Download - INTRODUCTION TO THE ASCOMYCETES IB 371 - GENERAL MYCOLOGY LECTURE 16 Tuessday, October 21, 2003
INTRODUCTION TO INTRODUCTION TO THE ASCOMYCETESTHE ASCOMYCETES
IB 371 - GENERAL MYCOLOGYIB 371 - GENERAL MYCOLOGY
LECTURE 16LECTURE 16
Tuessday, October 21, 2003Tuessday, October 21, 2003
ASCOMYCOTAASCOMYCOTA
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
Polysporous Asci (From David Geiser)
ASCOMYCETE LIFE CYCLEASCOMYCETE LIFE CYCLE
anamorph teleomorph asexual sexual imperfect perfect conidia ascospores mitospore meiospore entire organism is the holomorph
ASCOMYCETE LIFE CYCLEASCOMYCETE LIFE CYCLE
HOW DOES ONE PROVE THAT A HOW DOES ONE PROVE THAT A PARTICULAR ANAMORPH PARTICULAR ANAMORPH BELONGS TO A PARTICULAR BELONGS TO A PARTICULAR TELEOMORH?TELEOMORH?
ASCOMYCETE LIFE CYCLEASCOMYCETE LIFE CYCLE
anamorph (mitospore)
holomorph
teleomorph (meiospore)
ASCOMYCETE LIFE CYCLEASCOMYCETE 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.
SEXUAL SEXUAL INCOMPATIBILITYINCOMPATIBILITY
Homogenic incompatibility- controlled by mating type genes (unifactorial)
Somatic or vegetative incompatibility
SEXUAL REPRODUCTIONSEXUAL REPRODUCTION
Gametangial copulation
Gametangial contact and fusion
Hyphal fusion (somatogamy)
Spermatization
SEXUAL REPRODUCTIONSEXUAL 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
ASCOSPOROGENESISASCOSPOROGENESIS
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.
ASCOSPORE RELEASEASCOSPORE 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
FRUITING BODIESFRUITING 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.
ASEXUAL REPRODUCTIONASEXUAL 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
IN-CLASS ACTIVITYIN-CLASS ACTIVITY
What, if any, characteristics do the Ascomycetes and Basidiomycetes have in common?
How do the Ascomycetes and Basidiomycetes differ?