ABSTRACT
Nudicaulins are unique alkaloids responsible for the yellow color of the petals of some papaveraceaous plants. To elucidate the unknown biosynthetic origin of the skeleton, a (13) CO2 -pulse/chase experiment was performed with growing Papaver nudicaule plants. (13) C NMR analysis revealed more than 20 multiple (13) C-enriched isotopologues in nudicaulins from the petals of (13) CO2 -labeled plants. The complex labeling pattern was compared with the isotopologue composition of a kaempferol derivative that was isolated from petals of the same (13) CO2 -labeled plants. The deconvolution of the labeling profiles indicated that the nudicaulin scaffold is assembled from products or intermediates of indole metabolism, the phenylpropanoid pathway, and the polyketide biosynthesis. Naringenin-type compounds and tryptophan/tryptamine are potential substrates for the condensation reaction finally generating the aglycone skeleton of nudicaulins.
Subject(s)
Alkaloids/biosynthesis , Carbon Dioxide/metabolism , Papaver/metabolism , Alkaloids/chemistry , Carbon Dioxide/chemistry , Carbon Isotopes , Isotope Labeling , Molecular Structure , Papaver/chemistry , Papaver/growth & developmentABSTRACT
⢠A hallmark of the innate immune system of plants is the biosynthesis of low-molecular-weight compounds referred to as secondary metabolites. Tryptophan-derived branch pathways contribute to the capacity for chemical defense against microbes in Arabidopsis thaliana. ⢠Here, we investigated phylogenetic patterns of this metabolic pathway in relatives of A. thaliana following inoculation with filamentous fungal pathogens that employ contrasting infection strategies. ⢠The study revealed unexpected phylogenetic conservation of the pathogen-induced indole glucosinolate (IG) metabolic pathway, including a metabolic shift of IG biosynthesis to 4-methoxyindol-3-ylmethylglucosinolate and IG metabolization. By contrast, indole-3-carboxylic acid and camalexin biosyntheses are clade-specific innovations within this metabolic framework. A Capsella rubella accession was found to be devoid of any IG metabolites and to lack orthologs of two A. thaliana genes needed for 4-methoxyindol-3-ylmethylglucosinolate biosynthesis or hydrolysis. However, C. rubella was found to retain the capacity to deposit callose after treatment with the bacterial flagellin-derived epitope flg22 and pre-invasive resistance against a nonadapted powdery mildew fungus. ⢠We conclude that pathogen-inducible IG metabolism in the Brassicaceae is evolutionarily ancient, while other tryptophan-derived branch pathways represent relatively recent manifestations of a plant-pathogen arms race. Moreover, at least one Brassicaceae lineage appears to have evolved IG-independent defense signaling and/or output pathway(s).
Subject(s)
Arabidopsis/metabolism , Brassicaceae/metabolism , Brassicaceae/microbiology , Genetic Variation , Glucosinolates/metabolism , Indoles/metabolism , Phylogeny , Tryptophan/metabolism , Absorption/radiation effects , Amino Acid Sequence , Arabidopsis/immunology , Arabidopsis/microbiology , Arabidopsis/radiation effects , Ascomycota/physiology , Ascomycota/radiation effects , Botrytis/physiology , Botrytis/radiation effects , Brassicaceae/immunology , Glucosinolates/chemistry , Immunity, Innate/radiation effects , Indoles/chemistry , Molecular Sequence Data , Plant Diseases/microbiology , Plant Proteins/chemistry , Sequence Homology, Amino Acid , Species Specificity , Thiazoles/metabolism , Tryptophan/chemistry , Ultraviolet RaysABSTRACT
The structural elucidation of organic compounds in complex biofluids and tissues remains a significant analytical challenge. For mass spectrometry, the manual interpretation of collision-induced dissociation (CID) mass spectra is cumbersome and requires expert knowledge, as the fragmentation mechanisms of ions formed from small molecules are not completely understood. The automated identification of compounds is generally limited to searching in spectral libraries. Here, we present a method for interpreting the CID spectra of the organic compound's protonated ions by computing fragmentation trees that establish not only the molecular formula of the compound and all fragment ions but also the dependencies between fragment ions. This is an important step toward the automated identification of unknowns from the CID spectra of compounds that are not in any database.
Subject(s)
Organic Chemicals/chemistry , Statistics as Topic/methods , Tandem Mass Spectrometry/methods , Expert Systems , SoftwareABSTRACT
Beewolf digger wasps cultivate specific symbiotic bacteria (Streptomyces spp.) that are incorporated into the larval cocoon for protection against pathogens. We identified the molecular basis of this protective symbiosis in the natural context and demonstrate that the bacteria produce a 'cocktail' of nine antibiotic substances. The complementary action of all symbiont-produced antibiotics confers a potent antimicrobial defense for the wasp larvae that parallels the 'combination prophylaxis' known from human medicine.
