Differential expression of microRNA-2b with potential target coding P25 in the fifth instar larvae posterior silk gland of the silkworm

MicroRNAs (miRNAs) are a class of non-protein coding small RNAs that regulate a gene expression at the post-transcriptional level. Using in silico screening, we found that the 3'-untranslated regions of the P25 gene mRNA are perfectly complementary to nucleotides 2-8 at the 5' end of the miRNA-2b (miR-2b). The expression of miR-2b and the P25 gene in posterior silk gland of the fifth instar larval silkworm was investigated using real-time PCR detection method. The results indicated that expression of the P25 gene was very high in the posterior silk gland during the fifth instar larvae, whereas a level of miR-2b sharply decreased until reaching the lowest one on the 8th day. The expression patterns of miR-2b and P25 gene indicate that miR-2b might act as a fine-tuning regulator of expression of the P25 gene at the post-transcriptional level.