Poster: Protein targeting & vesicular trafficking

Abs # 656: Co-expression of δ-zein and β-zein in tobacco by agroinfiltration for studying protein-protein interaction.

Presenter:	Klypina, Nina , niklypin@nmsu.edu
Authors	Klypina, Nina  (A)   Bagga, Suman  (B)   Dennis, Sutton  (A)   Soumitra, Ghoshroy  (C)   Champa, Sengupta-Gopalan  (B)   Stephen, Hanson F (A)
Affiliations:	(A): New Mexico State University, EPPWS (B): New Mexico State University, Ag & Hort (C): New Mexico State University, Dept. Biology

Zeins, the seed storage proteins of maize, are of four distinct types: α, β, δ and γ. They are synthesized on the rough endoplasmic reticulum (ER) in a sequential manner and deposited in ER-derived protein bodies. It has been proposed that the β-zein or γ-zein or both are necessary for the assembly of protein bodies. When δ- and β-zein genes were expressed individually, the two zeins were localized in protein bodies distinct for each zein. However, co-expression of the two zein genes showed co-localization of the two zeins in the same protein bodies (Bagga et al.,1997; Hinchlife& Kemp, 2002), suggesting that the two proteins interact with each other and the interaction has a stabilizing effect on the δ-zein. Methionine rich δ-zeins are ideal candidates for transgenic approaches to increase methionine content in forage legumes and it is important to understand how these proteins can be stabilized in transgenic plants. In this study we have used agroinfiltration to check if this technique can be applied to understand β-zein/δ-zein interactions. Our studies show high accumulation of β-zein but low accumulation of δ-zein after infiltration with A.tumefaciens cells containing individual zein gene constructs. Co-infiltration of tobacco leaves with the two A.tumefaciens cell lines showed stabilization of the δ-zein in a manner comparable to that seen in transgenic plants. Agroinfiltration with gene constructs with two zein genes driven by two different promoters in one cassette resulted in accumulation pattern similar to that seen in the stable transformants. Experiments are in progress to check if protein body biogenesis in the transient assay follows the same pattern as in the stable transformants.