Bryological and Lichenological Section/ABLS
Athukorala, S.N.P. , Huebner, E. , Piercey-Normore, M.D. .
Quantitative comparison of morphology and gene expression of Cladonia rangiferina during the interaction with compatible and incompatible algae.
An understanding of the factors behind the success of growth and development of the lichen genus Cladonia is important since they form the dominant vegetation in northern ecosystems and are the main winter diet for Caribou and Reindeer. The objective of this study was to quantitatively compare morphological development of the interaction between the fungal partner C. rangiferina with its compatible alga (Asterochloris glomerata) and an incompatible alga (Chlorella ellipsoidea) and to compare expression of fungal and algal genes, which are involved in the recognition between partners. The fungus was co-inoculated with Asterochloris glomerata, and with Chlorella ellipsoidea separately. The first three stages of development of the lichen thallus were identified in the compatible interaction using scanning electron microscopy as the "pre-contact stage" (1 day post co-inoculation (PCI)), "contact stage" (8 days PCI) and "growth together stage" (21-28 days PCI). At each stage, quantitative variables such as internode length, number of new lateral branches of the fungus, haustorial frequency, and diameter of the algal cells, were statistically compared in both compatible and incompatible interactions. To compare the gene expression, pure cultures of C. rangiferina and A. glomerata were treated with liquid extracts collected from the compatible and incompatible interactions at three defined developmental stages. Real Time Polymerase Chain Reaction (RT-PCR) was performed to compare the expression of two fungal genes, arginase and catalase, during the interaction. Compatible interactions showed significantly different characteristics compared to incompatible interactions. Furthermore, at 21-28 days PCI, a parasitic interaction was observed between C. rangiferina and Ch. ellipsoidea suggesting the importance of recognition between compatible partners to develop a "controlled parasitic" interaction. Up-regulation of genes was observed in both compatible and incompatible interactions in the "pre-contact" stage. An increase in up-regulation of the arginase and catalase genes from early to late developmental stages was observed in the compatible interaction. In contrast, expression of both genes decreased in the interaction with Ch. ellipsoidea from early to late stages. This suggests that arginase and catalase genes are turned on non-specifically before the physical contact between partners and their expression is specific to the compatible interaction after the physical contact occurs. These findings suggest that arginase and catalase genes are potentially important in developing a compatible interaction that will lead to development of the lichen C. rangiferina. In addition, the expression of two genes of A. glomerata upon the extracts of compatible and incompatible interactions will also be discussed.
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1 - University of Manitoba, Biological Sciences, Winnipeg, MB, R3T 2N2, Canada
Presentation Type: Oral Paper:Papers for Sections
Location: Ascot/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 9:45 AM
Candidate for Awards:A. J. Sharp Award