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Record: oai:ARNO:532199

AuthorJoão S. Furtado
TitleSignificance of the clamp-connection in the Basidiomycetes
JournalPersoonia - Molecular Phylogeny and Evolution of Fungi
AbstractThe cytogenetic phenomena affecting clamp-connection formation and the interpretation of this peculiar type of septum in the classification of the higher Basidiomycetes were reviewed from the literature and discussed. The cytogenetic data available are restricted to a small number of basidiomycetous species, but the formation of clamp-connection is included among the major phenomena whose genetic control is generalized for the Basidiomycetes. Clamp-connection formation in heterothallic species is controlled by the factors affecting sexuality. Simple septa appear in the hyphae of clamp-connection bearing species when (1) the simple septa result from independent nuclear division of the dikaryon, with or without subsequent hyphal growth of the newly recovered monokaryon, (2) when there is production and further development of apomictic (asexual) spores containing only one of the nuclear components of the dikaryon, or (3) when there appears any kind of monokaryotic hyphal growth caused by the splitting of the dikaryon. The monokaryotic hyphae are invariably simple-septate. Genetic experiments also show that simple septa appear in successful crosses between monokaryons of tetrapolar heterothallic species carrying homoallelic A or B, or even both at the same time, incompatibility factors. Therefore, the clamped and simple-septate hyphae of the Basidiomycetes are genetically and cytologically distinct. In homothallic species the control of clamp-connection formation is not well known, but whenever clampconnections are formed there are nuclear pairings. In pseudohomothallic species the formation of clamp-connections follows the pattern of the heterothallic species, but masked by the dikaryotic nature of the basidiospores.
The taxonomic interpretation of the clamp-connection is somewhat divergent. In many cases the authors did not investigate the cytogenetic condition of the hyphae to formulate their hypothesis. This shows the necessity of the proper evaluation of the pattern of septation of the hyphae before any hypothesis is formulated.
Document typearticle
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