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. 2020 May 5;9:e56186. doi: 10.7554/eLife.56186

Figure 8. DAF-7/TGFβ signals that hydrogen-peroxide protection will be provided by catalases from E. coli and not by catalases from C. elegans.

(A) C. elegans was sensitive to killing by tert-butyl hydroperoxide (tBuOOH), but not by hydrogen peroxide, in the presence of E. coli OP50. (B) Hydrogen peroxide resistance of wild type and daf-7(ok3125) C. elegans in assays with wild type and Kat – Ahp – E. coli. (C) Overexpression of the three endogenous catalases protects nematodes from hydrogen peroxide in assays with Kat – Ahp – E. coli. (D) The cytosolic catalase ctl-1(ok1242) mutation suppressed part of the increased hydrogen peroxide resistance of daf-1(m40) in assays with Kat – Ahp – E. coli. (E) The DAF-7/TGFβ-pathway regulates ctl-1 mRNA expression via DAF-16/FOXO, determined by quantitative RT-PCR. Data are represented as mean ± s.e.m of three independent biological replicates, each with three technical replicates. For comparisons of ctl-1 mRNA expression between pairs of genotypes, ** indicates p < 0.001, * indicates p < 0.05, and ‘ns’ indicates p > 0.05 (Turkey HSD test). (F) Representative pictures of the expression of the chIs166[Pctl-1::ctl-1::gfp] reporter in wild type animals (left picture; category: medium) or daf-1(m40) mutants (right picture; category: very high). Scale bar = 100 µm. (G) The expression of the promoter of ctl-1 fused with GFP (chIs166[Pctl-1::ctl-1::gfp]) is higher in daf-1(m40) mutants (237 animals) than in wild type animals (145 animals), *** indicates p < 0.0001 (ordinal logistic regression). Scoring is described in Materials and methods. See Figure 8—figure supplement 1D for representative pictures of each expression category. (H) DAF-7/TGFβ signaling enables C. elegans to decide whether to induce its own hydrogen-peroxide defenses or, instead, freeload on protection provided by molecularly orthologous hydrogen-peroxide defenses from E. coli. See also Figure 8—figure supplement 1. Additional statistical analyses are in Supplementary file 8.

Figure 8.

Figure 8—figure supplement 1. DAF-7/TGFβ signals that hydrogen-peroxide protection will be provided by catalases from E. coli and not by catalases from C. elegans.

Figure 8—figure supplement 1.

(A) Genetic ablation of ASI sensory neurons increased peroxide resistance. (B) Gene expression levels within the genomic region encoding the three C. elegans catalase genes. Because these genes contain multiple regions with perfect identity, we determined the relative genome coverage of reads (including multimaps) between daf-7(ok3125) mutants and wild-type animals using BEDTools (Quinlan and Hall, 2010) and plotted the mean read count across six samples normalized using scran (Lun et al., 2016). Gene models show the positions and splicing pattern of each catalase gene, regions with 100% nucleotide identity (orange and green), and unique regions (grey and purple). (C) The peroxisomal catalase ctl-2(ok1137) did not suppresses the increased peroxide resistance of daf-1(m40). (D) Representative pictures of the low, medium, high and very high expression categories of the chIs166[Pctl-1::ctl-1::gfp] reporter. Scale bar = 100 µm. Statistical analyses are in Supplementary file 8.