Abstract
We describe a group of three acidic proteins, pathogenesis-related (PR)-p16.5a, PR-p16.5b, and PR-p16.5c, that accumulate in the leaves of Lupinus albus L. cv Rio Maior plants when infected with the fungus Colletotrichum gloeosporioides Penz. These proteins co-migrate in sodium dodecyl sulfate-polyacrylamide gels as a single band of 16.5 kD, behaving as charge isomers, and are related to several members of the defense-related PR-10 protein family. Localization of the proteins was investigated by techniques of tissue printing and immunogold electron microscopy; they are predominantly associated with the vascular system and are localized extracellularly. The accumulation of PR-p16.5a, PR-p16.5b, and PR-p16.5c also seems to be induced by cucumber mosaic virus and by two forms of abiotic stress, salicylic acid and ultraviolet, suggesting a general defense role for these proteins.