Purification and properties of growth stage-dependent antiviral proteins from the leaves of Celosia cristata

Two antiviral glycoproteins, active against mechanical transmission of two tobamoviruses, tobacco mosaic virus and sunnhemp rosette virus, and citrus ring spot virus (ungrouped), were purified from the dried leaves of Celosia cristata. These proteins, called CCP-25 and CCP-27, have M r 25 and 27 kDa, respectively. Their concentration was found to vary between the pre-flowering and post-flowering stages of C. cristata. Either of these proteins, obtained at different growth stages, inhibited by >90% lesion formation at a concentration of 20–30 μg ml −1. They were resistant to proteases in the native state, but were readily digested when denatured. Both of them imparted actinomycin D sensitive resistance by inhibiting local lesions on Nicotiana tabacum cv. Samsun NN by tobacco mosaic virus. Their application, individually, also resulted in high resistance in systemic hosts to sunnhemp rosette virus, and citrus ring spot virus, respectively.