Trehalose metabolism genes render rice white tip nematode, Aphelenchoides besseyi (Nematoda: Aphelenchoididae) resistant to anaerobic environment

Abstract

After experiencing anaerobic environments, Aphelenchoides besseyi will enter a state of suspended animation known as anoxybiosis, which may use trehalose for energy supply to survive. To identify the function of trehalose metabolism, two trehalose-6-phosphate synthase (TPS) genes (Ab-tps1 and Ab-tps2) encoding enzymes catalyzing trehalose synthesis and three trehalase (TRE) genes (Ab-ntre1, Ab-ntre2 and Ab-atre) encoding enzymes catalyzing the hydrolysis of trehalose were identified and investigated. Ab-tps1 and Ab-tps2 were active when A. besseyi was during certain periods of anoxybiosis and Ab-tps2, Ab-ntre1, Ab-ntre2 and Ab-atre were active when A. besseyi was during certain periods of recovery. The results of RNA interference experiments suggested that TRE genes regulated each other and both TPS genes; while a single TPS gene only regulated the other TPS gene but two TPS genes together could regulate TRE genes, which indicated a feedback mechanism between these genes. All these genes also positively regulated the survival and the resumption of active metabolism of the nematode. Whereas, genes functioning at reaeration impact more on nematode survival, revealing that these genes should play roles in anoxybiosis regulation but may function within restricted time frames. The quantity of trehalose level and TRE activity were complementary during the anoxybiosis-reaeration process, manifesting that trehalose may act as an energy supply source. The observation of obviously up-regulations of TPS genes during anoxybiosis suggested a possible signal role of trehalose. Also trehalose metabolism genes were supposed to work together to control trehalose level to a certain magnitude when the nematode was under anaerobic environment.