{"id":1440,"date":"2017-01-23T23:59:21","date_gmt":"2017-01-23T23:59:21","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology2\/?post_type=chapter&#038;p=1440"},"modified":"2024-04-25T18:50:59","modified_gmt":"2024-04-25T18:50:59","slug":"ascomycota","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-biology2\/chapter\/ascomycota\/","title":{"raw":"Ascomycota: The Sac Fungi","rendered":"Ascomycota: The Sac Fungi"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Identify characteristics and examples of fungi in the phylum Ascomycota<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idp2624016\">The majority of known fungi belong to the Phylum\u00a0<span id=\"term916\" data-type=\"term\">Ascomycota<\/span>, which is characterized by the formation of an\u00a0<span id=\"term917\" data-type=\"term\">ascus<\/span>\u00a0(plural, asci), a sac-like structure that contains haploid\u00a0<em data-effect=\"italics\">ascospores<\/em>. Filamentous ascomycetes produce hyphae divided by perforated septa, allowing streaming of cytoplasm from one cell to another. Conidia and asci, which are used respectively for asexual and sexual reproduction, are usually separated from the vegetative hyphae by blocked (non-perforated) septa. Many ascomycetes are of commercial importance. Some play a beneficial role for humanity, such as the yeasts used in baking, brewing, and wine fermentation, and directly as food delicacies such as truffles and morels.\u00a0<em data-effect=\"italics\">Aspergillus oryzae<\/em>\u00a0is used in the fermentation of rice to produce sake. Other ascomycetes parasitize plants and animals, including humans. For example, fungal pneumonia poses a significant threat to AIDS patients who have a compromised immune system. Ascomycetes not only infest and destroy crops directly; they also produce poisonous secondary metabolites that make crops unfit for consumption.<\/p>\r\n\r\n\r\n[caption id=\"attachment_1738\" align=\"aligncenter\" width=\"500\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/01\/26172307\/Figure_24_02_04.png\" target=\"_blank\" rel=\"noopener\"><img class=\"wp-image-1738\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/01\/26172307\/Figure_24_02_04.png\" alt=\" Ascomycetes have both sexual and asexual life cycles. In the asexual life cycle, the haploid (1n) mycelium branches into a chain of cells called the conidiophore. Spores bud from the end of the conidiophore and germinate to form more mycelia. In the sexual life cycle, a round structure called an antheridium buds from the male strain, and a similar structure called the ascogonium buds from the female strain. In a process called plasmogamy, the ascogonium and antheridium fuse to form a cell with multiple haploid nuclei. Mitosis and cell division result in the growth of many hyphae, which form a fruiting body called the ascocarp. The hyphae are dikaryotic, meaning they have two haploid nuclei. Asci form at the tips of these hyphae. In a process called karyogamy, the nuclei in the asci fuse to form a diploid (2n) zygote. The zygote undergoes meiosis without cell division, resulting in an ascus with four 1n nuclei arranged in a row. Each nucleus undergoes mitosis, resulting in eight ascospores, which are also arranged in a row at the tip of the hyphae. Dispersal and germination results in the growth of new mycelia.\" width=\"500\" height=\"635\" \/><\/a> Figure 1.\u00a0Click for a larger image. The lifecycle of an ascomycete is characterized by the production of asci during the sexual phase. The haploid phase is the predominant phase of the life cycle.[\/caption]\r\n\r\n[caption id=\"attachment_1739\" align=\"alignright\" width=\"400\"]<img class=\" wp-image-1739\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/01\/26180019\/Figure_24_02_05a.jpg\" alt=\"Micrograph shows asci, which appear as multiple, sphere-like shapes fused together into a structure about 7 microns across, and ascospores, which are small, light blue ovals about two microns wide by three microns long released from the asci.\" width=\"400\" height=\"266\" \/> Figure 2. The bright field light micrograph shows ascospores being released from asci in the fungus <i>Talaromyces flavus<\/i> var. <i>flavus<\/i>. (credit: modification of work by Dr. Lucille Georg, CDC; scale-bar data from Matt Russell)[\/caption]\r\n\r\nAsexual reproduction is frequent and involves the production of conidiophores that release haploid conidiospores. Sexual reproduction starts with the development of special hyphae from either one of two types of mating strains (Figure 1).\r\n\r\nThe \u201cmale\u201d strain produces an antheridium and the \u201cfemale\u201d strain develops an ascogonium. At fertilization, the antheridium and the ascogonium combine in plasmogamy, without nuclear fusion. Special dikaryotic ascogenous (ascus-producing) hyphae arise from this\u00a0<span id=\"term918\" data-type=\"term\">dikaryon<\/span>, in which each cell has pairs of nuclei: one from the \u201cmale\u201d strain and one from the \u201cfemale\u201d strain. In each ascus, two haploid nuclei fuse in karyogamy.\r\n\r\nThousands of asci fill a fruiting body called the\u00a0<span id=\"term919\" data-type=\"term\">ascocarp<\/span>. The diploid nucleus in each ascus gives rise to haploid nuclei by meiosis, and spore walls form around each nucleus. The spores in each ascus contain the meiotic products of a single diploid nucleus. The ascospores are then released, germinate, and form hyphae that are disseminated in the environment and start new mycelia (Figure 2).\r\n<div class=\"textbox exercises\">\r\n<h3>Practice Question<\/h3>\r\nWhich of the following statements is true?\r\n<ol style=\"list-style-type: lower-alpha;\">\r\n \t<li>A dikaryotic ascus that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores.<\/li>\r\n \t<li>A diploid ascus that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores.<\/li>\r\n \t<li>A haploid zygote that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores.<\/li>\r\n \t<li>A dikaryotic ascus that forms in the ascocarp undergoes plasmogamy, meiosis, and mitosis to form eight ascospores.<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"34326\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"34326\"]Statement a is true.[\/hidden-answer]\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/a1d98757-5a4e-4172-98a8-c7ad5349eced\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Identify characteristics and examples of fungi in the phylum Ascomycota<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idp2624016\">The majority of known fungi belong to the Phylum\u00a0<span id=\"term916\" data-type=\"term\">Ascomycota<\/span>, which is characterized by the formation of an\u00a0<span id=\"term917\" data-type=\"term\">ascus<\/span>\u00a0(plural, asci), a sac-like structure that contains haploid\u00a0<em data-effect=\"italics\">ascospores<\/em>. Filamentous ascomycetes produce hyphae divided by perforated septa, allowing streaming of cytoplasm from one cell to another. Conidia and asci, which are used respectively for asexual and sexual reproduction, are usually separated from the vegetative hyphae by blocked (non-perforated) septa. Many ascomycetes are of commercial importance. Some play a beneficial role for humanity, such as the yeasts used in baking, brewing, and wine fermentation, and directly as food delicacies such as truffles and morels.\u00a0<em data-effect=\"italics\">Aspergillus oryzae<\/em>\u00a0is used in the fermentation of rice to produce sake. Other ascomycetes parasitize plants and animals, including humans. For example, fungal pneumonia poses a significant threat to AIDS patients who have a compromised immune system. Ascomycetes not only infest and destroy crops directly; they also produce poisonous secondary metabolites that make crops unfit for consumption.<\/p>\n<div id=\"attachment_1738\" style=\"width: 510px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/01\/26172307\/Figure_24_02_04.png\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1738\" class=\"wp-image-1738\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/01\/26172307\/Figure_24_02_04.png\" alt=\"Ascomycetes have both sexual and asexual life cycles. In the asexual life cycle, the haploid (1n) mycelium branches into a chain of cells called the conidiophore. Spores bud from the end of the conidiophore and germinate to form more mycelia. In the sexual life cycle, a round structure called an antheridium buds from the male strain, and a similar structure called the ascogonium buds from the female strain. In a process called plasmogamy, the ascogonium and antheridium fuse to form a cell with multiple haploid nuclei. Mitosis and cell division result in the growth of many hyphae, which form a fruiting body called the ascocarp. The hyphae are dikaryotic, meaning they have two haploid nuclei. Asci form at the tips of these hyphae. In a process called karyogamy, the nuclei in the asci fuse to form a diploid (2n) zygote. The zygote undergoes meiosis without cell division, resulting in an ascus with four 1n nuclei arranged in a row. Each nucleus undergoes mitosis, resulting in eight ascospores, which are also arranged in a row at the tip of the hyphae. Dispersal and germination results in the growth of new mycelia.\" width=\"500\" height=\"635\" \/><\/a><\/p>\n<p id=\"caption-attachment-1738\" class=\"wp-caption-text\">Figure 1.\u00a0Click for a larger image. The lifecycle of an ascomycete is characterized by the production of asci during the sexual phase. The haploid phase is the predominant phase of the life cycle.<\/p>\n<\/div>\n<div id=\"attachment_1739\" style=\"width: 410px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1739\" class=\"wp-image-1739\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/01\/26180019\/Figure_24_02_05a.jpg\" alt=\"Micrograph shows asci, which appear as multiple, sphere-like shapes fused together into a structure about 7 microns across, and ascospores, which are small, light blue ovals about two microns wide by three microns long released from the asci.\" width=\"400\" height=\"266\" \/><\/p>\n<p id=\"caption-attachment-1739\" class=\"wp-caption-text\">Figure 2. The bright field light micrograph shows ascospores being released from asci in the fungus <i>Talaromyces flavus<\/i> var. <i>flavus<\/i>. (credit: modification of work by Dr. Lucille Georg, CDC; scale-bar data from Matt Russell)<\/p>\n<\/div>\n<p>Asexual reproduction is frequent and involves the production of conidiophores that release haploid conidiospores. Sexual reproduction starts with the development of special hyphae from either one of two types of mating strains (Figure 1).<\/p>\n<p>The \u201cmale\u201d strain produces an antheridium and the \u201cfemale\u201d strain develops an ascogonium. At fertilization, the antheridium and the ascogonium combine in plasmogamy, without nuclear fusion. Special dikaryotic ascogenous (ascus-producing) hyphae arise from this\u00a0<span id=\"term918\" data-type=\"term\">dikaryon<\/span>, in which each cell has pairs of nuclei: one from the \u201cmale\u201d strain and one from the \u201cfemale\u201d strain. In each ascus, two haploid nuclei fuse in karyogamy.<\/p>\n<p>Thousands of asci fill a fruiting body called the\u00a0<span id=\"term919\" data-type=\"term\">ascocarp<\/span>. The diploid nucleus in each ascus gives rise to haploid nuclei by meiosis, and spore walls form around each nucleus. The spores in each ascus contain the meiotic products of a single diploid nucleus. The ascospores are then released, germinate, and form hyphae that are disseminated in the environment and start new mycelia (Figure 2).<\/p>\n<div class=\"textbox exercises\">\n<h3>Practice Question<\/h3>\n<p>Which of the following statements is true?<\/p>\n<ol style=\"list-style-type: lower-alpha;\">\n<li>A dikaryotic ascus that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores.<\/li>\n<li>A diploid ascus that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores.<\/li>\n<li>A haploid zygote that forms in the ascocarp undergoes karyogamy, meiosis, and mitosis to form eight ascospores.<\/li>\n<li>A dikaryotic ascus that forms in the ascocarp undergoes plasmogamy, meiosis, and mitosis to form eight ascospores.<\/li>\n<\/ol>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q34326\">Show Answer<\/span><\/p>\n<div id=\"q34326\" class=\"hidden-answer\" style=\"display: none\">Statement a is true.<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_a1d98757-5a4e-4172-98a8-c7ad5349eced\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/a1d98757-5a4e-4172-98a8-c7ad5349eced?iframe_resize_id=assessment_practice_id_a1d98757-5a4e-4172-98a8-c7ad5349eced\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-1440\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 2e. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":9,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction\"}]","CANDELA_OUTCOMES_GUID":"b9d4a145-de19-481d-be62-380a77cd03eb, 3d21b2ce-fef1-4d99-8262-c9d5c8085939","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1440","chapter","type-chapter","status-publish","hentry"],"part":20,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/1440","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":10,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/1440\/revisions"}],"predecessor-version":[{"id":8338,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/1440\/revisions\/8338"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/parts\/20"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/1440\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/media?parent=1440"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapter-type?post=1440"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/contributor?post=1440"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/license?post=1440"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}