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3.5.3: Life Cycle

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    The ascomycota life cycle with dark blue and a lighter red representing two different mating types
    Figure \(\PageIndex{1}\): Ascomycota life cycle. On the right side of the diagram, there are haploid ascospores of two different mating types produced (dark blue and red). The life cycle follows one of each of these ascospores as they each germinate and grow by mitosis into a monokaryon (a haploid thallus). During this stage, asexual production might occur by producing haploid conidia by mitosis. If the two complementary monokaryons meet, a chemical exchange might occur to stimulate the production of sexual structures: either a globose ascogonium with a hairlike projection called a trichogyne or an elongate antheridium. Each of these structures are filled with haploid nuclei (gametes). When the antheridium fuses with the trichogyne, plasmogamy (P!) occurs and the new hyphae generated from the asogonium are dikaryotic, meaning there are two different, unfused nuclei. During this period, ascocarp formation would occur around these tissues. Ascogenous, dikaryotic hyphae would form the asci. This occurs by first forming a crozier--the two different nuclei undergo mitosis while the tip of the hypha hooks sideways and two new septa form, isolating one dark blue nucleus in the tip, one red nucleus and one dark blue nucleus together in the hooked over region, and another red nucleus below the hook. The two nuclei in the hooked over portion of the crozier (the ascus mother cell) fuse together (K!=karyogamy) to form a diploid nucleus. This diploid nucleus instantly divides by meiosis, forming 4 haploid nuclei (half red, half dark blue). Each of these nuclei then divides by mitosis and the ascus elongates. Cell walls for around each nucleus, forming the ascospores. The ascospores are released, completing the life cycle. Diagram from SiliconProphet, CC BY-SA 4.0, via Wikimedia Commons.

    This page titled 3.5.3: Life Cycle is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Maria Morrow (ASCCC Open Educational Resources Initiative) .

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