Abstract Detail

Emerging infectious diseases by zoosporic parasites

Chang, Ying [1], Sekimoto, Satoshi [2], Wang, Sishuo [1], Spatafora, Joseph W. [3], Berbee, Mary L.  [1].

Early diverging fungi and evolutionary origins of enzymes for breakdown of the pectins in plant cell walls.

Despite the effort to resolve the fungal tree of life in recent years, relationships among the early branches remain uncertain. To infer the fungal phylogeny, we sampled a total of 136 single-copy genes from sequenced genomes of 40 taxa that represent major fungal lineages and their relatives. We evaluated the information content of subsets of genes/sites, as well as the effects of subsampling on phylogenetic inference. The phylogenies we recovered were consistent across most analyses. Among the early diverging taxa, Rozella arose from the first split in fungi and the second split is represented by Blastocladiales. The core chytrids and the Neocallimastigales form one clade, sister to the terrestrial fungi.  A clade of Conidiobolus and Coemansia represented the first split in terrestrial fungi.  Rhizophagus (Glomus) shows affinity to Mucorales, instead of Dikarya. A robust phylogeny of fungi not only demonstrates relationships, but also serves as the framework for analysis of how fungal life styles and feeding strategies evolved over time.  While the vast majority of extant Dikarya are associated with plants, the sources of nutrition used among early-diverging taxa are much more variable. We hypothesized that we could recognize when the association with plants first evolved by analyzing the distribution of genes for the breakdown of plant material. As pectins are only found in cell walls of streptophytes, the presence of the pectinases in certain fungal lineages is indicative of their association with plants. To test our hypothesis, we extracted the pectinase sequences from the same set of 40 genomes and reconstructed the phylogeny for each pectinase family. We performed reconciliation between the pectinase gene phylogenies and the organismal fungal phylogeny. One of the chytrids, Gonapodya, possesses multiple pectinases that fall into clades with enzymes found in Dikarya. This suggests that the association between fungi and plants started early in fungal evolution and that at least some of the early fungi had the ability to degrade plant material.

1 - University of British Columbia , Department of Botany, 3529-6270 University Blvd. , Vancouver, BC, V6T 1Z4, Canada
2 - NITE Biological Resource Center (NBRC), Bio-resource Development Division, Chiba, Japan
3 - Oregon State University, Dept. of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331-2902, USA

Keywords:
phylogeny
phylogenomics
pectinase
evolution
chytrids
comparative genomics.

Presentation Type: Symposium or Colloquium Presentation
Session: SY7
Location: Auditorium/Kellogg Hotel and Conference Center
Date: Wednesday, June 11th, 2014
Time: 1:30 PM
Number: SY7002
Abstract ID:158
Candidate for Awards:None