A complete list of all significantly enriched GO terms can be found in Figure 4—source data 2.