Characterization and profiling of MicroRNAs in posterior silk gland of the silkworm ( Bombyx mori )

MicroRNAs (miRNAs) regulate expression of genes at post-transcriptional level by binding on complementary sequences of target mRNAs and play multiple roles in biological processes. To investigate the differential expression of miRNAs in posterior silk gland (PSG) of silkworm (Bombyx mori) in different periods and regulation of miRNAs on the expression of fibroin genes, Solexa sequencing technology was used to detect miRNAs in PSGs of fourth-instar day-2 larvae and fifth-instar day-3 larvae, respectively. As a result, 466 previously reported miRNAs, and 35 novel miRNAs were detected, and 499 of these detected miRNAs are predicted to target 13,383 genes by target prediction softwares. Additionally, 29 miRNAs expressed differently between the PSG of fourth-instar day-2 larvae and fifth-instar day-3 larvae were found, and the differential expression of these miRNAs may play an important role in the expression of fibroin genes.