Molecular, biochemical and structural characterization of osmotin-like protein from black nightshade (Solanum nigrum)

A full-length 910bp cDNA encoding osmotin-like protein with an open reading frame of 744bp encoding a protein of 247 amino acids with a calculated molecular mass of 26.8kDa was cloned from Solanum nigrum (SniOLP). Phylogenetic analysis revealed the evolutionary conservation of this protein among diverse taxa. The genomic DNA gel blot showed that SniOLP belongs to a small multigene family and it showed organ-specific expression. Time-course studies revealed that the expression of SniOLP was upregulated by treatment with various signaling molecules, osmotic and oxidative stress inducers. Recombinant protein purified from overexpressed Escherichia coli cells showed hyphal growth inhibition in Rhizoctonia batiticola and Sclerotinia sclerotiorum but without any endo-beta-1,3-glucanase activity. Model built by homology modeling showed that the protein consists of an acidic cleft region that is capable of interacting with the carbohydrate components of the fungal cell walls. Analysis of the structure and functional relationship was carried out by docking of the beta-(1,3)-glucan onto the acidic cleft region on the surface of the protein (SniOLP).