Browsing by Author "Muchlinski, Andrew"

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    Biosynthesis and Emission of Stress-Induced Volatile Terpenes in Roots and Leaves of Switchgrass (Panicum virgatum L.)
    Muchlinski, Andrew; Chen, Xinlu; Lovell, John T.; Köllner, Tobias G.; Pelot, Kyle A.; Zerbe, Philipp; Ruggiero, Meredith; Callaway, LeMar, III; Laliberte, Suzanne; Chen, Feng; Tholl, Dorothea (2019-09-19)
    Switchgrass (Panicum virgatum L.), a perennial C4 grass, represents an important species in natural and anthropogenic grasslands of North America. Its resilience to abiotic and biotic stress has made switchgrass a preferred bioenergy crop. However, little is known about the mechanisms of resistance of switchgrass against pathogens and herbivores. Volatile compounds such as terpenes have important activities in plant direct and indirect defense. Here, we show that switchgrass leaves emit blends of monoterpenes and sesquiterpenes upon feeding by the generalist insect herbivore Spodoptera frugiperda (fall armyworm) and in a systemic response to the treatment of roots with defense hormones. Belowground application of methyl jasmonate also induced the release of volatile terpenes from roots. To correlate the emission of terpenes with the expression and activity of their corresponding biosynthetic genes, we identified a gene family of 44 monoterpene and sesquiterpene synthases (mono-and sesqui-TPSs) of the type-a, type-b, type-g, and type-e subfamilies, of which 32 TPSs were found to be functionally active in vitro. The TPS genes are distributed over the K and N subgenomes with clusters occurring on several chromosomes. Synteny analysis revealed syntenic networks for approximately 30-40% of the switchgrass TPS genes in the genomes of Panicum hallii, Setaria italica, and Sorghum bicolor, suggesting shared TPS ancestry in the common progenitor of these grass lineages. Eighteen switchgrass TPS genes were substantially induced upon insect and hormone treatment and the enzymatic products of nine of these genes correlated with compounds of the induced volatile blends. In accordance with the emission of volatiles, TPS gene expression was induced systemically in response to belowground treatment, whereas this response was not observed upon aboveground feeding of S. frugiperda. Our results demonstrate complex above and belowground responses of induced volatile terpene metabolism in switchgrass and provide a framework for more detailed investigations of the function of terpenes in stress resistance in this monocot crop.
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    Diversity and function of terpene synthases in the production of carrot aroma and flavor compounds
    Muchlinski, Andrew; Ibdah, Mwafaq; Ellison, Shelby; Yahyaa, Mossab; Nawade, Bhagwat; Laliberte, Suzanne; Senalik, Douglas; Simon, Philipp; Whitehead, Susan R.; Tholl, Dorothea (2020-06-19)
    Carrot (Daucus carota L.) is an important root vegetable crop with high nutritional value, characteristic flavor, and benefits to human health. D. carota tissues produce an essential oil that is rich in volatile terpenes and plays a major role in carrot aroma and flavor. Although terpene composition represents a critical quality attribute of carrots, little is known about the biosynthesis of terpenes in this crop. Here, we functionally characterized 19 terpene synthase (TPS) genes in an orange carrot (genotype DH1) and compared tissue-specific expression profiles and in vitro products of their recombinant proteins with volatile terpene profiles from DH1 and four other colored carrot genotypes. In addition to the previously reported (E)-beta -caryophyllene synthase (DcTPS01), we biochemically characterized several TPS proteins with direct correlations to major compounds of carrot flavor and aroma including germacrene D (DcTPS7/11), gamma -terpinene (DcTPS30) and alpha -terpinolene (DcTPS03). Random forest analysis of volatiles from colored carrot cultivars identified nine terpenes that were clearly distinct among the cultivars and likely contribute to differences in sensory quality. Correlation of TPS gene expression and terpene metabolite profiles supported the function of DcTPS01 and DcTPS03 in these cultivars. Our findings provide a roadmap for future breeding efforts to enhance carrot flavor and aroma.
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    Identification of a Dolabellane Type Diterpene Synthase and other Root-Expressed Diterpene Synthases in Arabidopsis
    Wang, Qiang; Jia, Meirong; Huh, Jung-Hyun; Muchlinski, Andrew; Peters, Reuben J.; Tholl, Dorothea (Frontiers, 2016-11-25)
    Arabidopsis thaliana maintains a complex metabolism for the production of secondary or specialized metabolites. Such metabolites include volatile and semivolatile terpenes, which have been associated with direct and indirect defensive activities in flowers and leaves. In comparison, the structural diversity and function of terpenes in Arabidopsis roots has remained largely unexplored despite a substantial number of root-expressed genes in the Arabidopsis terpene synthase (TPS) gene family. We show that five root-expressed TPSs of an expanded subfamily-a type clade in the Arabidopsis TPS family function as class I diterpene synthases that predominantly convert geranylgeranyl diphosphate (GGPP) to different semi-volatile diterpene products, which are in part detectable at low levels in the ecotypes Columbia (Col) and Cape Verde Island (Cvi). The enzyme TPS20 produces a macrocyclic dolabellane diterpene alcohol and a dolabellane-related diterpene olefin named dolathaliatriene with a so far unknown C6- C11 bicyclic scaffold besides several minor olefin products. The TPS20 compounds occur in all tissues of Cvi but are absent in the Col ecotype because of deletion and substitution mutations in the Col TPS20 sequence. The primary TPS20 diterpene products retard the growth of the root rot pathogen Pythium irregulare but only at concentrations exceeding those in planta. Together, our results demonstrate that divergence and pseudogenization in the Arabidopsis TPS gene family allow for structural plasticity in diterpene profiles of above- and belowground tissues.
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    JGI Plant Gene Atlas: an updateable transcriptome resource to improve functional gene descriptions across the plant kingdom
    Sreedasyam, Avinash; Plott, Christopher; Hossain, Md Shakhawat; Lovell, John T.; Grimwood, Jane; Jenkins, Jerry W.; Daum, Christopher; Barry, Kerrie; Carlson, Joseph; Shu, Shengqiang; Phillips, Jeremy; Amirebrahimi, Mojgan; Zane, Matthew; Wang, Mei; Goodstein, David; Haas, Fabian B.; Hiss, Manuel; Perroud, Pierre-Francois; Jawdy, Sara S.; Yang, Yongil; Hu, Rongbin; Johnson, Jenifer; Kropat, Janette; Gallaher, Sean D.; Lipzen, Anna; Shakirov, Eugene; Weng, Xiaoyu; Torres-Jerez, Ivone; Weers, Brock; Conde, Daniel; Pappas, Marilia R.; Liu, Lifeng; Muchlinski, Andrew; Jiang, Hui; Shyu, Christine; Huang, Pu; Sebastian, Jose; Laiben, Carol; Medlin, Alyssa; Carey, Sankalpi; Carrell, Alyssa A.; Chen, Jin-Gui; Perales, Mariano; Swaminathan, Kankshita; Allona, Isabel; Grattapaglia, Dario; Cooper, Elizabeth A.; Tholl, Dorothea; Vogel, John P.; Weston, David J.; Yang, Xiaohan; Brutnell, Thomas P.; Kellogg, Elizabeth A.; Baxter, Ivan; Udvardi, Michael; Tang, Yuhong; Mockler, Todd C.; Juenger, Thomas E.; Mullet, John; Rensing, Stefan A.; Tuskan, Gerald A.; Merchant, Sabeeha S.; Stacey, Gary; Schmutz, Jeremy (Oxford University Press, 2023-08-01)
    Gene functional descriptions offer a crucial line of evidence for candidate genes underlying trait variation. Conversely, plant responses to environmental cues represent important resources to decipher gene function and subsequently provide molecular targets for plant improvement through gene editing. However, biological roles of large proportions of genes across the plant phylogeny are poorly annotated. Here we describe the Joint Genome Institute (JGI) Plant Gene Atlas, an updateable data resource consisting of transcript abundance assays spanning 18 diverse species. To integrate across these diverse genotypes, we analyzed expression profiles, built gene clusters that exhibited tissue/condition specific expression, and tested for transcriptional response to environmental queues. We discovered extensive phylogenetically constrained and condition-specific expression profiles for genes without any previously documented functional annotation. Such conserved expression patterns and tightly co-expressed gene clusters let us assign expression derived additional biological information to 64 495 genes with otherwise unknown functions. The ever-expanding Gene Atlas resource is available at JGI Plant Gene Atlas (https://plantgeneatlas.jgi.doe.gov) and Phytozome (https://phytozome.jgi.doe.gov/), providing bulk access to data and user-specified queries of gene sets. Combined, these web interfaces let users access differentially expressed genes, track orthologs across the Gene Atlas plants, graphically represent co-expressed genes, and visualize gene ontology and pathway enrichments.
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    De novo formation of an aggregation pheromone precursor by an isoprenyl diphosphate synthase-related terpene synthase in the harlequin bug
    Lancaster, Jason; Khrimian, Ashot; Young, Sharon; Lehner, Bryan; Luck, Katrin; Wallingford, Anna K.; Ghosh, Saikat Kumar B.; Zerbe, Philipp; Muchlinski, Andrew; Marek, Paul E.; Sparks, Michael E.; Tokuhisa, James G.; Tittiger, Claus; Köllner, Tobias G.; Weber, Donald C.; Gundersen-Rindal, Dawn E.; Kuhar, Thomas P.; Tholl, Dorothea (2018-09-11)
    Insects use a diverse array of specialized terpene metabolites as pheromones in intraspecific interactions. In contrast to plants and microbes, which employ enzymes called terpene synthases (TPSs) to synthesize terpene metabolites, limited information from few species is available about the enzymatic mechanisms underlying terpene pheromone biosynthesis in insects. Several stink bugs (Hemiptera: Pentatomidae), among them severe agricultural pests, release 15-carbon sesquiterpenes with a bisabolene skeleton as sex or aggregation pheromones. The harlequin bug, Murgantia histrionica, a specialist pest of crucifers, uses two stereoisomers of 10,11-epoxy-1-bisabolen-3-ol as a male-released aggregation pheromone called murgantiol. We show that MhTPS (MhIDS-1), an enzyme unrelated to plant and microbial TPSs but with similarity to trans-isoprenyl diphosphate synthases (IDS) of the core terpene biosynthetic pathway, catalyzes the formation of (15,6S,7R)-1,10-bisaboladien-1-ol (sesquipiperitol) as a terpene intermediate in murgantiol biosynthesis. Sesquipiperitol, a so-far-unknown compound in animals, also occurs in plants, indicating convergent evolution in the biosynthesis of this sesquiterpene. RNAi-mediated knockdown of MhTPS mRNA confirmed the role of MhTPS in murgantiol biosynthesis. MhTPS expression is highly specific to tissues lining the cuticle of the abdominal sternites of mature males. Phylogenetic analysis suggests that MhTPS is derived from a trans-IDS progenitor and diverged from bona fide trans-IDS proteins including MhIDS-2, which functions as an (E,E)-farnesyl diphosphate (FPP) synthase. Structure-guided mutagenesis revealed several residues critical to MhTPS and MhFPPS activity. The emergence of an IDS-like protein with TPS activity in M. histrionica demonstrates that de novo terpene biosynthesis evolved in the Hemiptera in an adaptation for intraspecific communication.
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    Sesquiterpene pheromone biosynthesis in stink bugs: An isopentenyl diphosphate synthase like protein produces the cyclic sesquiterpene alcohol precursor of the aggregation pheromone murgantiol in harlequin bug (Murgantia histrionica)
    Lancaster, Jason; Khrimian, Ashot; Young, Sharon; Lehner, Bryan; Luck, Katrin; Wallingford, Anna K.; Ghosh, Saikat Kumar B.; Zerbe, Philipp; Muchlinski, Andrew; Marek, Paul E.; Sparks, Michael E.; Tokuhisa, James G.; Tittiger, Claus; Köllner, Tobias G.; Weber, Donald C.; Gundersen-Rindal, Dawn E.; Kuhar, Thomas P.; Tholl, Dorothea (2018-08-23)
    Insects use a diverse array of specialized terpene metabolites as pheromones in intraspecific interactions. In contrast to plants and microbes, which employ enzymes called terpene synthases (TPSs) to synthesize terpene metabolites, limited information from few species is available about the enzymatic mechanisms underlying terpene pheromone biosynthesis in insects. Several stink bugs (Hemiptera: Pentatomidae), among them severe agricultural pests, release 15-carbon sesquiterpenes with a bisabolene skeleton as sex or aggregation pheromones. The harlequin bug, Murgantia histrionica, a specialist pest of crucifers, uses two stereoisomers of 10,11-epoxy-1-bisabolen-3-ol as a male-released aggregation pheromone called murgantiol. We show that MhTPS (MhIDS-1), an enzyme unrelated to plant and microbial TPSs but with similarity to trans-isoprenyl diphosphate synthases (IDS) of the core terpene biosynthetic pathway, catalyzes the formation of (1S,6S,7R)- 1,10-bisaboladien-1-ol (sesquipiperitol) as a terpene intermediate in murgantiol biosynthesis. Sesquipiperitol, a so-far-unknown compound in animals, also occurs in plants, indicating convergent evolution in the biosynthesis of this sesquiterpene. RNAi-mediated knockdown of MhTPS mRNA confirmed the role of MhTPS in murgantiol biosynthesis. MhTPS expression is highly specific to tissues lining the cuticle of the abdominal sternites of mature males. Phylogenetic analysis suggests that MhTPS is derived from a trans-IDS progenitor and diverged from bona fide trans-IDS proteins including MhIDS-2, which functions as an (E,E)-farnesyl diphosphate (FPP) synthase. Structure-guided mutagenesis revealed several residues critical to MhTPS and MhFPPS activity. The emergence of an IDS-like protein with TPS activity in M. histrionica demonstrates that de novo terpene biosynthesis evolved in the Hemiptera in an adaptation for intraspecific communication.