NOVEL DEFENSIN SUBFAMILY FROM SPINACH (SPINACIA-OLERACEA)

Antimicrobial peptides (So-D1-7) were isolated from a crude cell wall preparation from spinach leaves (Spinacia oleracea cv, Matador) and, j udged from their amino acid sequences, six of them (So-D2-7) represent ed a novel structural subfamily of plant defensins (group IV). Group-I V defensins were also functionally distinct from those of groups I-III . They were active at concentrations <20 mu M against Gram-positive (C lavibacter michiganensis) and Gram-negative (Ralstonia solanacearum) b acterial pathogens, as well as against fungi, such as Fusarium culmoru m, F, solani, Bipolaris maydis, and Colletotrichum lagenarium. Fungal inhibition occurred without hyphal branching. Group-IV defensins were preferentially distributed in the epidermal cell layer of leaves and i n the subepidermal region of stems. (C) 1998 Federation of European Bi ochemical Societies.