Silkworm coatomers and their role in tube expansion of posterior silkgland.
BACKGROUND
Coat protein complex I (COPI) vesicles, coated by seven coatomer subunits, are mainly responsible for Golgi-to-ER transport. Silkworm posterior silkgland (PSG), a highly differentiated secretory tissue, secretes fibroin for silk production, but many physiological processes in the PSG cells await further investigation.


RESULTS
Here, to investigate the role of silkworm COPI, we cloned six silkworm COPI subunits (α, β, β', δ, ε, and ζ-COP), determined their peak expression in day 2 in fifth-instar PSG, and visualized the localization of COPI, as a coat complex, with cis-Golgi. By dsRNA injection into silkworm larvae, we suppressed the expression of α-, β'- and γ-COP, and demonstrated that COPI subunits were required for PSG tube expansion. Knockdown of α-COP disrupted the integrity of Golgi apparatus and led to a narrower glandular lumen of the PSG, suggesting that silkworm COPI is essential for PSG tube expansion.


CONCLUSIONS
The initial characterization reveals the essential roles of silkworm COPI in PSG. Although silkworm COPI resembles the previously characterized coatomers in other organisms, some surprising findings require further investigation. Therefore, our results suggest the silkworm as a model for studying intracellular transport, and would facilitate the establishment of silkworm PSG as an efficient bioreactor.
Wang
Qiao
Q
The Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, College of Life Sciences, Peking University, Beijing, China.
Shen
Birong
B
Zheng
Pengli
P
Feng
Hui
H
Chen
Liang
L
Zhang
Jing
J
Zhang
Chuanxi
C
Zhang
Guozheng
G
Teng
Junlin
J
Chen
Jianguo
J
D000818:Animals; D012831:Bombyx; D003001:Cloning, Molecular; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D013347:Subcellular Fractions / Q000378:metabolism
D019476:Insect Proteins; D012333:RNA, Messenger