A novel nematode species from the Siberian permafrost shares adaptive mechanisms for cryptobiotic survival with C. elegans dauer larva

Abstract

Some organisms in nature have developed the ability to enter a state of suspended metabolism called cryptobiosis when environmental conditions are unfavorable. This state-transition requires execution of a combination of genetic and biochemical pathways that enable the organism to survive for prolonged periods. Recently, nematode individuals have been reanimated from Siberian permafrost after remaining in cryptobiosis. Preliminary analysis indicates that these nematodes belong to the genera Panagrolaimus and Plectus. Here, we present precise radiocarbon dating indicating that the Panagrolaimus individuals have remained in cryptobiosis since the late Pleistocene (~46,000 years). Phylogenetic inference based on our genome assembly and a detailed morphological analysis demonstrate that they belong to an undescribed species, which we named Panagrolaimus kolymaensis. Comparative genome analysis revealed that the molecular toolkit for cryptobiosis in P. kolymaensis and in C. elegans is partly orthologous. We show that biochemical mechanisms employed by these two species to survive desiccation and freezing under laboratory conditions are similar. Our experimental evidence also reveals that C. elegans dauer larvae can remain viable for longer periods in suspended animation than previously reported. Altogether, our findings demonstrate that nematodes evolved mechanisms potentially allowing them to suspend life over geological time scales.

Parthenogenomics: Insights on mutation rates and nucleotide diversity in parthenogenetic Panagrolaimus nematodes

“…Parthenogenetic Panagrolaimus nematodes analyzed in this study have been found to be triploid by Schiffer et al (2019) and other asexual representatives of the genus are also triploid (Shatilovich et al, 2023). The lower rate of differentiation among sexual lines from the MAL experiment in comparison to asexual lines could be explained by (i) lower standing genetic variation in the hermaphroditic parent at the beginning of the experiment and (ii) increased heterozygosity for asexuals arising from the third genome copy.…”

Understanding the factors regulating host–microbiome interactions using Caenorhabditis elegans

“…This is a fascinating area for future research in C. elegans, as it is likely that many host-microbiome co-evolutionary processes have occurred with the dauer state. Given that the dauer stage probably acts as a transport mechanism for some bacteria, dauers could possibly help in the survival of resident microbes between discontinuous food sources [51] and across geological time scales through suspended metabolism (cryptobiosis) [52]. The microbiome is known to play a major role in the development and maintenance of host immunity.…”

Revisiting genomes of non-model species with long reads yields new insights into their biology and evolution

“…This strain has been isolated in North Carolina, USA by Paul Sterneberg, and is thought to be a triploid allopolyploid (3n=12) [19]. Previous studies have found it shares a common origin of parthenogenesis with most Panagrolaimus asexual strains, from a hybridization event estimated to have occurred 1.3-8.5 Million years ago [19,20]. To date, over 140 strains of the genus have been documented (NCBI Taxonomy Browser), however only nine, largely fragmented, draft genome assemblies are available on GenBank (accessed on 06.10.2023).…”

“…This widely distributed group includes strains isolated from extreme environments such as Antarctica, the volcanic island of Surtsey and the Russian permafrost. Representatives of the genus from these locations have been found to be freezing-tolerant undergoing cryptobiosis [20,21], and P. sp. PS1159 has also shown anhydrobiotic potential as a fast desiccation strategist [22].…”