Characterization of two novel defense peptides from pea (Pisum sativum) seeds

A fraction that possesses antifungal activity against Aspergillus niger has been isolated from seeds of the pea (Pisum sativum) by ammonium sulfate fr actionation followed by gel filtration on Sephadex G-75, On further purific ation by reverse-phase high performance liquid chromatography, two small cy steine-rich polypeptides mere obtained (Psd1 and Psd2). They are localized primarily in vascular bundles and epidermis tissues of pea pods and exhibit high antifungal activity toward several fungi, displaying IC50 values rang ing from 0.04 to 22 mu g/ml. This inhibitory activity decreases when A. nig er growth medium is supplemented with cations such as Ca2+, Mg2+, Na+, and K+, Although the primary sequence of both Psd1 and Psd2 shows homology with other plant defensins, they cannot easily be assigned to any established g roup. (C) 2000 Academic Press.