Construction method using detoxiase gene as stable expression system in silkworm
A technology for stable expression and construction methods, which can be used in genetic engineering, plant genetic improvement, botanical equipment and methods, etc., and can solve problems such as the difficulty of separation and purification, and the inability of lipase B1 to undergo glycosylation modification.
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Embodiment 1
[0030] Construction of "silk protein L chain-lipase B1" fusion gene expression unit
[0031] First, extract the mRNA from the posterior silk gland of the silkworm, and design the upstream and downstream primers (upstream and downstream primer sequences are: 5'-tggatccgcggcgcgttaccatatatg-3', 5'-gcgatatcacgccctgatgg according to the known sequence of the silk protein L chain gene of the silkworm. -3'), the silkworm silk protein L chain cDNA was obtained by RT-PCR amplification, about 0.8Kb, including the signal peptide sequence.
[0032] From the total DNA of silkworm, design primers based on known sequences (upstream primer sequence: 5'-tggatccgcggcgcgttaccatatatg-3', downstream primer sequence: 5'-gcgatatcacgccctgatgg-3') to amplify the 5'end of the L chain and its upstream A DNA fragment of about 1.2Kb in the promoter region, and a 0.5Kb terminator fragment at the 3'end of the L chain.
[0033] According to the lipase B1cDAN sequence reported by Mouches et al. (Proc. Natl. Acad....
Embodiment 2
[0036] Construction of integrated gene vector
[0037] The genomic DNA of the silkworm was extracted, and the A3 promoter fragment was obtained by PCR amplification according to the sequence of the kinesin gene (A3) of the cytoplasmic muscle of the silkworm. The A3 promoter fragment was connected to the GFP gene coding region sequence in an appropriate reading frame. Insert the SV40polyA signal sequence into the downstream of the fused GFP gene to form a complete GFP gene expression unit. Add a 30bp long multi-cloning site (MCS) artificial linker upstream of the complete GFP gene fragment (the nucleotide sequence is:
[0038] 5'-ACCGCGGTCTAGAGGATCCCGGGCTGCAGT-3'). The L-EB1 expression unit of the fusion gene of the lipase B1 gene and the L chain and the complete GFP gene expression unit are linked together through a multiple cloning site region to obtain a recombinant DNA fragment. Add the inverted terminal repeat sequence of the piggyBac transposon (nucleotide sequence 5'-CGCCGCG...
Embodiment 3
[0040] Helper plasmid construction
[0041] The coding region sequence of the transposase in the piggyBac transposon was cloned by PCR technology. Add the A3 promoter in front of the coding region of the transposase gene and clone it into the plasmid pUC18, which is the helper plasmid of the gene transfer system. The L-EB1 gene vector plasmid and the helper plasmid together constitute the silkworm gene transfer system. The system achieves high-frequency integration of foreign genes in the silkworm genome through transposition, with a transformation frequency of up to 7%. The system can ensure the multi-copy and high-frequency integration of the foreign target gene in the silkworm genome, and further improve the expression level of the foreign gene.
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