Glycobiology Advance Access published online on July 14, 2004
Glycobiology, doi:10.1093/glycob/cwh130
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1 Department of Biochemistry, Karnatak University, Dharwad - 580 003, India
* To whom correspondence should be addressed. E-mail: sawmy_bm{at}yahoo.co.in.
Many fungi are known to secrete lectins but their functional roles are not clearly understood. Sclerotium rolfsii, a soil borne plant pathogenic fungus capable of forming fruiting bodies called sclerotial bodies, secrete a cell wall associated TF-antigen specific lectin. In order to understand the functional role of this lectin, we examined the occurrence and expression of the lectin during development of the fungus. Further, putative endogenous receptors of the lectin were examined to substantiate the functional role of the lectin. Immunolocalization studies using FITC labeled lectin antibodies, revealed discrete distribution of lectin sites at the branching points of the developing mycelia and uniformly occurring lectin sites on the mature sclerotial bodies. During development of the fungus the lectin is expressed in small amounts on the vegetative mycelia and reaching very high levels in mature sclerotial bodies with a sudden spurt in secretion at the maturation stage. Capping of the lectin sites on the sclerotial bodies by lectin antibodies or haptens inhibit strongly the germination of sclerotial bodies indicating functional significance of the lectin. At the maturation stage the lectin interacts with the cell wall associated putative endogenous receptor leading to the aggregation of mycelium to form sclerotial bodies. The lectin-receptor complex probably acts as signaling molecule in the germination process of sclerotial bodies. Using biotinylated lectin, the receptors were identified by determining the specific lectin binding to lipid components, extracted from sclerotial bodies and separated on thin layer chromatograms. Preliminary characterization studies indicated that the receptors are glycosphingolipids and resemble inositolphosphoceramides. These findings together demonstrate the importance of lectin-receptor interactions to explain hitherto speculated functional role of the lectins, and also the glycosphingolipids of fungi.
Revised July 9, 2004
Accepted July 12, 2004
ORIGINAL ARTICLES
Immunolocalization and functional role of Sclerotium rolfsii lectin in development of the fungus by interacting with its endogenous receptor
2 Department of Plant Pathology, University of Agricultural Sciences, Dharwad, India
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