Serine protease inhibitors (SPIs) play a key role in physiological responses by controlling protease activities. In this study, we studied the biochemical functions of serpin-15, an SPI, from Bombyx mori (Bmserpin-15). Recombinant Bmserpin-15 was expressed in Escherichia coli cells and used to raise rabbit anti-Bmserpin-15 polyclonal antibodies. Bmserpin-15 mRNA and protein expression was detected in all tested tissues, particularly in the fat body and silk gland. After challenge with four different microorganisms (Escherichia coli, Beauveria bassiana, Micrococcus luteus and B. mori nuclear polyhedrosis virus), the expressions of Bmserpin-15 mRNA and protein were induced significantly, particularly by B. bassiana and M. luteus. Recombinant Bmserpin-15 inhibited prophenoloxidase activation, but did not affect phenoloxidase activity, in B. mori hemolymph. Injection of recombinant Bmserpin-15 into B. mori larvae reduced significantly the transcript levels of antimicrobial peptides in fat body. Our results suggested that Bmserpin-15 plays an important role in the innate immunity of B. mori.
Keywords: AMPs; Bombyx mori; Immunity; Phenoloxidase; Serpin.
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