Poster: Cell walls

Abs # 614: Expression of Gum Arabic Glycoprotein Analogs with Transgenic Tobacco Cells

Presenter:	Xu, Jianfeng , jfeng@bobcat.ent.ohiou.edu
Authors	Xu, Jianfeng  (A)   Kieliszewski, Marcia  (A)
Affiliations:	(A): Department of Chemistry and Biochemistry, Ohio University

Gum arabic glycoprotein (GAGP), an arabinoglactan protein (AGP), is the surface-active component accounting for gum arabic¡¯s emulsification properties. The molecular cloning of GAGP gene has not yet been succeeded so far, nor has been the elucidation of the precise emulsification mechanism. However, the dominant amino acid sequence of GAGP polypeptide backbone was derived in this lab. It contains a repetitive 19-residue consensus motif SOOOTLSOSOTOTOOOGPH (O: hydroxyproline), thus providing us with the possibility to express GAGP analogs in transgenic plant cells by use of the synthetic gene technology. The genes encoding seven GAGP analogs were designed and constructed. They include three types: a) [Gum]3, [Gum]8 and [Gum]20 are the genes that encoded three, eight and twenty repeats of GAGP consensus motif, respectively; b) [Gum]8[HP]2 and [Gum]8[HP]4 are those of the combination of [Gum]8 with two and four repeats of the GAGP hydrophobic peptide (HP) that was also derived from GAGP backbone peptide; and c) [HP]4 and [HP]8 which are the genes encoding four and eight repeats of [HP] alone. These synthetic analogs were expressed in tobacco cells as fusion proteins with enhanced green fluorescence protein (EGFP). It was shown that all the GAGP analogs expressed by tobacco cells exhibited much lower emulsifying ability than the native GAGP. The order of emulsifying ability of these GAGP analogs is [HP]8> [HP]4> [Gum]8[HP]4 > [Gum]8[HP]2> [Gum]20 > [Gum]8 >[Gum]3. However, when the EGFP was attached to these synthetic GAGP analogs, all the fusion proteins exhibited better emulsifying ability than native GAGP.