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An ascus (from Ancient Greek ἀσκός (askós) 'skin bag, wineskin'; pl.: asci) [1] is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division.
Eight ascospores (green) are typically present in each ascus. Bitunicate asci in the pseudothecium of Leptosphaerulina sp. This is similar to a perithecium, but the asci are not regularly organised into a hymenium and they are bitunicate , having a double wall that expands when it takes up water and shoots the enclosed spores out suddenly to ...
The defining feature of this fungal group is the "ascus" (from Ancient Greek ἀσκός (askós) 'sac, wineskin'), a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of Ascomycota are asexual and thus do not form asci or ascospores.
The species of Sordaria are similar morphologically, producing black perithecia containing asci with eight dark ascospores in a linear arrangement. These species share a number of characteristics that are advantageous for genetic studies. They all have a short life cycle, usually 7–12 days, and are easily grown in culture. Most species are ...
A mature perithecium may contain as many as 300 asci, each derived from identical fusion diploid nuclei. Ordinarily, in nature, when the perithecia mature the ascospores are ejected rather violently into the air. These ascospores are heat resistant and, in the lab, require heating at 60 °C for 30 minutes to induce germination.
The asci are cylindrical with a thickened ascus tip. Ascospores are usually cylindrical, contain multiple septa , and disarticulate into part-spores or remain intact at maturity. [ 2 ]
P. capsellae is an ascomycete, meaning it produces ascospores housed in asci as means of sexual reproduction. Sexual structures are found in the sexual stage of this fungus, which has been classified as Mycosphaerella capsellae. The ascocarp of M. capsellae is a cleistothecium, meaning asci are shielded from the environment prior to ascospore ...
The asci form a layer lacking paraphyses, and they lack croziers. The ascospores frequently bud into multiple yeast cells within the asci. Phylogenetically, Taphrina is a member of a basal group within the Ascomycota, and type genus for the subphylum Taphrinomycotina , the class Taphrinomycetes , and order Taphrinales .