Expressional analysis of the silkworm storage protein 1 and identification of its interacting proteins

• Published in: Insect molecular biology 2020-02, Vol.29 (1), p.66-76
• Main Authors: Li, Ruilin, Hu, Congwu, Geng, Tao, Lv, Dingding, Gao, Kun, Guo, Xijie, Hou, Chengxiang
• Format: Article
• Language: English
• Subjects: Animals; Antigens; antimelanization; Baculovirus; BmLP6; BmSP1; Bombyx - genetics; Bombyx - growth & development; Bombyx - immunology; Bombyx - metabolism; Bombyx mori; Cell Line; Fat body; Fat Body - metabolism; Fluorescence; Green fluorescent protein; Green Fluorescent Proteins; Hemolymph; Hemolymph - immunology; Immunity, Innate; Immunoprecipitation; Innate immunity; Insect Proteins - genetics; Insect Proteins - metabolism; Insects; Instars; interacting protein; Larva - genetics; Larva - immunology; Larva - metabolism; Larvae; Low molecular weights; Melanization; Metamorphosis; Molecular weight; Multiplication; Pathogens; Proteins; Pupation; Recombinant Proteins; Silkworms; Storage; Storage proteins; Yeasts
• ISSN: 0962-1075; 1365-2583
• DOI: 10.1111/imb.12610

Storage proteins are haemolymph‐specific proteins in insects, mainly synthesized in the fat body, released into the haemolymph, and then selectively reabsorbed by the fat body before pupation. These storage proteins play an important role in insect metamorphosis and egg development. Some of these storage proteins are responsive to pathogen infection and can even suppress pathogen multiplication. However, the mechanisms of the physiological, biochemical and immune‐responsive functions of storage proteins remain unclear. In this study, the expression patterns of Bombyx mori storage protein 1 (BmSP1) during the larval stage were analysed. Then, BmSP1 protein fused with enhanced green fluorescent protein (EGFP) was successfully expressed in a B. mori baculovirus vector expression system. Quantitative real‐time PCR showed that the expression level of BmSP1 increased with the advance of instars and reached the highest level in the fifth instar, especially in the fat body. Recombinant BmSP1 expressed in silkworm larvae inhibited haemolymph melanization. Then, proteins that interact with BmSP1 were identified with EGFP used as an antigenic determinant by co‐immunoprecipitation. A 30 kDa low molecular weight lipoprotein PBMHP‐6 precursor (BmLP6) was shown to interact with BmSP1. Yeast two‐hybrid experiments confirmed the interaction between BmSP1 and BmLP6. The results obtained in this study will be helpful for further study of the functions of BmSP1 and BmLP6 in the regulatory network of silkworm development and innate immunity. Expression level of Bombyx mori storage protein 1 (BmSP1) increased with the advance of instars in silkworms and reached the highest level in the fifth instar especially in the fat body. Recombinant BmSP1 protein expressed with a baculovirus expression vector system in silkworm larvae showed the ability to inhibit haemolymph melanization. Low molecular 30 kDa lipoprotein PBMHP‐6 precursor was identified as a protein that interacts with BmSP1.