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.
Highlights
Plants have developed a variety of mechanisms to cope with abiotic and biotic stresses
Overexpression of a chimeric cleavable polyprotein precursor containing the mature domains of the plant defensins Dahlia merckii AMP1 (DmAMP1) and RsAFP2 resulted in the efficient release of both bioactive antifungal peptides (François et al, 2002; Thevissen et al, 2004)
Overexpression of the Capsicum annuum AMP1 (CaAMP1) gene in Arabidopsis (Arabidopsis thaliana) increased resistance against both bacterial and fungal pathogens, and tolerance to high salt and drought stresses (Lee et al, 2008; Lee and Hwang, 2009). Another example demonstrating the involvement of antimicrobial peptides (AMPs) in abiotic stress is the zinc stress tolerance in transgenic Arabidopsis lines obtained by overexpression of PLANT DEFENSIN (PDF) genes of Arabidopsis halleri (Mirouze et al, 2006)
Summary
Plants have developed a variety of mechanisms to cope with abiotic and biotic stresses. Overexpression of the Capsicum annuum AMP1 (CaAMP1) gene in Arabidopsis (Arabidopsis thaliana) increased resistance against both bacterial and fungal pathogens, and tolerance to high salt and drought stresses (Lee et al, 2008; Lee and Hwang, 2009) Another example demonstrating the involvement of AMPs in abiotic stress is the zinc stress tolerance in transgenic Arabidopsis lines obtained by overexpression of PLANT DEFENSIN (PDF) genes of Arabidopsis halleri (Mirouze et al, 2006). We characterized two Arabidopsis AMPs, designated ARACIN1 and ARACIN2, that are transcriptionally regulated by both biotic and abiotic stresses We demonstrate their antifungal activities in vitro against the broad-host necrotrophic plant fungus Botrytis cinerea, the causing agent of gray mold disease, and Alternaria brassicicola, which causes black spot disease on members of the Brassicaceae family (Neergaard and Andersen, 1945; Braverman, 1971; Lawrence et al, 2008). In planta overexpression of ARACIN1 significantly improved resistance against both pathogens
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