Structural and antifungal properties of a pathogenesis-related protein from wheat kernel

Abstract

We have purified and characterized a protein from the water-soluble fraction of wheat kernel (Triticum aestivum cv. S. Pastore) consisting of a single polypeptide chain blocked at its N-terminus by a pyroglutamate residue; the complete amino acid sequence has been determined by automated sequence analysis performed on peptide fragments obtained by enzymatic hydrolyses of the protein. Homology studies have shown that this protein is very similar (97% sequence identity) to the previously characterized wheatwin1 as well as to other members of the pathogenesis-related (PR) proteins of class 4; in analogy with wheatwin1, we have termed this protein wheatwin2. Both wheatwin1 and wheatwin2 have specific antifugal activity toward the wide-host-range pathogen Botrytis cinerea and the wheat-specific pathogenic fungi of wheat Fusarium culmorum and Fusarium graminearum of groups 1 and 2. On the basis of their structural and functional properties, wheatwin1 and wheatwin2 can be classified as members of the PR4 protein family; this represents the first report concerning the presence of this kind of protein in wheat.

Antifungal Proteins

“…Plants are also exposed to a large number of pathogenic fungi; although they do not have an immune system, plants have evolved a variety of potent defense mechanisms, including the synthesis of low-molecular-weight compounds, proteins, and peptides that have antifungal activity (16,18,47,80,104,127,151,159,177). Similarly, bacteria, insects, mollusks, fungi, and mammals synthesize a number of proteins and peptides that are antifungal (13, 19, 20, 30, 49, 51-54, 58, 68, 69, 79, 83, 109-111, 122, 126, 128, 153, 188, 189, 192).…”

Pathogenesis-related proteins in Brazilian wheat genotypes: protein induction and partial gene sequencing

“…Again, all genotypes presented the same sequences. Previous reports of PR proteins in wheat, detected with different methods, included PWIR2 (REBMANN et al, 1991;CHEONG et al, 1997); Tal 18 (CRUZ-ORTEGA & OWNBY, 1993); one chitinase (PR3) and one β-glucanase (PR2) (DARNETTY et al, 1993); wheatwin1 and wheatwin2 (CARUSO et al, 1996); and TaPR1.1 and TaPR1.2 (MOLINA et al, 1999). Two wheat protein sequences at the Prosite data bank (http:// expasy.hcuge.ch/sprot/sprot-top.html), E13B (PR2) and IAAS (PR6) were also found.…”

Antimicrobial Peptides from the Plants

“…After initial electrostatic binding of these positively charges peptides to negatively charged (phosphor) lipids on the target cell surface, they insert into the energized cell membrane and most likely form multimeric ion-permeable channels in a voltage-dependent manner [69][70][71][72]. The subsequent neutralization of the anionic lipid head groups disrupts the integrity of the lipid bilayers, causing transient gaps and allowing ions and larger molecules to cross the membrane [73,74]. Recently, the theory that many cationic peptides exert their antimicrobial activity not only through cytoplasmic targets has gained support [75].…”