Fungal Life Cycles Prof Khaled H AbuElteen Basic

Fungal Life Cycles Prof. Khaled H. Abu-Elteen

Basic fungal life cycle 1. Zygotic - haploid phase is dominant fig. 13. 5 b

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 WITH RESTRICTED DIPLOID HAPLOID-DIKARYOTIC HAPLOID-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) memnospores Exogenous (xenospores) xenospores

GERMINATION FACTORS Water Temperature Nutrition p. H (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. p. H. 4. O 2/CO 2 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 Note mostly haploid or heterokaryotic Dikaryotic if “hetero” is 2 haploid nuclei/cell Diploid only transient in most fungal species Mitosis products

Molds are asexually reproducing (i. e. , sporeforming), filamentous fungi (i. e. , not yeasts) 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 as a taxon would be polyphyletic Yeasts are single-celled fungi Yeasts tend to grow asexually (no spores)

Zygomycete Life Cycle

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

Asci with Ascospores

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

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 Best lignin decomposers of all fungi Basidiocarps produce basidiospores Like sac fungi, have a longlived dikaryotic stage

Basidiocarps 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”

Basidicarps and Basidia with basidiospores

Basidiomycete Life Cycle

The End