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Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Deckert, Ron J [1], Gehring, Catherine [2], Patterson, Adair [1].

Fungal and bacterial symbionts are common components of the pine seed microbiome.

Microbiome studies in a diversity of organisms have clearly demonstrated that microbes can produce extended phenotypes in multicellular organisms that result in changes to morphology, health, stress tolerance, competitiveness, behavior, and other aspects of performance. In plants, seed microbiomes of crop plants have been the focus of much research because of the potential for inexpensive microbially mediated crop improvement. The ecological roles of seed microbiomes of wild plants have received less attention and, least of these, the seeds of gymnosperms, despite the dominance of conifers in many forest ecosystems. Unlike angiosperm seeds, the seeds of conifers undergo a relatively long development time, retaining the gametophyte past fertilization as a major component of the mature seed. We predicted that the long seed development period in pines would be conducive to the assembly of a diverse seed microbiome. To test our prediction, we examined the seed of two pine species, pinyon (Pinus edulis), and ponderosa (P. ponderosa), in northern Arizona by culture-based and/or culture-independent methods. The culture-based studies resulted in three key findings: 1) more microbial isolates emerged from pinyon pine seeds than from the seeds of ponderosa pine. 2) of two phenotypes of pinyon pine, seeds of an herbivore-susceptible, drought-tolerant phenotype (H-D+) yielded more microbial isolates than did the seeds of an herbivore-resistant, drought intolerant (H+D-) phenotype. 3) the phyla of seed bacteria associated with H-D+ pinyon belonged primarily to the Gammaproteobacteria while in both H+D- pinyon and ponderosa pine seeds Firmicutes dominated the seed microbiome. In our culture-independent studies focused on fungi (ITS sequencing), we found that the ponderosa pine mycobiome consisted almost entirely of basidiomycete fungi, several of which formed ectomycorrhizal associations in conifers. The presence of symbiotic fungal species and the general lack of typical endophytic or environmentally common species of fungi in the seed prompts us to hypothesize involvement of the parent(s), particularly the gametophyte, in hosting or actively filtering available symbionts for inclusion in the seed microbiotic package. We propose that current concepts of endophyte transmission are inadequate to encompass the complexity of possible transmission mechanisms when considering seed-borne endophytes and offer a more nuanced view which includes a new category, reticulate transmission, combining elements that characterize both vertical and horizontal transmission.

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Related Links:
Pine Seeds Carry Symbionts: Endophyte Transmission Re-examined

1 - Northern Arizona University, Biological Sciences, Flagstaff, AZ, 86011, US
2 - Northern Arizona University, Department Of Biological Sciences, 617 S Beaver Street, Flagstaff, AZ, 86011, United States

Seed endophyte
Endophyte transmission
Reticulate transmission
Pinus endophyte
Seed-borne ectomycorrhizal fungi
Seed microbiome.

Presentation Type: Oral Paper
Session: SYMB1, Symbioses: Plant, Animal, and Microbe Interactions
Location: Tucson J/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 9:15 AM
Number: SYMB1006
Abstract ID:715
Candidate for Awards:None

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