Defensins of Grasses: A Systematic Review

Abstract

The grass family (Poaceae) is one of the largest families of flowering plants, growing in all climatic zones of all continents, which includes species of exceptional economic importance. The high adaptability of grasses to adverse environmental factors implies the existence of efficient resistance mechanisms that involve the production of antimicrobial peptides (AMPs). Of plant AMPs, defensins represent one of the largest and best-studied families. Although wheat and barley seed γ-thionins were the first defensins isolated from plants, the functional characterization of grass defensins is still in its infancy. In this review, we summarize the current knowledge of the characterized defensins from cultivated and selected wild-growing grasses. For each species, isolation of defensins or production by heterologous expression, peptide structure, biological activity, and structure–function relationship are described, along with the gene expression data. We also provide our results on in silico mining of defensin-like sequences in the genomes of all described grass species and discuss their potential functions. The data presented will form the basis for elucidation of the mode of action of grass defensins and high adaptability of grasses to environmental stress and will provide novel potent molecules for practical use in medicine and agriculture.

Structural Diversity and Highly Specific Host-Pathogen Transcriptional Regulation of Defensin Genes Is Revealed in Tomato

“…The majority of the tomato defensin peptides analyzed in the current study had the 1–8, 2–5, 3–6, 4–7 cysteine connectivity, as reported for C8 defensins. This is in accordance with several structural studies since plant defensins are characterized by two parallel disulfide bonds that connect the third beta-strand to the alpha-helix [ 23 , 28 ]. Moreover, it has been established that the evolution of disulfide bonds and tertiary structure undoubtedly occurs.…”

The γ-Core Motif Peptides of AMPs from Grasses Display Inhibitory Activity against Human and Plant Pathogens

“…The γ-core peptides DEFL1-20 65-82 and DEFL1-23 65-82 were also very similar, differing in three amino acid residues in the loop between the first two cysteines, two of which were conserved substitutions. The DEFL1-16 γ-core DEFL1-16 65-82 possessed a highly basic hexapeptide RGFRRR, which was discovered in a number of defensins found in plants of different families [ 23 ].…”

“…For example, the γ-core sequence of DEFL1-16 shown to exert potent antimicrobial properties was detected in DEFLs from different species of grasses including both cultivated and wild-growing ( Figure S8 ). Furthermore, this sequence was found in the defensins of plants beyond the grass family [ 23 ].…”

Insights of the Neofusicoccum parvum–Liquidambar styraciflua Interaction and Identification of New Cysteine-Rich Proteins in Both Species

“…In turn, during the defense response, the plants can produce proteins rich in cysteines with antifungal activity, such as defensins, lipid-transfer proteins, snakins, hevein-like peptides, knottins, hairpinins [29], and cyclopeptides [30]. Snakins/GASA proteins StSN1 from potato and MsSN1 from alfalfa, showed antifungal activity against many fungi and overexpression of StSN1 in potato and wheat improved plant resistance to commercially important pathogens [31].…”