Elicitor treatment of bean or soybean cell suspension cultures causes rapid cross-linking of preexisting structural proteins in the plant cell wall, following a burst of oxidative metabolism and generation of hydrogen peroxide at the plant cell surface. Oxidative cross-linking is also under developmental control associated with cellular maturation, eg., during hypocotyl growth, and in tissues subject to mechanical stress, eg., the stem-petiole junction. Stimulus-dependent oxidative cross-linking of pre- existing structural proteins in the plant cell wall is a novel site of cellular regulation, with potentially important functions in the flexible realization of the final functional architecture of cell walls during plant development, and rapid toughening of walls in the initial stages of microbial attack or related stresses. Moreover, the rapid response to defined elicitors, which is initiated within 1-2 minutes and complete within 5-10 minutes, provides the basis for functional dissection of the initial steps in the perception and transduction of elicitor signals. The present proposal seeks to explore the regulation of oxidative cross-linking, underlying signal mechanisms and the impact of cross-linking on cell wall properties.//