Plant defensins (formerly gamma-thionins) are a family of primitive, highly stable, cysteine-rich defensins found in plants that function to defend them against pathogens and parasites.[1] Defensins are integral components of the innate immune system and belong to the ancient superfamily of antimicrobial peptides (AMPs). AMPs are also known as host defense peptides (HDPs),[2] and they are thought to have diverged about 1.4 billion years ago before the evolution of prokaryotes and eukaryotes.[3][4] They are ubiquitous in almost all plant species, functionally diverse, and their primary structure varies significantly from one species to the next, except for a few cysteine residues, which stabilize the protein structure through disulfide bond formation.[1] Plant defensins usually have a net positive charge due to the abundance of cationic amino acids[5] and are generally divided into two classes. Those in the class II category contain a C-terminal pro-peptide domain of approximately 33 amino acids[5] and are targeted to the vacuole,[6] while the class I defensins lack this domain and mature in the cell wall. Unlike their class I counterparts, class II plant defensins are relatively smaller, and their acidic C-terminal prodomain is hypothesized to contribute to their vacuolar targeting.[7] The first plant defensins were discovered in barley and wheat in 1990 and were initially designated as γ-thionins.[8][9] In 1995, the name was changed to 'plant defensin' when it was identified that they are evolutionarily unrelated to other thionins and were more similar to defensins from insects and mammals.[10][11]
^Carvalho A, Gomes VM (December 2011). "Plant defensins and defensin-like peptides - biological activities and biotechnological applications". Current Pharmaceutical Design. 17 (38): 4270–4293. doi:10.2174/138161211798999447. PMID22204427.
^Javaux EJ, Knoll AH, Walter MR (July 2001). "Morphological and ecological complexity in early eukaryotic ecosystems". Nature. 412 (6842): 66–69. doi:10.1038/35083562. PMID11452306. S2CID205018792.
