中文摘要：

丝氨酸蛋白酶参与昆虫对抗入侵病原体及保护受伤组织的黑化反应。为了探讨家蚕黑化反应过程中丝氨酸蛋白酶在酚氧化酶原前体级联体系的作用,克隆了家蚕的一个新的丝氨酸蛋白酶基因,命名为BmHP21（GenBank登录号：JF431073）。该基因由1 233个核苷酸组成,编码410个氨基酸。通过SMART网站预测蛋白结构显示BmHP21包括一个clip结构域和一个胰蛋白酶结构域。BmHP21蛋白和烟草天蛾Ms-HP21的氨基酸序列有55%的相似性,推测BmHP21在家蚕黑化反应中起着激活酚氧化酶原前体激酶（PPAE）的作用。RT-PCR检测结果表明,BmHP21在家蚕大部分组织包括脂肪体中都有表达,其mRNA转录几乎贯穿于整个家蚕的幼虫、蛹和成虫发育阶段,推测BmHP21除了参与黑化反应外,还有其它的生理功能。

英文摘要：

Serine proteases are involved in melanization which is used to combat with the intrusive pathogens and protect the damaged tissue in insect.To explore the role of serine proteases in the cascade activating system of prophenoloxidase during melanization in silkworm（Bombyx mori）,we cloned a novel serine protease gene,designated as BmHP21（GenBank accession No.JF431073）.The full-length cDNA of BmHP21 is 1 233 bp,encoding a putative protein with 410 amino acids.Protein structure prediction on SMART website displayed that BmHP21 contains a clip domain and a trypsin domain.The amino acid sequence of BmHP21 shares 55% identity with that of Ms-HP21 in Manduca sexta,suggesting that BmHP21 might function in the activation of prophenoloxidase-activating enzyme during melanization in silkworm.RT-PCR detection revealed that BmHP21 was expressed in almost all tissues including fat body.The developmental expression profile of BmHP21 indicated that BmHP21 mRNA was expressed constitutively in larval,pupal and adult stages,suggesting that,besides of involvement in melanization,BmHP21 has other physiological functions as well.