Multiple Signaling Pathways Coordinately Regulate Forgetting of Olfactory Adaptation through Control of Sensory Responses in Caenorhabditis elegans

MACO-1 regulates forgetting of adaptation to diacetyl in the nervous system. A, Schematic depiction of the maco-1 gene and of lesions in maco-1 mutants. Arrows indicate locations of the two maco-1 alleles, and the solid bar indicates a deleted region of qj143. B, Retention of adaptation to diacetyl in maco-1 mutant animals. Chemotaxis of naive, adapted, and 4-h-recovered animals were analyzed (n = 6, 2-way ANOVA, F_strain(3,60) = 8.3, p < 0.001). C–F, Transgenic rescue of maco-1 (qj143) mutant animals by expressing wild-type gene products under the following promoters: Primb-1, Pmyo-3, Podr-1, Podr-10, Prig-3, Pnmr-1, Punc-9, Pglr-4, Pacr-15, and Pasic-1 (Primb-1: n = 12, 2-way ANOVA, F_strain(2,99) = 11.3, p < 0.001; Pmyo-3: n ≥ 6, 2-way ANOVA, F_{strain(2,117)} = 316, p < 0.001; Podr-1: n = 8, 2-way ANOVA, F_strain(2,63) = 16.3, p < 0.001; Podr-10: n = 6, 2-way ANOVA, F_strain(2,45) = 36.1, p < 0.001; Prig-3: n = 8, 2-way ANOVA, F_strain(2,63) = 14.2, p < 0.001; Pnmr-1: n = 10, 2-way ANOVA, F_strain(2,81) = 5.2, p < 0.001; Punc-9: n = 8, 2-way ANOVA, F_strain(2,63) = 7.9, p < 0.001; Pglr-4: n = 14, 2-way ANOVA, F_{strain(2,117)} = 30.5, p < 0.001; Pacr-15: n = 14, 2-way ANOVA, F_{strain(2,117)} = 10.1, p < 0.001; Pasic-1: n ≥ 4, 2-way ANOVA, F_strain(2,75) = 28.2, p < 0.001). **p < 0.01; post hoc t test with Bonferroni's correction (B–F). Error bars represent SEM.

SCD-2 and HEN-1 regulate forgetting of adaptation to diacetyl in the same signaling pathway. A, Schematic depiction of the scd-2 gene and of lesions in scd-2 mutants. Arrows indicate the sites of the two scd-2 alleles, and the solid bar indicates a deleted region of ok565. B, Retention of adaptation to diacetyl in scd-2 mutant animals. Chemotaxis of naive, adapted, and 4-h-recovered animals were analyzed (n = 14, 2-way ANOVA, F_{strain(3,156)} = 15.3, p < 0.001). C, Transgenic rescue of scd-2 (qj141) mutant animals by expressing wild-type gene products under the following promoters: Primb-1 and Punc-14 (Primb-1: n = 12, 2-way ANOVA, F_strain(2,99) = 11.7, p < 0.001; Punc-14: n = 6, 2-way ANOVA, F_strain(2,45) = 17.8, p < 0.001). D, Retention of adaptation to diacetyl in hen-1 (tm501) mutant animals (n = 8), and transgenic rescue of hen-1 (tm501) mutant animals by expressing wild-type gene products under a pan-neuronal promoter (n = 10, 2-way ANOVA, F_strain(2,81) = 3.8, p = 0.0259). E, Retention of adaptation to diacetyl in wild-type, scd-2 (sa249); hen-1 (tm501), and each single mutant (n = 12, 2-way ANOVA, F_{strain(3,132)} = 7.6, p < 0.001). *p < 0.05, **p < 0.01; post hoc t test with Bonferroni's correction (B–E). Error bars represent SEM.

MACO-1 and SCD-2/HEN-1 function in the distinct signaling pathway. A, Retention of adaptation to diacetyl in wild-type and in maco-1 (qj143); scd-2 (ok565), and each single mutant (n ≥ 8, 2-way ANOVA, F_{strain(2,132)} = 457.2, p = 0.0049). B, Retention of adaptation to isoamyl alcohol in wild-type, maco-1 (qj143), scd-2 (qj141), and hen-1 (tm501) animals (n ≥ 6). **p < 0.01; post hoc t test with Bonferroni's correction (A) or Student's t test (B). Error bars represent SEM.

Ca²⁺ responses of AWA sensory neurons after adaptation and recovery. A, Averaged traces of Ca²⁺ response in AWAs in naive, diacetyl-adapted, and 4-h-recovered animals (n ≥ 8). Timing of the diacetyl stimulation is shown as black bars. R represents the YFP/CFP ratio, and R₀ represents the averaged ratio 30 s before diacetyl stimulation. B, Quantification of Ca²⁺ responses of wild-type, maco-1 (qj143), and scd-2 (qj141) animals (n ≥ 8, 2-way ANOVA, F_{strain(2,114)} = 88.7, p < 0.001). Data were normalized to the averages in the naive animals. C, Transgenic rescue of maco-1 (qj143) mutant animals by expressing wild-type gene under a pan-neuronal promoter (n ≥ 5, 2-way ANOVA, F_{strain(4,148)} = 88.2, p < 0.001). D, Transgenic rescue of scd-2 (qj141) mutant animals by expressing wild-type gene under rimb-1 and odr-10 promoters (n ≥ 6, 2-way ANOVA, F_{strain(4,150)} = 7.4, p < 0.001). *p < 0.05, **p < 0.01; post hoc t test with Bonferroni's correction (B–D). Error bars represent SEM.

The activity of AWC neurons during recovery is important for forgetting adaptation. A, Retention of olfactory adaptation to pyrazine in wild-type and tir-1 (tm3036) animals (n = 6). B, Retention of olfactory adaptation to pyrazine in wild-type animals expressing the Drosophila histamine-gated chloride channel in AWC neurons. The timing of application of histamine is shown in the figure. Chemotaxis of naive, adapted, and 4-h-recovered animals was analyzed (n = 12). C, Quantification of Ca²⁺ responses in AWA neurons of wild-type animals expressing histamine-gated chloride channels in AWC neurons (n ≥ 8). Data were normalized to the averages in the naive animals. **p < 0.01; t test with Bonferroni's correction (A) or Student's t test (B, C). Error bars represent SEM.