Xanthoria parietina
Encyclopedia
Xanthoria parietina is a foliose, or leafy, lichen
. It has wide distribution, and many common names such as common orange lichen, yellow scale, maritime sunburst lichen and shore lichen. It can be found near the shore on rocks or walls (hence the epithet parietina meaning "on walls"), and also on inland rocks, walls, or tree bark. It was chosen as a model organism
for genomic
sequencing (planned in 2006) by the US Department of Energy Joint Genome Institute
(JGI). In the past it was used as a remedy for jaundice
because of its yellow color.
body of the lichen, the thallus, is foliose, and typically less than 8 centimetres (3.1 in) wide. The lobes of the thallus are 1–4 mm in diameter, and flattened down. The upper surface is some shade of yellow, orange, or greenish yellow, while the lower surface is white, with a cortex, and with sparse pale rhizines or hapters. The vegetative reproductive structures soredia and isidia are absent in this species, however, apothecia are usually present.
The outer "skin" of the lichen, the cortex, is composed of closely packed fungal hypha
e and serves to protect the thallus from water loss due to evaporation
as well as harmful effects of high levels of irradiation
. In Xanthoria parietina, the thickness of the thalli is known to vary depending on the habitat is which it grows. Thalli are much thinner in shady locations than in those exposed to full sunshine; this has the effect of protecting the algae that cannot tolerate high light intensities. The lichen pigment
parietin
gives this species a deep yellow or orange-red color.
X. parietina prefers growing on bark and wood; it is found more rarely on rock. Nutrient enrichment by bird droppings enhances the ability of X. parietinato grow on rock.
In one study, the photobiont was shown to occupy 7% of the volume of the thallus. The density of pigmentation of the upper cortex also varies and seems to control the amount of light reaching the algae.
s in riparian areas in agricultural and populated areas. It is often associated with high level of nitrogen
and favored by eutrophication
and can be often found near farmland and around livestock.
X. parietina is a widespread lichen, and has been reported from Australia, Africa, Asia, North America and throughout much of Europe. In eastern North America and Europe, it is found more frequently near coastal locations. The increases in NO3 deposition as a result of industrial and agricultural developments in southern Ontario, Canada in the 20th century are thought to be responsible for the reappearance of this species in the local lichen flora.
For these reasons, this species has found use as a biomonitor for measuring levels of toxic elements.
X. parietina produces an orange colored anthraquinone
pigment, parietin
, that gets deposited as tiny crystals in the top layer of the upper cortex. Parietin synthesis is enhanced by UV-B, and stimulated by photosynthates, such as those provided by the green algal Trebouxia symbiont. X. parietina also produces the metabolite 2-methoxy-4,5,7-trihydroxy-anthraquinone.
, inhibiting the replication of human parainfluenza virus type 2.
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
. It has wide distribution, and many common names such as common orange lichen, yellow scale, maritime sunburst lichen and shore lichen. It can be found near the shore on rocks or walls (hence the epithet parietina meaning "on walls"), and also on inland rocks, walls, or tree bark. It was chosen as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
for genomic
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
sequencing (planned in 2006) by the US Department of Energy Joint Genome Institute
Joint Genome Institute
The U.S. Department of Energy Joint Genome Institute was created in 1997 to unite the expertise and resources in genome mapping, DNA sequencing, technology development, and information sciences pioneered at the DOE genome centers at Lawrence Berkeley National Laboratory , Lawrence Livermore...
(JGI). In the past it was used as a remedy for jaundice
Jaundice
Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
because of its yellow color.
Taxonomy
The species was first described by Carl Linnaeus in 1753, as Lichen parietinus.Description
The vegetativeVegetative
Vegetative describes vegetation.Vegetative may also refer to:*Vegetative reproduction, a type of asexual reproduction for plants*Persistent vegetative state, a condition of people with severe brain damage...
body of the lichen, the thallus, is foliose, and typically less than 8 centimetres (3.1 in) wide. The lobes of the thallus are 1–4 mm in diameter, and flattened down. The upper surface is some shade of yellow, orange, or greenish yellow, while the lower surface is white, with a cortex, and with sparse pale rhizines or hapters. The vegetative reproductive structures soredia and isidia are absent in this species, however, apothecia are usually present.
The outer "skin" of the lichen, the cortex, is composed of closely packed fungal hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e and serves to protect the thallus from water loss due to evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
as well as harmful effects of high levels of irradiation
Irradiation
Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to...
. In Xanthoria parietina, the thickness of the thalli is known to vary depending on the habitat is which it grows. Thalli are much thinner in shady locations than in those exposed to full sunshine; this has the effect of protecting the algae that cannot tolerate high light intensities. The lichen pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
parietin
Parietin
Parietin is the predominant cortical pigment of lichens in the genus Caloplaca, a secondary product of the lichen Xanthoria parietina, and a pigment found in the roots of Curled Dock...
gives this species a deep yellow or orange-red color.
X. parietina prefers growing on bark and wood; it is found more rarely on rock. Nutrient enrichment by bird droppings enhances the ability of X. parietinato grow on rock.
Photobiont
The photosynthetic symbionts, or photobionts, associated with X. parietina are from the green algal genus Trebouxia. Species that have been found include Trebouxia arboricola and T. irregularis. Both of these photobionts are known to occur free-living in nature, having been found on bark colonized by X. parietina as well as on bark not colonized by lichens.In one study, the photobiont was shown to occupy 7% of the volume of the thallus. The density of pigmentation of the upper cortex also varies and seems to control the amount of light reaching the algae.
Reproduction and dispersal
A large number of lichens disperse very effectively by means of symbiotic vegetative propagules such as soredia, isidia and blastidia, and thallus fragmentation. However, X. parietina does not produce the vegetative propagules, but has to establish the symbiotic state at each reproductive cycle. It has been demonstrated that two orbatid mite species, Trhypochtonius tectorum, and Trichoribates trimaculatus, common inhabitant and consumers of X. parietina, are vectors of the photobiont cells. Faecal pellets of both species contain both viable ascospores and photobiont cells, and are suggested to be a common mode of vegetative short- and long-distance dispersal of this species.Habitat and distribution
Hardwood forests in low-elevation broad valleys; scattered on Populus and other hardwoodHardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
s in riparian areas in agricultural and populated areas. It is often associated with high level of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and favored by eutrophication
Eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
and can be often found near farmland and around livestock.
X. parietina is a widespread lichen, and has been reported from Australia, Africa, Asia, North America and throughout much of Europe. In eastern North America and Europe, it is found more frequently near coastal locations. The increases in NO3 deposition as a result of industrial and agricultural developments in southern Ontario, Canada in the 20th century are thought to be responsible for the reappearance of this species in the local lichen flora.
Pollution tolerance
Xanthoria parietina is a very pollution-tolerant species. In laboratory experiments, this species can tolerate exposure to air contaminants and bisulphite ions with little or no damaging effect. It is also tolerant of heavy metal contamination.For these reasons, this species has found use as a biomonitor for measuring levels of toxic elements.
Bioactive compounds
Anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula . Several isomers are possible, each of which can be viewed as a quinone derivative...
pigment, parietin
Parietin
Parietin is the predominant cortical pigment of lichens in the genus Caloplaca, a secondary product of the lichen Xanthoria parietina, and a pigment found in the roots of Curled Dock...
, that gets deposited as tiny crystals in the top layer of the upper cortex. Parietin synthesis is enhanced by UV-B, and stimulated by photosynthates, such as those provided by the green algal Trebouxia symbiont. X. parietina also produces the metabolite 2-methoxy-4,5,7-trihydroxy-anthraquinone.
Medicinal properties
The water extract of X. parietina has good antiviral activity in vitroIn vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
, inhibiting the replication of human parainfluenza virus type 2.
External links
- http://www.jgi.doe.gov/sequencing/why/CSP2006/Xparietina.html
- http://www.lichen.com/bigpix/Xparietina.html
- http://www.hiddenforest.co.nz/lichens/family/teloschistaceae/teloschistaceae.htm