''Puccinia monoica'' is a
parasitic rust fungus of the
genus ''
Puccinia'' that inhibits
flowering in its
host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
plant (usually a ''
Boechera'' species) and radically transforms host morphology in order to facilitate its own
sexual reproduction.
History
It was originally described and published by American mycologist
Charles Horton Peck (1833–1917) as ''Aecidium monoicum'' in Bot. Gaz. 4(11): 230 in 1879. It was found on the leaves of ''
Arabis retrofracta'' in
Colorado, USA. Then in 1912, mycologist Joseph C. Arthur transferred it to the ''Puccinia'' genus, as ''Puccinia monoica''.
Life cycle
Infection of host plants (including ''Boechera'' and several other members of the
mustard family
Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The le ...
) occurs via wind-borne
basidiospores in late summer. Upon germination of the spores, fungal
hypha
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one or ...
e penetrate the stem of the mustard plant and siphon off nutrients. However, in order to reproduce sexually, the fungus must facilitate the transfer of
spermatia
Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...
from the
spermatogonia
A spermatogonium (plural: ''spermatogonia'') is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testis.
There are three subtypes of spermatogonia in humans:
* ...
on this plant to receptive hyphae borne in the spermatogonia on another infected mustard plant. To accomplish this, the fungus sterilizes the host plant, preventing it from producing true flowers. Instead, it forces the infected plant to grow clusters of leaves into brilliant yellow "
pseudoflowers" bearing the fungal spermatogonia. Insects visiting the pseudoflowers transfer spermatia from one host plant to another, in the same way that
pollinators transfer pollen between the true flowers of uninfected plants.
Spermatia transferred in this way fuse with receptive spermatogonial hyphae on the recipient plant. The resulting hyphae subsequently form
aecia. At this time, the pseudoflowers lose their green colour and stop producing
nectar
Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...
. Spores produced in the aecia, referred to as
aeciospores, are responsible for infecting ''P. monoicas alternate host plant (a grass species of ''
Koeleria'', ''
Trisetum
''Trisetum'' is a genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biologica ...
'', or ''
Stipa'').
Upon germination hyphae produced by the aeciospores penetrate the grass, leading to the production of
uredia. The uredia produce
urediniospores capable of infecting more grass plants. Ultimately,
telia are produced on the infected grasses. This leads to production of
basidia and
basidiospores. When released the basidiospores may infect new mustard plants, completing the life cycle.
Pseudoflowers
The pseudoflowers are borne from basal leaf rosettes of the host mustard and
mimic the yellow, early spring
corollae of distantly related wildflowers (e.g.
buttercups), not only in
visible light but also in
ultraviolet. Since bees and many pollinating insects "see" in the ultraviolet range, these pseudoflowers are highly attractive. In addition, the fungus produces a distinct scent to attract insects; this
olfactory
The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste.
In humans, it ...
appeal has allowed the fungus to evolve and "improve" upon the mimicry system by facilitating proper transfer of fungal spermatia. The bees feed on a sweet, sticky substance similar to nectar that the fungus forces the plant to produce on the imitation flowers.
Taxonomic variation
Researchers have noted that ''Puccinia monoica'' is just one of a complex of closely related species which show considerable variation with regard to specific hosts and life cycle. ''P. monoica'' has a life cycle involving two alternate hosts (a mustard and a grass), whereas other species may not. The ''P. monoica'' life cycle is
macrocyclic, including the production of
basidia,
telia,
spermatia
Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...
,
aecia, and uredia. By contrast, ''
Puccinia thlaspeos'' also produces pseudoflowers, but has no aecia or uredia phase, completing its entire life cycle on ''Arabis''.
[Roy, BA (1993) Patterns of Rust Infection as a Function of Host Genetic Diversity and Host Density in Natural Populations of the Apomictic Crucifer, ''Arabis holboellii''. Evolution 47: 111-124.]
See also
*
List of ''Puccinia'' species
References
{{Taxonbar, from=Q1420516
monoica
Fungi described in 1912
Fungus species