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Phytomyxea

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Phytomyxea
Resting spores of different species
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Phylum: Endomyxa
Class: Phytomyxea
Cavalier-Smith, 1993
Orders
Synonyms
  • Phytomyxini Schröter, 1886:133
  • Phytomyxinae MacBride 1892:111; 1899:16; Schröter in Engler & Prantl, 1897; Doflein, 1911:672
  • Phytomyxinea Poche 1913:197
  • Phytomixida Calkins, 1926:328
Life cycle of Plasmodiophora brassicae in cabbage.
Clubroot on cauliflower

The Phytomyxea are a class of parasites that are cosmopolitan, obligate biotrophic protist parasites of plants, diatoms, oomycetes and brown algae.[1] They are divided into the orders Plasmodiophorida (ICZN, or Plasmodiophoromycota, ICBN) and Phagomyxida.[2] Plasmodiophorids are best known as pathogens or vectors for viruses of arable crops (e.g. club root in Brassicaceae, powdery scab in potatoes, and rhizomania in beets, especially sugar beets and some spinaches).[3]

Life cycle

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They typically develop within plant cells, causing the infected tissue to grow into a gall or scab. Important diseases caused by phytomyxeans include club root in cabbage and its relatives, and powdery scab in potatoes.[4] These are caused by species of Plasmodiophora and Spongospora, respectively.[5]

The vegetative form is a multinucleate cell, called a plasmodium. This ultimately divides to form new spores, which are released when the host's cells burst. Both resting spores and motile zoospores, which generally have two smooth flagella, are produced at different stages. Within the plasmodium, dividing nuclei have a distinctive cross-like appearance.

Classification

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Plasmodiophorids were traditionally considered slime moulds, because of the plasmodial stage and are often wrongly classified as fungi, and given names such as the Plasmodiophoromycota. However, genetic and ultrastructural studies indicate they belong to a diverse group of protists called the Cercozoa, are closely related to them.

References

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  1. ^ Neuhauser, Sigrid; Kirchmair, Martin; Bulman, Simon; Bass, David (2014). "Cross-kingdom host shifts of phytomyxid parasites". BMC Evolutionary Biology. 14 (1): 33. doi:10.1186/1471-2148-14-33. PMC 4016497. PMID 24559266.
  2. ^ David Bass; Ema E.-Y. Chao; Sergey Nikolaev; Akinori Yabuki; Ken-ichiro Ishida; Cédric Berney; Ursula Pakzad; Claudia Wylezich; Thomas Cavalier-Smith (February 2009). "Phylogeny of novel naked filose and reticulose Cercozoa: Granofilosea cl. n. and Proteomyxidea revised". Protist. 160 (1): 75–109. doi:10.1016/j.protis.2008.07.002. PMID 18952499.
  3. ^ Schwelm, Arne; Badstöber, Julia; Bulman, Simon; Desoignies, Nicolas; Etemadi, Mohammad; Falloon, Richard E.; Gachon, Claire M. M.; Legreve, Anne; Lukeš, Julius; Merz, Ueli; Nenarokova, Anna; Strittmatter, Martina; Sullivan, Brooke K.; Neuhauser, Sigrid (2018). "Not in your usual Top 10: protists that infect plants and algae". Molecular Plant Pathology. 19 (4): 1029–1044. doi:10.1111/mpp.12580. PMC 5772912. PMID 29024322.
  4. ^ Schwelm, Arne; Badstöber, Julia; Bulman, Simon; Desoignies, Nicolas; Etemadi, Mohammad; Falloon, Richard E.; Gachon, Claire M. M.; Legreve, Anne; Lukeš, Julius; Merz, Ueli; Nenarokova, Anna; Strittmatter, Martina; Sullivan, Brooke K.; Neuhauser, Sigrid (2018). "Not in your usual Top 10: protists that infect plants and algae". Molecular Plant Pathology. 19 (4): 1029–1044. doi:10.1111/mpp.12580. PMC 5772912. PMID 29024322.
  5. ^ Agrios, George N. (2005). Plant Pathology. 5th ed. Academic Press. link.