Magnaporthe Rhizophila
   HOME

TheInfoList



OR:

''Magnaporthe rhizophila'' is a fungus species in the family
Magnaporthaceae The Magnaporthaceae are a family of fungi in the order Magnaporthales. It was circumscribed by Paul F. Cannon in 1994 for a group of grass-associated fungi centered on ''Magnaporthe'' (''Nakataea''). Magnaporthaceae have a harpophora-like asexua ...
. These dark mycelial fungi are common
pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
s of cereal and grass roots.
Rice blast ''Magnaporthe grisea'', also known as rice blast fungus, rice rotten neck, rice seedling blight, blast of rice, oval leaf spot of graminea, pitting disease, ryegrass blast, Johnson spot, neck blast, wheat blast and , is a plant-pathogenic fungus ...
is one disease known to be caused by M. rhizophila and presents with vascular discoloration in the host organism. The fungus lives best in drier humid conditions, explaining why it is most often found in the soils of Australia, South Africa, and the Southeastern United States.


Development

Similar to other
ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...
, the lifecycle of ''M. rhizophila'' is split into two parts: the sexual and asexual stages. The sexual lifestage is characterized by a globose (400-500 um wide) fruit-like body that contains the sexual spores, called a
perithecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascoc ...
, which occurs in either singles or multiples. Perithecia are flask-like shaped and contain asci, which are septated,
unitunicate An ascus (; : asci) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some gener ...
stalks of 8
ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...
s. The ascospores are biseriate, fusiform, and slightly curved or helical when naive. The perithecia is lined with cells called the peridium and has accessory structures called periphyses and paraphyses that surround the outside and inside of the structure, respectively. Paraphyses inside the perithecia dissolve once asci reach maturity. The asexual lifestage is characterized by asexual conidial structures (6-20x2-6 um).
Conidiophores A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...
are either simple or branched.
Compared to the fruiting bodies of other Magnaporthe species, ''rhizophila'' is considered faster growing (0.8 cm/d at 28 °C) with slightly longer and wider conidial cells.
''M. rhizophila'' is
homothallic In fungi and algae, homothallism refers to the condition in which a single individual or thallus carries the genetic determinants (i.e., both mating types or sexes) required to undergo sexual reproduction without the need for a distinct mating partn ...
, so it is self-fertile and can mate with similar mating types within its own mycelia.


Ecology

''Magnaporthe rhizophila'' is considered a
necrotrophic A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the traditi ...
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
because it relies on the nutrients and support of other organisms to thrive. It is a
heterotroph A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
since it is unequipped to sequester energy on its own, hence its symbiotic behavior. Magnaporthacaea are family-specific soil-borne parasites of
Gramineae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated i ...
; ''rhizophila'' specifically colonizes the roots of millet.
Spores from ''M. rhizophila'' are dispersed by natural manners such as wind, water, and animals. These spores then settle in soil where they grow and mature through asexual life cycles until it is optimal for the hyphae to resume a sexual cycle and a host organism is near. ''Rhizophila'' is only root-infecting; however many of its Magnaporthe relatives are both soil and aerial-infecting. The fungus has an
appressorium An appressorium is a specialized cell typical of many fungal plant pathogens that is used to infect host plants. It is a flattened, hyphal "pressing" organ, from which a minute infection peg grows and enters the host, using turgor pressure capable ...
structure which functions to elicit
effector Effector may refer to: *Effector (biology), a molecule that binds to a protein and thereby alters the activity of that protein * ''Effector'' (album), a music album by the Experimental Techno group Download * ''EFFector'', a publication of the El ...
hormones to increase host susceptibility (2 clade-specific types of small specific proteins (SSP) ). Lignitubers have been considered a response by host cells after infection as a response to fungal invasion. However, ''rhizophila'' kills host cells in 5–6 weeks.
''M. rhizophila'' has darkly pigmented
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 o ...
e, composing
mycelia Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...
that has a gray-brown color, darker than species in the rest of its family. It is able to be cultured in vitro and survives on PDA (potato dextrose agar) plates.


Geographical distribution

''Magnaporthe rhizophila'' does not necessarily require much water to survive, localizing in drier humid regions of
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
,
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
, and the
Southeastern United States The Southeastern United States, also known as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States located in the eastern portion of the Southern United States and t ...
.


Genetics

From data derived from
genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
, it was found that ''M. rhizophila'' originated in South Africa. Fungal fossils demonstrated that the phyla diverged 31 million years ago from other
Sordariomycetes Sordariomycetes is a class of fungi in the subdivision Pezizomycotina (Ascomycota). It is the second-largest class of Ascomycota, with a worldwide distribution that mostly accommodates terrestrial based taxa, although several can also be found in ...
, and the
phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...
diverged 21 million years ago from
pezizomycotina Pezizomycotina is the largest subdivision of Ascomycota, containing the filamentous ascomycetes and most lichenized fungi. It is more or less synonymous with the older taxon Euascomycota. These fungi reproduce by fission rather than budding. Thi ...
.
Magnaporthe species are grouped into three divergent
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s; rhizophila is in clade classification D along with ''M. poae'' and ''G. incrustans''. ''Rhizophila'' belongs to the Magnaporthe family based on its ascospore morphology; however, it has been considered for the ''
Gaeumannomyces ''Gaeumannomyces'' is a genus of fungi in the family Magnaporthaceae. Species *''Gaeumannomyces amomi'' *''Gaeumannomyces caricis'' *''Gaeumannomyces cylindrosporus'' *''Gaeumannomyces graminis'' **''Gaeumannomyces graminis var. avenae'' **'' Gae ...
'' because they also produce
phialophora ''Phialophora'' is a form genus of fungus with short conidiophores, sometimes reduced to phialides; their conidia are unicellular. They may be parasites (including on humans), or saprophytic (including on apples). Genetic analysis of ''Phialop ...
-like
anamorphs In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an asex ...
instead of
sympodial In botany, sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, als ...
pyricularia. ''M. rhizophila'' is the only known Magnaporthe species with a phialophora anamorph. Given these similarities between families, ''M. rhizophila'' is highly hybridized with other species among these groups.
The ''M. rhizophila'' genome is composed of 5.8%
transposable element A transposable element (TE), also transposon, or jumping gene, is a type of mobile genetic element, a nucleic acid sequence in DNA that can change its position within a genome. The discovery of mobile genetic elements earned Barbara McClinto ...
s, lower than other species in its family.


References

{{Taxonbar, from=Q10575280 Magnaporthales Fungus species