Publications (Centre for Forest Biology)

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    Fungal community composition as affected by litter chemistry and weather during four years of litter decomposition in rainshadow coastal Douglas-fir forests
    (Journal of Fungi, 2022) Shay, Philip-Edouard; Winder, Richard S.; Constabel, C. Peter; Trofymow, J. A. (Tony)
    Climate and litter chemistry are major factors influencing litter decay, a process mediated by microbes, such as fungi, nitrogen-fixing bacteria and ammonia-oxidizing bacteria. Increasing atmospheric CO2 concentrations can decrease nitrogen (N) and increase condensed tannin (CT) content in foliar litter, reducing litter quality and slowing decomposition. We hypothesized that reduced litter quality inhibits microbes and is the mechanism causing decomposition to slow. Litterbags of Douglas-fir needles and poplar leaves with a range of N (0.61–1.57%) and CT (2.1–29.1%) treatment and natural acid unhydrolyzable residue (35.3–41.5%) concentrations were placed along climatic gradients in mature Douglas-fir stands of coastal British Columbia rainshadow forests. The structure (diversity, richness and evenness) and composition of microbial communities were analyzed using DGGE profiles of 18S, NifH-universal and AmoA PCR amplicons in foliar litter after 7, 12, 24 and 43 months of decay. High CT and low N concentrations in leaf litter were associated with changes in microbial community composition, especially fungi. Contrary to our hypothesis, high CT and low N treatments did not inhibit microbial colonization or diversity. The joint effects of air temperature and soil moisture on microbial community composition at our sites were more important than the effects of initial litter chemistry.
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    Diatom responses to long-term climate and sea-level rise at low-elevation lake in coastal British Columbia, Canada
    (Ecosphere, 2019) Neil, Karen; Lacourse, Terri
    Diatom assemblages from Lake Stowell, a low‐elevation lake in coastal British Columbia, were used to assess limnological responses associated with changes in relative sea level (RSL) and climate over the past 14,500 yr. Marine diatom taxa dominated the early record and disappeared abruptly by 14,000 cal yr BP in response to glacio‐isostatic uplift and an ensuing decrease in RSL. A brackish‐freshwater phase from 14,200 to 13,400 cal yr BP was marked by increases in several diatom taxa with tolerance for low‐to‐moderate salinity, after which assemblages became strictly freshwater. Biostratigraphic changes in both diatom and chironomid assemblages from Lake Stowell occurred more or less simultaneously throughout the record in response to long‐term changes in climate forcings, such as temperature. Increases in cold‐adapted diatom (Staurosirella pinnata, Staurosira construens, Staurosirella dubia ) and chironomid (Sergentia ) taxa between 12,900 and 11,700 cal yr BP coincided with Younger Dryas cooling, suggesting a direct link with summer temperature. Shifts in aquatic biota also reflected indirect mechanisms through which climate affected the Lake Stowell ecosystem, for example, by altering thermal stratification, disturbance regimes, and nutrient concentrations. For instance, high summer insolation and warm summer temperatures from 11,700 to 8500 cal yr BP were associated with greater abundances of Stephanodiscus hantzschii and especially Aulacoseira subarctica . A concurrent opening of the forest canopy triggered by warming would have exposed the lake to strong winds and enhanced mixing, favoring these more heavily silicified taxa as an indirect consequence of climatic changes. Diatom assemblages appear to have been impacted by the deposition of Mount Mazama tephra at 7600 cal yr BP; a notable increase in Aulacoseira tenella suggests a response to increased silica availability in association with tephra deposition.
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    Late Pleistocene vegetation and sedimentary charcoal at Kilgii Gwaay archaeological site in coastal British Columbia, Canada, with possible proxy evidence for human presence by 13,000 cal bp
    (Vegetation History and Archaeobotany, 2020) Mathewes, Rolf W.; Lacourse, Terri; Helmer, E. F.; Howarth, C. R.; Fedje, Daryl
    Kilgii Gwaay is an early Holocene archaeological wet site located in the intertidal zone of Ellen Island in the southern Haida Gwaii archipelago of coastal British Columbia, Canada. The Kilgii site includes one of the oldest shell middens in western North America and provides evidence of early maritime adaptations by humans. Radiocarbon-dated cultural deposits that surround a small palaeopond (Kilgii Pond) include hearth features, abundant lithic, bone and wood artifacts, and a diverse fossil fauna and flora. The known occupation dates between 10,800 and 10,500 cal bp, when relative sea level was 1–3 m lower than today. The site was submerged and capped by marine deposits by 10,500 cal bp as relative sea level rose. We conducted multi-proxy palaeoenvironmental analyses (magnetic susceptibility, pollen, charcoal, macrofossils) on Kilgii Pond sediments from a core taken beneath the coarse intertidal deposits. Pollen analysis indicates establishment of herb–shrub tundra by 14,500 cal bp, followed by pine-dominated communities after 13,800 cal bp and spruce forest with abundant ferns from about 13,250 cal bp. Macroscopic charcoal in the core is most abundant during the period of confirmed human occupation; however, significant peaks in charcoal abundance are present well below the known occupation horizon. Since lightning and natural forest fires are infrequent in this wet hypermaritime setting, we consider that the charcoal peaks from Kilgii Pond may serve as a proxy for human presence, potentially as early as 13,000 cal bp, approximately 2,200 years earlier than indicated by the AMS-dated cultural deposits and artifacts.
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    Peatland formation, succession and carbon accumulation at a mid-elevation poor fen in Pacific Canada
    (The Holocene, 2019) Lacourse, Terri; Adeleye, Matthew A.; Stewart, Johanna R.
    We reconstructed peatland formation, succession and long-term rates of carbon (C) accumulation at a mid-elevation poor fen on Vancouver Island in coastal British Columbia, Canada. Multi-proxy paleoecological analyses including bulk chemistry, peat composition, macrofossils, pollen and non-pollen palynomorphs show terrestrialization starting from a small oligotrophic lake 14,000 cal BP. Peat accumulation began by 11,600 cal BP with the transition to an emergent Nuphar-dominated shallow-water marsh. Terrestrialization in the center of the peatland was more or less complete by 10,400 cal BP with the development of a Sphagnum-dominated poor fen that continues to the present. Outward expansion by paludification appears to have brought the peatland close to its modern lateral extent by 10,000 cal BP, suggesting that terrestrialization and paludification played important concurrent roles in the early development of this poor fen. Mean long-term rates of C accumulation (13 g C/m2/yr) are lower than at most Northern Hemisphere peatlands including nearby lowland bogs. Maximum rates of 43 g C/m2/yr occurred in the early Holocene during accumulation of Nuphar peat and the transition to Sphagnum peat and coincided with high summer temperatures and increased seasonality, which promote growing season productivity and reduce winter decomposition. Early Holocene increases in C accumulation rates occurred at two nearby lowland bogs during similar wetland stages. Collectively, these studies demonstrate that climate and autogenic succession, including changes in relative water table depth and plant functional groups, interacted to drive Holocene peatland dynamics and C accumulation rates in the maritime setting of coastal British Columbia.
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    Postglacial wetland succession, carbon accumulation and forest dynamics on the east coast of Vancouver Island, British Columbia, Canada
    (Quaternary Research, 2019) Lacourse, Terri; Beer, Kyle W.; Craig, Kira B.; Canil, Dante
    Peatland development and carbon accumulation on the Pacific coast of Canada have received little attention in paleoecological studies, despite wetlands being common landscape features. Here, we present a multi–proxy paleoenvironmental study of an ombrotrophic bog in coastal British Columbia. Following decreases in relative sea level, the wetland was isolated from marine waters by 13,300 cal yr BP. Peat composition, non-pollen palynomorph, and C and N analyses demonstrate terrestrialization from an oligotrophic lake to a marsh by 11,600 cal yr BP, followed by development of a poor fen, and then a drier ombrotrophic bog by 8700 cal yr BP. Maximum carbon accumulation occurred during the early Holocene fen stage, when seasonal differences in insolation were amplified. This highlights the importance of seasonality in constraining peatland carbon sequestration by enhancing productivity during summer and reducing decomposition during winter. Pollen analysis shows that Pinus contorta dominated regional forests by 14,000 cal yr BP. Warm and relatively dry summers in the early Holocene allowed Pseudotsuga menziesii to dominate lowland forests 11,200–7000 cal yr BP. Tsuga heterophylla and P. menziesii formed coniferous forest in the mid- and late Holocene. Tephra matching the mid-Holocene Glacier Peak–Dusty Creek assemblage provides evidence of its most northwesterly occurrence to date.
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    Latitudinal limits to the predicted increase of the peatland carbon sink with warming
    (Nature Climate Change, 2018) Gallego-Sala, Angela V.; Charman, Dan J.; Brewer, Simon; Page, Susan E.; Prentice, I. Colin; Friedlingstein, Pierre; Moreton, Steve; Lacourse, Terri; et. al.
    The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around ad 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.
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    Fossil chironomid assemblages and inferred summer temperatures for the past 14,000 years from a low-elevation lake in Pacific Canada
    (Journal of Paleolimnology, 2018-04) Lemmen, J.; Lacourse, Terri
    Fossil midge remains in a sediment core from Lake Stowell, a low-elevation lake in coastal British Columbia, Canada, were used to assess temporal changes in chironomid communities and to produce quantitative estimates of mean July air temperature (MJAT) for the past 14,000 years based on two different transfer functions. Chironomid assemblages are diverse throughout much of the record, with most taxa present at low relative abundances. The basal portion of the sediment record is characterized by low head capsule concentrations, taxonomic diversity and organic matter content, all of which increase towards the early Holocene. Inferred temperatures suggest a cool late-glacial interval with a minimum MJAT of 12.5 °C, ~2 °C cooler than the inferred modern temperature. Summer temperatures gradually increased from this minimum until a brief cooling of as much as ~3 °C relative to modern that coincides with the Younger Dryas chronozone. An interval of warmer summers with MJAT of ~16 to 18 °C (2–3 °C warmer than modern) is inferred between ~10,500 and 8000 cal year BP. This early Holocene warm period was followed by generally cooler inferred temperatures in the middle and late Holocene. The midge-inferred temperature record from Lake Stowell is generally consistent with other temperature reconstructions from the region based on chironomid remains and other climate proxies. This research underscores the potential of low-elevation, mid-latitude sites for chironomid-based temperature reconstructions. In order to maximize the availability of modern analogues for robust temperature reconstructions from similar sites, calibration datasets should be expanded to include more sites from the warm end of the temperature gradient.
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    A multi-proxy peat study of Holocene vegetation history, bog development and carbon accumulation on northern Vancouver Island, Pacific coast of Canada
    (The Holocene, 2015) Lacourse, Terri; Davies, Marissa A.
    We present a multi-proxy paleoenvironmental study on a 10,400 cal. yr peat sequence from an ombrotrophic bog in coastal British Columbia, Canada. Pollen, non-pollen palynomorph, plant macrofossil, and physicochemical analyses (bulk density, %C, %N, δ13C, and δ15N isotopes) were used to document changes in vegetation, bog development, and carbon and nitrogen accumulation. Pollen assemblages indicate that regional vegetation in the warm, relatively dry early Holocene was mixed coniferous forest with scattered Pseudotsuga menziesii. Herbaceous peat with a C:N of ~28, combined with Nuphar microfossils and relatively high %N, suggests the presence of a herb-dominated peatland with standing water and/or bog pools. Carbon and nitrogen accumulation were at their highest during this early Holocene period at mean rates of 30.6 and 1.2 g/m2/cal. yr, respectively. By 8000 cal. yr BP and under a cooler, wetter climate, northern Vancouver Island supported Tsuga heterophylla rainforest similar to today. Decreasing relative water table, inferred from testate amoebae and fungal remains, facilitated the establishment of a Sphagnum bog by 8000 cal. yr BP with abundant ericaceous shrubs after 5000 cal. yr BP. Temporal variation in carbon accumulation rates corresponds with changes in plant functional types and hydrological conditions: rates were lowest in the early to mid-Holocene during accumulation of Sphagnum peat (7.1 g/m2/cal. yr) and increased in late Holocene ligneous peat (12.4 g/m2/cal. yr). Our multi-proxy approach not only demonstrates the overarching control of climate on bog development and carbon and nitrogen accumulation, with seasonality likely playing a major role, but also highlights the strong influence of autogenic processes at a local scale.
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    Phylogenetic and functional signals in gymnosperm ovular secretions
    (Annals of Botany, 2017-11) Nepi, Massimo; Little, Stefan; Guarnieri, Massimo; Nocentini, Daniele; Prior, Natalie; Gill, Julia; Tomlinson, P. Barry; Ickert-Bond, Stefanie M.; Pirone, Cary; Pacini, Ettore; von Aderkas, Patrick
    Background and Aims: Gymnosperms are either wind-pollinated (anemophilous) or both wind- and insect-pollinated (ambophilous). Regardless of pollination mode, ovular secretions play a key role in pollen capture, germination and growth; they are likely also involved in pollinator reward. Little is known about the broad-scale diversity of ovular secretions across gymnosperms, and how these may relate to various reproductive functions. This study analyses the sugar and amino acid profiles of ovular secretions across a range of ambophilous (cycads and Gnetales) and anemophilous gymnosperms (conifers) to place them in an evolutionary context of their possible functions during reproduction. Methods: Ovular secretions from 13 species representing all five main lineages of extant gymnosperms were sampled. High-performance liquid chromatography techniques were used to measure sugar and amino acid content. Multivariate statistics were applied to assess whether there are significant differences in the chemical profiles of anemophilous and ambophilous species. Data were compared with published chemical profiles of angiosperm nectar. Chemical profiles were placed in the context of phylogenetic relationships. Key results: Total sugar concentrations were significantly higher in ovular secretions of ambophilous species than wind-pollinated taxa such as Pinaceae and Cupressophyta. Ambophilous species had lower amounts of total amino acids, and a higher proportion of non-protein amino acids compared with anemophilous lineages, and were also comparable to angiosperm nectar. Results suggest that early gymnosperms likely had ovular secretion profiles that were a mosaic of those associated with modern anemophilous and ambophilous species. Ginkgo, thought to be anemophilous, had a profile typical of ambophilous taxa, suggesting that insect pollination either exists in Gingko, but is undocumented, or that its ancestral populations were insect-pollinated. Conclusions: Chemical profiles of ovular secretions of ambophilous gymnosperms show a clear signal of pollinator-driven selection, including higher levels of carbohydrates than anemophilous taxa, lower levels of amino acids, and the presence of specific amino acids, such as β-alanine, that are known to influence insect feeding behaviour and physiology.
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    Fungal colonizers and seed loss in lodgepole pine orchards of British Columbia
    (Botany, 2018) de la Bastide, Paul Y.; LeBlanc, Jonathon; Kong, Lisheng; Finston, Terrie; May, Emily M.; Reich, Richard; Hintz, William E.; von Aderkas, Patrick
    Lodgepole pine is an important lumber species in Canada and seed orchards are expected to meet the increased demand for seed. However, seed production has been consistently low in the Okanagan region orchards of British Columbia. To determine whether the fungal microbiome contributes to seed loss, histological and molecular approaches were used. Seed production was studied at seven Okanagan orchards, all outside the natural range of lodgepole pine, and at one near Prince George, within its natural range. Seed losses were highest in the Okanagan, compared with Prince George. The role of fungal colonizers in consuming seed during the last stages of maturation is described. Fungal hyphae were frequently observed at all locations in developing seed, particularly once storage substances accumulated. Fungi identified from host tissues using molecular and morphological techniques included Alternaria, Cladosporium, Fusarium, Penicillium, and Sydowia. The opportunistic foliar pathogen Sydowia polyspora, which is known to have a variable biotrophic status, was detected at most orchards within different host tissues (seeds, needles and conelets), in association with pollen and in the air column. Reduced seed viability observed in Okanagan orchards is most likely due to a combination of factors, including the composition of the fungal microbiome.
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    Effects of stem-injected gibberellins and 6-benzylaminopurine on phytohormone profiles and cone yield in two lodgepole pine genotypes
    (Trees, 2018) Kong, Lisheng; von Aderkas, Patrick; Zaharia, Irina
    Effects of exogenously applied gibberellins (GAs) and 6-benzylaminopurine (BA) on profiles of phytohormones and some of their metabolites relative to controls in long-shoot buds of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were analyzed during cone bud initiation and differentiation. Differential responses in phytohormones and in cone yield were observed in ramets of the two tested genotypes (478 and 276) to stem-injected mixtures of GA4 and GA7 (GA4/7) and /or BA. Injected GA4/7 affected bud concentrations of GA4 and GA7. Injected PGRs, with the exception of BA injection, decreased concentrations of abscisic acid (ABA) and ABA glucose-ester at week 5 and/or week 7. Internal concentrations of trans-zeatin riboside (t-ZR) increased in response to all treatments at week 3 in genotype 276. In genotype 478, t-ZR only increased with treatments of BA or GA4/7 plus BA. Dihydrozeatin riboside concentrations increased in response to GA4/7 plus BA treatment at week 7 in genotype 276. Concentrations of isopentenyl adenosine declined with treatments of GA4/7 and GA4/7 plus BA in genotype 276 at week 5. In genotype 478, a similar decrease was caused by GA4/7 plus BA treatment. For both genotypes, the highest ratio of zeatin-type cytokinins to isopentenyl-type cytokinins occurred at weeks 5 and 7 after injection with GA4/7 plus BA. Stem-injection of GA4/7, especially in combination with BA, increased female cone yields significantly in genotype 276, but not in genotype 478.
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    Nitrate and ammonium uptake in twenty-one common moss species from Vancouver Island, British Columbia
    (Botany, 2017) Hawkins, B.J.; May, E.; Robbins, S.
    Mosses play key ecological roles in water and nutrient retention in many ecosystems, yet relatively little is known of the functional characteristics of moss species, particularly nutritional characteristics. We investigated the net flux of ammonium, nitrate, and protons, using a microelectrode ion flux measurement system, in the gametophytes of 21 common species of moss from three contrasting locations in southern coastal British Columbia. The general location from which mosses were collected did not significantly affect ammonium or nitrate uptake. Proton efflux was greatest in mosses from locations with high rainfall. Rates of nitrate uptake differed among moss families, but there were no significant differences in uptake among species within families. Ammonium net flux differed among moss families, but also among species nested within family, with some species showing uptake and other showing ammonium efflux. In general, moss species native to dry habitats appeared to have higher rates of nitrogen uptake when ammonium and nitrate were available under favourable conditions.
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    Saprotrophic and ectomycorrhizal fungal sporocarp stoichiometry (C : N : P) across temperate rainforests as evidence of shared nutrient constraints among symbionts
    (New Phytologist, 2018-08) Kranabetter, J. Marty; Harman-Denhoed, Rachael; Hawkins, Barbara J.
    Quantifying nutritional dynamics of free-living saprotrophs and symbiotic ectomycorrhizal fungi in the field is challenging, but the stoichiometry of fruiting bodies (sporocarps) may be an effective methodology for this purpose. Carbon (C), nitrogen (N) and phosphorus (P) concentrations of soils, foliage and 146 sporocarp collections were analyzed from 14 Pseudotsuga menziesii var. menziesii stands across a podzolization gradient on Vancouver Island (Canada). N and P concentrations were considerably higher in saprotrophic fungi. Fungal N% increased with soil N content at a greater rate for saprotrophs than ectomycorrhizal fungi, while fungal P% of saprotrophs was more constrained. Fungal N : P was more responsive to soil N : P for ectomycorrhizal fungi (homeostatic regulation coefficient ‘H’ = 2.9) than saprotrophs (H = 5.9), while N : P of ectomycorrhizal fungi and host tree foliage scaled almost identically. Results underscore the role of ectomycorrhizal fungi as nutrient conduits, supporting host trees, whereas saprotrophs maintain a greater degree of nutritional homeostasis. Site nutrient constraints were shared in equal measure between ectomycorrhizal fungi and host trees, particularly for P, suggesting neither partner benefits from enhanced nutrition at the expense of the other. Sporocarp stoichiometry provides new insights into mycorrhizal relationships and illustrates pervasive P deficiencies across temperate rainforests of the Pacific Northwest.
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    Evolution of a Secondary Metabolic Pathway from Primary Metabolism: Shikimate and quinate biosynthesis in plants
    (the Plant Journal, 2018-06) Carrington, Yuriko; Guo, Jia; Le, Cuong H.; Fillo, Alexander; Kwon, Junsu; Tran, Lan T.; Ehlting, Jurgen
    The shikimate pathway synthesizes aromatic amino acids essential for protein biosynthesis. Shikimate dehydrogenase (SDH) is a central enzyme of this primary metabolic pathway, producing shikimate. The structurally similar quinate is a secondary metabolite synthesized by quinate dehydrogenase (QDH). SDH and QDH belong to the same gene family, which diverged into two phylogenetic clades after a defining gene duplication just prior to the angiosperm/gymnosperm split. Non-seed plants that diverged before this duplication harbour only a single gene of this family. Extant representatives from the chlorophytes (Chlamydomonas reinhardtii), bryophytes (Physcomitrella patens) and lycophytes (Selaginella moellendorfii) encoded almost exclusively SDH activity in vitro. A reconstructed ancestral sequence representing the node just prior to the gene duplication also encoded SDH activity. Quinate dehydrogenase activity was gained only in seed plants following gene duplication. Quinate dehydrogenases of gymnosperms, represented here by Pinus taeda, may be reminiscent of an evolutionary intermediate since they encode equal SDH and QDH activities. The second copy in P. taeda maintained specificity for shikimate similar to the activity found in the angiosperm SDH sister clade. The codon for a tyrosine residue within the active site displayed a signature of positive selection at the node defining the QDH clade, where it changed to a glycine. Replacing the tyrosine with a glycine in a highly shikimate-specific angiosperm SDH was sufficient to gain some QDH function. Thus, very few mutations were necessary to facilitate the evolution of QDH genes.
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    A phenol-enriched cuticle is ancestral to lignin evolution in land plants
    (Nature Communications, 2017-03) Renault, Hugues; Alber, Annette; Horst, Nelly A.; Basilio Lopes, Alexandra; Fich, Eric A.; Kriegshauser, Lucie; Wiedemann, Gertrud; Ullmann, Pascaline; Herrgot, Laurence; Erhardt, Mathieu; Pineau, Emmanuelle; Ehlting, Jürgen; Schmitt, Martine; Rose, Jocelyn K.C.; Reski, Ralf; Werck-Reichhart, Danièle
    Lignin, one of the most abundant biopolymers on Earth, derives from the plant phenolic metabolism. It appeared upon terrestrialization and is thought critical for plant colonization of land. Early diverging land plants do not form lignin, but already have elements of its biosynthetic machinery. Here we delete in a moss the P450 oxygenase that defines the entry point in angiosperm lignin metabolism, and find that its pre-lignin pathway is essential for development. This pathway does not involve biochemical regulation via shikimate coupling, but instead is coupled with ascorbate catabolism, and controls the synthesis of the moss cuticle, which prevents desiccation and organ fusion. These cuticles share common features with lignin, cutin and suberin, and may represent the extant representative of a common ancestor. Our results demonstrate a critical role for the ancestral phenolic metabolism in moss erect growth and cuticle permeability, consistent with importance in plant adaptation to terrestrial conditions.
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    An assessment of Pinus contorta seed production in British Columbia: Geographic variation and dynamically-downscaled climate correlates from the Canadian Regional Climate Model
    (Agricultural and Forest Meteorology, 2017-04) Lew, Alicia; von Aderkas, Patrick; Berland, Anne; Curry, Charles L.; Lacourse, Terri; Tencer, Bárbara; Weaver, Andrew
    The ecological and economic importance of lodgepole pine (Pinus contorta Douglas ex Louden) in British Columbia (BC) has heightened interest in the adaptability and effective management of the species,especially as climate changes. The relationship between climate and the seed production of natural populations is a key management issue that has yet to be assessed. The purpose of this study is to determine if variation in P. contorta seed yield is related to the climate of BC.Regional differences in the seed production of lodgepole pine were examined using 1924 archived seedlot collections across 18 different natural stand seed planning zones (SPZs) in BC. The relationship between climate variation and the seed production of P. contorta was then evaluated using dynamically-downscaled output from the Canadian Regional Climate Model (CRCM). Seed production is relatively consistent across SPZs spanning a wide range of climate regimes, with the exception of Nass Skeena Transition (NST) where seed yield is an order of magnitude higher than else where. Significant temporal correlations between overall trends in seed production and both temperature and precipitation were found using the CRCM output. However, only three of the 18 SPZs showed a significant overall trend in mean annual seed yield based on cone collections made between 1963 and2013, suggesting that the reproductive capacity of natural populations is well adapted to decadal-scale climate change. Tolerance to significant variation in climate likely plays an important role in explaining the ability of this species to thrive well outside its natural range.
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    Transcriptome Analysis Provides Insight into Venom Evolution in a Seed-Parasitic Wasp, Megastigmus spermotrophus
    (Insect Molecular Biology, 2016-10) Paulson, Amber; Le, Cuong; Dickson, Jamie; Ehlting, Jürgen; von Aderkas, Patrick; Perlman, Steve
    One of the most striking host range transitions is the evolution of plant parasitism from animal parasitism. Parasitoid wasps that have secondarily evolved to attack plants (ie gall wasps and seed-feeders) demonstrate intimate associations with their hosts, yet the mechanism of plant–host manipulation is currently not known. There is, however, emerging evidence suggesting that ovipositional secretions play a role in plant manipulation. To investigate whether parasites have modified pre-existing adaptations to facilitate dramatic host shifts we aimed to characterize the expression of venom proteins in a plant parasite using a collection of parasitoid venom sequences as a guide. The transcriptome of a seed-feeding wasp, Megastigmus spermotrophus, was assembled de novo and three putative venoms were found to be highly expressed in adult females. One of these putative venoms, aspartylglucosaminidase, has been previously identified as a major venom component in two distantly related parasitoid wasps (Asobara tabida and Leptopilina heterotoma) and may have originated via gene duplication within the Hymenoptera. Our study shows that M. spermotrophus, a specialized plant parasite, expresses putative venom transcripts that share homology to venoms identified in Nasonia vitripennis (both superfamily Chalcidoidea), which suggests that M. spermotrophus may have co-opted pre-existing machinery to develop as a plant parasite.
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    Degradome and Secretome of Pollination Drops of Ephedra
    (Botanical Review, 2015-03) von Aderkas, Patrick; Prior, Natalie; Gagnon, Susannah; Little, Stefan; Cross, Tyra; Hardie, Darryl; Borchers, Christoph; Thornburg, Robert; Hou, Chen; Lunny, Alexandra
    Although secreted proteins (a secretome) are known to occur in gymnosperm pollination drops, this study shows evidence for the presence of a protein degradome for the first time. A protein degradome is composed of protein and peptide fragments, a product of protein breakdown, whereas a secretome is composed of whole, secreted, and often biologically active extracellular proteins. Harvested Ephedra pollination drops from seven species were pooled either by collection date or, in the case of less abundant sample volumes, by species. Samples were processed by one of two methods: 1. gel electophoresis or by 2. liquid-liquid extraction, followed by chromatographic separation. Processed samples were trypsin-digested and analyzed with a Thermo Scientific LTQ Orbitrap Velos. On average, two-thirds of the detected and characterized proteins found in Ephedra spp. pollination drops were intracellular proteins, such as ubiquitin. The remaining third represent proteins known to be secreted, often involved in apoplastic processes such as defense and carbohydrate-modification, typical of known conifer pollination drop proteins. Characterized proteins detected in our comparative study of Ephedra spp drops ranged from 6 in E. monosperma to 20 in E. foeminea. We propose that the intracellular proteins detected are present as the result of nucellar tissue degeneration during pollination drop formation; previous proteomic investigations of pollination drops were in taxa that lack nucellar degeneration during drop formation Discovery of a degradome in pollination drops is novel and significant in that its presence has biological implications for pollination biology. We predict that degradomes in pollination drops are not restricted to Ephedra, but should also occur in species with nucellar tissue breakdown that coincides with pollination drop formation, such as in cycads and Ginkgo and some Pinaceae. Analysis of several collection dates of E. monosperma shows a large number of proteins that change over the course of the pollination drop secretion period, which suggests that variation in pollination drop contents over time may be important in the pollination biology of Ephdera.
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    Host-Parasite Interactions from the Inside: Plant Reproductive Ontogeny Drives Specialization in Parasitic Insects
    (PLoS One, 2015-10) Boivin, Thomas; Gidoin, Cindy; von Aderkas, Patrick; Safrana, Jonathan; Candau, Jean- Noël; Chalon, Alain; Sondo, Marion; El Maâtaoui, Mohamed
    Host plant interactions are likely key drivers of evolutionary processes involved in the diversification of phytophagous insects. Granivory has received substantial attention for its crucial role in shaping the interaction between plants and their seed parasites, but fine-scale mechanisms explaining the role of host plant reproductive biology on specialization of seed parasites remain poorly described. In a comparative approach using plant histological techniques, we tested the hypotheses that different seed parasite species synchronize their life cycles to specific stages in seed development, and that the stage they target depends on major differences in seed development programs. In a pinaceous system, seed storage products are initiated before ovule fertilization and the wasps target the ovule’s nucellus during megagametogenesis, a stage at which larvae may benefit from the by-products derived from both secreting cells and dying nucellar cells. In a cupressaceous system, oviposition activity peaks later, during embryogenesis, and the wasps target the ovule’s megagametophyte where larvae may benefit from cell disintegration during embryogenesis. Our cytohistological approach shows for the first time how, despite divergent oviposition targets, different parasite species share a common strategy that consists of first competing for nutrients with developing plant structures, and then consuming these developed structures to complete their development. Our results support the prediction that seed developmental program is an axis for specialization in seed parasites, and that it could be an important parameter in models of their ecological and taxonomic divergence. This study provides the basis for further investigating the possibility of the link between plant ontogeny and pre-dispersal seed parasitism.
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    Effects of Exogenously Applied Gibberellins and Thidiazuron on Phytohormone Profiles of Long-Shoot Buds and Cone Gender Determination in Lodgepole Pine
    (Journal of Plant Growth Regulation, 2016-03) Kong, Lisheng; von Aderkas, Patrick; Zaharia, L. Irina
    In long-shoot buds of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm), cone-bud initiation and gender differentiation occur in a site-specific manner: female cone buds are normally restricted to the distal portion, whereas male cone buds are located in the proximal portion. Application of a paste containing two plant growth regulators gibberellins A4 + A7 (GA4/7) combined with thidiazuron (TDZ) to long-shoot buds prior to cone-bud gender determination altered endogenous phytohormone profiles and induced female cone-bud formation in the proximal portion of the long-shoot bud, where male cone buds normally occur. Induced cone clusters observed in the following spring were either entirely female or a mixture of both female and male cones. Endogenous phytohormones in the long-shoot bud tissues were quantified by the stable isotope dilution method using high performance liquid chromatography-electrospray ionization tandem mass spectrometry in multiple-reaction monitoring mode. Applied GA4/7 + TDZ led to increased concentrations of endogenous zeatin-type cytokinins, that is, trans-zeatin riboside and dihydrozeatin riboside, whereas concentrations of abscisic acid (ABA) and its catabolite, ABA glucose ester, were decreased, all relative to control, in untreated long-shoot bud tissue. Concentrations of extractable GA4 and GA7 declined in long-shoot bud tissues over 4 weeks following treatment with exogenous GA4/7. This study demonstrates that high levels of endogenous zeatin-type cytokinins, together with reduced levels of ABA, both induced by applied GA4/7 + TDZ, are positively associated with an increased female cone-bud formation in long-shoot buds.