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Abstract Detail


MSA - Systematics/Evolution

Weete, John D.  [1], Abril, Maritza [2], Blackwell, Meredith [2].

Sterol distributions support phylogenetic placement of diverse fungal clades.

Ergosterol was discovered over 100 years ago as a component of the plant pathogenic ergot fungus Claviceps purpurea. Since, ergosterol has been identified as the major sterol in a large number of fungi and has become known as the ‘fungal sterol.’ Lanosterol is a common intermediate in the synthesis of both cholesterol and ergosterol, and a bifurcation in the sterol biosynthetic pathway leads to the formation of ergosterol or cholesterol. Ergosterol is not a precursor to cholesterol and vice versa. Although several sterols may be detected in organisms, a single major sterol is usually present. Ergosterol occurs in more recently diverged lineages (most Basidiomycota, Ascomycota, zygosporic fungi including Mucorales, Zoopagales, Dimargaritales) and other sterols distinguish other zygosporic groups (Mortierellales, Kickxellales, Entomophthorales, and Basidiobolaceae). Early-diverging zoosporic lineages have a variey of sterols, usually ergosterol intermediates. These taxa include the few zoosporic fungi tested (Chytridiomycota, Blastocladiomycota) and certain zygosporic groups. Interestingly, several symbiotic taxa stand out from close relatives because they accumulate C29 sterols rather than C28 sterols like ergosterol. Plant associated Pucciniomycotina and Glomeromycota synthesize major sterols differing only by the position of a single double bond. Taphrina, Protomyces, Tuber, and Terfezia, also close associates of plants, produce brassicasterol as the major sterol but no ergosterol. More information at position C24 is required to know whether these sterols resemble those of other fungi. Pneumocystis spp., obligate parasites of mammalian hosts, have cholesterol membranes, which were suggested as derived from mammalian hosts. Distribution of specific sterols corresponds with many clades defined by current phylogenies but not probable evolutionary pathways. More information on the stereochemistry of basal groups outside Fungi is needed, but cholesterol and ergosterol are both reported in Amoebidium spp. (Mesomycetozoea) and sterols with characteristics of both fungi and sponges, in a choanoflagellate.


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1 - Auburn University, Auburn Research and Technology Foundation, Auburn, Alabama, 36832, USA
2 - Louisiana State University, Biological Sciences, Baton Rouge, Louisiana, 70803, USA

Keywords:
evolution
nonmolecular traits
phylogeny.

Presentation Type: Oral Paper:Papers for Topics
Session: 37
Location: Cottonwood A/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 9:00 AM
Number: 37005
Abstract ID:699


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