MAPK phosphorylation is implicated in the adaptation to desiccation stress in nematodes

Some nematodes can survive almost complete desiccation by entering an ametabolic state called anhydrobiosis requiring the accumulation of protective molecules such as trehalose and LEA proteins. However, it is not known how anhydrobiotic organisms sense and regulate the response to water loss. Mitogen-activated protein kinases (MAPKs) are highly conserved signalling proteins that regulate adaptation to various stresses. Here, we first compared the anhydrobiotic potential of three nematode species, Caenorhabditis elegans, Aphelenchus avenae and Panagrolaimus superbus, and then determined the phosphorylation status of the MAPKs p38, JNK and ERK during desiccation and rehydration. Caenorhabditis elegans was unable to undergo anhydrobiosis even after an initial phase of slow drying (preconditioning), while A. avenae did survive desiccation after preconditioning. In contrast, P. superbus withstood desiccation under rapid drying conditions, although survival rates improved with preconditioning. These results characterise C. elegans as desiccation sensitive, A. avenae as a slow desiccation strategist anhydrobiote and P. superbus as a fast desiccation strategist anhydrobiote. Both C. elegans and A. avenae showed increased MAPK phosphorylation during drying, consistent with an attempt to mount protection systems against desiccation stress. In P. superbus, however, MAPK phosphorylation was apparent prior to water loss and then decreased on dehydration, suggesting that signal transduction pathways are constitutively active in this nematode. Inhibition of p38 and JNK in P. superbus decreased its desiccation tolerance. This is consistent with the designation of P. superbus as a fast desiccation strategist and its high level of preparedness for anhydrobiosis in the hydrated state. These findings show that MAPKs play an important role in the survival of organisms during anhydrobiosis.