Calreticulin is required for responding to stress, foraging, and fertility in the white-tip nematode, Aphelenchoides besseyi

Abstract

Calreticulin (CRT) regulates a wide array of cellular responses in physiological and pathological processes. A full-length cDNA-encoding CRT protein, namely AbCRT-1, was isolated from Aphelenchoides besseyi, an ectoparasitic plant nematode and the agent of white tip disease of rice. The deduced amino acid sequence of AbCRT-1 was highly homologous with other nematode CRTs, and showed the closest evolutionary relationship with BxCRT-1. In-situ hybridization showed that AbCRT-1 is specifically located in the oesophageal gland and gonads of A. besseyi, suggesting its potential role in parasitism and reproduction. Quantity real-time PCR analysis showed that AbCRT-1 is highly expressed in female nematodes but poorly expressed in eggs, juveniles, and male nematodes. Exposing the nematode to relatively low osmotic stress promotes the transcription of AbCRT-1 whereas extreme desiccation suppresses the transcription significantly. Nematodes in which AbCRT-1 mRNA level had been knocked down by soaking them in AbCRT-1 dsRNA solution distributed randomly and did not aggregate temporally, with a decreased capacity of food discernment. Thus the affected nematodes were markedly less fecund. These results demonstrate that AbCRT-1 is required in A. besseyi for responding to stress, foraging, and fertility.

Keywords: Aphelenchoides besseyi; Calreticulin; RNAi; cDNA cloning.