Cellular internalization of arginine-rich peptides into tobacco suspension cells: a structure-activity relationship...

Translocation of several fluorescently labeled arginine-rich peptides into intact plant cells was quantitatively examined in order to investigate the structural factors required for efficient cellular internalization, and thereby, to evaluate the potential of arginine-rich peptides as intracellular delivery vectors in plants. Cell-penetrating peptides (CPPs) such as arginine-rich peptides permit the direct introduction of biologically active macromolecules into plant cytoplasm to manipulate various intracellular processes. While a significant level of adsorption of applied arginine-rich peptides was observed in the cell walls rich in negative charges, removal of adsorbed peptides by trypsin treatment allowed determination of the amount of internalized peptides in a quantitative manner using spectrofluorometric analysis. The internalization of arginine-rich peptides depended on the number of arginine residues, and the peptide containing eight arginine residues showed most effective internalization. Besides, the position of small cargoes attached to the arginine-rich peptides markedly affected the internalization efficiency. The results obtained in this study provide useful information for the development of efficient intracellular delivery tools in plant science.