Expression profiling and cross-species RNA\ud interference (RNAi) of desiccation-induced\ud transcripts in the anhydrobiotic nematode\ud Aphelenchus avenae

摘要

Background: Some organisms can survive extreme desiccation by entering a state of suspended animation known\udas anhydrobiosis. The free-living mycophagous nematode Aphelenchus avenae can be induced to enter\udanhydrobiosis by pre-exposure to moderate reductions in relative humidity (RH) prior to extreme desiccation. This\udpreconditioning phase is thought to allow modification of the transcriptome by activation of genes required for\uddesiccation tolerance.\udResults: To identify such genes, a panel of expressed sequence tags (ESTs) enriched for sequences upregulated in\udA. avenae during preconditioning was created. A subset of 30 genes with significant matches in databases,\udtogether with a number of apparently novel sequences, were chosen for further study. Several of the recognisable\udgenes are associated with water stress, encoding, for example, two new hydrophilic proteins related to the late\udembryogenesis abundant (LEA) protein family. Expression studies confirmed EST panel members to be upregulated\udby evaporative water loss, and the majority of genes was also induced by osmotic stress and cold, but rather fewer\udby heat. We attempted to use RNA interference (RNAi) to demonstrate the importance of this gene set for\udanhydrobiosis, but found A. avenae to be recalcitrant with the techniques used. Instead, therefore, we developed a\udcross-species RNAi procedure using A. avenae sequences in another anhydrobiotic nematode, Panagrolaimus\udsuperbus, which is amenable to gene silencing. Of 20 A. avenae ESTs screened, a significant reduction in survival of\uddesiccation in treated P. superbus populations was observed with two sequences, one of which was novel, while\udthe other encoded a glutathione peroxidase. To confirm a role for glutathione peroxidases in anhydrobiosis, RNAi\udwith cognate sequences from P. superbus was performed and was also shown to reduce desiccation tolerance in\udthis species.\udConclusions: This study has identified and characterised the expression profiles of members of the anhydrobiotic\udgene set in A. avenae. It also demonstrates the potential of RNAi for the analysis of anhydrobiosis and provides the\udfirst genetic data to underline the importance of effective antioxidant systems in metazoan desiccation tolerance.