Design, synthesis and characterization of antifungal peptides derived from the sequence of two thistle flowers defensins.

AGUSTINA FERNÁNDEZ; ISMAEL MALBRÁN; ROMINA VÁZQUEZ; SABINA MATÉ; FANNY GUZMÁN; LUCRECIA CURTO; LAURA SUSANA BAKÁS; SANDRA ELIZABETH VAIRO CAVALLI

La Plata

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofísica

Plantdefensins and defensin-like (DEFL) proteins are small basic, cysteine-richproteins ubiquitously expressed in the plant kingdom and mostly involved inhost defence. They present a highly variablesequence but a conserved structure. Sequence diversityappears to be correlated with differential functions exhibited (antifungal andantimicrobial, among others). Two highly conserved regions have been identifiedamong plant defensins, which are important for their activity: the g-core locatedin the C-terminal region with a β hairpin structure and the α-core located inthe N-terminal region. The importance of these motifs lies in the presence ofpositive residues which would allow the interaction with negative charges onthe pathogen membrane and/orcell wall.  In this work, potential antifungal peptideswere designed from these regions, through the use of bioinformatic tools andusing as template the sequence of two defensins (DefSm1D and DefSm2) of Silybum marianum previously cloned fromthistle flowers. Five peptides were synthesized, from DefSm1D sequence: 3243,3245 and 3246; and from DefSm2:3248 and 3250. Then, peptides were purified andcharacterized by HPLC-RP, MALDI-TOF-MS and CD. Their activity against thephytopathogenic fungus Fusariumgraminearum, their surface-active properties, as well as the ability toexclude the membrane-impermeable dye propidium iodide (PI) of conidia aftertreatment with the peptides were assessed. Peptides 3248 and 3250 were active againstF. graminearum at micromolarconcentration and produced PI uptake on conidia. The present work contributes to the knowledge ofdefensins, which are defense cysteine-rich proteins present in S. marianum flowers, which grows in Argentinaas a wild weed naturally resistance to fungal pathogens.