Developmental accumulation of lectin in Rhizoctonia solani: a potential role as a storage protein

Abstract

The lectin in Rhizoctonia solani is a major protein, although its function was previously unknown. An enzymelinked immunosorbent assay was developed to quantify the lectin content in mycelium, sclerotia and culture filtrate during the development of R. solmi 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.

Entomotoxic and nematotoxic lectins and protease inhibitors from fungal fruiting bodies

“…In fungi, lectins have been implicated in defense against fungivores , in fungal developmental processes including fruiting body formation (Luan et al 2010;Swamy et al 2004;Wang et al 1998), in molecular recognition during mycorrhization or parasitism (Guillot et al 1994;Guillot and Konska 1997;Wang et al 1998), and in storage of nutrients (Kellens and Peumans 1990). Most experimental evidence is in support of the defensive function of fungal lectins, which is mediated by binding of the lectin to non-self glycans on the cells of the target organism (Künzler 2015).…”

“…Expression of RSA was found to be developmentally regulated, lectin expression being low in vegetative mycelium and the protein accumulating in adult sclerotia (Hamshou et al 2007;Kellens and Peumans 1990). Based on the accumulation of protein during sclerotium formation and its depletion during mycelium germination, a storage function for RSA in R. solani has been proposed.…”

Lectin Variation in Members of <i>Rhizoctonia</i> Species

“…The Rhizoctonia lectins isolated to date have been characterized as dimers or tetramers with rare cases of monomers, suggesting that they are more active as aggregates and do play a major biological role in the species 1,3,11,12,13,24) . Although lectin on the hyphal surfaces of Rhizoctonia fungi have previously been demonstrated to be a fungal-fungal recognition component, preliminarily, our data did not correlate lectin with the anastomosis recognition process.…”

“…Media containing L-asparigine have been reported to strongly affect the lectin content in R. solani cultures 12) . The introduction of L-asparagine monohydrate (4 g L -1 ) in 2% WA bioassay setups had a significant increase on the FF of SAIs but had no effect on that of NSAIs.…”

“…Recently, the presence of lectins on the hyphal surfaces and tissues of Rhizoctonia fungi has been reported 4,11,12,13,24) . These findings, however, were based on limited groups of Rhizoctonia spp.…”