Wall‐protein antibodies as inhibitors of growth and of autolytic reactions of isolated cell wall

Abstract

Antiserum raised against protein prepared from corn (Zea mays L. hybrid B73 X Mo17) seedling cell wall exhibits antigrowth activity and inhibits autolytic reactions of isolated cell wall. The growth of corn coleoptile segments pretreated in wall‐protein antiserum was inhibited 35% compared to tissue which had been exposed to normal serum. Since the cuticle constituted a barrier to the entry of serum protein the coleoptile surface was abraded prior to exposure to the serum. Growth inhibition observed in nonabraded sections (8 to 10%) was apparently the result of the entry of serum protein via the cut ends of the tissue. Subsections recut from the central region of antiserum‐treated, nonabraded coleoptiles responded normally in growth experiments. Antiserum brought in contact with isolated cell wall prior to its use with intact coleoptiles was less effective as a growth inhibitor, which suggested that the antibodies which impede growth responses bind to cell wall.Wall‐protein antiserum also strongly inhibited autolytic reactions of isolated cell wall. Wall treated in normal serum or buffer liberated sugars at a rate of 8.6 μg‐ (mg wall dry‐weight)−1·h−1 while antiserum‐treated wall autolyzed at a rate of 2.6 μg·mg−1·h−1 representing a 70% reduction in autolytic potential. After 24 h yields from antiserum‐treated wall were 50% lower than yields obtained from control wall. The antiserum had no effect on the molecular‐weight distribution of the autolytically‐liberated products, and direct assays of wall‐bound and solubilized endo‐ and exo‐β‐d‐glucanases involved in autolytic reactions demonstrated no significant impairment of their catalytic activity. However, the addition to antiserum‐treated wall of a wall‐protein preparation containing autolytic enzymes resulted in a significant enhancement (132%) in autolytic potential. The evidence suggests that enzyme mobility may be critical in the autolytic hydrolytsis of plant cell wall.