Poster: Late and Moved Abstracts

Abs # 1026: The integrin-binding peptide, RGD, limits embryogenic potential in somatic cell suspensions of Daucus carota L., cv. Scarlet Nantes.

Presenter:	Blackman, Sheila , blackmas@gvsu.edu
Authors	Taylor, Sarah  (A)   Gataoulin, Dan  (A)   Dafoe, Nicole  (B)   Staves, Mark  (A)   Blackman, Sheila  (A)
Affiliations:	(A): Grand Valley State University, Biology Department (B): University of Victoria, Biology Department

Carrot (Daucus carota cv. Scarlet nantes) suspension cells grown in the presence of high concentrations of the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) form un-differentiated “proembryos” that, within 3 days, organize into embryo-like structures when they are placed in embryogenic medium from which the 2,4-D has been withdrawn. We have previously shown that the peptide Arginine-Glycine-Aspartic acid (RGD) inhibits this process of somatic embryo formation, a result which implicates integrin in plant developmental processes. Integrins are plasma membrane proteins that link the extracellular matrix with the interior of the cell that have well-characterized important roles in animal development. The aim of this work was to characterize the interaction between RGD and the cell. RGD applied to non-embryogenic cultures limited the embryogenic potential of cultures upon subsequent transfer to embryogenic medium. Non-embryogenic cultures were treated with RGD for various times, and subsequently washed in RGD-free medium and transferred to embryogenic medium. Although RGD neither inhibited growth nor reduced viability, its inhibitory effect on embryogenesis was long-lasting. Furthermore, peptide was removed from the medium supernatant by the cells in parallel with inhibition of embryogenic potential. Our results suggest that RGD either directly or indirectly disrupts a process necessary for differentiation but not growth of carrot suspension cells.