Abstract Detail

Biochemistry, metabolism, carbon flux

Fortier, Colleen [1], Cooke, Janice [1].

Responses of Pine Phenolic Defenses to Water Deficit and Inoculation with the Mountain Pine Beetle Fungal Symbiont, Grosmannia clavigera.

As the mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak has advanced eastward, it has spread beyond its historic host species, lodgepole pine (Pinus contorta var. latifolia), to a new host, jack pine (Pinus banksiana). Available evidence suggests that jack pine has never been exposed to MPB. This lack of co-evolutionary relationship might indicate that jack pine has fewer defense mechanisms specialized for protection against MPB. Understanding whether host quality differs between lodgepole and jack pine is important in predicting further eastward spread of MPB. Phenolic compounds are a cornerstone of plant defenses against herbivores such as MPB, and their pathogenic fungal associates such as Grosmannia clavigera. Phenolics comprise a large class of secondary metabolites with diverse functions, from photo-protective flavonoids to antifungal stilbenes, that are primarily produced via the phenylpropanoid pathway. The aims of this project are to (1) characterize constitutive phenolic defenses in lodgepole and jack pine, (2) compare phenolic defenses that are invoked in lodgepole and jack pine in response to G. clavigera inoculation, and (3) determine if abiotic stresses such as water deficit impact phenolic defenses. To examine phenolic defenses in lodgepole and jack pine, we inoculated seedlings with G. clavigera. Some trees were also subjected to water deficit conditions, which is thought to compromise tree defenses. Microscopy analyses demonstrated that both drought and inoculation increased accumulation of phenolics within polyphenolic parenchyma cells of the phloem. Sequences encoding many putative phenolic biosynthetic enzymes were identified from lodgepole and jack pine cDNA resources, based on sequence similarity to functionally characterized phenolic biosynthetic genes from other species, together with phylogenetic analyses. An extensive microarray dataset of bark tissue was mined to identify putative phenolic biosynthetic genes responsive to G. clavigera inoculation and/or water deficit. Several genes putatively involved in stilbene, proanthocyanidin and general phenylpropanoid metabolism were strongly upregulated in both pine species in response to G. clavigera, and this response was affected by water deficit. A subset of these putative phenolic biosynthetic genes will be used for comprehensive transcript expression profiling using quantitative RT-PCR. I am also planning to conduct biochemical quantification of pathway compounds by HPLC and LC-MS. With these results, I aim to assess the relative importance of phenolic defenses in the responses of lodgepole and jack pine to water deficit stress, MPB and G. clavigera, and to determine whether differences exist between these sister pine species.

1 - University of Alberta, Biological Sciences, Biological Sciences Building, University of Alberta, Edmonton, AB, T6G 2E9, CAN

Keywords:
none specified

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PBC007
Abstract ID:378
Candidate for Awards:CSPB President's Award for Best Student Presentation