Neuronal detection triggers systemic digestive shutdown in response to adverse food sources in Caenorhabditis elegans
Figures

Caenorhabditis elegans shuts down its digestion for survival when fed harmful food, specifically Staphylococcus saprophyticus (SS).
(A) Microscopic images showing worms fed with SS arrested at the L1 stage 3 days after hatching. (B) Schematic model illustrating our hypothesis: C. elegans can sense or evaluate inedible food, such as SS, and subsequently shut down their digestion to arrest development as a protective survival strategy. (C) Schematic drawing and quantitative data of the food dwelling/avoidance assay. Yellow circles indicate the food spot for OP50 or SS bacteria, respectively. The animals were scored at the indicated times after L1 worms were placed on the food spot. The red point indicates the position of each worm. Data are represented as mean ± SD. Scale bar = 1000 μm. ***p<0.001; **p<0.01 by Student’s t-test. (D) Schematic drawing, microscopic images, and quantitative data of the food choice assay. L1 worms were placed at the center spot (origin). OP50 (yellow) and SS (blue) bacteria were placed on opposite sides of the plate. The red point indicates the position of each worm. The percentage of worms on each spot was calculated at the indicated times. Data are represented as mean ± SD. Scale bar = 1000 μm. ****p<0.0001; **p<0.01 by Student’s t-test. (E, F) Schematic drawing and quantitative data of the lifespan of animals fed with SS or OP50. L1 worms were seeded onto OP50 and grown to the L4 stage. L4 worms were then moved to SS or OP50 food to measure lifespan. **p<0.01 by log-rank test. All data are representative of at least three independent experiments.
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Figure 1—source data 1
Numerical data of Figure 1C–F.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig1-data1-v1.xlsx

Staphylococcus saprophyticus (SS) is harmful food that animals cannot digest.
Related to Figure 1. (A) Schematic drawing, microscopic images, and quantitative data from the food choice assay. L1 worms were placed at the center spot (origin). OP50 (yellow), and heat-killed OP50 (blue) bacteria were positioned on opposite sides of the plate. The red point indicates the position of each worm. The percentage of worms on each spot was calculated at the indicated times. Data are represented as mean ± SD. Scale bar = 1000 μm. ****p<0.0001; ***p<0.001; **p<0.01 by Student’s t-test. (B) Schematic drawing, microscopic images, and quantitative data from the food choice assay. L1 worms were placed at the center spot (origin). Heat-killed OP50 (blue) and SS (red) bacteria were positioned on opposite sides of the plate. The red point indicates the position of each worm. The percentage of worms on each spot was calculated at the indicated times. Data are represented as mean ± SD. Scale bar = 1000 μm. ****p<0.0001; n.s. not significant by Student’s t-test. (C) Schematic drawing and quantitative data of the lifespan of animals fed with SS or OP50. L1 worms were seeded on plates with no food (NGM) or SS bacteria to measure lifespan. n.s., not significant by log-rank test. (D) Schematic drawing and quantitative data of the developmental progression of wild-type N2 under different feeding conditions. L1 animals were seeded onto OP50 plates and grown to the L2 stage. L2 animals were then transferred to OP50, SS, or no food (NGM) plates to measure worm length at the indicated time points. All data are representative of at least three independent experiments.
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Figure 1—figure supplement 1—source data 1
Numerical data of Figure 1—figure supplement 1A–D.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig1-figsupp1-data1-v1.xlsx

Caenorhabditis elegans senses Staphylococcus saprophyticus (SS) and shuts down digestion through NSY-1.
(A) Developmental phenotype of wild-type N2 and nsy-1(ag3) mutant worms fed with SS bacteria. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n = number of animals which were scored. (B) Schematic drawing, microscopic images, and quantitative data of the food dwelling/avoidance assay. Yellow circles indicate the food spot for SS bacteria. The animals were scored at the indicated times after L1 worms were placed on the food spot. The blue circle indicates the edge of the bacterial lawn, and the red point indicates the position of each worm. Data are represented as mean ± SD. Scale bar = 1000 μm. *p<0.05; **p<0.01 by Student’s t-test. (C) Schematic drawing, microscopic images, and quantitative data of the food choice assay. L1 nsy-1(ag3) worms were placed at the center spot (origin). Heat-killed OP50 (yellow) and SS (blue) bacteria were placed on opposite sides of the plate. The red point indicates the position of each worm. The percentage of worms on each spot was calculated at the indicated times. Data are represented as mean ± SD. Scale bar = 1000 μm. **p<0.01; ***p<0.001 by Student’s t-test. (D) Survival curves of wild-type N2 and nsy-1(ag3) mutant worms fed with SS bacteria. L4 worms, previously fed OP50 bacteria, were transferred to SS food to measure lifespan. ****p<0.0001 by log-rank test. All data are representative of at least three independent experiments.
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Figure 2—source data 1
Numerical data of Figure 2A–D.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig2-data1-v1.xlsx

Ethyl methanesulfonate (EMS) screen to identify genes involved in shutting down digestion of Staphylococcus saprophyticus (SS).
(A) Schematic illustration of the EMS screen strategy to identify ‘Y’ genes involved in shutting down digestion after sensing SS. In mutants with defects in ‘Y’ genes, digestion of SS is restored, allowing the mutants to grow on SS. (B) Developmental phenotype of wild-type N2 and ylf6 mutant worms fed with SS bacteria. Scale bar = 200 μm. (C) Schematic drawing showing the mutation sites in nsy-1(ylf6) and nsy-1(ag3).

NSY-1 plays a critical role in AWC neurons to inhibit Staphylococcus saprophyticus (SS) digestion.
(A) Microscopic image showing the expression pattern of nsy-1. The head of an adult transgenic animal carrying Pnsy-1::GFP and Podr-1::RFP shows colocalization of nsy-1 and odr-1. Scale bar = 20 μm. (B) Developmental progression of nsy-1(ag3) mutant worms carrying Podr-1::nsy-1::gfp (AWC neuron-specific expression) grown on SS bacteria. Control animals are labeled with white stars, and animals carrying the transgenes (rescued animals) are labeled with yellow stars. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (C) Developmental progression of wild-type N2 and AWC neuron-specific knockout nsy-1 animals (AWC nsy-1 KO) grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 500 μm. ***p<0.001 by Student’s t-test. n=number of animals which were scored. (D) Microscopic images show Pstr-2::GFP, a marker for AWC neuron states, in L1-staged wild-type and nsy-1(ky397) mutant worms grown on OP50 or SS bacteria for 6 h. AWC neuron positions are highlighted with red and yellow arrows. Scale bar = 20 μm. (E, F) Percentage of animals with different AWC neuron states. nsy-1 mutation promotes a 2AWCON state under SS feeding conditions (E), with approximately 50% of animals exhibiting 2AWCOFF neurons when feeding on SS (F). Data are represented as mean ± SD. **p<0.01 by Student’s t-test. n=number of animals which were scored. (G) Developmental progression of wild-type N2, tir-1(qd4), and nsy-1(ag3) mutant worms grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. All data are representative of at least three independent experiments.
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Figure 3—source data 1
Numerical data of Figure 3B–G.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig3-data1-v1.xlsx

Construction of nsy-1-specific knockout in AWC neurons using CRISPR-Cas9.
Related to Figure 3. Representative DNA gels showing NheI digestion of PCR-amplified genomic DNA extracted from wild-type (WT) worms and worms with nsy-1-specific knockout in AWC neurons (odr-1p::Cas9+u6p::nsy-1-sg).
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Figure 3—figure supplement 1—source data 1
Original gels for Figure 3—figure supplement 1, indicating the relevant bands and treatments.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig3-figsupp1-data1-v1.zip
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Figure 3—figure supplement 1—source data 2
Original files for gels analysis displayed in Figure 3—figure supplement 1.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig3-figsupp1-data2-v1.zip

NSY-1 functions in the intestine to shut down Staphylococcus saprophyticus (SS) digestion.
(A) Microscopic image showing the expression pattern of nsy-1. nsy-1 is mainly expressed in the head neurons and intestine. Scale bar = 50 μm. (B) Developmental progression of nsy-1(ag3) mutant worms carrying Pvha-6::nsy-1::gfp (intestine-specific expression) grown on SS bacteria. Control animals are labeled with white stars, and animals carrying the transgenes (rescued animals) are labeled with yellow stars. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored.
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Figure 3—figure supplement 2—source data 1
Numerical data of Figure 3—figure supplement 2B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig3-figsupp2-data1-v1.xlsx

NSY-1 functions in AWC neurons to influence the recognition of Staphylococcus saprophyticus (SS).
(A) Microscopic images and quantitative data of the food dwelling/avoidance assay. The animals were scored at the indicated times after L1 worms were placed on the food spot. The blue circle indicates the edge of the bacterial lawn, and the red point indicates the position of each worm. Data are represented as mean ± SD. Scale bar = 500 μm. *p<0.05 by Student’s t-test. (B) Microscopic images and quantitative data of the food dwelling/avoidance assay. The animals were scored at the indicated times after L1 worms were placed on the food spot. The blue circle indicates the edge of the bacterial lawn, and the red point indicates the position of each worm. Data are represented as mean ± SD. Scale bar = 500 μm. **p<0.01; *p<0.05 by Student’s t-test. (C) Microscopic images, and quantitative data from the food choice assay. L1 worms were placed at the center spot (origin). Heat-killed OP50 and SS bacteria were positioned on opposite sides of the plate. The red point indicates the position of each worm. The percentage of worms on each spot was calculated at the indicated times. Data are represented as mean ± SD. Scale bar = 2 mm. ****p<0.0001; ***p<0.001; **p<0.01 by Student’s t-test. (D) Microscopic images and quantitative data from the food choice assay. L1 worms were placed at the center spot (origin). Heat-killed OP50 and SS bacteria were positioned on opposite sides of the plate. The red point indicates the position of each worm. The percentage of worms on each spot was calculated at the indicated times. Data are represented as mean ± SD. Scale bar = 2 mm. **p<0.01; *p<0.05; n.s. not significant by Student’s t-test.
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Figure 3—figure supplement 3—source data 1
Numerical data of Figure 3—figure supplement 3A–D.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig3-figsupp3-data1-v1.xlsx

AWC neurons are essential for initiating Staphylococcus saprophyticus (SS) digestion.
Developmental phenotype of wild-type N2 and AWC(-) worms fed with SS bacteria. Data are represented as mean ± SD. Scale bar = 500 μm. n.s., not significant by Student’s t-test. n=number of animals which were scored.
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Figure 3—figure supplement 4—source data 1
Numerical data of Figure 3—figure supplement 4.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig3-figsupp4-data1-v1.xlsx

NSY-1 inhibits animals from digesting Staphylococcus saprophyticus (SS) by inducing str-130.
(A) Schematic illustration showing that ‘X’ genes rely on NSY-1 to shut down SS digestion. ‘X’ genes induced by SS food are dependent on NSY-1, and their induction aids in shutting down SS digestion. (B) Venn diagram showing the overlap of genes that respond to SS and rely on NSY-1. The number of genes is indicated in the diagram (also see Supplementary file 1). (C) Transcriptome analysis showing str-130 mRNA expression, which relies on NSY-1 in response to SS. Data are represented as mean ± SD. **p<0.01 by Student’s t-test. (D) Developmental progression of wild-type animals treated with control RNAi or str-130 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (E) Microscopic images and quantitative data of AWC neuron states in L1 animals treated with control RNAi or str-130 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 20 μm. ***p<0.001 by Student’s t-test (1AWCON/1AWCOFF: control vs str-130 RNAi). n=number of animals which were scored. (F) Developmental progression of nsy-1(ag3) mutant worms carrying Pstr-130::str-130::mCherry grown on SS bacteria. Control animals are labeled with white stars, and animals carrying transgenes are labeled with yellow stars. Data are represented as mean ± SD. Scale bar = 400 μm. ***p<0.001 by Student’s t-test. n=number of animals which were scored. (G) Microscopic images and quantitative data of AWC neuron states in L1 animals carrying Pstr-130::str-130::mCherry. Transgenic animals with overexpression of str-130 (carrying Pord-1::GFP as a co-injection marker) show an increased 2AWCOFF state. Data are represented as mean ± SD. Scale bar = 20 μm. ****p<0.001 by Student’s t-test (2AWCOFF: Control vs Transgene). n=number of animals which were scored. All data are representative of at least three independent experiments.
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Figure 4—source data 1
Numerical data of Figure 4B–G.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig4-data1-v1.xlsx

str-130 is induced in wild-type in response to Staphylococcus saprophyticus (SS), dependent on NSY-1.
(A) GO enrichment analysis of 304 NSY-1-dependent candidate genes responding to SS (Supplementary file 2). Genes related to sensory perception (sra-32, str-87, str-112, str-130, str-160, str-230) are highlighted as enriched (red arrow). (B) Relative mRNA expression levels of sensory perception-related genes (sra-32, str-87, str-112, str-130, str-160, str-230) extracted from RNA-seq data. These genes are induced in wild-type N2 animals in response to SS, but their expression is reduced in nsy-1(ag3) mutant animals under SS feeding conditions, indicating that the induction of these genes in wild-type in response to SS is dependent on NSY-1.
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Figure 4—figure supplement 1—source data 1
Numerical data of Figure 4—figure supplement 1A and B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig4-figsupp1-data1-v1.xlsx

str-130 as the dominant effector of NSY-1-mediated Staphylococcus saprophyticus (SS) response regulation.
(A) Developmental progression of wild-type animals treated with control RNAi, str-130 RNAi, sra-32 RNAi, str-230 RNAi, str-87 RNAi, str-112 RNAi, or str-160 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001; ***p<0.001; *p<0.05; n.s. not significant by Student’s t-test (candidate RNAi vs Control RNAi). n=number of animals which were scored. (B) Developmental progression of nsy-1(ag3) mutant animals treated with control RNAi, str-130 RNAi, sra-32 RNAi, str-230 RNAi, str-87 RNAi, str-112 RNAi, or str-160 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 500 μm. n.s., not significant by Student’s t-test (candidate RNAi vs Control RNAi). n=number of animals which were scored.
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Figure 4—figure supplement 2—source data 1
Numerical data of Figure 4—figure supplement 2A, B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig4-figsupp2-data1-v1.xlsx

NSY-1 inhibits Staphylococcus saprophyticus (SS) digestion by inducing GPCR str-130.
Developmental progression of wild-type or nsy-1(ag3) mutant animals treated with control RNAi or str-130 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001; n.s., not significant by Student’s t-test. n=number of animals which were scored.
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Figure 4—figure supplement 3—source data 1
Numerical data of Figure 4—figure supplement 3.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig4-figsupp3-data1-v1.xlsx

NSY-1 mutation activates animals to digest Staphylococcus saprophyticus (SS) by inducing insulin signaling.
(A) Schematic illustration showing that NSY-1 inhibits the expression of ‘Y’ genes, which promote SS digestion. Some genes induced by the nsy-1 mutation under SS feeding conditions could facilitate SS digestion in the nsy-1 mutant. (B) Venn diagram showing the overlap of genes that respond to SS but are limited by NSY-1. A total of 308 candidate genes induced by the nsy-1 mutation under SS feeding conditions could potentially promote SS digestion. (C) Transcriptome analysis showing that ins-23 expression is induced in animals with the nsy-1 mutation under SS feeding conditions. Data are represented as mean ± SD. **p<0.01; n.s., not significant by Student’s t-test. n=3 biological replicates. (D) Developmental progression of nsy-1(ag3) mutant animals treated with control RNAi or ins-23 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 500 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (E) Developmental progression of nsy-1(ag3), daf-2(e1370), and nsy-1(ag3);daf-2(e1370) double mutant animals grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 500 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. All data are representative of at least three independent experiments.
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Figure 5—source data 1
Numerical data of Figure 5B–E.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig5-data1-v1.xlsx

nsy-1 mutation induces the expression of insulin-related genes.
Related to Figure 5. (A) GO enrichment analysis of 308 genes induced by the nsy-1 mutation under Staphylococcus saprophyticus (SS) feeding conditions (also see Supplementary file 2). (B) Relative mRNA expression levels of insulin-related genes (ins-23, ins-22, ins-27, ins-24) extracted from RNA-seq data. These genes are upregulated in nsy-1(ag3) mutant animals under SS feeding conditions, which may contribute to SS digestion in the nsy-1 mutant.
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Figure 5—figure supplement 1—source data 1
Numerical data of Figure 5—figure supplement 1A and B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig5-figsupp1-data1-v1.xlsx

NSY-1 mutation promotes Staphylococcus saprophyticus (SS) digestion by inducing ins-23.
Developmental progression of nsy-1(ag3) mutant animals treated with control RNAi, ins-22 RNAi; ins-23 RNAi; ins-24 RNAi; or ins-27 RNAi grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 500 μm. ****p<0.0001; n.s., not significant by Student’s t-test (candidate RNAi vs Control RNAi). n=number of animals which were scored.
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Figure 5—figure supplement 2—source data 1
Numerical data of Figure 5—figure supplement 2.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig5-figsupp2-data1-v1.xlsx

INS-23 induction in nsy-1 mutants promotes digestion independently of intestinal DAF-2 function.
(A) CeNGEN predicts showing the head neurons expression pattern of ins-23. ins-23 is expressed in AWC neurons. (B) Developmental progression of nsy-1(ag3);daf-2(e1370) mutant worms carrying Pges-1::daf-2::gfp (intestine-specific expression) grown on Staphylococcus saprophyticus (SS) bacteria. Control animals are labeled with white stars, and animals carrying the transgenes (rescued animals) are labeled with yellow stars. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (C) Microscopic images and quantitative data showing fluorescence of Pins-23::ins-23::GFP animals treated with control RNAi or pmk-1 RNAi. Data are represented as mean ± SD. Scale bar = 10 μm. n.s., not significant by Student’s t-test. n=number of animals which were scored.
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Figure 5—figure supplement 3—source data 1
Numerical data of Figure 5—figure supplement 3B and C.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig5-figsupp3-data1-v1.xlsx

NSY-1 mutation promotes animals to digest Staphylococcus saprophyticus (SS) through inducing intestinal bcf-1.
(A) Microscopic images and quantitative data showing fluorescence of Pbcf-1::bcf-1::GFP in L1-staged wild-type (WT) and nsy-1(ag3) mutant animals fed with OP50 or SS bacteria for 6 h. Data are represented as mean ± SD. Scale bar = 100 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (B) Microscopic images and quantitative data showing fluorescence of Pbcf-1::bcf-1::GFP in L1-staged wild-type and AWC nsy-1 KO mutant (AWC neuron-specific knockout nsy-1 animals) fed with SS bacteria for 6 h. Data are represented as mean ± SD. Scale bar = 50 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (C) Developmental progression of wild-type N2, nsy-1(ag3), bcf-1(ok2599), and nsy-1(ag3);bcf-1(ok2599) double mutant animals grown on SS bacteria. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (D) Microscopic images and quantitative data showing fluorescence of Pbcf-1::bcf-1::GFP in nsy-1(ag3) mutant animals treated with control RNAi or ins-23 RNAi under normal RNAi feeding conditions. Data are represented as mean ± SD. Scale bar = 200 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. All data are representative of at least three independent experiments.
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Figure 6—source data 1
Numerical data of Figure 6A–D.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig6-data1-v1.xlsx

INS-23 and STR-130 are functions in AWC neurons to affect BCF-1 expression.
(A) Microscopic images and quantitative data showing fluorescence of Pbcf-1::bcf-1::GFP animals treated with control RNAi or AWC ins-23 RNAi. Data are represented as mean ± SD. Scale bar = 100 μm. ****p<0.0001 by Student’s t-test. n=number of animals which were scored. (B) Microscopic images and quantitative data showing fluorescence of Pbcf-1::bcf-1::GFP animals treated with control RNAi or AWC str-130 RNAi. Data are represented as mean ± SD. Scale bar = 100 μm. **p<0.01 by Student’s t-test. n=number of animals which were scored.
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Figure 6—figure supplement 1—source data 1
Numerical data of Figure 6—figure supplement 1A and B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-fig6-figsupp1-data1-v1.xlsx

A model reveals a neural-digestive mechanism for evaluating harmful food.
(A) AWC neuron-expressed NSY-1 detects Staphylococcus saprophyticus (SS) as harmful food and shuts down digestion by inducing the AWCOFF neural circuit and NSY-1-dependent STR-130. This mechanism protects animals and helps them avoid harmful food. (B) Mutations in NSY-1 lead to SS digestion by activating the insulin/IGF-1 signaling (IIS) pathway and BCF-1 expression, thereby reducing the animals' ability to avoid harmful food and decreasing their protection.
Additional files
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Supplementary file 1
List of genes induced by SS food that are dependent on NSY-1.
Related to Figure 4B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-supp1-v1.xlsx
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Supplementary file 2
GO enrichment analysis of 304 NSY-1-dependent candidate genes responding to SS.
Related to Figure 4—figure supplement 1A and B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-supp2-v1.xlsx
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Supplementary file 3
List of genes induced in nsy-1(ag3) mutant animals feeding on SS.
Related to Figure 5B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-supp3-v1.xlsx
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Supplementary file 4
GO enrichment analysis of 308 genes induced by the nsy-1 mutation under SS feeding conditions.
Related to Figure 5—figure supplement 1A and B.
- https://cdn.elifesciences.org/articles/104028/elife-104028-supp4-v1.xlsx
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MDAR checklist
- https://cdn.elifesciences.org/articles/104028/elife-104028-mdarchecklist1-v1.docx