Identification of responsible gene polymorphisms that determine temperature acclimation diversity
Because temperature is important environmental information for survival, organisms have accumulated natural variation in the genomes and adapted to temperature changes in their respective habitats. This study identified the smrn-1 gene as the responsible gene polymorphism for temperature acclimation diversity exhibited by natural variation strains of the nematode Caenorhabditis elegans. The AB1 strain from Australia quickly acclimated to the new temperature, whereas CB4856 from Hawaii slowly acclimated. smrn-1 which is the gene responsible for this difference in temperature acclimation accumulated small RNA (sRNA) during embryogenesis and was loaded onto Argonaute proteins, including HRDE-1. Transcriptome profiling of smrn-1 and hrde-1 mutant identified a key neurogenesis regulator (crml-1) as one of the downstream targets. In adult stages, smrn-1 was expressed in the O2 and CO2 sensory neuron BAG and controlled axonogenesis. O2 information from BAG O2 sensory neurons regulated temperature acclimation by affecting the thermoresponsivity of ADL thermosensory neurons. AB1 and CB4856 showed diversity of ADL thermoresponsivity and temperature acclimation when cultivated at high O2 concentrations but did not show these diversities under low O2 concentrations. This study proposed a model in which C. elegans natural variation strains respond to their environment by modulating the sRNA pathway and diversifying neural circuits during embryogenesis.