Alternaria tenuissima

Alternaria tenuissima is a saprophytic fungus and opportunistic plant pathogen. It is cosmopolitan in distribution, and can colonize a wide range of plant hosts.[1] Colonies of A. tenuissima produce chains on agar growth media.[1] The fungus often forms concentric ring patterns on infected plant leaves.[2] This species produces the allergen Alt a 1, one of the most important outdoor seasonal fungal allergens associated with allergy and asthma provocation.[3] In rare circumstances, this species is also known to infect immunosuppressed humans and animals.[4]

Alternaria tenuissima
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Dothideomycetes
Order: Pleosporales
Family: Pleosporaceae
Genus: Alternaria
Species:
A. tenuissima
Binomial name
Alternaria tenuissima
Samuel Paul Wiltshire (1933)
Synonyms

Growth and morphology

Unlike many other species of Alternaria, the conidiophores of A. tenuissima can develop in darkness after the colony has been exposed to light even very briefly; however its growth is more robust with longer periods of light exposure.[5] After 5–7 days in culture, colonies of A. tenuissima reach a diameter of 5 cm on PCA or V-8 agar (vegetable juice agar).[1] Colonies grown on PCA are brown in colour with a loose, cottony texture and bearing golden-brown conidia in chains.[1] Conidia are on the areas of the colony that receive the most light exposure, forming concentric sporulating rings of uncrowded conidial chains growing from branching hyphae on PCA.[1] Sporulation tends to be much more crowded in colonies grown on V-8 agar.[1] Simple unbranched and branched conidial chains of moderate length as well as solitary conidia are interspersed across the colony especially areas that receive little light.[1]

The light, golden-brown colour of the conidia, and their tendency to taper into long beaks, distinguish A. tenuissima from similar species notably A. alternata which produces dark brown conidia with short beaks.[4] Conidia of A. tenuissima also grow individually or in short chains[6] of 2-5 units,[1] while A. alternata tends to grow in longer chains.[7] Alternaria tenuissima conidia are smooth-walled[6] and have a median and subconstricting transverse septum.[1] Colonies of A. tenuissima on natural substrates (e.g., plant leaves) often develop a concentric, ringed pattern.[2]

Physiology

Alternaria tenuissima is a saprophyte, living on dead matter.[8] It produces the mycotoxins alternariol (AOH), alternariol methyl ester (AME), altenuene (ALT), altertoxin (ATX), and tenuazonic acid (TA), that are variously involved pathogenicity and interference competition.[8] Mycotoxins of this species are optimally produced at 25 °C.[9]

Habitat and ecology

Alternaria tenuissima is a cosmopolitan species, common on an array of various plant hosts in many countries spanning a range of environmental conditions.[10] It often colonizes blueberries,[11] tomatoes, grapevine, and strawberries.[7] It has also been found on several cereal grain species.[8] Optimal growth occurs between 25–30 °C (77–86 °F).[12] Although A. tenuissima is normally an opportunistic pathogen of plants, rare cases of skin infections in immunocompromised people have been reported.[13][14]

Medical significance

Cutaneous and subcutaneous alternariosis is a skin or tissue infection caused by members of the genus Alternaria, most commonly A. alternata and A. tenuissima.[4] Because of the inability of A. tenuissima to invade healthy host tissue, alternariosis tends to be restricted to people with abrogated cellular immunity and occasionally the elderly.[4] Complication following organ transplantion, Cushing's syndrome and immunosuppressive therapies are some of the typical settings in which alternariosis has been reported.[4] Alternariosis appears on the skin as red pustules that may produce ulcers over time.[4] Alternaria tenuissima is a prolific producer of the allergen Alt a 1.[15] Exposure to this protein can induce an allergic reaction in sensitized individuals by reacting with circulating IgE antibody.[3] Exposure to Alt a 1 has been associated with asthmatic exacerbation.[16] Alternaria tenuissima also produces the mycotoxin tenuazonic acid[17] which has received attention as a candidate antitumor medication.[18]

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References
  1. Simmons, Emory G. (2007). Alternaria: An Identification Manual (fully illustrated and with catalogue raisonné 1796-2007). Utrecht, The Netherlands: CBS Fungal Biodiversity Centre. pp. 500–502. ISBN 978-90-70351-68-7.
  2. Nasehi, A.; Kadir, J. B.; Abidin, M. A. Zainal; Wong, M. Y.; Mahmodi, F. (August 2012). "First Report of Alternaria tenuissima Causing Leaf Spot on Eggplant in Malaysia". Plant Disease. 96 (8): 1226–1226. doi:10.1094/PDIS-03-12-0237-PDN.
  3. Ibarrola, Ignacio; Suárez-Cervera, María; Arilla, M. Carmen; Martínez, Alberto; Monteseirín, Javier; Conde, José; Asturias, Juan A. (December 2004). "Production profile of the major allergen Alt a 1 in Alternaria alternata cultures". Annals of Allergy, Asthma & Immunology. 93 (6): 589–593. doi:10.1016/S1081-1206(10)61268-9.
  4. Pastor, F.J.; Guarro, J. (August 2008). "Alternaria infections: laboratory diagnosis and relevant clinical features". Clinical Microbiology and Infection. 14 (8): 734–746. doi:10.1111/j.1469-0691.2008.02024.x.
  5. Rotem, Joseph (1998). The genus Alternaria : biology, epidemiology, and pathogenicity (2nd print ed.). St. Paul, Minn: APS-Press. ISBN 978-0890541524.
  6. Ellis, Martin B.; Ellis, J. Pamela (1997). Microfungi on land plants : an identification handbook (New enl. ed.). Slough: RP Richmond Publ. p. 289. ISBN 085546-245-0.
  7. Domsch, K.H.; Gams, Walter; Andersen, Traute-Heidi (1980). Compendium of soil fungi (2nd ed.). London, UK: Academic Press. ISBN 9780122204029.
  8. Chełkowski, J; Visconti, A (1992). Alternaria: biology, plant diseases and metabolites. Amsterdam [u.a.]: Elsevier. pp. 364–365. ISBN 0-444-88998-1.
  9. Weidenbörner, Martin (2001). Encyclopedia of Food Mycotoxins. Berlin, Heidelberg: Springer Berlin Heidelberg. ISBN 978-3-662-04464-3.
  10. Farr, David F.; Bills, Gerald F.; Chamuris, George P.; Rossman, Amy Y. (1989). Fungi: on plants and plant products in the United States. Minnesota, USA: The American Phytopathological Society.
  11. Lee, Hyang Burm; Patriarca, Andrea; Magan, Naresh (2015). "Alternaria in Food: Ecophysiology, Mycotoxin Production and Toxicology". Mycobiology. 43 (2): 93–106. doi:10.5941/MYCO.2015.43.2.93. PMC 4505009. PMID 26190916.
  12. Patriarca, A.; Medina, A.; Pinto, V. Fernández; Magan, N. (January 2014). "Temperature and water stress impacts on growth and production of altertoxin-II by strains of Alternaria tenuissima from Argentinean wheat". World Mycotoxin Journal. 7 (3): 329–334. doi:10.3920/WMJ2013.1711.
  13. Robertshaw, H.; Higgins, E. (2005). "Cutaneous infection with Alternaria tenuissima in an immunocompromised patient". British Journal of Dermatology. 153 (5): 1047–1049. doi:10.1111/j.1365-2133.2005.06833.x.
  14. Romano, C; Fimiani, M; Pellegrino, M; Valenti, L; Casini, L; Miracco, C; Faggi, E (1996). "Cutaneous phaeohyphomycosis due to Alternaria tenuissima". Mycoses. 39 (5–6): 211–215. doi:10.1111/j.1439-0507.1996.tb00127.x.
  15. Saenz-de-Santamaria, M.; Postigo, I.; Gutierrez-Rodriguez, A.; Cardona, G.; Guisantes, J. A.; Asturias, J.; Martinez, J. (March 2006). "The major allergen of Alternaria alternata (Alt a 1) is expressed in other members of the Pleosporaceae family". Mycoses. 49 (2): 91–95. doi:10.1111/j.1439-0507.2006.01195.x.
  16. Denning, David W; Pashley, Catherine; Hartl, Domink; Wardlaw, Andrew; Godet, Cendrine; Del Giacco, Stefano; Delhaes, Laurence; Sergejeva, Svetlana (2014). "Fungal allergy in asthma–state of the art and research needs". Clinical and Translational Allergy. 4 (1): 14. doi:10.1186/2045-7022-4-14. PMC 4005466. PMID 24735832.
  17. Davis, ND; Diener, UL; Morgan-Jones, G (August 1977). "Tenuazonic acid production by Alternaria alternata and Alternaria tenuissima isolated from cotton". Applied and Environmental Microbiology. 34 (2): 155–7. PMC 242614. PMID 562128.
  18. Antony, M; Gupta, KP; Janardanan, KK; Mehrotra, NK (9 December 1991). "Inhibition of mouse skin tumor promotion by tenuazonic acid". Cancer Letters. 61 (1): 21–5. doi:10.1016/0304-3835(91)90072-p. PMID 1764695.
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