title: High-level accumulation of recombinant miraculin protein in transgenic tomatoes expressing a synthetic miraculin gene with optimized codon usage terminated by the native miraculin terminator.
abstract: In our previous study, a transgenic tomato line that expressed the MIR gene under control of the cauliflower mosaic virus 35S promoter and the nopaline synthase terminator (tNOS) produced the taste-modifying protein miraculin (MIR). However, the concentration of MIR in the tomatoes was lower than that in the MIR gene's native miracle fruit. To increase MIR production, the native MIR terminator (tMIR) was used and a synthetic gene encoding MIR protein (sMIR) was designed to optimize its codon usage for tomato. Four different combinations of these genes and terminators (MIR-tNOS, MIR-tMIR, sMIR-tNOS and sMIR-tMIR) were constructed and used for transformation. The average MIR concentrations in MIR-tNOS, MIR-tMIR, sMIR-tNOS and sMIR-tMIR fruits were 131, 197, 128 and 287 μg/g fresh weight, respectively. The MIR concentrations using tMIR were higher than those using tNOS. The highest MIR accumulation was detected in sMIR-tMIR fruits. On the other hand, the MIR concentration was largely unaffected by sMIR-tNOS. The expression levels of both MIR and sMIR mRNAs terminated by tMIR tended to be higher than those terminated by tNOS. Read-through mRNA transcripts terminated by tNOS were much longer than those terminated by tMIR. These results suggest that tMIR enhances mRNA expression and permits the multiplier effect of optimized codon usage.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Hiwasa-Tanase
authors.forename: Mpanja
authors.initials: M
authors.lastname: Nyarubona
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Hirai
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Kato
authors.forename: Takanari
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ezura
mesh_terms: D001483:Base Sequence; D015139:Blotting, Southern; D003062:Codon / Q000235:genetics*; D005638:Fruit / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D005966:Glucuronidase / Q000378:metabolism; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D026723:Polyadenylation / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism*; D013728:Terminator Regions, Genetic / Q000235:genetics*; D014158:Transcription, Genetic; D019076:Transgenes / Q000235:genetics
chemical_list: D003062:Codon; D006023:Glycoproteins; D011994:Recombinant Proteins; C008533:miraculin protein, Synsepalum dulcificum; D005966:Glucuronidase