ARACINs, Brassicaceae-Specific Peptides Exhibiting Antifungal Activities against Necrotrophic Pathogens in Arabidopsis  

Abstract

Plants have developed a variety of mechanisms to cope with abiotic and biotic stresses. In a previous subcellular localization study of hydrogen peroxide-responsive proteins, two peptides with an unknown function (designated ARACIN1 and ARACIN2) have been identified. These peptides are structurally very similar but are transcriptionally differentially regulated during abiotic stresses during Botrytis cinerea infection or after benzothiadiazole and methyl jasmonate treatments. In Arabidopsis (Arabidopsis thaliana), these paralogous genes are positioned in tandem within a cluster of pathogen defense-related genes. Both ARACINs are small, cationic, and hydrophobic peptides, known characteristics for antimicrobial peptides. Their genes are expressed in peripheral cell layers prone to pathogen entry and are lineage specific to the Brassicaceae family. In vitro bioassays demonstrated that both ARACIN peptides have a direct antifungal effect against the agronomically and economically important necrotrophic fungi B. cinerea, Alternaria brassicicola, Fusarium graminearum, and Sclerotinia sclerotiorum and yeast (Saccharomyces cerevisiae). In addition, transgenic Arabidopsis plants that ectopically express ARACIN1 are protected better against infections with both B. cinerea and A. brassicicola. Therefore, we can conclude that both ARACINs act as antimicrobial peptides.

The Brassicaceae‐specific secreted peptides, STMPs, function in plant growth and pathogen defense

“…However, none of the peptides had antibacterial activity against Escherichia coli (Figure S10C, D). These results demonstrate that STMP1, STMP2, and STMP10 are AMPs, which is consistent with the previous finding that ARACIN2/STMP9 functions as an AMP (Neukermans et al ).…”

“…Transgenic Arabidopsis overexpressing the STMPs exhibited severely retarded growth (Figure ), suggesting that they play a distinct role in plant growth and development in Brassicaceae plants. To date, 1,789 Brassicaceae‐specific genes have been identified (Neukermans et al ). Interestingly, these Brassicaceae‐specific genes are enriched for plant AMPs (Neukermans et al ).…”

“…To date, 1,789 Brassicaceae‐specific genes have been identified (Neukermans et al ). Interestingly, these Brassicaceae‐specific genes are enriched for plant AMPs (Neukermans et al ). Our in vitro assays showed that STMP1, STMP2, and STMP10 have direct antibacterial effects against Pst DC3000, R. solanacearum , B. subtilis , and A. tumefaciens (Figure ).…”

“…We identified the secreted transmembrane peptides (STMPs), a novel family of secreted peptides in Arabidopsis . Among these proteins, only one family member, ARACIN2/STMP9, was previously shown to have antifungal activity against Fusarium graminearum , Alternaria brassicicola , and yeast, thereby functioning as an antimicrobial peptide (AMP) (Neukermans et al ). Plant AMPs are generally small (up to 100 aa residues), hydrophobic, secreted peptides that function as fundamental components of the nonspecific defense system in host plants (Nawrot et al ; Salas et al ).…”

The Plant Peptidome: An Expanding Repertoire of Structural Features and Biological Functions

“…The mature peptides of 39 to 40 amino acids are derived from a preproprotein and contain two Cys residues (Figure 3). Chemically synthesized ARACINs displayed in vitro antifungal activity while overexpression of the ARACIN1 precursor in Arabidopsis resulted in increased resistance against Botrytis cinerea and Alternaria brassicicola (Neukermans et al, 2015).…”