title: Deposition mode of transforming growth factor-β expressed in transgenic rice seed.
abstract: Mouse TGF-β highly accumulated by expressing as a secretory homodimeric protein in transgenic rice endosperm. It was tightly deposited in ER-derived PBs by interaction with cysteine-rich prolamins. TGF-β is one of the key players involved in the induction and maintenance of mucosal immune tolerance to dietary proteins through the induction of regulatory T cells. In order to utilize rice-based TGF-β as a tool to promote oral immune tolerance induction, high production of TGF-β is essentially required. When the codon-optimized mTGF-β was expressed as a secretory protein by ligating an N-terminal signal peptide and C-terminal KDEL ER retention signal under the control of the endosperm-specific rice storage protein glutelin GluB-1 promoter, accumulation level was low in stable transgenic rice seeds. Then, to increase the accumulation level of mTGF-β, it was expressed as fusion proteins by inserting into the C terminus of acidic subunit of glutelin GluA and the variable region of 26 kDa globulin. When fused with the glutelin, it could accumulate well as visible bands by CBB staining gel, but not for the 26 kDa globulin. Unexpectedly, expression of homodimeric mTGF-β linked by a 6×Gly1×Ser linker as secretory protein resulted in higher level of accumulation. This expression level was further enhanced by reduction of some endogenous prolamins by RNA interference. The monomeric and dimeric mTGF-βs were deposited in ER-derived PBs containing prolamins. When highly produced in rice seed, it is notable that most of ER-derived PBs were distorted and granulated. Step-wise extraction of storage proteins from rice seeds suggested that the mTGF-β strongly interacted with cysteine-rich prolamins via disulfide bonds. This result was also supported by the finding that reducing agent was absolutely required for mTGF-β extraction.
authors: Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan. takaiwa@affrc.go.jp.
authors: Fumio
authors: F
authors: Takaiwa
authors: Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan.
authors: Lijun
authors: L
authors: Yang
authors: Division of Agronomy and Horticultural Science, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
authors: Nobuyuki
authors: N
authors: Maruyama
authors: Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan.
authors: Yuhya
authors: Y
authors: Wakasa
authors: Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan.
authors: Kenjiro
authors: K
authors: Ozawa
mesh_terms: D000818:Animals; D003545:Cysteine / Q000378:metabolism; D056625:Endosperm / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D012275:Oryza / Q000166:cytology / Q000235:genetics* / Q000648:ultrastructure; D010434:Pepsin A / Q000378:metabolism; D030821:Plants, Genetically Modified; D055315:Prolamins / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000235:genetics* / Q000648:ultrastructure; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D056811:Unfolded Protein Response
chemical_list: D055315:Prolamins; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D010434:Pepsin A; D003545:Cysteine
keywords: ER stress; Endosperm; Prolamin; Protein body; Seed storage protein; TGF-β; Transgenic rice