title: Serine protease P-IIc is responsible for the digestion of yolk proteins at the late stage of silkworm embryogenesis.
abstract: In silkworms, yolk proteins comprise vitellin, egg-specific protein and 30K proteins, which are sequentially degraded by endogenous proteases strictly regulated during embryogenesis. Although the process has been extensively investigated, there is still a gap in the knowledge about the degradation of silkworm yolk proteins on the last two days of embryonic development. In the present study, we isolated and purified a gut serine protease P-IIc, which demonstrated optimal activity at 25 °C and pH 11. Semi-quantitative RT-PCR combined with western blotting showed that P-IIc was actively expressed and significantly accumulated in the gut on the last two days of embryogenesis. When natural yolk proteins were incubated with P-IIc in vitro, vitellin and ESP were selectively degraded. P-IIc also demonstrated activity towards 30K proteins as evidenced by rapid and complete digestion of BmLP1 and partial digestion of BmLP2 and BmLP3. Furthermore, RNAi knockdown of P-IIc in silkworm embryos significantly reduced the degradation rate of residual yolk proteins on embryonic day 10. Taken together, our results indicate that P-IIc represents an embryonic gut protease with a relatively broad substrate specificity, which plays an important role in the degradation of yolk proteins at the late stage of silkworm embryogenesis.
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Zhaoming
authors.initials: Z
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Pengchao
authors.initials: P
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Sanyuan
authors.initials: S
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Kaiyu
authors.initials: K
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
authors.forename: Qingyou
authors.initials: Q
authors.lastname: Xia
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China. Electronic address: zhaop@swu.edu.cn.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
mesh_terms: D000818:Animals; D012831:Bombyx / Q000196:embryology / Q000201:enzymology / Q000235:genetics*; D004527:Egg Proteins / Q000378:metabolism*; D047108:Embryonic Development; D057057:Serine Proteases / Q000235:genetics* / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D004527:Egg Proteins; D057057:Serine Proteases
keywords: 30K proteins; Degradation; Serine protease; Silkworm; Yolk proteins