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Abstract Detail

Mycological Section

Shaffer, Justin P. [1], Gallery, Rachel E. [2], Baltrus, David A. [1], Arnold, A. Elizabeth [3].

Endohyphal bacteria of tropical plant-associated Sordariomycetes.

Plant-associated fungi are major drivers of tropical tree demography, population structure, and community dynamics, and are one of the most critical but least-studied aspects of tropical forest ecology. Research on plant-microbe interactions in tropical forests has focused on mycorrhizal or pathogenic fungi that infect seedlings, saplings, or adult plants, ignoring the most critical component of reproduction and recruitment for most plants: seeds. Diverse Ascomycota associate with seeds of tropical trees both before and especially after soil contact. These fungi can enhance or decrease seed survival and germination in a host-specific or spatially explicit manner, altering seed bank structure and regeneration. Studies have revealed the taxonomic and functional diversity of tropical seed-associated fungi, and have indicated that many are host-generalists with regard to seed colonization. However, closely related fungi vary markedly in their effects on seed survival and germination in particular hosts. The mechanisms underlying this variation and the potentially synergistic roles of co-infecting microbes have not yet been elucidated. Bacteria inhabiting living hyphae (endohyphal bacteria, EHB) occur within diverse plant-associated fungi, and shape plant-fungus interactions by modulating fungal phenotypes. My research in a lowland tropical forest indicates that EHB are diverse and widespread in two of the most common and ecologically important genera of seed-associated fungi (Xylaria, Fusarium). These EHB are easily observed within living hyphae of 80-97% of fungal isolates, and represent Tenericutes, Firmicutes, Actinobacteria, Cyanobacteria, Bacteroidetes, and three classes of Proteobacteria. Many of these EHB are closely related to those occurring within endophytic Xylaria and Fusarium, as well as bacteria that occur in seeds and soil from the same sites. In general they appear to be facultative and horizontally transmitted, reflect multiple evolutionary origins, and are distinct and diverse relative to previously known EHB of root-associated Mucoromycotina, Mortierellomycotina, and Glomeromycota. Experiments with EHB-infected and cured clones of exemplar fungi have shown that EHB significantly influence fungal growth, seed colonization by fungi, and subsequent seed germination of infected seeds. The outcomes of such tripartite interactions are context dependent, varying among seed-fungus-bacterium trios. Ongoing work is focused on revealing the genomic bases of the observed effects, and exploring the evolutionary origins and ecological implications of these EHB in the context of tropical forest dynamics.

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1 - University of Arizona, School of Plant Sciences, 303 Forbes Building, 1140 E. South Campus Drive, Tucson, AZ, 85721, USA
2 - University of Arizona, School of Natural Resources and the Environment, 1311 E. 4th St., Tucson, AZ, 85721, USA
3 - University Of Arizona, School Of Plant Sciences, 1140 E South Campus Drive, Forbes 303, Tucson, AZ, 85721, USA

Tropical forest
fungal endophyte.

Presentation Type: Oral Paper:Papers for Sections
Session: 40
Location: Salon 1/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 11:15 AM
Number: 40005
Abstract ID:662
Candidate for Awards:MSA Best Oral Presentation Award by a Graduate Student

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