Abiotic Stress/Whole Plant Bio

Abstract

CS-14-5 - Uncovering the role of phenolics in pine defenses against mountain pine beetle and their fungal associates

Monday, July 16
2:43 PM - 2:45 PM

The current outbreak of mountain pine beetle (MPB; Dendroctonus ponderosae) has advanced beyond its historic host species, lodgepole pine (Pinus contorta var. latifolia), to a new host, jack pine (Pinus banksiana). Available evidence suggests jack pine has never been exposed to MPB prior to this outbreak. Lack of a co-evolutionary relationship might indicate that jack pine has fewer specialized mechanisms for defense against MPB and their pathogenic fungal associates such as Grosmannia clavigera. Furthermore, water limitation is thought to compromise plant defenses. Understanding whether host quality differs between lodgepole and jack pine, and how abiotic stresses affect host quality, is important in predicting further spread of MPB. In response to G. clavigera or MPB attack, pines develop lesions that constitute cellular changes such as accumulated phenolics. We have demonstrated that lesion length is not well correlated with G. clavigera growth, but instead is indicative of the tree’s defense response. Given this, lesion length analyses suggest that lodgepole respond more rapidly than jack pine, and water deficit reduces defense response times in both species. Putative phenolic biosynthesis genes were identified from lodgepole and jack pine transcriptome datasets. Expression profiling for these genes in xylem and bark was completed using a large microarray experiment comparing lodgepole and jack pine responses to G. clavigera under well-watered or water deficit conditions. More detailed expression profiling was completed with qRT-PCR for a subset of these genes. Some branches of phenolic biosynthesis, like stilbene and flavonoid biosynthesis, showed strong gene regulation in response to inoculation,and patterns differ between species. Water deficit negatively affected transcript abundance in both species, but was more pronounced in lodgepole pine. With these results and ongoing work, I aim to determine whether phenolics contribute to differences in defenses between lodgepole and jack pine hosts, and whether water limitation compromises these defenses.


 

Co-Authors

Chandra McAllister – University of Alberta; Kate St. Onge – University of Alberta; Bianca Sacchi – University of Alberta; Adriana Arango-Velez – Connecticut Agricultural Experiment Station; Miranda Meents – University of British Columbia; Janice Cooke – University of Alberta

Colleen E. Fortier

Graduate Student
University of Alberta

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CS-14-5 - Uncovering the role of phenolics in pine defenses against mountain pine beetle and their fungal associates



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