Abstract: Testis is the generative gland in silkworm Bombyx mori that produces spermatozoa. A complete understanding of proteins expressed in the testis will provide biological information on development and reproduction in males of the silkworm. We investigated the testis proteins of 5th instar day 5 larvae of the silkworm using two-dimensional polyacrylamide gel electrophoresis and silver staining, followed by computer-assisted analysis. Then, the matrix-assisted laser desorption ionization time of flight mass spectrometry was applied to identify the major protein spots of the 2D map with peptide mass fingerprinting data. The results showed that over 1 000 spots were obtained by silver staining. The profiles of silkworm tissue proteins were established in a pI range of 3.5-9 and a molecular mass range of 15 kD to 90 kD. Among them, 60 proteins were identified successfully, which were divided into 8 groups according to their known or putative functions, including cytoskeleton and cell structure （cell differentiation）, membrane protein receptors or cell signaling related, stress response （chaperones）, mitochondrial and energy production related, translational and transcriptional regulation or DNA/RNA binding related, enzymes and blood components. Many proteins play important roles in flagellar formation, energy metabolism and meiosis. These results may provide valuable biological information for investigating spermiogenesis in the silkworm.

Key words: Bombyx mori, testis, spermiogenesis, proteins, 2D-electrophoresis, peptide mass fingerprinting, mass spectrometry, bioinformatical analysis