MUT-7 participates in generating small regulatory RNAs in a wide range of biological processes, but how it has multiple cellular functions and whether these roles work together still remain unclear. In an odor signal transduction in AWC olfactory neurons, we present evidence that MUT-7 not only has a dual function in different cellular localization, but also coordinates each other in promoting long-term odor adaptation. We showed previously that prolonged exposure to the AWC-sensed odor butanone results in cGMP dependent protein kinase EGL-4 accumulation in the AWC nucleus. EGL-4 activates both the HP1 homolog HPL-2 and MUT-7. Further, a guanylyl cyclase ODR-1 is downregulated by increased
odr-1 siRNA directing HPL-2 bound to tri-methylated histone H3 lysine 9 (H3K9) to silence transcription. Here, we show that the cytoplasmic MUT-7 conducts
odr-1 siRNA production by using TaqMan quantitative reverse transcription PCR assays. Bimolecular fluorescence complementation analysis shows that the
odr-1 siRNAs bound to an Argonaute protein NRDE-3 are imported into the AWC nucleus to induce the nuclear MUT-7 phosphorylation by nuclear EGL-4. Moreover, appropriate dual-function MUT-7 is required for the interaction between HPL-2 and methylated H3K9 in a transcriptional silencing event. Thus, MUT-7 displays dual localization and their dual function is important to fine tune how an environmental signal dynamically regulates small RNA-mediated epigenetic modification to shape behavior.