Ascus

Encyclopedia : A : AS : ASC : Ascus

Asci of Hypomyces chrysospermus (they are unitunicate-operculate)

An ascus (plural asci) is the spore-bearing container produced in the ascocarps of ascomycete fungi. Each ascus contains eight ascospores, produced by a meiotic cell division followed by a mitotic cell division. Asci release their spores by bursting. When one ascus bursts, it triggers the bursting of all the other asci in the ascocarp. This is an example of positive feedback.

The form of the ascus wall (unitunicate-operculate, unitunicate-inoperculate, bitunicate, or prototunicate) is important in the classification of ascus fungi.

Asci, notably those of Neurospora crassa, have been used in laboratories for studying the process of meiosis, because the four cells produced by meiosis line up in regular order. By modifying a gene coding for spore color, the biologist can study crossing over and other phenomena.

External links

• [IMA Mycological Glossary: Ascus]
• [APSnet Illustrated Glossary of Plant Pathology: Ascus]

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