''Xanthoria parietina'' is a

foliose lichen Foliose lichen is one of the morphological classes of lichens, which are complex organisms that arise from the symbiotic relationship between fungi and a photosynthetic partner, typically algae. This partnership allows lichen to live in diverse ...

in the family

Teloschistaceae The Teloschistaceae are a large family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The family, estimated to contain over 1800 species, was extensively revised in 2013, including the creation o ...

. 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 A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

for

genomic Genomics is an interdisciplinary field of biology focusing on the structure, function, evolution, mapping, and editing of genomes. A genome is an organism's complete set of DNA, including all of its genes as well as its hierarchical, three-dim ...

sequencing (planned in 2006) by the US Department of Energy

Joint Genome Institute The U.S. Department of Energy (DOE) Joint Genome Institute (JGI), first located in Walnut Creek then Berkeley, California, was created in 1997 to unite the expertise and resources in genome mapping, DNA sequencing, technology development, and i ...

(JGI). ''X. parietina'' growing on brick... ... on a branch of '' Cornus mas'' ... ... and on a dead branch.

Taxonomy

The species was first

scientifically described A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in 1753, as ''Lichen parietinus''. ''Xanthoria coomae'', described from

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

in 2007, and ''Xanthoria polessica'', described from Belarus in 2013, were later determined to be

synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

of ''Xanthoria parietina''.

Description

The vegetative body of the lichen, the thallus, is foliose, and typically less than wide. The lobes of the

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

are 1–4 mm in diameter, and flattened down. The upper surface is some shade of yellow, orange, or greenish yellow, almost green when growing in shady situations, while the lower surface is white, with a cortex, and with sparse pale

rhizine In lichens, rhizines are multicellular root-like structures, arising mostly from the lower surface. A lichen with rhizines is termed rhizinate, while a lichen lacking rhizines is termed erhizinate. Rhizines serve only to anchor the lichen to their ...

s or . The vegetative reproductive structures

soredia Soredia are common reproductive structures of lichens. Lichens reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungal hyphae wrapped around cyanobacteria or gr ...

and

isidia An isidium is a vegetative reproductive structure present in some lichens. Isidia are outgrowths of the thallus surface, and are corticated (i.e., containing the outermost layer of the thallus), usually with a columnar structure, and consisting o ...

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 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 and serves to protect the thallus from water loss due to

evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

as well as harmful effects of high levels of

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 ...

. In ''Xanthoria parietina'', the thickness of the thalli is known to vary depending on the habitat in 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 A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

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 (''Rumex crispus''). It has an orangy-yellow color and ...

gives this species a deep yellow or orange-red color. ''Xanthoria parietina'' prefers growing on bark and wood; it is found more rarely on rock. Nutrient enrichment by bird droppings enhances the ability of ''X. parietina'' to grow on rock.

Photobiont

The photosynthetic symbionts, or photobionts, associated with ''X. parietina'' are from the green algal genus ''

Trebouxia ''Trebouxia'' is a unicellular green alga.Silverside, A. J. (2009). Retrieved from http://www.bioref.lastdragon.org/Chlorophyta/''Trebouxia''.html It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and ...

''. 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 such vegetative propagules, but must establish the symbiotic state at each reproductive cycle. Two oribatid mite species, '' Trhypochtonius tectorum'' and '' Trichoribates trimaculatus'', which are common inhabitants 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 short- and long-distance dispersal of this species.

Habitat and distribution

''Xanthoria parietina'' occurs in hardwood forests in broad, low-elevation valleys, as well as scattered on ''

Populus ''Populus'' is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar (), aspen, and cottonwood. The we ...

'' and other

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

s in

riparian A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...

areas in agricultural and populated areas. It is often associated with high level of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and favored by

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

, and can be often found near farmland and around livestock. The lichen is used as a food source and shelter for the snail '' Balea perversa''. The species is widespread, 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

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

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 and to pollution nitrogen. For these reasons, this species has found use as a

biomonitor A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example, copepods and other sm ...

for measuring levels of toxic elements.

Bioactive compounds

Structure of parietin, orange-colored pigment found in ''X. parietina''. ''Xanthoria parietina'' produces an orange colored

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Isomers include various quinone derivatives. The term anthraquinone however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxo ...

pigment,

, that is deposited as tiny crystals in the top layer of the upper cortex. Parietin synthesis is enhanced by

UV-B Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

, 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 vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...

'', inhibiting the replication of

human parainfluenza virus Human parainfluenza viruses (HPIVs) are the viruses that cause human parainfluenza. HPIVs are a paraphyletic group of four distinct single-stranded RNA viruses belonging to the ''Paramyxoviridae'' family. These viruses are closely associated wit ...

type 2. In the past it was used as a remedy for

jaundice Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...

because of its yellow color.

Gallery

File:Xanthoria parietina Messinglav.jpg, alt=orange lichen on rock, ''Xanthoria parietina'' File:Xanthoria parietina (06 03 31).jpg, alt=yellowish lichen on rock, ''Xanthoria parietina'' File:Lichen growing on a twig, scanned.png, alt=close-up of orange lichen, ''X. parietina'', close-up File:Xantoria-by-color.jpg, Different colors from green to red

References

External links

* * Radoslaw Walkowiak, Akira Takeuchi,
Short Note of Xanthoria parietina
', CTC PAPER 2020 *http://www.jgi.doe.gov/sequencing/why/CSP2006/Xparietina.html *http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/climate-change/xanthoria-parietina/index.html {{Taxonbar, from=Q475341 Teloschistales Lichen species Lichens of Australia Lichens described in 1753 Lichens of Africa Lichens of North Africa Lichens of North America Lichens of Asia Lichens of Europe Taxa named by Carl Linnaeus