Research ArticleCell Biology

Olfactory experience primes the heat shock transcription factor HSF-1 to enhance the expression of molecular chaperones in C. elegans

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Science Signaling  17 Oct 2017:
Vol. 10, Issue 501, eaan4893
DOI: 10.1126/scisignal.aan4893
  • Fig. 1 Olfactory learning enhances HSF-1 activation.

    (A) Schematic of olfactory training and subsequent choice assay. Animals were reared on OP50, and naïve animals or animals pre-exposed to PA14 or OP50 odors were given a choice between PA14 lawns and OP50 lawns. The PA14 and OP50 lawns on the choice plate were 1 inch apart and grown as described in Materials and Methods. Animals were placed in the center, equidistant from both lawns, and the number of animals that migrated onto each lawn was tracked over time. A choice index (CI) at each time point scored, over 4 hours was calculated as shown. (B) CI for PA14 of wild-type animals pre-exposed to the odor of either OP50 or PA14 and then offered the choice between OP50 and PA14 lawns. Preference was recorded at the times indicated on the x axis. n = 16 to 17 experiments of 30 animals per condition. Student’s paired t test, *P < 0.05 and **P < 0.01. (C) Survival of hsf-1 knockdown animals on PA14. n = 3 experiments of 50 animals per condition. Log-rank test, P = 0. See table S1. (D to F) hsp-70 (F44E5.4/F44E5.5), hsp-16.2 (Y46H3A.3), and hsp-16.41 (Y46H3A.2) mRNA abundance measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR) upon exposing animals that had been trained on OP50 or PA14 odor to a lawn of PA14. Values were normalized to wild-type animals pre-exposed to OP50 odor. n = 38 (D), n = 12 (E), and n = 10 (F) experiments of 30 animals per condition. Pairwise mean comparison from linear mixed model analysis, **P < 0.01 and ***P < 0.001. Data represent means ± SEM for (B), (D), (E), and (F). Data in (C) represent total animals across all experiments. n.s., not significant.

  • Fig. 2 2AA enhances olfactory avoidance behavior and HSF-1 activation.

    (A) CI of wild-type animals for PA14 after pre-exposure to the odor of either water or 2AA and then offered the choice between OP50 and PA14 lawns. Preference was recorded at the times indicated on the x axis. n = 10 experiments of 30 animals per condition. Student’s t test, *P < 0.05, **P < 0.01, and ***P < 0.001. (B) hsp-70 (F44E5.4/F44E5.5) mRNA abundance measured by qRT-PCR in wild-type animals that were pre-exposed to the odor of water or 2AA and subsequently placed on a PA14 or OP50 lawn. Values are relative to animals pre-exposed to water. n = 3 to 21 experiments of 30 animals per condition. Pairwise mean comparison from linear mixed model analysis, ***P < 0.001. (C and D) Life-span curves of animals (C) continuously exposed to water (control) or 2AA odor, or (D) in physical contact with water-treated (control) or 2AA-treated OP50. n = 3 experiments of 50 animals per condition. Log-rank tests indicated no significant differences between experimental groups. (E) Survival of wild-type animals on PA14 after pre-exposure to OP50 or PA14 odor. n = 8 experiments of 50 animals per condition. Log-rank test, P < 0.001. Also see table S4. Data in (A) and (B) represent means ± SEM, and data in (C) to (E) represent total animals across all experiments.

  • Fig. 3 Serotonin is required for HSF-1 activation in response to olfactory learning.

    (A) CI for PA14 of wild-type and tph-1(mg280)II animals pre-exposed to the odor of PA14 before being offered the choice between OP50 and PA14 lawns. Preference was recorded at the times indicated on the x axis. n = 3 to 4 experiments of 30 animals per condition. Student’s two-sample t test (unequal variance), *P < 0.05. (B) CI for PA14 of tph-1(mg280)II animals pre-exposed to the odor of PA14 compared to the choice indices in tph-1(mg280)II animals treated with exogenous 5-HT and pre-exposed to PA14 odor before being offered the choice between OP50 and PA14 lawns. n = 4 experiments of 30 animals per condition. Student’s paired t test, *P < 0.05, **P < 0.01, and ***P < 0.001. (C) hsp-70 (F44E5.4/F44E5.5) mRNA abundance measured by qRT-PCR upon PA14 exposure in wild-type and tph-1(mg280)II animals pre-exposed to the odor of OP50 or PA14. Values are relative to wild-type animals pre-exposed to the odor of OP50. n = 9 experiments of 30 animals per condition. Pairwise mean comparison from linear mixed model analysis, **P < 0.01 for wild type (odor + PA14 lawn). No significance for tph-1(mg280)II (odor + PA14 lawn). (D) hsp-70 (F44E5.4/F44E5.5) mRNA abundance measured by qRT-PCR after exposure of animals to exogenous 5-HT. Values are relative to control water-treated animals. n = 7 experiments of 20 to 30 animals per condition. Student’s paired t test, *P < 0.05.

  • Fig. 4 Serotonin-mediated learning activates HSF-1 throughout the animal.

    (A to C) smFISH confocal micrographs showing hsp-70 (F44E5.4/F44E5.5) mRNA and 4′,6-diamidino-2-phenylindole (DAPI) in wild-type and tph-1(mg280)II animals pre-exposed to OP50 or PA14 odor and subsequently placed on a PA14 lawn. Images are projected z-stack images of 10-μm sections across the (A) head, (B) intestine, and (C) germ line. Arrowheads indicate hsp-70 (F44E5.4/F44E5.5) mRNA foci. Scale bars, 10 μm. (D to F) Quantification of the number of hsp-70 (F44E5.4/F44E5.5) foci in projected images. n = 8 to 11 animals per tissue per genotype per condition, quantified from two to three independent experiments. Student’s paired t test, *P < 0.05 for wild type (OP50 odor + PA14 lawn) compared to (PA14 odor + PA14 lawn). No significance for tph-1(mg280)II (OP50 odor + PA14 lawn) compared to (PA14 odor + PA14 lawn). Data represent means ± SEM.

  • Fig. 5 Olfactory learning primes HSF-1 through the formation of HSF-1 nuclear bodies.

    (A) HSF-1::GFP localization in germline nuclei of control animals at ambient temperature, animals on a PA14 lawn, animals exposed to water or 2AA odor, and animals after 30 min of recovery after exposure to water or 2AA odor. Arrowheads indicate HSF-1 nuclear bodies. Scale bar, 5 μm. (B) Quantification of HSF-1 nuclear bodies under all conditions listed in (A). n = 33 to 39 nuclei per animal, 17 to 25 animals per condition, across three to four independent experiments. Student’s two-sample t test (unequal variance), **P < 0.01 for odor only. No significance was detected for (odor + 30-min recovery). (C) hsp-70 (F44E5.4/F44E5.5) mRNA abundance measured by qRT-PCR after exposure of animals to the odor of water or 2AA and allowed to recover for 30 min on OP50 lawn before being placed on PA14 lawns. n = 5 to 9 experiments of 30 animals per experiment. Pairwise mean comparison from linear mixed model analysis. No significance was detected. (D) Confocal micrographs (individual z-sections) showing HSF-1 localization in germline nuclei of wild-type and tph-1(mg280)II animals exposed to water odor or exposed to 2AA odor alone before being placed on a PA14 lawn. Scale bar, 5 μm. (E) Quantification of HSF-1 nuclear bodies under all conditions shown in (D). n = 50 to 55 nuclei per animal, 8 to 18 animals per condition, across two to three independent experiments. Student’s two-sample t test (unequal variance), *P < 0.05.

  • Fig. 6 Olfactory learning primes HSF-1 by increasing its association with RNA pol II.

    (A) Immunofluorescence confocal micrographs (individual z-sections) showing HSF-1, NPCs, and DAPI in germline nuclei of wild-type animals exposed to water odor, 2AA odor, or heat shock. Scale bar, 5 μm. (B) Quantification of numbers of total HSF-1 nuclear bodies per nucleus and (C) HSF-1 nuclear bodies per nucleus that colocalize with NPCs. n = 30 to 36 nuclei per animal, four to six animals per condition per experiment, two independent experiments. (B) Student’s two-sample t test (unequal variance), *P < 0.05 when water odor is compared to heat shock. (C) No significance between all conditions. (D) Immunofluorescence confocal micrographs (individual z-sections) of HSF-1, RNA pol II, and DAPI in germline nuclei of dissected animals expressing HSF-1::GFP after exposure to water odor, 2AA odor, water odor + PA14 lawn, 2AA odor + PA14 lawn, or heat shock. Scale bar, 5 μm. (E and F) Quantification of numbers of (E) total HSF-1::GFP nuclear bodies per nucleus and (F) HSF-1 nuclear bodies per nucleus that colocalize with RNA pol II in (D). n = number of nuclear bodies per nucleus in 68 to 82 nuclei per animal, 8 to 12 animals per condition per experiment, three independent experiments. Student’s two-sample t test (unequal variance), *P < 0.05. (B, D, and F). Data represent means ± SEM.

  • Fig. 7 5-HT signaling couples olfactory information with HSF-1 activation to mark sensory stimuli as threats.

    (A) CI for PA14 of wild-type animals subjected to control RNAi (empty vector) or hsf-1 RNAi after being exposed to the odor of PA14 or to the odor of the control RNAi–expressing bacteria. Preference was recorded 4 hours after animals were exposed to the corresponding odors and placed on the choice plates. n = 5 to 6 experiments of 30 animals per condition. Student’s two-sample t test (unequal variance), *P < 0.05. Data represent means ± SEM. (B) Schematic of olfactory pre-exposure to HT115 odor in conjunction with optogenetic excitation of serotonergic neurons followed by behavioral choice assay. ATR+ indicates the presence of all-trans-retinal (ATR), which is required for the light-induced excitation of channelrhodopsin in the serotonergic neurons and subsequent release of 5-HT. ATR− indicates control, mock-excited animals. (C) CI for HT115 in animals ± ATR after optogenetic excitation of serotonergic neurons. The choice offered was between HT115 and PA14 lawns. n = 6 experiments in triplicate of 10 animals per condition. Student’s paired t test, *P < 0.05. Data represent means ± SEM. (D) Model: 5-HT–dependent olfactory learning facilitates the association between RNA pol II and HSF-1, resulting in enhanced avoidance behavior as well as enhanced transcription of HSF-1 targets in a stressor-specific manner.

Supplementary Materials

  • www.sciencesignaling.org/cgi/content/full/10/501/eaan4893/DC1

    Fig. S1. Design and specificity of olfactory pre-exposure and choice assay.

    Fig. S2. The compound 2AA made by PA14 specifically modulates olfactory avoidance behavior and protects against PA14-induced death.

    Fig. S3. Serotonin is required for learning-mediated HSF-1 activation.

    Fig. S4. Characterization of C. elegans HSF-1.

    Fig. S5. Characterization of C. elegans HSF-1 after exposure to water odor and 2AA odor.

    Fig. S6. The formation of HSF-1 nuclear bodies does not require RNA pol II.

    Fig. S7. HSF-1 is required for olfactory learning.

    Table S1. Survival of animals on PA14 is dependent on HSF-1.

    Table S2. Statistical analyses.

    Table S3. 2AA does not appear to be toxic to C. elegans.

    Table S4. Pre-exposure to the odor of PA14 protects animals from subsequent exposure to PA14.

    Table S5. Primers used for qRT-PCR analysis.

    Table S6. Primers used for ChIP-PCR and ChIP-qPCR analysis.

  • Supplementary Materials for:

    Olfactory experience primes the heat shock transcription factor HSF-1 to enhance the expression of molecular chaperones in C. elegans

    Felicia K. Ooi and Veena Prahlad*

    *Corresponding author. Email: veena-prahlad{at}uiowa.edu

    This PDF file includes:

    • Fig. S1. Design and specificity of olfactory pre-exposure and choice assay.
    • Fig. S2. The compound 2AA made by PA14 specifically modulates olfactory avoidance behavior and protects against PA14-induced death.
    • Fig. S3. Serotonin is required for learning-mediated HSF-1 activation.
    • Fig. S4. Characterization of C. elegans HSF-1.
    • Fig. S5. Characterization of C. elegans HSF-1 after exposure to water odor and 2AA odor.
    • Fig. S6. The formation of HSF-1 nuclear bodies does not require RNA pol II.
    • Fig. S7. HSF-1 is required for olfactory learning.
    • Table S1. Survival of animals on PA14 is dependent on HSF-1.
    • Table S2. Statistical analyses.
    • Table S3. 2AA does not appear to be toxic to C. elegans.
    • Table S4. Pre-exposure to the odor of PA14 protects animals from subsequent exposure to PA14.
    • Table S5. Primers used for qRT-PCR analysis.
    • Table S6. Primers used for ChIP-PCR and ChIP-qPCR analysis.

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    Citation: F. K. Ooi, V. Prahlad, Olfactory experience primes the heat shock transcription factor HSF-1 to enhance the expression of molecular chaperones in C. elegans. Sci. Signal. 10, eaan4893 (2017).

    © 2017 American Association for the Advancement of Science

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