A midgut-specific serine protease, BmSP36, is involved in dietary protein digestion in the silkworm, Bombyx mori.
Serine proteases play important roles in digestion and immune responses during insect development. In the present study, the serine protease gene BmSP36, which encodes a 292-residue protein, was cloned from the midgut cells of Bombyx mori. BmSP36 contains an intact catalytic triad (H57, D102 and S195) and a conserved substrate-binding site (G189, H216 and G226), suggesting that it is a serine protease with chymotrypsin-like specificity. The temporal and spatial expression patterns of BmSP36 indicated that its messenger RNA and protein expression mainly occurred in the midgut at the feeding stages. Western blotting, immunofluorescence and liquid chromatography-tandem mass spectrometry analyses revealed secretion of BmSP36 protein from epithelial cells into the midgut lumen. The transcriptional and translational expression of BmSP36 was down-regulated after starvation but up-regulated after refeeding. Moreover, expression of the BmSP36 gene could be up-regulated by a juvenile hormone analogue. These results enable us to better define the potential role of BmSP36 in dietary protein digestion at the feeding stages during larval development.
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Hua-Wei
HW
Liu
Vitamin D Research Institute, Shaanxi Sci-Tech University, Hanzhong, Shaanxi Province, China.
You-Shan
YS
Li
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Xin
X
Tang
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Peng-Chao
PC
Guo
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Dan-Dan
DD
Wang
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Chun-Yan
CY
Zhou
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Qing-You
QY
Xia
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Ping
P
Zhao
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D012831:Bombyx / Q000201:enzymology*; D004044:Dietary Proteins / Q000378:metabolism; D004063:Digestion; D005455:Fluorescent Antibody Technique; D005508:Food Deprivation; D041981:Gastrointestinal Tract / Q000201:enzymology; D005786:Gene Expression Regulation; D019476:Insect Proteins / Q000378:metabolism*; D007605:Juvenile Hormones; D007814:Larva / Q000201:enzymology; D011679:Pupa / Q000201:enzymology; D060888:Real-Time Polymerase Chain Reaction; D057057:Serine Proteases / Q000378:metabolism*
D004044:Dietary Proteins; D019476:Insect Proteins; D007605:Juvenile Hormones; D057057:Serine Proteases
Bombyx mori; dietary digestion; expression profile; juvenile hormone; midgut; serine protease