Alfalfa snakin-1 prevents fungal colonization and probably coevolved with rhizobia

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.

Expression, purification and characterization of the recombinant cysteine-rich antimicrobial peptide snakin-1 in Pichia pastoris

“…The snakin family is a novel plant antimicrobial peptide family which shows good similarity with the members of the gibberellic acid stimulated transcript (GAST) and gibberellic acid stimulated in Arabidopsis (GASA) protein families in Arabidopsis [20]. These cysteine-rich peptides are widely distributed among plant species, including potato, tomato, avocado, petunia, French bean, gerbera, strawberry, maize, soybean, pepper, rice, Arabidopsis, and alfalfa [20][21][22][23]. All snakin peptides are characterized by twelve conserved cysteine residues that are involved in the formation of six disulfide bonds [19].…”

The role of Cercospora zeae-maydis homologs of Rhodobacter sphaeroides1O2-resistance genes in resistance to the photoactivated toxin cercosporin

“…Snakin/GASA peptides, which were initially isolated from potato (LopezSolanilla, Garcia-Olmedo and Rodriguez-Palenzuela 1998), are widely distributed among plant species and were found to be active against bacterial, fungal and nematode pathogens (Segura et al, 1999;Berrocal-Lobo et al, 2002;Almasia et al, 2008;Kovalskaya and Hammond 2009;Balaji, Sessa and Smart 2011;Kovalskaya, Zhao and Hammond 2011;Mao et al, 2011), suggesting a critical role of snakin peptides in biotic stress tolerance. Interestingly, phylogenetic and functional analysis of snakin-1 from alfalfa further support that snakin peptides have important and ancestral roles in land plant innate immunity (García et al, 2014).…”

“…In recent years, plant antimicrobial peptides snakin-1 and snakin-2 have been the subject of interest as primary candidates for generating broad-spectrum biotic stress tolerance in crops (Kovalskaya et al, 2011;Balaji and Smart 2012;GuzmanRodriguez et al, 2013;Rong et al, 2013;García et al, 2014;Meiyalaghan et al, 2014;Mohan et al, 2014). Despite the importance of roles played by snakin peptides in plant-microbe interactions in nature and the potential of these peptides to improve crop production, the molecular mechanisms underlying its inhibition of microbial cells are poorly understood.…”

“…Previously, we experimentally demonstrated the antimicrobial activity of alfalfa snakin-1 (MsSN1) against bacterial strain Pseudomonas fluorescens Pf-5 both in vitro and in planta (García et al, 2014). As a strategy for discovering the cellular pathways affected in bacteria by snakin-1, we here screened a genomewide mutant library of P. fluorescens Pf-5 for resistance to MsSN1.…”

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

“…The mature peptide is derived from a preprotein, in the case of S. tuberosum St-GSL1 (previously known as St-SN1), or a preproprotein, in the case of St-GSL2 (St-SN2) harboring a 15-amino acid region between the NSS and the mature St-GSL2. Both St-GSL peptides, as well as the alfalfa SNAKIN Ms-SN1, display in vitro broad antimicrobial activity (Segura et al, 1999;Berrocal-Lobo et al, 2002;García et al, 2014) and overexpression of their corresponding genes in several plants resulted in increased resistance against fungal and bacterial pathogens (Almasia et al, 2008;Rong et al, 2013;García et al, 2014). Additionally, SNAKIN/GASA peptides have been suggested to have an important role in plant development.…”