Histology of resin vesicles and oleoresin terpene composition of conifer seeds

The seed coats of several conifers contain terpene-filled resin vesicles, which may be involved in the protection of the dormant embryo and the seed storage tissue against herbivores or pathogens. We analyzed the terpenoid composition of seeds from four Abies species (A. amabilis, A. balsamea, A. grandis, and A. lasiocarpa), two Thuja species (Th. plicata and Th. occidentalis), and three Tsuga species (Ts. canadensis, Ts. mertensiana, and Ts. heterophylla) and examined histological features of resin vesicles in seeds from one species from each genus. Resin vesicle morphology was generally similar among the species analyzed. The composition of the seed terpenes varied largely between species. The described seed terpene profiles of the nine species will serve as a foundation for future studies into the function of seed terpenes and resin vesicles in the seed coat.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

White ash trees (Fraxinus americana) originally from colder, drier areas are more susceptible to emerald ash borer (Agrilus planipennis)

Trees are dying prematurely across the globe at alarming rates, often due to drought and/or insects. Insect attacks can range in severity with some tree species surviving (e.g., the American beech and beech bark disease) and some species becoming essentially extinct (e.g., the American chestnut and the chestnut blight). Tree responses may also vary because of genetic differences among “families” of trees (i.e., intraspecific variation). It is thus hard to predict how tree species will respond to insect attacks. To this avail, we examined tree canopy dieback (leaf loss), drought stress, wound healing, and chemical defense responses of 44 families of white ash (Fraxinus americana) from across the species range to a recent emerald ash borer (Agrilus planipennis) outbreak in an arid common garden in Kansas. At our site, white ash families originally from drier, colder areas (northern USA) exhibited more canopy dieback than families from wetter, warmer regions (southern USA). We also found that tree families that were sensitive to drought and/or slower to heal bark wounds were more likely to show canopy dieback. Overall, we are the first to demonstrate significant intraspecific variation in white ash canopy dieback due to emerald ash borer and connect it to temperature and precipitation conditions of original seed sources. If this canopy dieback pattern holds for mortality, southern white ash may be suitable for reintroduction to the American north, where 99% of white ash has already died

Gene discovery of modular diterpene metabolism in nonmodel systems

Plants produce over 10,000 different diterpenes of specialized (secondary) metabolism, and fewer diterpenes of general (primary) metabolism. Specialized diterpenes may have functions in ecological interactions of plants with other organisms and also benefit humanity as pharmaceuticals, fragrances, resins, and other industrial bioproducts. Examples of high-value diterpenes are taxol and forskolin pharmaceuticals or ambroxide fragrances. Yields and purity of diterpenes obtained from natural sources or by chemical synthesis are often insufficient for large-volume or high-end applications. Improvement of agricultural or biotechnological diterpene production requires knowledge of biosynthetic genes and enzymes. However, specialized diterpene pathways are extremely diverse across the plant kingdom, and most specialized diterpenes are taxonomically restricted to a few plant species, genera, or families. Consequently, there is no single reference system to guide gene discovery and rapid annotation of specialized diterpene pathways. Functional diversification of genes and plasticity of enzyme functions of these pathways further complicate correct annotation. To address this challenge, we used a set of 10 different plant species to develop a general strategy for diterpene gene discovery in nonmodel systems. The approach combines metabolite-guided transcriptome resources, custom diterpene synthase (diTPS) and cytochrome P450 reference gene databases, phylogenies, and, as shown for select diTPSs, single and coupled enzyme assays using microbial and plant expression systems. In the 10 species, we identified 46 new diTPS candidates and over 400 putatively terpenoid-related P450s in a resource of nearly 1 million predicted transcripts of diterpene-accumulating tissues. Phylogenetic patterns of lineage-specific blooms of genes guided functional characterization