1 / 22

INTRODUCTION TO THE ASCOMYCETES

INTRODUCTION TO THE ASCOMYCETES. IB 371 - GENERAL MYCOLOGY LECTURE 16 Tuessday, October 21, 2003. ASCOMYCOTA. products of meiosis contained in a sac called an ascus well-developed mycelium with septa at regular intervals

lundy
Download Presentation

INTRODUCTION TO THE ASCOMYCETES

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. INTRODUCTION TO THE ASCOMYCETES IB 371 - GENERAL MYCOLOGY LECTURE 16 Tuessday, October 21, 2003

  2. ASCOMYCOTA • products of meiosis contained in a sac called an ascus • well-developed mycelium with septa at regular intervals • septa with simple pores (sometimes numerous micropores) & Woronin bodies • haploid w. restricted diploid life cycle • asexual reproduction by conidia

  3. Polysporous Asci (From David Geiser)

  4. ASCOMYCETE LIFE CYCLE • anamorphteleomorph • asexual sexual • imperfect perfect • conidia ascospores • mitospore meiospore • entire organism is the holomorph

  5. ASCOMYCETE LIFE CYCLE • HOW DOES ONE PROVE THAT A PARTICULAR ANAMORPH BELONGS TO A PARTICULAR TELEOMORH?

  6. ASCOMYCETE LIFE CYCLE • anamorph (mitospore) holomorph teleomorph (meiospore)

  7. ASCOMYCETE LIFE CYCLE • homothallic - mycelium from a uninucleate 1N ascospore is capable of producing ascospores • heterothallic - requires 2 mycelia, each from a single haploid ascospore of different mating types • 2o homothallic - appears homothallic because a single ascospore may contain 2 nuclei (one of each mating type). If an ascospore contains two nuclei of the same mating type, the fungus will be sterile.

  8. SEXUAL INCOMPATIBILITY • Homogenic incompatibility- controlled by mating type genes (unifactorial) • Somatic or vegetative incompatibility

  9. SEXUAL REPRODUCTION • Gametangial copulation • Gametangial contact and fusion • Hyphal fusion (somatogamy) • Spermatization

  10. SEXUAL REPRODUCTION • dikaryotic stage is not usually of long duration • after karyogamy, meiosis occurs immediately to produce 4, 8, or more ascospores in an ascus • ascospores are formed by free cell formation within the ascus

  11. ASCOSPOROGENESIS • An enveloping membrane system (EMS) that originates from the ascus membrane delimits portions of cytosplasm surrounding a nucleus. • Wall material is deposited between the two membranes to form the ascospore wall.

  12. ASCOSPORE RELEASE • Breakdown (deliquescence) of the ascus wall • Forcibly shot out through an apical opening • Ascus wall layers separate and ascospores are shot out through a pore in the apex of the inner ascus

  13. FRUITING BODIES • General term is ascoma (pl. ascomata). • Cleistothecium - completely closed, no preformed opening. • Perithecium - often flask-shaped, with an apical opening. • Apothecium - ascomata open and saucer-shaped at maturity. • Pseudothecium - asci formed in a stromatal cavity.

  14. ASEXUAL REPRODUCTION • Spores produced by mitosis • Spores called conidia (also called mitospores) • Formed by (1) fragmentation, (2) fission, (3) budding, or (4) blastic development. • Chlamydospores - thick-walled resistant cells

  15. IN-CLASS ACTIVITY • What, if any, characteristics do the Ascomycetes and Basidiomycetes have in common? • How do the Ascomycetes and Basidiomycetes differ?

More Related