Classification of Fungi

Fungi are more closely related to animals than plants: Animals and fungi have flagellate cells Animals and fungi have flagellate cells Example: chytrid gametes and spores Example: chytrid gametes and spores Propel themselves with single posterior flagellum Propel themselves with single posterior flagellum Like animal cells, fungal cells have plate- like cristae in their mitochondria Like animal cells, fungal cells have plate- like cristae in their mitochondria

Classification Historically classified by characteristics of sexual spores and fruiting bodies Historically classified by characteristics of sexual spores and fruiting bodies More recently, molecular data More recently, molecular data DNA DNA RNA RNA Currently, 5 phlya Currently, 5 phlya

Fungal Evolution

Phylum Chytridiomycota Earliest fungal phlyum to diverge Earliest fungal phlyum to diverge Relatively simple; most unicellular Relatively simple; most unicellular ONLY FUNGI with flagellated cells ONLY FUNGI with flagellated cells Most have no sexual reproduction Most have no sexual reproduction Most decomposers; few cause disease Most decomposers; few cause disease

Phylum Glomeromycota Recently classified (2002) Recently classified (2002) Form symbiotic mycorrihizae Form symbiotic mycorrihizae Coenocytic hyphae Coenocytic hyphae No known sexual reproduction No known sexual reproduction

Phylum Zygomycota Coenocytic hyphae Coenocytic hyphae Ex: black bread mold (Rhizopus) Ex: black bread mold (Rhizopus) Most decomposers, some mycorrhizae, few disease Most decomposers, some mycorrhizae, few disease

Zygomycete Reproduction Hyphae of 2 different mating types (+) and (-) come in contact with one another Hyphae of 2 different mating types (+) and (-) come in contact with one another Tips of hyphae form gametangia, fuse Tips of hyphae form gametangia, fuse Karyogamy  zygote (2n) Karyogamy  zygote (2n)

Zygote develops into zygospore surrounded by zygosporangium Zygote develops into zygospore surrounded by zygosporangium zygospores - undergoes meiosis, creating haploid spores zygospores - undergoes meiosis, creating haploid spores Zygospore germinates, develops aerial hyphae with sporangium at tip Zygospore germinates, develops aerial hyphae with sporangium at tip Haploid spores produced through mitosis Haploid spores produced through mitosis May be all +, all -, or mix May be all +, all -, or mix online.com/objects/index_tj.asp?objID=BIO504 online.com/objects/index_tj.asp?objID=BIO504 online.com/objects/index_tj.asp?objID=BIO504 online.com/objects/index_tj.asp?objID=BIO504

Ascomycetes and Basidiomycetes are sister phyla

Phylum Ascomycota aka “sac fungi” or “cup fungi” aka “sac fungi” or “cup fungi” Includes yeasts, powdery mildews, molds Includes yeasts, powdery mildews, molds Hyphae with perforated septa Hyphae with perforated septa Asexual reproduction by conidiophores Asexual reproduction by conidiophores

Sexual Reproduction in Ascomycetes Opposite mating types produce coenocytic sexual hyphae Opposite mating types produce coenocytic sexual hyphae Hyphae fuse and nuclei migrate Hyphae fuse and nuclei migrate Pairs of nuclei associate but do not fuse Pairs of nuclei associate but do not fuse (n + n) (n + n)

New hyphae with dikaryotic cells develop and branch repeatedly New hyphae with dikaryotic cells develop and branch repeatedly Sac-shaped asci develop; karyogamy occurs Sac-shaped asci develop; karyogamy occurs Diploid zygote Diploid zygote Meiosis forms 4 haploid nuclei Meiosis forms 4 haploid nuclei Mitosis of each results in 8 haploid nuclei Mitosis of each results in 8 haploid nuclei Each haploid nucleus becomes enclosed in ascospore, released at tip of ascus Each haploid nucleus becomes enclosed in ascospore, released at tip of ascus

Phylum Basidiomycota aka “club fungi” aka “club fungi” Mushrooms, bracket fungi, puffballs Mushrooms, bracket fungi, puffballs Asexual reproduction less common Asexual reproduction less common

Basidiomycete Sexual Reproduction Hyphae of different mating types of primary mycelium come in contact and fuse Hyphae of different mating types of primary mycelium come in contact and fuse Form dikaryotic cell which develops into secondary mycelium Form dikaryotic cell which develops into secondary mycelium Under favorable conditions, form buttons along mycelium Under favorable conditions, form buttons along mycelium Button develops into mushroom Button develops into mushroom

Karyogamy – zygote is only diploid stage Karyogamy – zygote is only diploid stage Meiosis forms 4 haploid nuclei Meiosis forms 4 haploid nuclei Nuclei move to outer edge of basidium, form extensions  basidiospore Nuclei move to outer edge of basidium, form extensions  basidiospore Septum forms Septum forms

Key things to remember: Chytrids – only flagellated fungi Chytrids – only flagellated fungi Glomeromycetes – no sexual stage Glomeromycetes – no sexual stage Zygomycetes - gametangia Zygomycetes - gametangia Ascomycetes – dikaryotic stage; produce 8 haploid spores in ascus Ascomycetes – dikaryotic stage; produce 8 haploid spores in ascus Basidiomycetes – dikaryotic stage; produce 4 haploid spores in basidia Basidiomycetes – dikaryotic stage; produce 4 haploid spores in basidia