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lipid. glycogen. Littlefield and Heath 1979 Ultrastructure of Rust Fungi. Storage compounds – retaining nutrients. Nutrition of biotrophs. Components are extracted through haustoria Nutrients are soluble and organic Extracellular degradation for cell penetration

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storage compounds retaining nutrients

lipid

glycogen

Littlefield and Heath 1979

Ultrastructure of Rust Fungi

Storage compounds – retaining nutrients
nutrition of biotrophs
Nutrition of biotrophs
  • Components are extracted through haustoria
  • Nutrients are soluble and organic
  • Extracellular degradation for cell penetration
  • Extracellular factors establish/maintain a compatible infection
  • Suppress senescence
suppressing senescence
Suppressing senescence

www.mpiz-koeln.mpg.de/schlef/PSL_webpage.html

livning substrates exploited by fungi
Livning substrates exploited by fungi

What is the nutrient flow direction?

http://www.ucmp.berkeley.edu/fungi/rhyniefungus.jpg

secondary metabolites
Secondary metabolites
  • Glucose-derived – polysaccharides, peptidopolysaccharides, and sugar alcohols.
  • Condensation products of acetate – derived from the acetate-malonate pathway of fatty acid synthesis, e.g. polyketides and phenolics.
  • Condensation products of acetate derived from the mevalonic acid pathway, e.g. terpenes.
  • Phenolics derived from the shikimic acid pathway of aromatic amino acid synthesis.
  • Derivatives of other amino acid syntheses.
slide8

Secondary

metabolites

Pigments

Hormones

Toxins

Co-regulated with

sporulation

secondary metabolites of saccharomyces
Secondary metabolites of Saccharomyces

www.crc.dk/flab/ newpage13.htm

genetics study of heredity
Genetics – study of heredity
  • Transmission - the passage of traits from one generation to the next
genetics study of heredity11
Genetics – study of heredity
  • Population - genetic diversity and change within natural populations
genetics study of heredity12
Genetics – study of heredity
  • Molecular - details of gene structure and function
our focus for genetics
Our focus for genetics
  • transmission and molecular genetics in experimental systems
  • defining a population
    • organisms in culture
    • humungous fungus
    • vegetative incompatibility
transmission genetics
Transmission genetics
  • Typical characteristics of fungal genomes Small
    • S. cerevisiae 6 MB – 6000 genes
    • A. nidulans 13 MB – 12000 genes
    • H. sapiens 1300 MB – 30000 genes
typical characteristics of fungal genomes
Typical characteristics of fungal genomes
  • Little repetitive DNA – single copy genes
    • 50-60% of nuclear genome is transcribed into mRNA in S cerevisiae
    • 33% in S. commune (basidiomycete)
    • 1% in humans
  • Introns
    • few, often none
    • small – 50-200bp vs ≥10 kb in mammals
most higher fungi are vegetative haploids
Most higher fungi are vegetative haploids
  • One genome copy per nucleus
  • Alternatives?
    • Plants?
    • Algae?
    • Animals?
risks of haploidy
Risks of haploidy
  • No backup copy in case of genetic damage from UV or chemical mutagens
  • Yeasts tend to be diploid (S. cerevisiae except for lab strains) or have short G1 (S. pombe)

Chant and Pringle JCB 129:751

advantages of haploidy
Advantages of haploidy
  • A multinucleate cell can expose genome to mutagens
    • most mutations are deleterious
    • select for advantageous mutations in a heterokaryotic system
  • Phenotypes of recessive mutations are obvious in the vegetative state, without generating homozygous recessives
  • Lab strains of S. cerevisiae now generally include a mutation which stabilizes the haploid state
transmission genetics passage of inheritance
Transmission genetics – passage of inheritance
  • Similar to more familiar mammalian systems, with bulk of life cycle haploid
  • ‘Genders' are ‘mating types’
    • cells are biochemically distinct but morphologically identical
no mating factors a nidulans
No mating factorsA. nidulans
  • Inbreeding possible
    • disadvantage – sex does not necessarily increase genetic diversity
    • advantage – can form resistant spores even if no mating partner is available
    • A. nidulans ascospores from 1995 still viable after 4°C storage, whereas conidia viability is severely reduced after several months at 4°C
one factor zygo asco some basids
One factor (zygo, asco, some basids)
  • Bipolar mating system
  • meiosis will give two types of segregants
    • N. crassaa and 
    • Rhizopus+ and –
one factor zygo asco some basids23
One factor (zygo, asco, some basids)
  • Advantage – outbreeding
  • Disadvantage – cannot produce resistant sexual spores unless a partner is available
  • ‘Coping’ with one-factor mating systems
    • Some fungi have multiple alleles at the mating locus
    • Mating type switching in Saccharomyces
one factor zygo asco some basids25
One factor (zygo, asco, some basids)
  • In S. cerevisiae "a" cells produce a-factor, a peptide sexual hormone, and -receptor; converse for  cells
  • hormones/receptors interaction promotes schmooing, wall changes promote adhesion
two factors a b often in basids
Two factors, A/B (often in basids)
  • Tetrapolar mating system  meiosis give four types of segregants
  • A1B1 :: A2B2A1B1, A1B2, A2B1, A2B2
a and b functions are distinct
A and B functions are distinct
  • in homobasids (.....?)
    • A controls pairing and synchronous division of nuclei, hook cell formation;
    • B controls septal dissolution and hook cell fusion (b-glucanase activity) and nuclear migration
a and b functions are distinct28
A and B functions are distinct
  • in heterobasids (....?)
    • A controls pathogenicity;
    • B controls filamentous growth
systems restricting outcrossing in one factor mating type systems
Systems restricting outcrossing in one-factor mating type systems
  • self-fertilityS. cerevisiae has "mating type switching"
  • molecular basis both mating genes have a storage site and an expression site.
  • if the appropriate partner cell is not available when mating conditions are presented (how would this be detected?)will induce swi expression
systems restricting outcrossing in one factor mating type systems30
Systems restricting outcrossing in one-factor mating type systems
  • vegetative (somatic) incompatibility
  • het genes are important for mating, but prevent vegetative fusion
systems restricting outcrossing in one factor mating type systems31
Systems restricting outcrossing in one-factor mating type systems
  • vegetative (somatic) incompatibility
  • in Fusarium – vegetative incompatibility is important for maintaining distinct populations with different host specificities
  • Fusarium oxysporum f. sp. groups
mutants in experimental fungal systems
Mutants in experimental fungal systems
  • spontaneous mutations or mutagenesis (uv, chemicals)
  • each gene is named for 1st described mutation
  • Example: gene for pigmentation is called “white” because the mutant lacked colouration
different species different naming system
Different species,different naming system
  • Saccharomyces cerevisiae
  • Schizosaccharomyces pombe
  • Aspergillus nidulans
  • Neurospora crassa
  • Generally, three-letters plus a letter or number – hypA, CDC2, cdc28