Abstract: Phosphatidylinositol 3-kinase, as one of important signal transduction factors, plays an important role in cell growth and regulation activities. Silkworm phosphatidylinositol 3-kinase gene, named as Bmpi3k, was cloned by searching the silkworm (Bombyx mori) expressed sequence tags (EST), genomic DNA prediction, and RT-PCR. Its mRNA was 3 368 bp in full-length with an open reading frame (ORF) of 3 165 bp encoding a protein of 1 055 amino acids. The protein molecular weight was 122.79 kDa with the isoelectric point of 7.32. It contains five specific conserved domains of PI3K protein. The results suggested that BmPI3K was involved in a major life activity of silkworm．

Key words: Bombyx mori, Bmpi3k, silico cloning, expression sequence tag (EST)