Modified antimicrobial peptides
Antimicrobial defensin peptide variants comprising modified C-terminal fragments of a defensin and nucleic acids encoding the same are disclosed. Compositions comprising the defensin variant peptides and methods of their use to control microbial infections of plants and vertebrate subjects as well as contamination of feedstuffs and foodstuffs are also disclosed.
1. An antifungal peptide comprising a modified C-terminal plant defensin peptide wherein:
(i) the unmodified C terminal plant defensin peptide comprises from N-terminus to C-terminus the conserved amino acid sequence GXCX3-10(C)(X)(C) (SEQ ID NO: 592) and a conserved cysteine residue located at the C-terminus of the unmodified C terminal plant defensin peptide;
(ii) the conserved amino acid sequence GXCX3-10(C)(X)(C) (SEQ ID NO: 592) of the unmodified C terminal plant defensin peptide is replaced with a modified gamma-core consensus sequence GXCX3-10(F/W/Y)(F/W/Y)(F/W/Y) (SEQ ID NO: 587) in the modified C-terminal plant defensin peptide;
(iii) the modified C-terminal plant defensin peptide retains the conserved cysteine residue located at the C-terminus of the unmodified C terminal plant defensin peptide;
(iv) the modified C-terminal plant defensin peptide has a net positive charge of at least 3 at neutral pH and a hydrophobic amino acid content at least 18%, wherein the hydrophobic amino acids are alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan, and methionine; and
(v) the modified C-terminal plant defensin peptide exhibits antifungal activity.
2. The antifungal peptide of claim 1 , wherein the modified C-terminal plant defensin peptide comprises a disulfide bond between the cysteine residue in the modified gamma-core consensus sequence and the conserved cysteine residue located at the C-terminus of the modified C-terminal defensin peptide.
3. The antifungal peptide of claim 1 , wherein the modified C-terminal plant defensin peptide consists of 15 to 30 amino acid residues.
4. A composition comprising the antifungal peptide of claim 1 and an agriculturally, pharmaceutically, or veterinary-practicably acceptable carrier, diluent, or excipient.
5. The composition of claim 4 , wherein the antifungal peptide is provided at a concentration of about 0.1 pg/ml to about 100 mg/ml or at a concentration of about 0.1 pg/gram to about 100 mg/gram and optionally wherein the composition comprises a sodium salt at a concentration of at least 100 mM and/or a calcium salt at a concentration of at least 2 mM.
6. A method for preventing or reducing crop damage by a plant pathogenic microbe comprising the step of contacting a plant, a plant seed, or other part of said plant with an effective amount of the composition of claim 4 .
7. The method of claim 6 , wherein the plant pathogenic microbe is a Fusarium sp., Alternaria sp., Verticillium sp., Phytophthora sp., Colletotrichum sp., Botrytis sp., Cercospora sp., Phakopsora sp., Rhizoctonia sp., Sclerotinia sp., Pythium sp., Phoma sp., Leptosphaeria sp., Gaeumannomyces sp., Puccinia sp., Septoria sp., Penicillium sp., Lasiodiplodia sp., Phomopsis sp., Mycosphaerella sp., Golovinomyces sp., Erisyphe sp., Albugo sp., Setosphaeria sp., Cochliobolus sp., Helminthosporium sp., Diplodia sp., or Stenocarpella sp.
8. A medical device comprising the device and the composition of claim 4 , wherein the device comprises at least one surface that is topically coated and/or impregnated with the composition.
9. The medical device of claim 8 , wherein said device is a stent, a catheter, a contact lens, a condom, a patch, or a diaphragm.
10. A method for treating, preventing, or inhibiting a fungal Candida species infection in a subject in need thereof comprising administering to said subject an effective amount of the composition of claim 4 .
11. The method of claim 10 , wherein said administration comprises topical, enteral, parenteral, and/or intravenous introduction of the composition.
12. The method of claim 10 , wherein the subject is a human, livestock, poultry, fish, or a companion animal.
13. The method of claim 10 , wherein the fungal or Candida species infection is of a mucosal membrane, eye, skin, and/or a nail and the composition is applied to the mucosal membrane, eye, skin, and/or nail.
14. The method of claim 10 , wherein the fungal infection is by a dermatophyte, and wherein the dermatophyte is optionally selected from the group consisting of Trichophyton rubrum, Trichophyton interdigitale, Trichophyton violaceum, Trichophyton tonsurans, Trichophyton soudanense, Trichophyton mentagrophytes, Microsporum flavum, Epidermophyton floccosum , and Microsporum gypseum.
15. The method of claim 10 , wherein the microbial infection is by an Aspergillus, Cryptococcus, Penicillium, Rhizopus, Apophysomyces, Cunninghamella, Saksenaea, Rhizomucor, Syncephalostrum, Cokeromyces, Actinomucor, Pythium, Fusarium, Histoplasmosis , or Blastomyces species.
16. The method of claim 10 , wherein the microbial infection is by a Candida species and wherein the Candida species is Candida albicans ( C. albicans ), C. auris, C. glabrata, C. parasilosis, C. tropicalis , or C. krusei.
17. A plant part that is at least partly coated with the composition of claim 4 .
18. The plant part of claim 17 , wherein the part is a seed and the seed is optionally a corn, soybean, wheat, rice, cotton, Brassica sp., or tomato seed.
19. The plant part of claim 17 , wherein the plant part is a fruit, vegetable, or flower.
20. A recombinant polynucleotide comprising a polynucleotide encoding a peptide comprising the antifungal peptide of claim 1 , wherein the polynucleotide encoding the antifungal peptide is operably linked to a polynucleotide comprising a promoter which is heterologous to the polynucleotide encoding the antifungal peptide.
21. The peptide of claim 1 , wherein the conserved cysteine residue located at the C-terminus of the modified C-terminal defensin peptide is amidated.