Transcriptomic and proteomic analysis of anhydrobiosis in Panagrolaimus superbus and Caenorhabditis elegans dauer larvae

Many organisms are able to survive the loss of up to 95% of their cellular fluid by entering a state of suspended animation known as anhydrobiosis. The mechanisms which allow these organisms to survive desiccation are poorly understood. The nematodes Panagrolaimus superbus and Caenorhabditis elegans are able to survive extreme desiccation. These nematodes have contrasting strategies for surviving desiccation perhaps defined by the habitats in which they evolved. P. superbus was originally isolated in 1981 from a gull’s nest in Surtsey, Iceland. In contrast C. elegans adults inhabit rotting fruit, a stable environment, less susceptible to desiccation. However, C. elegans does possess a stress resistant dauer larval stage in which the larvae are able to survive desiccation. The aim of this project was to identify the genes and proteins involved in desiccation tolerance in P. superbus and C. elegans dauer larvae. The genes which were differentially expressed in response to desiccation and recovery in P. superbus and C. elegans dauer larvae were identified using RNA-seq technology. The mechanisms of desiccation tolerance were further investigated in P. superbus and C. elegans dauer larvae by using quantitative proteomic methods. In C. elegans dauer larvae and P. superbus, the following processes and pathways were implicated in the response to desiccation at both the transcriptome and proteome level: molecular chaperone activity, molecular shield activity, antioxidants, compatible solutes, the ubiquitin proteasome system, autophagy, DNA repair, cellular repair and response to pathogens. While there was much overlap in the identities of the genes and proteins which were up-regulated in response to dehydration, differences were also observed, which could be a reflection of the differences in the adaptive strategies used by these two nematode species to combat desiccation. Desiccation responsive gene candidates were selected for functional analyses using RNAi in C. elegans dauer larvae. This RNAi study revealed the importance of genes encoding hydrophilic proteins, molecular chaperones, trehalose phosphate synthase and glycerol kinase, as well as previously uncharacterised genes in enabling C. elegans dauer larvae to successfully survive desiccation. The data presented in this thesis show that substantial reorganisation of cellular structures and mobilization of cellular protection repair systems occurs in C. elegans dauer larvae and P. superbus in response to desiccation, indicating that anhydrobiotic survival requires a major, integrated organismal response