Poster: Metabolic Engineering

Abs # 998: The expression of a lysine-rich protein in transgenic rice is highly enhanced through fusion protein approach

Presenter:	Liu, Qiao-quan , liuqiaoquan@hotmail.com
Authors	Liu, Qiao-quan  (A) (B)  Gu, Ming-hong  (B)   Sun, Samuel S.M. (A)
Affiliations:	(A): Department of Biology,The Chinese University of Hong Kong,Hong Kong (B): College of Bioscience and Biotechnology, Yangzhou University, Jiangsu, China

Rice is deficient in the essential amino acid lysine. In the present study, the gene encoding a lysine-rich protein (LRP) from winged bean was transferred and highly expressed in the endosperm of transgenic rice. The stable accumulation of LRP in mature rice seeds amounted to 12% of the total soluble seed protein. To further enhance the expression of LRP, a fusion protein approach was attempted, that is, LRP was fused with glutelin, the major storage protein in rice seed. Three categories of fusion, Gt::LRP(A), Gt::LRP(B) and Gt::LRP(AB) were generated, by inserting the LRP cDNA into the glutelin Gt1 coding sequence, in frame, in the region of acidic subunit (A), basic subunit (B), or both subunits (AB), respectively. All these fusion protein genes, driven by the rice Gt1 promoter, could be expressed in the transgenic rice seeds. The accumulation of these three fusion proteins in maturing endosperm could be visualized by SDS-PAGE and confirmed by immunoblot analysis. While the expressed protein products differed among the three fusions, the highest expressing fusion protein accounted for 2.7 % of the rice grain by dry weight and 30% of the total rice seed protein. Changes in endogenous glutelin expression were observed in transgenic seeds highly expressing the fusion protein. The results sufficiently demonstrated that the expression of foreign proteins in rice grains can be significantly enhanced via fusion protein strategy and the endogenous rice glutelin can well serve as a fusion receptor protein. (Supported by an AoE grant from the UGC-HKSAR.).