title: Influence of water deficit on the molecular responses of Pinus contorta × Pinus banksiana mature trees to infection by the mountain pine beetle fungal associate, Grosmannia clavigera.
abstract: Conifers exhibit a number of constitutive and induced mechanisms to defend against attack by pests and pathogens such as mountain pine beetle (Dendroctonus ponderosae Hopkins) and their fungal associates. Ecological studies have demonstrated that stressed trees are more susceptible to attack by mountain pine beetle than their healthy counterparts. In this study, we tested the hypothesis that water deficit affects constitutive and induced responses of mature lodgepole pine × jack pine hybrids (Pinus contorta Dougl. ex Loud. var. latifolia Engelm. ex S. Wats. × Pinus banksiana Lamb.) to inoculation with the mountain pine beetle fungal associate Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield. The degree of stress induced by the imposed water-deficit treatment was sufficient to reduce photosynthesis. Grosmannia clavigera-induced lesions exhibited significantly reduced dimensions in water-deficit trees relative to well-watered trees at 5 weeks after inoculation. Treatment-associated cellular-level changes in secondary phloem were also observed. Quantitative RT-PCR was used to analyze transcript abundance profiles of 18 genes belonging to four families classically associated with biotic and abiotic stress responses: aquaporins (AQPs), dehydration-responsive element binding (DREB), terpene synthases (TPSs) and chitinases (CHIs). Transcript abundance profiles of a TIP2 AQP and a TINY-like DREB decreased significantly in fungus-inoculated trees, but not in response to water deficit. One TPS, Pcb(+)-3-carene synthase, and the Class II CHIs PcbCHI2.1 and PcbCHI2.2 showed increased expression under water-deficit conditions in the absence of fungal inoculation, while another TPS, Pcb(E)-β-farnesene synthase-like, and two CHIs, PcbCHI1.1 and PcbCHI4.1, showed attenuated expression under water-deficit conditions in the presence of fungal inoculation. The effects were observed both locally and systemically. These results demonstrate that both constitutive and induced carbon- and nitrogen-based defenses are affected by water deficit, suggesting potential consequences for mountain pine beetle dynamics, particularly in novel environments.
authors: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9.
authors: Adriana
authors: A
authors: Arango-Velez
authors: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9.
authors: Leonardo M Galindo
authors: LM
authors: González
authors: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9.
authors: Miranda J
authors: MJ
authors: Meents
authors: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9.
authors: Walid
authors: W
authors: El Kayal
authors: Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, AB, Canada T6H 3S5.
authors: Barry J
authors: BJ
authors: Cooke
authors: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9.
authors: Jean
authors: J
authors: Linsky
authors: Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada T6E 2E3.
authors: Inka
authors: I
authors: Lusebrink
authors: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9 janice.cooke@ualberta.ca.
authors: Janice E K
authors: JE
authors: Cooke
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D002244:Carbon / Q000378:metabolism; D002678:Chimera; D002688:Chitinases / Q000235:genetics; D001517:Coleoptera / Q000382:microbiology*; D003681:Dehydration; D004777:Environment; D005656:Fungal Proteins / Q000235:genetics; D020869:Gene Expression Profiling; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D055155:Ophiostomatales / Q000502:physiology*; D052585:Phloem; D010788:Photosynthesis / Q000502:physiology; D028223:Pinus / Q000166:cytology / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D014867:Water / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D014867:Water; D002244:Carbon; D019883:Alkyl and Aryl Transferases; C108877:terpene synthase; D002688:Chitinases
keywords: DREB; Dendroctonus ponderosae; aquaporin; blue stain fungi; chitinase; drought; jack pine; lodgepole pine; naïve host; range expansion; systemic; terpene synthase