Costunolide Influences Germ Tube Orientation in Sunflower Broomrape - A First Step Toward Understanding Chemotropism.

WALLR. is a host-specific root parasite of cultivated sunflowers with increasing economic importance in Europe, North Africa, and parts of Asia. While sesquiterpene lactones (STLs) released from sunflower roots were identified as natural germination stimulants of seeds in the soil, the chemical nature of the signals guiding the emerging germ tube toward the host root has remained unknown hitherto.

Ultrastructural Alterations in Cells of Sunflower Linear Glandular Trichomes during Maturation.

Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of the trichome have not been studied in detail so far. Light, fluorescence and transmission electron microscopy were employed to investigate the functional structure of different trichome cells and their subcellular compartmentation in the pre-secretory, secretory and post-secretory phase.

"Jumping Jack": Genomic Microsatellites Underscore the Distinctiveness of Closely Related and and Provide New Insights Into Their Evolutionary Past.

Downy mildews caused by obligate biotrophic oomycetes result in severe crop losses worldwide. Among these pathogens, and , two closely related oomycetes, adversely affect cucurbits and hop, respectively. Discordant hypotheses concerning their taxonomic relationships have been proposed based on host-pathogen interactions and specificity evidence and gene sequences of a few individuals, but population genetics evidence supporting these scenarios is missing.

Microsatellite Markers from , the Cause of Blue Mold of Tobacco, Reveal Species Origin, Population Structure, and High Gene Flow.

is an obligate parasite that causes blue mold of tobacco. The pathogen reproduces primarily by sporangia, whereas the sexual oospores are rarely observed. A collection of 122 isolates of was genotyped using nine microsatellites to assess the population structure of individuals from subpopulations collected from central, southern, and western Europe; the Middle East; Central America; North America; and Australia.

Phytochemical characterization of different yarrow species ( sp.) and investigations into their antimicrobial activity.

Various species are rich in bioactive compounds and are important medicinal plants in phytotherapy. In the present study, L., Wulfen, and L.

Metabolomic and Gene Expression Studies Reveal the Diversity, Distribution and Spatial Regulation of the Specialized Metabolism of Yacón (, Asteraceae).

, also known as yacón, is an Andean crop species commercialized for its nutraceutical and medicinal properties. The tuberous roots of yacón accumulate a diverse array of probiotic and bioactive metabolites including fructooligosaccharides and caffeic acid esters. However, the metabolic diversity of yacón remains unexplored, including the site of biosynthesis and accumulation of key metabolite classes.

CYP71BL9, the missing link in costunolide synthesis of sunflower.

Despite intensive research in recent years, the biosynthetic route to costunolide in sunflower so far remained obscured. Additional P450 sequences from public sunflower transcriptomic database were screened to search for candidate enzymes which are able to introduce the 6α-hydroxy-group required for the esterification with the carboxy group of germacarane A acid, the final step in costunolide formation. CYP71BL9, a new P450 enzyme from sunflower was shown to catalyze this hydroxylation, hence being identified as HaCOS.

Spatial and developmental synthesis of endogenous sesquiterpene lactones supports function in growth regulation of sunflower.

Tissue-specific occurrence and formation of endogenous sesquiterpene lactones has been assessed and suggests physiological function as antagonists of auxin-induced plant growth in sunflower. Sunflower, Helianthus annuus, accumulate high concentrations of bioactive sesquiterpene lactones (STL) in glandular trichomes, but in addition, structurally different STL occur in only trace amounts in the inner tissues. The spatial and temporal production of these endogenous STL during early phases of plant development is widely unknown and their physiological function as putative natural growth regulators is yet speculative.

Characterization of CYP71AX36 from Sunflower (Helianthus annuus L., Asteraceae).

Sesquiterpene lactones (STL) are a subclass of isoprenoids with many known bioactivities frequently found in the Asteraceae family. In recent years, remarkable progress has been made regarding the biochemistry of STL, and today the biosynthetic pathway of the core backbones of many STLs has been elucidated. Consequently, the focus has shifted to the discovery of the decorating enzymes that can modify the core skeleton with functional hydroxy groups.

Metabolomic and gene expression approaches reveal the developmental and environmental regulation of the secondary metabolism of yacón (Smallanthus sonchifolius, Asteraceae).

Acting as chemical defense or signaling compounds, secondary metabolites (SMs) play an essential role in the evolutionary success of many angiosperm plant families. However, the adaptive advantages that SMs confer, and the influence of environmental and developmental factors on SMs expression, remains poorly understood. A study of taxa endemic to the variable Andean climate, using a metabolomics approach, may provide further insight.

Development of phloem connection between the parasitic plant Orobanche cumana and its host sunflower.

Orobanche cumana is a root parasitic plant causing considerable yield losses in sunflower cultivation. The holoparasite fulfills its entire demand for water, minerals, and organic nutrients from the host's vascular system. In this study, the ultrastructure of the phloem connection between the haustorium of young O.

Up-regulated RxLR effector genes of Plasmopara viticola in synchronized host-free stages and infected leaves of hosts with different susceptibility.

Fast recognition of host signals and early activation of infection mechanisms in Plasmopara viticola are decisive for successful infestation of Vitis vinifera. To better understand interactive processes at the first front line of combat between the pathogen and its host, a specific pre-infective stage was generated in a host-free system. Zoospore encystment was triggered within minutes after treatment with CaCl.

Biosynthesis of Eupatolide-A Metabolic Route for Sesquiterpene Lactone Formation Involving the P450 Enzyme CYP71DD6.

Sesquiterpene lactones are a class of natural compounds well-known for their bioactivity and are characteristic for the Asteraceae family. Most sesquiterpene lactones are considered derivatives of germacrene A acid (GAA). GAA can be stereospecifically hydroxylated by the cytochrome P450 enzymes (CYP) Lactuca sativa costunolide synthase CYP71BL2 (LsCOS) and Helianthus annuus GAA 8β-hydroxylase CYP71BL1 (HaG8H) at C6 (in α-orientation) or C8 (in β-orientation), respectively.

Direct Analyses of Secondary Metabolites by Mass Spectrometry Imaging (MSI) from Sunflower (Helianthus annuus L.) Trichomes.

(sunflower) displays non-glandular trichomes (NGT), capitate glandular trichomes (CGT), and linear glandular trichomes (LGT), which reveal different chemical compositions and locations in different plant tissues. With matrix-assisted laser desorption/ionization (MALDI) and laser desorption/ionization (LDI) mass spectrometry imaging (MSI) techniques, efficient methods were developed to analyze the tissue distribution of secondary metabolites (flavonoids and sesquiterpenes) and proteins inside of trichomes. Herein, we analyzed sesquiterpene lactones, present in CGT, from leaf transversal sections using the matrix 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA) (mixture 1:1) with sodium ions added to increase the ionization in positive ion mode.

ssRNA viruses from biotrophic Oomycetes form a new phylogenetic group between Nodaviridae and Tombusviridae.

Plasmopara halstedii virus (PhV) is one of the few characterized oomycete viruses. Although it is fully sequenced and well-studied in its genetic diversity, the exact classification and phylogenetic relationships of PhV remain uncertain. The only known virus with characteristics similar to PhV is the Sclerophthora macrospora Virus A (SmV-A).

Comparative Metabolite Profiling of Triterpenoid Saponins and Flavonoids in Flower Color Mutations of Primula veris L.

L. is an important medicinal plant with documented use for the treatment of gout, headache and migraine reaching back to the Middle Ages. Triterpenoid saponins from roots and flowers are used in up-to-date phytotherapeutic treatment of bronchitis and colds due to their expectorant and secretolytic effects.

Asexual Recombinants of Plasmopara halstedii Pathotypes from Dual Infection of Sunflower.

Genetically homogenous strains of Plasmopara halstedii differing in host specificity and fungicide tolerance were used to test the hypothesis that asexual genetic recombination occurs and may account for the high genotype diversity of this homothallic reproducing oomycete, which causes downy mildew in sunflower. Dual inoculation of sunflower seedlings with single zoospore strains of complementary infection characteristics caused sporulation under conditions where inoculation with each strain alone failed to infect. PCR-based investigation with strain-specific primers proved the presence of genetic traits from both progenitors in single sporangia collected from sporangiophores of such infections.

Identification and characterization of two bisabolene synthases from linear glandular trichomes of sunflower (Helianthus annuus L., Asteraceae).

Sunflower is known to produce a variety of bisabolene-type sesquiterpenes and accumulates these substances in trichomes of leaves, stems and flowering parts. A bioinformatics approach was used to identify the enzyme responsible for the initial step in the biosynthesis of these compounds from its precursor farnesyl pyrophosphate. Based on sequence similarity with a known bisabolene synthases from Arabidopsis thaliana AtTPS12, candidate genes of Helianthus were searched in EST-database and used to design specific primers.

Genome analyses of the sunflower pathogen Plasmopara halstedii provide insights into effector evolution in downy mildews and Phytophthora.

Background: Downy mildews are the most speciose group of oomycetes and affect crops of great economic importance. So far, there is only a single deeply-sequenced downy mildew genome available, from Hyaloperonospora arabidopsidis. Further genomic resources for downy mildews are required to study their evolution, including pathogenicity effector proteins, such as RxLR effectors.

The nonvolatile metabolome of sunflower linear glandular trichomes.

Uniseriate linear glandular trichomes occur on stems, leaves and flowering parts of Helianthus species and related taxa. Their metabolic activity and biological function are still poorly understood. A phytochemical study documented the accumulation of bisabolene type sesquiterpenes and flavonoids as the major constituents of the non-volatile metabolome of linear glandular trichomes in the common sunflower, Helianthus annuus.

Genome Sequence and Architecture of the Tobacco Downy Mildew Pathogen Peronospora tabacina.

Peronospora tabacina is an obligate biotrophic oomycete that causes blue mold or downy mildew on tobacco (Nicotiana tabacum). It is an economically important disease occurring frequently in tobacco-growing regions worldwide. We sequenced and characterized the genomes of two P.

Localization of sesquiterpene lactone biosynthesis in cells of capitate glandular trichomes of Helianthus annuus (Asteraceae).

Capitate glandular trichomes (CGT) of sunflower, Helianthus annuus, synthesize bioactive sesquiterpene lactones (STLs) within a short period of only a few days during trichome development. In the current project, the subcellular localization of H. annuus germacrene A monooxygenase (HaGAO), a key enzyme of the STL biosynthesis in sunflower CGT, was investigated.

Sesquiterpene Lactone Composition of Wild and Cultivated Sunflowers and Biological Activity against an Insect Pest.

Sesquiterpene lactones in sunflowers, Helianthus spp., are important to interactions with pathogens, weeds, and insects. Across a broad range of Helianthus annuus, differences in composition of sesquiterpene lactones extracted from disc florets were found between wild and cultivated sunflowers and also between distinct groups of inbreds used to produce sunflower hybrids.

Occurrence and genetic diversity of the Plasmopara halstedii virus in sunflower downy mildew populations of the world.

Plasmopara halstedii virus (PhV) is a ss(+)RNA virus that exclusively occurs in the sunflower downy mildew pathogen Plasmopara halstedii, a biotrophic oomycete of severe economic impact. The virus origin and its genomic variability are unknown. A PCR-based screening of 128 samples of P.