Trehalose metabolism genes of Aphelenchoides besseyi (Nematoda: Aphelenchoididae) in hypertonic osmotic pressure survival

Abstract

Some organisms can survive extreme desiccation caused by hypertonic osmotic pressure by entering a state of suspended animation known as osmobiosis. The free-living mycophagous nematode Aphelenchoides besseyi can be induced to enter osmobiosis by soaking in osmolytes. It is assumed that sugars (in particular trehalose) are instrumental for survival under environmental stress. In A. besseyi two putative trehalose-6-phosphate synthase genes (TPS) encode enzymes catalyzing trehalose synthesis and a putative trehalase genes (TRE) encodes enzymes that catalyze hydrolysis of trehalose were identified and then characterized based on its transcriptome. RT-qPCR analyses showed that each of these genes is expressed as mRNA when A. besseyi is entering in, during and recovering from osmobiosis, but only for certain periods. The changes of TRE activity were consisted with the transcript level changes of TRE gene and the trehalose level declined a lot at certain periods when the nematodes were in osmobiosis as well as recovering from osmobiosis. Which suggested that the hydrolysis of threhalose is essential. The feeding method of RNA interference (RNAi) was used to temporarily knock down the expression of each of the TPS and TRE genes. No obviously different phenotype was observed from any of the genes silenced individually or simultaneously but the survival under hypertonic osmotic pressure reduced significantly and the recovery was delayed. These results indicated that trehalose metabolism genes should play a role in osmobiosis regulation and also function within a restricted time frame.