PS 72-79 - Development of laboratory-based methods to detect cryptic hereditary fungal symbiont in Ipomoea tricolor

Friday, August 16, 2019
Exhibit Hall, Kentucky International Convention Center
Lekeah A. Duden, Department of Biology, Indiana University, Bloomington, IN, Quinh Quach, Tulane University, New Orleans, LA and Keith Clay, Ecology and Evolutionary Biology, Tulane University, New Orleans, LA
Background/Question/Methods

Many groups of plants support cryptic hereditary fungal symbionts that are not easily visualized morphologically or microscopically, especially early in plant development. Many morning glory species (Convolvulaceae) within the Ipomoea genus are infected with unculturable fungal symbionts classified in the genus Periglandula. While some species exhibit epiphytic hyphae on young leaf surfaces of mature hosts, other species such as Ipomoea tricolor do not. Prior research with I. tricolor has shown that gall formation by root knot nematodes was reduced by 50% in symbiotic plants compared to non-symbiotic plants, demonstrating Periglandula’s defensive role against biotic enemies. In this study, we tested whether molecular characterization of endosymbiont status could be detected prior to host maturity. Using genomic DNA isolated from I. tricolor and other Ipomoea species, we aimed to detect cryptic fungal symbiont using the dmaW gene for ergot pathways by comparing endosymbiotic (E+) and endosymbiotic negative (E-) samples. Given that I. tricolor has become a model research system, developing molecular tools to identify symbiont-positive plants early in development. This would provide a valuable tool for future plant endosymbiont research that could be expanded to other plant families exhibiting similar cryptic symbioses like the grasses (Poaceae) and legumes (Fabaceae) and to explore these symbiotic relationships through in vivo studies.

Results/Conclusions

We have explored several sets of primers specific for fungi and to fungi in the family Clavicipitaceae, to which Periglandula belongs in order to identify diagnostic sequences for these cryptic symbionts. The fungal gene dmaW codes for the initial biosynthetic pathway for ergot alkaloid production in Clavicipitaceae fungi and has been detected in several species of morning glories. We explored different primer sequences and PCR conditions applied to I. tricolor and related congeners. Amplification of dmaW sequences was successful in several other plant-fungal combinations but provided ambiguous results. Although research is ongoing, our results show that amplification for endosymbiotic (E+) seedlings show visible bands at the expected 1050bp region after adjusting PCR conditions. Preliminary results indicate that detection of cryptic symbiont is possible to be amplified from the I. tricolor leaves from E+ seedlings. Short-term future research will adjust sample biomass, plant tissue type and plant age to optimize conditions for identifying cryptic symbiosis in I. tricolor and E+ congeners prior to host maturity. Long-term research will lead to increased understanding of the mechanisms influencing the coevolution of this and other plant-fungal symbioses while improving molecular genetic approaches for further probe development.