DEVELOPMENTAL ACCUMULATION OF LECTIN IN RHIZOCTONIA-SOLANI - A POTENTIAL ROLE AS A STORAGE PROTEIN

The lectin in Rhizoctonia solani is a major protein, although its function was previously unknown. An enzyme linked immunosorbent assay was developed to quantify the lectin content in mycelium, sclerotia and culture filtrate during the development of R. solani grown in a synthetic medium. Lectin content was low in young mycelium but increased dramatically at the onset of sclerotium formation, reaching a maximum in adult sclerotia. Upon myceliogenic germination, the lectin content of the sclerotia rapidly decreased. It thus appears that the lectin is a developmentally regulated sclerotium-specific protein accumulating during sclerotium formation and disappearing during germination. Its relative abundance and the pattern of developmental control suggests that the lectin is probably a storage protein. Lectin accumulation was also influenced by the composition of the medium. Addition of supplementary carbohydrate (D-glucose) caused a marked reduction in lectin content whereas increased nitrogen in the form of L-asparagine led to a higher lectin content. However, when the L-asparagine concentration was too high, autolysis occurred and part of the lectin was released into the medium.