Abstract
Sericulture has been greatly advanced by applying hybrid breeding techniques to the domesticated silkworm, Bombyx mori, but has reached a plateau during the last decades. For the first time, we report improved silk yield in a GAL4/UAS transgenic silkworm. Overexpression of the Ras1CA oncogene specifically in the posterior silk gland improved fibroin production and silk yield by 60%, while increasing food consumption by only 20%. Ras activation by Ras1CA overexpression in the posterior silk gland enhanced phosphorylation levels of Ras downstream effector proteins, up-regulated fibroin mRNA levels, increased total DNA content, and stimulated endoreplication. Moreover, Ras1 activation increased cell and nuclei sizes, enriched subcellular organelles related to protein synthesis, and stimulated ribosome biogenesis for mRNA translation. We conclude that Ras1 activation increases cell size and protein synthesis in the posterior silk gland, leading to silk yield improvement.
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Acknowledgements
The transgenic silkworm Fil-GAL4/UAS-Ras1CA has been protected by the Chinese Intellectual Property Deputy under the patent 201010118072.8. This study was supported by 2007AA10Z155, KSCX-YW-N-009, 30770271, 10JC1416700, 2007CB947100, 2006CB943902, 30870299, 2006AA10A119, and Hundred Talent Project to SL as well as 2005CB121000 to QX. We are grateful to Drs Jian Fei, Zhugang Wang, and Hongjiu Dai in Shanghai Research Center for Model Organisms for their support of the initial transgenic silkworm studies. We thank Dr David Stanley for improving this manuscript.
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Supplementary information, Figure S1
MAPK phosphorylation level correlates and slightly precedes the growth rate of posterior silk gland. (PDF 64 kb)
Supplementary information, Figure S2
Inhibition of PI3K110 activity reduces silk gland size. (PDF 428 kb)
Supplementary information, Figure S3
Increasing posterior silk gland size by Ras1CA overexpression greatly improves silk yield. (PDF 108 kb)
Supplementary information, Figure S4
BrdU labeling in the posterior silk gland from [D(+)E(+)] (A') is stronger than those in the controls [D(−)E(−)] (A). (PDF 76 kb)
Supplementary information, Figure S5
Ras1 activation increases the posterior silk gland size observed under optical microscopy. (PDF 22 kb)
Supplementary information, Figure S6
A proposed model shows that increasing posterior silk gland size and stimulating fibroin protein synthesis by Ras1CA overexpression in the transgenic silkworm Fil-GAL4/UAS-Ras1CA. (PDF 91 kb)
Supplementary information, Table S1
All primers used in this paper (PDF 7 kb)
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Ma, L., Xu, H., Zhu, J. et al. Ras1CA overexpression in the posterior silk gland improves silk yield. Cell Res 21, 934–943 (2011). https://doi.org/10.1038/cr.2011.36
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DOI: https://doi.org/10.1038/cr.2011.36
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