A Fluorescent Dauer Marker in Caenorhabditis inopinata Enables Comparative Analysis of Dauer-Inducing Mechanisms

Dauer larvae are a dormant developmental stage in nematodes that is induced by a range of environmental cues. The molecular mechanisms that transduce these cues to regulate dauer entry have been well characterized in Caenorhabditis elegans, whereas those in other nematode species remain unclear. The closest known sibling species of C. elegans, Caenorhabditis inopinata, occupies a distinct ecological niche and shows an extremely low frequency of dauer formation by starvation in laboratory conditions, suggesting that it could serve as a useful comparative model for analyzing dauer-inducing mechanisms. To support such analysis, we generated a fluorescent dauer reporter, Cin-col-183p::mCherry, in C. inopinata based on a previously reported dauer-specific reporter in C. elegans. This reporter showed fluorescence specifically in the pre-dauer and dauer stages, but not in other developmental stages, indicating that it functions as a dauer-specific marker in C. inopinata. Using these marker strains, we compared the responses to high temperature and RNAi-mediated knockdown of insulin/IGF-1 pathway genes (daf-2, age-1, and pdk-1), and found that dauer induction differs mechanistically between C. elegans and C. inopinata. This dauer-specific fluorescent strain will be a useful tool for investigating the diversity of dauer-inducing mechanisms across nematode species. Article SummaryDauer is a dormant developmental stage in nematodes induced by environmental stress. Although its regulation is well studied in Caenorhabditis elegans, the mechanisms in other species remain unclear. Here, we developed a fluorescent dauer reporter, Cin-col-183p::mCherry, in Caenorhabditis inopinata, a close relative of C. elegans. The reporter was specifically expressed in pre-dauer and dauer stages, confirming its usefulness as a dauer marker. Using this strain, we found that responses to high temperature and insulin/IGF-1 pathway gene knockdown differ between C. elegans and C. inopinata. This reporter will help reveal diversity in dauer-inducing mechanisms across nematode species.