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Abstract Detail



Systematics

Dee, Jaclyn M. [1], Chang, Ying [1], Sekimoto, Satoshi [2], Berbee, Mary L.  [1].

Hyphally Inclined: Septins and the Search for an Ancient Morphogenetic Toolkit for Hyphal Growth.

Ancestral state reconstructions of the evolution of the hyphal form indicate that hyphae arose independently at least four times in diverse fungal phyla.  The repeated emergence of hyphae could reflect the presence of an ancient molecular toolbox for filamentous growth in the fungal ancestor.  To test this hypothesis, we have begun investigating the evolution of the septins in the fungi and their closest relatives  emphasizing data from fungal genomes newly sequenced through our JGI Community Sequencing Project.  Septins comprise a family of proteins known to mediate polarized growth and cell division in model fungi and thus they may belong to that putative morphogenetic toolkit.  Previous analyses of the evolutionary relationships among septins in fungi and animals have shown that Group 1 and 2 septins predate the fungi-metazoa divergence.  In contrast, Groups 3 to 5 are apparently fungal-specific and Group 5 septins were found only in regularly septate, hyphal fungi.  For the most part, species that lacked representative orthologues from particular groups of septins were unicellular, possibly coinciding with the loss of a filamentous habit.               We searched for septin sequences from the genomes of aseptate hyphal fungi, zoosporic chytrids and other close relatives of fungi using standalone BLAST and inferred an opisthokont-wide phylogeny of the genes using maximum likelihood methods.   The chytrid Gonapodya prolifera represents one of the earliest branches in the fungal tree. Unlike most chytrids G. prolifera produces hyphae.   In our preliminary analyses, both G. prolifera and the non-hyphal chytrids possessed Group 1 to 4 septins indicating that these genes are not exclusively tied to hyphal growth.  Group 5 septins were previously known only from non-zoosporic Ascomycota and Basidiomycota. Our analyses revealed that the chytrids and aseptate terrestrial fungi might also possess Group 5 septins.   Because some early diverging fungi with and without hyphae share all five groups, the septins must have radiated prior to Fungi’s conquest of land.  Septins are excellent candidate components of an ancestral, fungal morphogenetic toolkit.


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1 - University of British Columbia, Botany, 6270 University Boulevard, Vancouver, BC, V6T-1Z4, Canada
2 - NITE Biological Resource Center, Bio-Resource Development Division, 2-5-8 Kazusakamatari, Kisarazu-shi, Chiba Prefecture, 292-0818, Japan

Keywords:
septin
evolution
hyphae
Gonapodya prolifera
chytrid
zygomycete
early-diverging fungi
morphogenetic toolkit
comparative genomics.

Presentation Type: Offered Paper - Paper
Session: 8
Location: Room 103 AB/Kellogg Hotel and Conference Center
Date: Tuesday, June 10th, 2014
Time: 9:00 AM
Number: 8003
Abstract ID:90
Candidate for Awards:Graduate Student Oral Presentation Award


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