Storage compounds retaining nutrients lipid glycogen Littlefield and

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Storage compounds – retaining nutrients lipid glycogen Littlefield and Heath 1979 Ultrastructure of Rust

Storage compounds – retaining nutrients lipid glycogen Littlefield and Heath 1979 Ultrastructure of Rust Fungi

Nutrition of biotrophs • • Components are extracted through haustoria Nutrients are soluble and

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

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

Livning substrates exploited by fungi What is the nutrient flow direction? http: //www. ucmp.

Livning substrates exploited by fungi What is the nutrient flow direction? http: //www. ucmp. berkeley. edu/fungi/rhyniefungus. jpg

Arbuscular and ectomycorrhizal fungi

Arbuscular and ectomycorrhizal fungi

Amino acid biosynthesis

Amino acid biosynthesis

Secondary metabolites • Glucose-derived – polysaccharides, peptidopolysaccharides, and sugar alcohols. • Condensation products of

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.

Secondary metabolites Pigments Hormones Toxins Co-regulated with sporulation

Secondary metabolites Pigments Hormones Toxins Co-regulated with sporulation

Secondary metabolites of Saccharomyces www. crc. dk/flab/ newpage 13. htm

Secondary metabolites of Saccharomyces www. crc. dk/flab/ newpage 13. htm

Genetics – study of heredity • Transmission - the passage of traits from one

Genetics – study of heredity • Transmission - the passage of traits from one generation to the next

Genetics – study of heredity • Population - genetic diversity and change within natural

Genetics – study of heredity • Population - genetic diversity and change within natural populations

Genetics – study of heredity • Molecular - details of gene structure and function

Genetics – study of heredity • Molecular - details of gene structure and function

Our focus for genetics • transmission and molecular genetics in experimental systems • defining

Our focus for genetics • transmission and molecular genetics in experimental systems • defining a population – organisms in culture – humungous fungus – vegetative incompatibility

Transmission genetics • Typical characteristics of fungal genomes Small – S. cerevisiae 6 MB

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 • Little repetitive DNA – single copy genes –

Typical characteristics of fungal genomes • Little repetitive DNA – single copy genes – 50 -60% of nuclear genome is transcribed into m. RNA in S cerevisiae – 33% in S. commune (basidiomycete) – 1% in humans • Introns – few, often none – small – 50 -200 bp vs ≥ 10 kb in mammals

Most higher fungi are vegetative haploids • One genome copy per nucleus • Alternatives?

Most higher fungi are vegetative haploids • One genome copy per nucleus • Alternatives? – Plants? – Algae? – Animals?

Risks of haploidy • No backup copy in case of genetic damage from UV

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 G 1 (S. pombe) Chant and Pringle JCB 129: 751

Advantages of haploidy • A multinucleate cell can expose genome to mutagens – most

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 • Similar to more familiar mammalian systems, with

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

Fungal mating systems

Fungal mating systems

No mating factors A. nidulans • Inbreeding possible – disadvantage – sex does not

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) • Bipolar mating system • meiosis will give

One factor (zygo, asco, some basids) • Bipolar mating system • meiosis will give two types of segregants – N. crassa a and – Rhizopus + and –

One factor (zygo, asco, some basids) • Advantage – outbreeding • Disadvantage – cannot

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 basids) • In S. cerevisiae "a" cells produce a-factor,

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) • Tetrapolar mating system meiosis give four types

Two factors, A/B (often in basids) • Tetrapolar mating system meiosis give four types of segregants • A 1 B 1 : : A 2 B 2 A 1 B 1, A 1 B 2, A 2 B 1, A 2 B 2

A and B functions are distinct • in homobasids (. . . ? )

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 distinct • in heterobasids (. . ? ) –

A and B functions are distinct • in heterobasids (. . ? ) – A controls pathogenicity; – B controls filamentous growth

Systems restricting outcrossing in one-factor mating type systems • self-fertility S. cerevisiae has "mating

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 onefactor mating type systems • vegetative (somatic) incompatibility • het

Systems restricting outcrossing in onefactor mating type systems • vegetative (somatic) incompatibility • het genes are important for mating, but prevent vegetative fusion

Systems restricting outcrossing in one-factor mating type systems • vegetative (somatic) incompatibility • in

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 • spontaneous mutations or mutagenesis (uv, chemicals) • each

Mutants in experimental fungal systems • spontaneous mutations or mutagenesis (uv, chemicals) • each gene is named for 1 st described mutation • Example: gene for pigmentation is called “white” because the mutant lacked colouration

Different species, different naming system • • • Saccharomyces cerevisiae Schizosaccharomyces pombe Aspergillus nidulans

Different species, different naming system • • • Saccharomyces cerevisiae Schizosaccharomyces pombe Aspergillus nidulans Neurospora crassa Generally, three-letters plus a letter or number – hyp. A, CDC 2, cdc 28