Abstract Detail

The negotiated surveillance of parts and wholes: a symbioses-centered perspective on plant biology research

Clay, Keith [1], Beaulieu, Wesley [1], Panaccione, Daniel [2], Cook, Daniel [3].

Hereditary Fungal Symbiosis in Plants.

Hereditary symbiosis is well-known in arthropods where symbiotic bacteria are passed on to the next generation through the eggs of the host, but is thought to be rare in plants outside of cool-season grasses infected by seed-transmitted clavicipitaceous fungal endophytes. However, recent research has revealed a more widespread distribution of hereditary fungal symbiosis in locoweed genera (Fabaceae) and in morning glory species (Convolvulaceae), with likely cases in several other major plant families. Similarly, some South African Rubiaceae are infected with symbiotic Burkholderia bacteria forming leaf nodules. In all of these examples, the symbionts are systemic, transmitted through seeds and produce animal toxins, suggesting independent evolutionary origins of functionally similar symbioses. We have focused on morning glory species where two distinct types of hereditary fungal symbiosis occur. From herbarium sheets, seeds from 241 species of Convolvulaceae were analyzed for the presence of ergot alkaloids, indicative of Periglandula symbiosis. We found that 56 species contained ergot alkaloids, including 34 species never before reported. Species with larger seeds were significantly more likely to contain ergot alkaloids and to have them at higher concentrations, consistent with the Resource Availability Hypothesis. There was a nonsignificant trend for tropical species to more frequently contain ergot alkaloids but there was no relationship between latitude and alkaloid concentration, which is not consistent with the Latitudinal Defense Hypothesis. Population sampling of Ipomoea leptophylla revealed no variation in ergot alkaloids across a 700 km latitudinal gradient in the western USA, but we did find significantly higher levels of ergot alkaloids in I. pes-caprae on the Gulf Coast compared to the Atlantic Coast of Florida, USA and with decreasing latitude. Independent of symbiosis with Periglandula, several species of Ipomoea and Turbina (Convolvulaceae) contain the toxic alkaloid swainsonine. In I. carnea, swainsonine is produced by a seed-transmitted Chaetothyriales fungal endophyte. Both ergot alkaloids and swainsonine were found in T. cordata, but not in the same samples, suggesting that this plant may associate with alternate fungal partners with different biosynthetic capabilities. It is apparent that we do not have a full understanding of range of hereditary fungal symbiosis in plants. Future research should address the diversity, distribution and functional consequences of these interactions.

1 - Indiana University, Biology, 1005 E. 3rd St., Bloomington, IN, 47405, USA
2 - West Virginia University, Division of Plant & Soil Sciences, Morgantown, WV, 26506, USA
3 - Poisonous Plant Research Laboratory, USDA/ARS, Logan, UT, 84322, USA

Keywords:
fungal endophyte
symbiosis
plants
seed transmission
toxin
mutualism
Plant defense 
diversity.

Presentation Type: Symposium Presentation
Session: SY16
Location: Salon 4/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 8:15 AM
Number: SY16002
Abstract ID:806
Candidate for Awards:None