ABSTRACT
Plant defensins belong to a superfamily of antimicrobial peptides with a cysteinestabilized
αβ
motif that has representatives in vertebrates, invertebrates, and plants. This feature underscores the importance of these defense molecules as central components of a widespread defense strategy of multicellular organisms. In plants, antimicrobial plant defensins can be constitutively expressed during critical developmental stages and in particular cell types. Other plant defensin genes can be induced upon microbial infection. At least in
Arabidopsis
, induction of a plant defensin gene as a response to fungal attack appears to involve the synthesis of jasmonates as signaling molecules. The signal transduction pathway dependent on salicylic acid (SA) and leading to systemic acquired resistance (SAR) is not required for the induction of expression of this plant defensin gene. Similar to defensins from insects and mammals, the action of plant defensins on microorganisms involves changes in ion fluxes across the plasma membrane. However, a direct interaction with phospholipids of microbial membranes does not appear to occur, and the role of a receptor as an anchor for membrane insertion of plant defensins has been postulated.
