Programmed cell death mediated by ced-3 and ced-4 protects Caenorhabditis elegans from Salmonella typhimurium-mediated killing

Abstract

Programmed cell death (PCD) in mammals has been implicated in several disease states including cancer, autoimmune disease, and neurodegenerative disease. In Caenorhabditis elegans, PCD is a normal component of development. We find that Salmonella typhimurium colonization of the C. elegans intestine leads to an increased level of cell death in the worm gonad. S. typhimurium-mediated germ-line cell death is not observed in C. elegans ced-3 and ced-4 mutants in which developmentally regulated cell death is blocked, and ced-3 and ced-4 mutants are hypersensitive to S. typhimurium-mediated killing. These results suggest that PCD may be involved in the C. elegans defense response to pathogen attack.

Figure 1

S. typhimurium induces PCD in the C. elegans germ line. (A) Cell corpses were counted over time in one gonad arm, starting with young adult animals fed on E. coli OP50 or S. typhimurium SL1344. Data (mean ± SD) are from at least three independent experiments; more than 15 animals were scored at each time point. (B–E) Confocal images showing 1-day-old hermaphrodite worms fed on E. coli OP50 (B and C) or S. typhimurium SL1344 (D and E) for 12 h. In the transmission images (B and D), the cell corpses are indicated with arrows. Merged images (C and E) show corpses stained with SYTO 12. (Bar = 30 μm.)

Figure 2

ced-3 and ced-4 mutants are more susceptible to S. typhimurium-mediated killing. One-day-old adult animals were fed either E. coli or S. typhimurium. (A) Wild type and ced-3(n717). (B) Wild type, ced-3(n1286), and ced-3(n2433). (C) Wild type, ced-4(n1162), and ced-4(n1894). More than 10 animals were used in each case and data (mean ± SD) were from duplicates. The results are representative of at least three experiments.

Figure 3

Mutants deficient in stress-induced germ-line cell death are more susceptible to S. typhimurium-mediated killing. One-day-old adult animals were exposed to either E. coli or S. typhimurium. (A) Wild type, ced-9(n1950) (gf), and egl-1(n1084n3082) (lf) (gf, gain-of-function; lf, loss-of-function). B, wild type and ced-9(n1653ts) (lf). (C) Wild type, ced-3 (n717), ced-4(n1162), ced-9(n1653ts) (lf), ced-9(n1950) (gf), egl-1(n1084n3082), ces-1(n703), and ces-2(n732). The TD₅₀s were calculated in each case and the relative mortality was calculated as described in Materials and Methods. More than 10 animals were used in each case; data (mean ± SD) were from three to five experiments.