BACKGROUNDThe stage-specific expression of genes is one of the most characteristics of parasites. It has been found that a lot of genes of Spriometra erinaceieuropaei are specifically expressed in pleroceroid in large amount, but not expressed when the plerocercoid development into adult worm. The study is to screen other stage-specific ecpression genes of plerocercoid of Spirtmetra erinceieuropaei.

METHODSRNA was separately extracted by acid guanidinium thiocyanate-phenol-chloroform from plerocercoids and adult worms of Spirometra erinaceieuropaei, DNA contaminated in the RNA was digested by RNase-free DNase. After the RNA was reverse transcripted to cDNA using T12MA, T12MC, T12MG and T12MT anchor-primers, PCR was done using the same T12MN and one random primer with alpha 35S-dATP in the system. The PCR products were fractionated on an 8% denatured polyacrylamide gel. Differential bands of the plerocercoid found in the gel were cut out, amplified by PCR and sequenced. Northern hybridization was used to identify the stage-specific expression genes.

RESULTSEleven differential bands were selected from the gel and classified into 3 kinds of gene fragments by hybridization, after they were amplified by PCR. Fragments 1 (238 bp) and 2 (383 bp), were confirmed by Northern hybridization, as being expressed in the plerocercoid. However, fragment 3 (433 bp), was expressed in both the plerocercoid and the adult worm. Data from the 3 gene fragments underwent homological analysis in GenBank. The sequence which was homologous with fragments 1 and 2 was not found, but fragment 3 had high homology with many kinds of 28S rRNA.

CONCLUSIONSThe gene expressions of plerocercoids are different from adult worms because they live in different hosts. Two types of different gene fragments from the plerocercoid were found by mRNA differential display technique.