Download Neurospora are haploid organisms that can reproduce asexually or

A detailed description of the life cycle of Neurospora crassa
Neurospora are haploid organisms that can reproduce asexually or sexually. The body of fungus is the
Mycelium. The mycelium is the vegetative part of a fungus consisting of a mass of branching threadlike
hyphae that exists below the ground or within another substrate.
There are two different mating types
(sexes?) of mycelia. These are
physically the same and they can
only be differentiated by DNA
analysis. These are known as mating
type A and a.
Confocal image showing tip-growing and branched,
multinucleate hyphae of Neurospora crassa. The nuclei are
shown in green (nuclear-targeted GFP) and membranes,
especially the plasma membrane and secretory vesicles, are
shown in red (stained with FM4-64)(Hickey & Read 2003).
Each of these mycelium
(body) produce spores
called “conidia”. Conidia
can be easily identified by
their orange color.
Germination and growth of
these haploid asexual
spores (conidia) results in a
mass of branched threads
(hyphae), which constitute
a colony. A colony buds off
millions more conidia and
these disperse and repeat the
asexual cycle .
Neurospora crassa hyphae in the peripheral region of
the colony stained with FM1-43. (B) is of the same
region as (A) but was imaged 28 min later. Note the
pronounced staining of septa (arrows in B). Bar = 50
µm (Hickey et al., 2005).
In the sexual phase, when
colonies of different
mating type A an a come
into contact, their cell
walls and nuclei fuse
resulting in hypha with
diploid nuclei. These
structures produce fruiting
buddies called perithecia
and inside the perithecia the formation of the ascus will take
place. These structures are all diploid with two nuclei.
Inside the perithecia, the two haploid nuclei fuse and then each
diploid nucleus undergoes meiosis. The four haploid products
of one meiosis stay together in a sac called an ascus. Meiosis
takes place producing four cells: two type a and two type A.
Scanning electron micrograph of germinated conidia of
Neurospora crassa interconnected by fused conidial
anastomosis tubes (CATs) (Roca et al., 2005a).

In Neurospora crassa each of the four products of meiosis undergoes a further mitotic division, resulting
in an octad of eight ascospores within each ascus.

When the ascus is ripe, it opens and the Ascospores are shot into the air and dispersed by the wind. The
ascosporas will germinate and produce hyphae and mycellia resulting in colonies exactly like those
produced by the conidia or asexual spores.