Fruiting body formation in the basidiomycete Coprinus cinereus is a developmental process that occurs as a response of the mycelium to external stimuli. First, localized, highly branched hyphal structures (knots) are formed as a reaction to nutritional depletion. Hyphal-knot formation is repressed by light ; however, light signals are essential for the development of the hyphal knot into an embryonic fruiting body (primordium) as well as karyogamy, meiosis and fruiting body maturation. The role of the different environmental signals in the initial phases of fruiting body development was analysed. It was observed that two fungal galectins, Cgl1 and Cgl2, are differentially regulated during fruiting body formation. cgl2 expression initiated in early stages of fruiting body development (hyphal knot formation) and was maintained until maturation of the fruiting body, whereas cgl1 was specifically expressed in primordia and mature fruiting bodies. Immunofluorescence and immunoelectron microscopy studies detected galectins within specific fruiting body tissues. They localized in the extracellular matrix and the cell wall but also in membrane-bound bodies in the cytoplasm. Heterologous expression of Cgl2 in Saccharomyces cerevisiae indicated that secretion of this protein occurred independently of the classical secretory pathway.

Primordial bud formation in Coprinus lagopus is strictly light dependent, but only [Formula: see text]exposure to light is required. However, continued exposure to light is mandatory for further development and hymenium differentiation into a mature basidiocarp. Without light, the stipe of the primordial bud elongates as if the basidiocarp is maturing and the primordial bud eventually aborts. The optimum light intensity is less than 1 ft-c at a wavelength of 410–450 nm. It is possible that cap and stipe are initiated by the same stimulus, but further development of each is under different controls. The former is light dependent whereas the latter is not.The primordial bud development was studied at daily intervals for 3 days until meiosis started and their structural differentiations were studied by paraffin section and squash preparations. The cap of the primordial bud has three zones: the veil, the hymenium, and the stipe. The veil cells are large and multinucleate and lack clamp connections. The stipe includes a central column of dikaryotic hyphae and a cortex of giant multinucleate cells. The hymenium contains only dikaryotic hyphae, which later develop into basidia, cystidia, and medullar cells. The gill development is started by structural organization of dikaryotic hyphae into dome-shaped ridges, which is followed by disintegration of cells surrounding these ridges to form gills. The gill expansion is also light dependent.When the primordial buds were exposed to light, there was a thrust of mitotic activity. Mitotic metaphase, anaphase, and telophase configurations were clearly demonstrated.

Meiosis in the basidiomycete Coprinus cinereus was analyzed by three dimensional reconstructions of nuclei covering the period from leptotene to telophase II. Crosses involving three different strains (JR52, PR2301 and E991) were used.The analysis of 94 completely reconstructed nuclei arranged in a temporal sequence according to the morphology of the synaptonemal complex, the centromeres and the centrosomes permitted the following observations and conclusions: (1) The haploid chromosome number of Coprinus cinereus is 13. (2) Reciprocal translocations have been identified in strains PR2301 and E991. In the former strain, the translocation is between chromosomes 3 and 5 and in the latter between chromosomes 1 and 9. (3) Interlockings and chromosome breaks are present during zygotene but at a lower frequency than in organisms with longer chromosomes. The translocation quadrivalents are more often than normal bivalents involved in interlockings and have more chromosome breaks. (4) Tranformation of a translocation quadrivalent into two heteromorphic bivalents was only observed once in agreement with the contention that the turnover of the synaptonemal complex required for this transformation is prevented in bivalent regions where crossing over has occurred. (5) Correction of interlockings by the ~breakage-reunion~ mechanism is complete before mid-late pachytene. (6) The presence of two apparently normal bivalents replacing the translocation quadrivalent in at least one, possibly several, cases suggests that a ~retranslocation~ has taken place, possibly by a mechanism similar to that responsible for the resolution of interlockings. The implications of this possibility are discussed. (7) During early diplotene the synaptonemal complexes are eliminated from the bivalent arms while synaptonemal complex constituents often remain associated with the centromeres and the chiasmata until late diplotene. (8) Homologous centromere regions remain fused at least until early diakinesis. It is the suggested that this association may serve the same function as chiasmata in maintaining the bivalent configuration up to metaphase I and hence improve the chances of a regular disjunction in bivalents without chiasmata. (9). Recombination nodules are readily identified in the central region of the synaptonemal complex from early zygotene to late diplotene. The total number of nodules expected upon completion of synaptonemal complex formation at late zygotene amounts to 37 and is the same as that observed at early pachytene. The total number of nodules is reduced to 26 before midlate pachytene, a reduction similar to that reported in other organisms. (10) An increasing fraction of the nodules becomes larger and surrounded by chromatin during pachytene -diplotene and by late diplotene, all nodules are replaced by small chromatin condensations -chiasmata. ( 11 ) The distribution of nodules among and along the bivalents has been analyzed by comparing the observed distributions and those produced by computer simulation of a random positioning ...

Galectins are members of a genetically related family of ␤-galactoside-binding lectins. At least eight distinct mammalian galectins have been identified. More distantly related, but still conserving amino acid residues critical for carbohydrate-binding, are galectins in chicken, eel, frog, nematode, and sponge. Here we report that galectins are also expressed in a species of fungus, the inky cap mushroom, Coprinus cinereus. Two dimeric galectins are expressed during fruiting body formation which are 83% identical to each other in amino acid sequence and conserve all key residues shared by members of the galectin family. Unlike most galectins, these have no N-terminal post-translational modification and no cysteine residues. We expressed one of these as a recombinant protein and studied its carbohydrate-binding specificity using a novel nonradioactive assay. Binding specificity has been well studied for a number of other galectins, and like many of these, the recombinant C. cinereus galectin shows particular affinity for blood group A structures. These results demonstrate not only that the galectin gene family is evolutionarily much older than previously realized but also that fine specificity for complex saccharide structures has been conserved. Such conservation implies that galectins evolved to perform very basic cellular functions, presumably by interaction with glycoconjugates bearing complex lactoside carbohydrates resembling blood group A.Galectins are animal lectins that are related in amino acid sequence and specifically bind to ␤-galactoside carbohydrates such as lactose (1). Members of this gene family all include a conserved carbohydrate-binding domain but vary in inclusion of other domains and in tissue expression patterns. More distantly related, but conserving critical amino acid residues involved in carbohydrate-binding, are galectins in chicken, eel, frog, nematode, and sponge (2).Although galectins have been studied for 20 years now, physiological functions for these proteins have not yet been clearly established. Their affinity for oligosaccharides found on glycoconjugates on cell surfaces or in extracellular matrix has suggested that galectins function extracellularly by binding to such ligands. Indeed, certain galectins have particular affinity for specific glycoprotein ligands, such as polylactosamine chains on laminin (1, 3). When added to cells or overexpressed after transfection, galectins can have major effects on cell adhesion, proliferation, apoptosis, metastasis, and immune function (1-6). However, evidence has also been presented for intracellular functions of galectins, for instance in message splicing (7) or as nuclear proteins (8). Therefore, efforts are being directed at exploring the evolutionary origin of galectins in the hope that their functions will be easier to define in simple model organisms.Here we report that a species of fungus, the inky cap mushroom, Coprinus cinereus, expresses two lectins related in sequence and carbohydrate-binding specificity to other galectins. T...

The close synchrony of meiotic events within the basidiocarp of Coprinus lagopus permits the time sequence study of division stages. It takes about 16 h from the beginning of karyogamy to the completion of meiosis (zygotene to tetrad formation). Nuclear fusion and chromosome pairing occupy about 4 h, pachytene 5 h, diplotene 4 h, and all the other stages including the second meiotic division appear to be very transitory and together occupy less than 3 h. The centrosome divides at late diplotene. The entire second meiotic division takes about 1 hour and different stages overlap a great deal. The four sterigmata are formed after the completion of second division. The basidiospores mature in 8–10 h after the tetrad formation.