Surface lipids and plant defenses.

The major function of the plant epidermis is to form the cuticle, a functional permeability barrier of the cell wall which prevents excessive water loss and the entry of harmful substances and pathogens into the host. This type of cell wall modification is mainly composed of a polyester matrix, cutin, and soluble waxes embedded in the matrix and deposited on the external surface. Cuticle-associated proteins may also be important. Recent observations are starting to reveal complex inter-relationships between cuticular lipids and immunity. This suggests that the cuticle is not simply a physical barrier, but a dynamic host defense with signaling circuits and effector molecules. Furthermore, these studies have also demonstrated that cuticular lipids and immunity may intersect in common pathways, although the significance of this is not fully understood. In this review, we examine the functions of the plant cuticle in host-pathogen interactions, and discuss the possibilities of integrating the membrane and cuticular glycerolipid biosynthesis.