Fig. 4
The Toll pathway is responsible for the sexual dimorphism in survival. a Sexual dimorphism in susceptibility in a loss-of-function mutant for the Toll pathway (spaetzle mutants). The probability of dying from P. rettgeri infection was the same for female and male hosts (Cox-ph: Sex: df = 1, χ2 = 1.12, P = 0.29). b Sexual dimorphism in susceptibility in loss-of-function mutant for the ModSP branch of the Toll pathway. Females were more susceptible than males (Cox-ph: Sex: df = 1, χ2 = 7.66, P = 0.005). Recognition of P. rettgeri by the ModSP component of the Toll pathway is not the reason for the sexual dimorphism in susceptibility. c Sexual dimorphism in susceptibility in loss-of-function mutant for the Persephone branch of the Toll pathway. The probability of dying from P. rettgeri infection was not different between female and male hosts (Cox-ph: Sex: df = 1, χ2 = 0.11, P = 0.74). The recognition of the virulence factor of the pathogenic Gram-negative bacteria P. rettgeri by the Toll pathway allows the sexual dimorphism. d Sexual dimorphism in susceptibility in loss-of-function mutant for the ModSP branch and for the Persephone branch of the Toll pathway. Females were less susceptible to E. faecalis infection than males for both mutant lines; males, but not the females, mutant for the Persephone branch where likely to die earlier than males mutant for the ModSP branch (Cox-ph: Line: df = 2, χ2 = 3.71, P = 0.05; Sex: df = 1, χ2 = 72.45, P < 0.0001; Line/Sex: df = 2, χ2 = 7.46, P = 0.006). Recognition of host damage or virulence factors is likely to be more important than the direct recognition of pathogenic bacteria. e Relative expression of Drosomycin to RpL32 in both sexes in response to the infection by P. rettgeri. Toll response (i.e., difference in Drosomycin expression between unchallenged and infected) was stronger 8 h post-injection in male wildtypes and mutants for modSP (Interaction Sex x Treatment: Canton S: df = 1, F = 13.68, P = 0.002; modSP: df = 1, F = 17.18, P = 0.0048) but this dimorphism was not present in mutants of Persephone and spaetzle (psh: df = 1, F = 0.35, P = 0.46; spz: df = 1, F = 0.03, P = 0.86)