Abstract
BackgroundThe production of antimicrobial peptides is a common defense strategy of living cells against a wide range of pathogens. Plant snakin peptides inhibit bacterial and fungal growth at extremely low concentrations. However, little is known of their molecular and ecological characteristics, including origin, evolutionary equivalence, specific functions and activity against beneficial microbes. The aim of this study was to identify and characterize snakin-1 from alfalfa (MsSN1).ResultsPhylogenetic analysis showed complete congruence between snakin-1 and plant trees. The antimicrobial activity of MsSN1 against bacterial and fungal pathogens of alfalfa was demonstrated in vitro and in vivo. Transgenic alfalfa overexpressing MsSN1 showed increased antimicrobial activity against virulent fungal strains. However, MsSN1 did not affect nitrogen-fixing bacterial strains only when these had an alfalfa origin.ConclusionsThe results reported here suggest that snakin peptides have important and ancestral roles in land plant innate immunity. Our data indicate a coevolutionary process, in which alfalfa exerts a selection pressure for resistance to MsSN1 on rhizobial bacteria. The increased antimicrobial activity against virulent fungal strains without altering the nitrogen-fixing symbiosis observed in MsSN1-overexpressing alfalfa transgenic plants opens the way to the production of effective legume transgenic cultivars for biotic stress resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0248-9) contains supplementary material, which is available to authorized users.
Highlights
The production of antimicrobial peptides is a common defense strategy of living cells against a wide range of pathogens
Identification and evolutionary analysis of MsSN1 To analyze the evolution and function of MsSN1, a 276bp cDNA fragment was isolated from roots by RT-PCR, using specific primers designed for a putative snakin-1 peptide predicted from the genome of the model legume Medicago truncatula (MtSN1, MTR_1g018640)
Our evolutionary study suggests that MsSN1 from Medicago sativa (JQ517286) presented in this work is the ortholog of the StSN1 from Solanum tuberosum (Q948Z4), the gibberellinstimulated transcript 1 (OsGASR1) from Oryza sativa (AB192574) and the GASA7 from Arabidopsis thaliana (AEC06348) previously described [3,42,43], offering a starting point for experimental data integration to indepth understanding of SN1 function in plants
Summary
The production of antimicrobial peptides is a common defense strategy of living cells against a wide range of pathogens. Alfalfa (Medicago sativa L.), known as the “Queen of Forages”, is a perennial legume This species is native to Asia, and is considered one of the first known crops with a cultivation history of at least 3500 years. Elite alfalfa cultivars must have high forage yields and maintain their productivity and stands over several years to provide substantial economic benefits. Regarding this complex topic, improved fungal disease resistance has been identified as the critical trait in alfalfa persistence [1]. In this context, it is proposed that the use of snakin-1 peptide (SN1), a powerful
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