Model for regulation of VAMP721/722-mediated secretion: growth vs. stress responses.

The PEN1-SNAP33-VAMP721/722 exocytic pathway is a conserved immunity-associated secretory pathway between monocotyledonous barley and dicotyledonous Arabidopsis plants. In Arabidopsis, this secretory pathway plays an additional role in plant growth and development. However, how this pathway can be manipulated to engage in both growth/development and immunity remains to be answered. To understand its regulation, we recently analyzed the expression of VAMP721/722 genes whose products drive secretory vesicles to the target plasma membrane. By investigating their transcript and protein levels, we found that plants distinctly control the activity of this secretory pathway during biotic or abiotic stress responses. Since stress responses are in general accompanied by growth inhibition in plants and since plants in nature are simultaneously threatened by a number of environmental stresses, understanding of this growth/immunity-related secretory pathway would help to generate more efficiently growth/immunity-balancing plants.