Prof. Khaled H. Abu-Elteen Fungal Life Cycles Prof. Khaled H. Abu-Elteen

Basic fungal life cycle 1. Zygotic - haploid phase is dominant fig. 13.5b

Basic fungal life cycle 2. Fertilization doesn’t happen all at once Plasmogamy - fusion of cytoplasm Karyogamy - fusion of nuclei (gametes) heterokaryotic dikaryotic fig. 31.2

3. Yeast for brewing and baking: Saccharomyces cerevisiae

B. Zygomycota 1. No dikaryotic growth 2. Both sexual and asexual sporangia

C. Ascomycota - Life cycle 1. Dikaryotic growth 2. Fruiting body: ascocarp 3. Fertile layer with asci 4. Eight ascospores per ascus (sac) 5. Asexual reproduction via conidia

D. Basidiomycota - Life cycle 1. Dikaryotic growth 2. Fruiting body: basidiocarp 3. Fertile layer on gills with basidia (“clubs”) 4. Four spores per basidium 5. Asexual reproduction is rare

D. Basidiomycota - structure 2. Fruiting body: basidiocarp 3. Fertile layer on gills with basidia (“clubs”) 4. Four spores per basidium

E. Deuteromycota - “fungi imperfecti” 1. Not a true phylum (not a natural group): polyphyletic 2. Fungi with no known sexual reproduction 3. Asexual reproduction by conidia

III. Fungal Mutualisms Definitions: Symbiosis - 2 organisms living together in intimate physical contact Mutualism - both organisms benefit from the relationship Parasitism - one benefits, one loses Commensalism - one benefits, other not affected

III. Fungal Mutualisms Questions: 1. Definition of mutualism vs. symbiosis 2. What fungal and photosynthetic partners are involved? 3. What is the “currency” of the mutualism? How do the partners benefit? 4. What is the structure and/or morphology of the organismal interaction? 5. What is the ecological importance?

FUNGAL LIFE CYCLES ASEXUAL HAPLOID HAPLOID WITH RESTRICTED DIPLOID HAPLOID-DIKARYOTIC DIKARYOTIC HAPLOID-DIPLOID DIPLOID

MITOSPORES Result from mitosis and cell division No change in nuclear ploidy Usually produced in great quantities Resistance to unfavorable environmental conditions varies Are important in dispersal

MITOSPORES motile - zoospores non-motile - produced from hyphae - conidia non-motile - produced from sporangia - sporangiospores

MEIOSPORES Result from meiosis Are haploid Are genetically different from parent hyphae May serve as a resistant stage Are important in dispersal

CHLAMYDOSPORES Nuclear ploidy same as parent cell Formed from a vegetative cell or cells Shape may reflect cell shape Wall may become thickened and dark in color Are resistant to unfavorable environmental conditions

SPORE GERMINATION DORMANCY Constitutional (memnospores) Exogenous (xenospores)

GERMINATION FACTORS Water Temperature Nutrition pH (4.5-6.5) Oxygen

GERMINATION PROCESS Water content increases; spore swells; enzymes go into solution. Vacuolation increases. Endoplasmic reticulum & other organelles increase Respiration increases & mitochondria enlarge and form more cristae.

GERMINATION PROCESS Vesicles involved in wall synthesis appear. Lipids disappear as they are used up as an energy source. An opening on the spore wall appears or the plug in a germ pore is removed. A hyphal tube, called the germ tube, emerges from the opening or pore.

SPORE FORMATION Metabolic state - sporulation competence Initiation factors - 1. nutrition - concentration, qualitative composition, relative quantitative composition, sequence of available nutrients. 2. water. 3. pH. 4. O2/CO2 ratio. 5. light - quality/quantity. 6. biological interactions. 7. temperature. Method of formation.

SPORE CHARACTERISTICS Low water content. Large quantities of storage compounds. Wall structure different from parent hyphae. Wall differentiation (pitted, warted, spinulose, gelatinous sheaths, appendages). All cellular organelles are present except a vacuole.

General Fungi Life Cycle Dikaryotic if “hetero” is 2 haploid nuclei/cell Note mostly haploid or heterokaryotic Diploid only transient in most fungal species Mitosis products

Molds are asexually reproducing (i. e Molds are asexually reproducing (i.e., spore-forming), filamentous fungi (i.e., not yeasts) Molds This is the mold Penicillium from which the antibiotic penicillin is isolated

Yeasts tend to inhabit very moist habitats, which includes plant and animal tissues Yeasts are single-celled fungi Yeasts Yeasts tend to grow asexually (no spores) Yeasts as a taxon would be polyphyletic

Zygomycete Life Cycle

Ascomycetes: Sac Fungi Asexually produced reproductive cells are called conidia Ascomycete form asci, which are linear sacs containing eight ascospores Have extended dikaryotic stage Ascomycetes: Sac Fungi In many the ascomycetes the asci are arrayed into fruiting bodies called ascocarps Many ascomycetes are important plant saprobes: they decompose dead plant material

Asci with Ascospores Sordaria macrospora is a filamentous ascomycete which is closely related to Neurospora crassa. But in contrast to Neurospora, Sordaria is homothallic, which means that a single strain produces fruiting bodies without the need for a partner of opposite mating type. The life cycle of S. macrospora is shown in the picture. It starts with an ascospore which germinates and produces a mycelium. Within a week, fruiting bodies develop in which asci are produced that contain eight ascospores each. The ascospores are ejected from the fruiting body and the cycle starts again. http://homepage.ruhr-uni-bochum.de/Minou.Nowrousian/projects.html

Ascomycetes: Sac Fungi These are not mushrooms!!! They are ascocarps Ascomycetes: Sac Fungi

Ascomycete Life Cycle

Basidiomycetes: Club Fungi Both mushrooms and shelf fungi are club fungi Club fungi are not limited to just mushrooms and shelf fungi, however Basidiocarps produce basidiospores Basidiomycetes: Club Fungi Like sac fungi, have a long-lived dikaryotic stage Best lignin decomposers of all fungi

Mushrooms, etc., are basidiocarps “By concentrating growth in the hyphae of mushrooms, a basidiomycete mycelium can quickly erect its fruiting structures in just a few hours” Basidiocarps

Basidicarps and Basidia Basidia with basidiospores

Basidiomycete Life Cycle

The End