Major Sclerotial Polypeptides Of Psychrophilic Fungi: Identification, Immunological Relatedness, Localization And In Vivo Synthesis
Major sclerotial polypeptides have been identified by one and two-dimensional gel electrophoresis in Myriosclerotinia borealis, Coprinus psychromorbidus, Typhula idahoensis and Typhula incarnata. The number, molecular mass, relative proportions and isoelectric points of the major sclerotial polypeptides varied from species to species. Furthermore, several of the major sclerotial polypeptides were shown to be antigenically related by Ouchterlony double-diffusion and Western blot analysis. Polyclonal antibodies used for localizing the major sclerotial polypeptides in the sclerotia by immunofluorescence microscopy showed that the major polypeptides were sequestered in sclerotial protein bodies in all four species. This indicates that the major sclerotial polypeptides may play a role as storage proteins. Major sclerotial polypeptides were not detected in vegetative hyphae of M. borealis and C. psychromorbidus at 5{dollar}spcirc{dollar}C, but significant accumulations were observed at 25{dollar}spcirc{dollar}C by Western blot analysis. Major sclerotial polypeptides were detected in the vegetative hyphae of the Typhula species incubated at 5{dollar}spcirc{dollar}C. Fluorographic analysis combined with Western blotting showed that synthesis of the major sclerotial polypeptides was induced when vegetative hyphae of M. borealis and C. psychromorbidus were shifted from 5{dollar}spcirc{dollar}C to 10{dollar}spcirc{dollar}C, whereas vegetative hyphae of T. idahoensis and T. incarnata showed constitutive synthesis of some of the major sclerotial polypeptides at 5{dollar}spcirc{dollar}C. A shift from 5{dollar}spcirc{dollar}C to 10{dollar}spcirc{dollar}C had little effect on the synthesis of major sclerotial polypeptides in the Typhula spp. Thus, vegetative hyphae of M. borealis and C. psychromorbidus appeared to be much more sensitive to temperature as a cue for inducing synthesis of the major sclerotial polypeptides than vegetative hyphae of the Typhula spp. The significance of these observations and their bearing on sclerotial development in the species examined is discussed.
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