Poster: Cell Walls

Abs # 1273: The Dipeptides RG and GD of the Integrin-Binding Motif, RGD Inhibit Somatic Embryogenesis in Daucus carota

Presenter:	Dafoe, Nicole , stavesm@gvsu.edu
Authors	Dafoe, Nicole  (A)   Foster, Nicole  (A)   Staves, Mark P (A)   Blackman, Sheila A (A)
Affiliations:	(A): Grand Valley State University

Integrins are integral membrane proteins important in communication between the cytoplasm of a cell and the surrounding extracellular matrix. The extracellular matrix contains molecules such as fibronectin, laminin, and collagen, which contain an arginine-glycine-aspartic acid (RGD) integrin binding domain. The addition of synthetic RGD peptide inhibits natural ligand binding thereby inhibiting integrin function. To date, the roles of integrins in the growth and development of animals and fungi have been well documented, but there is little research addressing a potential role for integrins in plant development. Existing research centers around three key findings. First, certain plasma membrane plant proteins cross-react with integrin antibodies from animals; second, there are sequence similarities between animal integrins and some Arabidopsis genes and; third, addition of synthetic RGD inhibits several plant growth and development-related responses, including somatic embryogenesis in Daucus carota. The aim of this work was to probe the latter effect of RGD. We report that whereas none of the single amino acids R, G or D, either singly or in combination, dramatically inhibit somatic embryogenesis, both the dipeptides RG and GD do. RG is as effective an inhibitor as RGD, whereas GD is somewhat less inhibitory. We also report that neither RGD nor the dipeptides are acting through inhibiting cell viability. We know of no other case in which the dipeptides RG or GD have shown a physiological effect either in plants or in animals.