View source for Amanita exitialis

{{Italic title}}
{{stack begin}}
{{Speciesbox
| name = Guangzhou destroying angel
| genus = Amanita
| species = exitialis
| authority = Z.L.Yang & T.H.Li (2001)
| range_map = China Guangdong.svg
| range_map_caption = Range of ''Amanita exitialis'' in China ...
| range_map2 = India Orissa locator map.svg
| range_map2_caption = ... and suspected range in India
}}
{{mycomorphbox
| name = ''Amanita exitialis''
| whichGills = free
| capShape = convex
| hymeniumType=gills
| stipeCharacter=ring and volva
| ecologicalType=mycorrhizal
| sporePrintColor=white
| howEdible=deadly
}}
{{stack end}}

'''''Amanita exitialis''''', also known as the '''Guangzhou destroying angel''', is a [[mushroom]] of the large genus ''[[Amanita]]''. It is distributed in eastern Asia, and probably also in India where it has been misidentified as ''[[Amanita verna|A.&nbsp;verna]]''. Deadly [[poisonous mushroom|poisonous]], it is a member of [[section (biology)|section]] Phalloideae and related to the death cap ''[[Amanita phalloides|A.&nbsp;phalloides]]''. The [[basidiocarp|fruit bodies]] (mushrooms) are white, small to medium-sized with [[pileus (mycology)|caps]] up to {{convert|7|cm|in|1|abbr=on}} in diameter, a somewhat [[friable]] [[annulus (mycology)|ring]] and a firm [[volva (mycology)|volva]]. Unlike most [[agaric]] mushrooms which typically have four-spored [[basidia]] (spore-bearing cells), the basidia of ''A.&nbsp;exitialis'' are almost entirely two-spored. Eight people were fatally poisoned in China after consuming the mushroom in 2000, and another 20 have been fatally poisoned since that incident. [[Molecular phylogenetics|Molecular analysis]] shows that the species has a close [[phylogenetic]] relationship with three other toxic white Amanitas: ''[[Amanita subjunquillea|A.&nbsp;subjunquillea]]'' var. ''alba'', ''[[Amanita virosa|A.&nbsp;virosa]]'' and ''[[Amanita bisporigera|A.&nbsp;bisporigera]]''.

==Taxonomy, classification, and phylogeny==
Zhu-Liang Yang and Tai-Hui Li discovered the species by reexamining various [[herbarium]] specimens of white ''Amanita'' typically referred to as either ''[[Amanita verna|A.&nbsp;verna]]'' or ''[[Amanita virosa|A.&nbsp;virosa]]''. They realized that collections referred to as these European species actually comprised three [[taxon|taxa]] new to science or the region.<ref>The other two ''Amanita'' taxa identified in the publication were ''[[Amanita oberwinklerana]]'', new to China, and [[Amanita subjunquillea|''Amanita subjunquillea'' var. ''alba'']], which had its known Chinese range greatly extended.</ref> The [[holotype]] specimen of ''A.&nbsp;exitialis'' is located in the Mycological Herbarium of Guangdong Institute of Microbiology.<ref name=Yang2001/>
{{cladogram|align=left|title=
| clade=
{{clade
|style=font-size:75%;line-height:75%
| label1=
| 1={{clade
     |1={{clade
          |1={{clade
               |1={{clade
                    |1={{clade
                        |1={{clade
                             |1='''''A. exitialis'''''
                             |2=''[[Amanita subjunquillea|A. subjunquillea]]'' var. ''alba''
                            }}
                        |2=''[[Amanita virosa|A. virosa]]''
                       }}
                    |2=''[[Amanita bisporigera|A. bisporigera]]''
                   }}
               |2=''[[Amanita fuliginea|A. fuliginea]]''
              }}
     |2=''[[Amanita hemibapha|A. hemibapha]]''
  }}
}}
}}
| caption=Phylogeny and relationships of ''Amanita exitialis'' and related species based on ITS sequence data. The ''A.&nbsp;virosa'' specimen was collected from Japan, ''A.&nbsp;bisporigera'' was from the USA, and the other species from China.<ref name=Zhang2005/>
}}
In 2005, Zhang and colleagues performed a [[phylogenetic]] analysis based on the [[Internal transcribed spacer|ITS]] sequences of several white-bodied toxic ''Amanita'' species. Their results support a [[clade]] containing four lethal ''Amanita'' species with white fruit bodies. ''A.&nbsp;exitialis'' has two-spored basidia similar to the North American species ''[[Amanita bisporigera|A.&nbsp;bisporigera]]'', but ''A.&nbsp;exitialis'' has a closer phylogenetic relationship with [[Amanita subjunquillea|''Amanita subjunquillea'' var. ''alba'']], a four-spored white lethal species from China.<ref name=Zhang2005/> The [[specific name (botany)|specific epithet]] ''exitialis'' derives from the [[Latin]] word "destructive", and refers to the lethally poisonous nature of the mushroom.<ref name=Yang2001/>

''Amanita exitialis'' is [[classification (biology)|classified]] in the [[section (biology)|section]] Phalloideae of the genus ''[[Amanita]]''. Species of this section share the following characteristics: spores that are not strongly elongated, and never with a cylindrical shape; flesh not reddening upon bruising; lamellulae (short [[lamella (mycology)|gills]] that do not reach the edge of the cap) abruptly cut off; a well-formed pouch- or sac-like membranous [[volva (mycology)|volva]]. All species of Phalloideae are [[mycorrhiza#Types of mycorrhiza|ectomycorrhizal]] and contain [[amatoxins]].<ref name=Singer1986/>

==Description==
[[image:Amanita verna-02.jpg|thumb|160px|left|''A.&nbsp;exitialis'' has been misidentified as the European species ''[[Amanita verna|A.&nbsp;verna]]'', shown here.]]
The [[pileus (mycology)|cap]] is {{convert|4|–|7|cm|in|1|abbr=on}} in diameter, initially egg-shaped, then convex but flattening with age, and sometimes slightly depressed at the center. The cap surface is smooth, white, but cream-colored in the center. The margin (cap edge) is non-striate, non-appendiculate (without any [[partial veil]] remnants hanging along the cap margin); the [[trama (mycology)|flesh]] white. The [[lamella (mycology)|gills]] are free from attachment to the stem, white to whitish, crowded closely together, and up to 5&nbsp;mm in height. The lamellulae are long and tapering, plentiful, and arranged in 2–3 tiers. The [[stipe (mycology)|stem]] is {{convert|7|–|9|cm|in|1|abbr=on}} by {{convert|0.5|–|1|cm|in|1|abbr=on}}, roughly cylindrical or slightly tapering upward, with apex slightly expanded. The surface is white to whitish, smooth, or sometimes with fibrous small scales. The bulb at the base of the stem is roughly spherical and {{convert|1|–|2|cm|in|1|abbr=on}} wide. The [[volva (mycology)|volva]] is limbate (has a distinct edge), thin, membranous, with free limb up to 7&nbsp;mm in height, and both surfaces are white. The [[annulus (mycology)|ring]] is near the top of the stem, thin, membranous, white, persistent or may be torn from the stem during expansion of the cap.<ref name=Yang2001/> All tissues of the fruit body will turn yellow if a drop of dilute [[potassium hydroxide]] is applied.<ref name="urlAmanita exitialis"/>

The [[spore]]s are spherical or nearly so, rarely broadly ellipsoid, and measure 9.5–12 by 9–11.5&nbsp;[[micrometre|µm]]. They are [[hyaline]] (translucent) and colorless, [[amyloid (mycology)|amyloid]] (absorbing [[iodine]] when stained with [[Melzer's reagent]]), thin-walled, smooth, and have a small [[wikt:apiculus|apiculus]]. The spore-bearing cells, the [[basidia]], are 27–55 by 10–15&nbsp;µm, club-shaped, and two-spored (rarely one-spored). They have [[sterigmata]] (slender projections that attach the spores) that are 5–7&nbsp;µm long.<ref name=Yang2001/>

===Similar species===
''Amanita exitialis'' is similar to ''[[Amanita bisporigera|A.&nbsp;bisporigera]]'', a species originally described by [[George Francis Atkinson]] from the United States. In comparison to ''A.&nbsp;exitialis'', ''A.&nbsp;bisporigera'' differs by its lower placement of the ring on the stem, smaller spores (typically 8–9.5 by 7–8.5&nbsp;µm), and different structure of the volva. American specimens of ''A.&nbsp;bisporigera'' have more abundant inflated cells than that of ''A.&nbsp;exitialis''. Two other white Asian species, ''A.&nbsp;oberwinklerana'' and ''A.&nbsp;subjunquillea'' var. ''alba'' also resemble ''A.&nbsp;exitialis'', but are four-spored.<ref name=Yang2001/>

==Habitat and distribution==
The fruit bodies of ''A.&nbsp;exitialis'' grow solitarily or in groups on the ground in [[coniferous forest]]s. It is known only from the [[type locality (biology)|type locality]], [[Guangdong Province]].<ref name=Yang2001/> In a 2003 survey of [[India]]n ''Amanita'' species, the authors mention several collections identified as ''[[Amanita verna|A.&nbsp;verna]]'', from various locations in the Indian states [[Maharashtra]], [[Odisha]], and [[Rajasthan]]. As Bhatt ''et al.'' explain, the material collected by Dhanchiola in Odisha and identified as ''A.&nbsp;virosa''<ref name=Dhancholia1989/> has two-spored basidia, and his description matches that of ''A.&nbsp;exitialis''.<ref name=Bhatt2003/>

Field observations suggest that the mushroom associates [[mycorrhiza]]lly with the plant ''[[Castanopsis fissa]]'', a [[deciduous]] tree found only in the southern provinces of China, such as [[Guangdong]], [[Yunnan]] and [[Hunan]].<ref name=Zhang2005/> Mushroom fruitings are abundant in the warm spring rains of March and April, although they are also seen in May to July.<ref name="urlGDFS"/>

==Toxicity==
[[image:Phallacidin.png|thumb|right|Phallacidin is one of several phallotoxins in ''A.&nbsp;exitialis''.]]
The content and distribution of the main [[amatoxin]]s ([[alpha-amanitin]], [[beta-amanitin]]) and [[phallotoxin]]s (phallacidin, phallisin, phalloin, phalloidin) in the three tissues (cap, stipe and volva) of ''Amanita exitialis'' have been determined using [[high-performance liquid chromatography]]. The cap had the highest content of total toxins, reaching over 8000&nbsp;[[microgram|µg]]/g [[dry matter|dry weight]] (µg of toxin per gram of dried tissue), the toxins content in the stem was over 3700&nbsp;µg/g dry weight, whereas the volva had the lowest content of total toxins, with about 1150&nbsp;µg/g dry weight. Amatoxins content (alpha-amanitin and beta-amanitins especially alpha-amanitin) in the cap, stem or volva of ''A.&nbsp;exitialis'' was higher than that of Phallotoxins (Phallacidin, Phallisin, Phalloidin and Phalloin), but the content of phallotoxins (especially phallacidin) was gradually higher from cap to stem and to volva.<ref name=Hu2003/> A 2011 study reported the presence of additional toxins [[amaninamide]], phallacin, phallisacin and desoxoviridin.<ref name=Deng2011/> A Chinese study concluded that this species had the highest mortality rate of all toxic mushrooms in China.<ref name=Deng2005/> It has been estimated that about {{convert|50|g|oz}} of fresh mushrooms contains sufficient toxin to cause the death of a {{convert|50|kg|lb|adj=on}} adult.<ref name="urlGDFS"/> In March 2000, nine people consumed the mushroom in [[Guangzhou]], and only one survived.<ref name=Yang2001/> Since 2000, another 20 people have died in the southern provinces of China from consuming the mushroom.<ref name=Zhang2005/>

Toxic peptides from ''Amanita'' species have been widely used in biological research as chemical agents to inhibit [[RNA polymerase II]], an [[enzyme]] essential for [[protein synthesis]]. However, these toxic peptides can only be obtained from fruit bodies collected from natural habitats, and are consequently expensive. Some success has been reported in extracting peptide toxins directly from the [[mycelia]] of ''Amanita exitialis'' grown in [[microbiological culture|liquid culture]]. Although the toxin concentration in the mycelium is only about 10% of that in fruiting bodies, the authors suggest that is possible to increase the amatoxin production by optimizing the growth conditions.<ref name=Zhang2005/>

==Bioactive compounds==

The fruit bodies of ''Amanita exitialis'' contain a unique [[purine]] [[nucleoside]] that is coupled with an [[amino acid]] [[derivative (chemistry)|derivative]] named ''N''<sup>2</sup>-(1-methoxycarbonylethyl)guanosine. The discovery and identification of this chemical was the first report of a naturally occurring nucleoside in which an amino acid derivative is bonded through its α-amino [[nitrogen]] (the nitrogen bonded to the [[Alpha and beta carbon|α-carbon]]) to a [[nucleobase]] [[aglycone]] by a C-N (carbon to nitrogen) bond. The new compound was determined to be toxic in the [[brine shrimp lethality test]], but it did not have [[cytoxicity|cytotoxic activity]] against a variety of human cancer [[cell culture|cell lines]]. Other compounds isolated from the fungus include [[beta-Carboline|β-carboline]] and russulaceramide (a [[ceramide]] formerly found in some ''[[Russula]]'' mushrooms).<ref name=Chi2009/>

==See also==
{{Portal|Fungi}}
*[[List of Amanita species|List of ''Amanita'' species]]
*[[List of deadly fungi]]

==References==
{{Reflist|colwidth=30em|refs=

<ref name=Bhatt2003>{{cite journal |vauthors=Bhatt RP, Tulloss RE, Semwal KC, Bhatt VK, Moncalvo JM, Stephenson SL |year=2003 |title=Amanitaceae reported from India. A critically annotated checklist |journal=Mycotaxon |volume=88 |pages=249–270 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0088/0249.htm}}</ref>

<ref name=Chi2009>{{cite journal |vauthors=Chi YL, Zhang HY, Xue JH, Hao J, Liu MF, Wei XY |year=2009 |title=N-2-(1-Methoxycarbonylethyl)guanosine, a new nucleoside coupled with an amino acid derivative from ''Amanita exitialis'' |journal=Chinese Chemical Letters |volume=20 |issue=7 |pages=830–832 |doi=10.1016/j.cclet.2009.02.008 }}</ref>

<ref name=Deng2011>{{cite journal |vauthors=((Deng W-Q)), ((Li T-H)), ((Xi P-G)), ((Gan L-X)), ((Jiang Z-D)) |title=Peptide toxin components of ''Amanita exitialis'' basidiocarps |journal=Mycologia |year=2011 |volume=103 |issue=5 |pages=946–949 |doi=10.3852/10-319 |pmid=21471295|url=https://zenodo.org/record/1038605 }}</ref>

<ref name=Dhancholia1989>{{cite journal |author=Dhancholia S |year=1989 |title=Noteworthy records of the genus ''Amanita'' from Orissa (India) |journal=Acta Botanica Indica |volume=17 |pages=279–282}}</ref>

<ref name=Deng2005>{{cite journal |vauthors=((Deng W-Q)), ((Li T-H)), Song B, ((He J-Y)), ((Mao X-W)) |year=2005 |title=Species of poisonous mushrooms known in Guangdong Province |journal=Journal of Fungal Research |volume=3 |issue=1 |pages=7–12 |language=Chinese |issn=1672-3538}}</ref>

<ref name=Hu2003>{{cite journal |vauthors=Hu J, Chen ZH, Zhang ZG, Zhang P |year=2003 |title=Analysis of the main amatoxins and phallotoxins in ''Amanita exitialis'', a new species in China |journal=Weishengwu Xuebao |volume=43 |issue=5 |pages=642–646 |issn=0001-6209}}</ref>

<ref name=Singer1986>{{cite book |author=Singer R. |title=The Agaricales in Modern Taxonomy |edition=4th |publisher=Koeltz Scientific Books |location=Königstein im Taunus, Germany |year=1986 |page=450 |isbn=3-87429-254-1}}</ref>

<ref name=Yang2001>{{cite journal |vauthors=Yang Z, Li T |year=2001 |title=Notes on three white Amanitae of section Phalloideae (Amanitaceae) from China |journal=Mycotaxon |volume=78 |pages=439–48 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0078/0439.htm}}</ref>

<ref name=Zhang2005>{{cite journal |vauthors=Zhang P, Chen Z, Hu J, Wei B, Zhang Z, Hu W |year=2005 |title=Production and characterization of Amanitin toxins from a pure culture of ''Amanita exitialis'' |journal=FEMS Microbiology Letters |volume=252 |issue=2 |pages=223–8 |doi=10.1016/j.femsle.2005.08.049 |pmid=16198510}}</ref>

<ref name="urlAmanita exitialis">{{cite web |url=http://www.eticomm.net/~ret/amanita/species/exitiali.html |title=''Amanita exitialis'' Zhu L. Yang and T. H. Li |work=''Amanita'' studies |date=2 October 2009 |vauthors=Yang ZL, Tulloss RE |accessdate=2010-04-30 |archive-url=https://web.archive.org/web/20110716104255/http://www.eticomm.net/~ret/amanita/species/exitiali.html |archive-date=2011-07-16 |url-status=dead }}</ref>

<ref name="urlGDFS">{{cite web |url=http://www.gdfs.gov.cn/rdgz/ShowArticle.asp?ArticleID=1507 |title=广东常见毒蘑菇之致命鹅膏（致命白毒伞）（剧毒）――广东省食品安全网 |publisher=Food Safety Commission, Guangdong Province |accessdate=2010-05-03 |archive-url=https://web.archive.org/web/20110720144108/http://www.gdfs.gov.cn/rdgz/ShowArticle.asp?ArticleID=1507 |archive-date=2011-07-20 |url-status=dead }}</ref>

}}

==External links==
*{{IndexFungorum|467883}}
{{Good article}}
{{Amanitas}}
{{Poisonous Amanitas}}
{{Taxonbar|from=Q2841084}}

[[Category:Amanita|exitialis]]
[[Category:Deadly fungi]]
[[Category:Fungi of Asia]]
[[Category:Poisonous fungi]]
[[Category:Fungi described in 2001]]