Biology subjects

Paetz, C.

Publications and source records attributed to Paetz, C..

7 recordsLinked to original sources

bioRxiv2024

Phenylphenalenones and Linear Diarylheptanoid Derivatives are Biosynthesized via Parallel Routes in Musella lasiocarpa, the Chinese Dwarf Banana

Phenylphenalenones (PPs) are complex polycyclic natural products that play an important role in the chemical defense system of banana and plantain (Musaceae). Although suggestions for how plants synthesize the PP scaffold were first proposed more than 50 years ago, no biosynthetic information is yet available at the enzyme level. Here, we use transcriptomic data from seeds of Musella lasiocarpa, the Chinese dwarf banana, to identify five biosynthetic genes involved in the formation of dihydrocurcuminoids. Characterization of the substrate specificities of the enzymes reveals two distinct dihydrocurcuminoid pathways leading to the two types of major aromatic seed metabolites, the PPs and the linear diarylheptanoid derivatives. Furthermore, through multiple rounds of feeding potential intermediates to M. lasiocarpa root protein extract, followed by high-resolution mass spectrometry profiling, product isolation, and NMR-based elucidation, we demonstrate the stepwise conversion of a dihydrocurcumin-type precursor to the PP 4-hydroxylachnanthocarpone. In contrast to the commonly hypothesized Diels-Alder cyclization mechanism, we propose an unexpected two-step cyclization route to the PP scaffold.

biochemistry↗

bioRxiv2022

Recycling upstream redox enzymes expands the regioselectivity of cycloaddition in pseudo-aspidosperma alkaloid biosynthesis

Nature uses cycloaddition reactions to generate complex natural product scaffolds. Dehydrosecodine is a highly reactive biosynthetic intermediate that undergoes cycloaddition to generate several alkaloid scaffolds that are the precursors to pharmacologically important compounds such as vinblastine and ibogaine. Here we report how dehydrosecodine can be subjected to redox chemistry, which in turn allows cycloaddition reactions with alternative regioselectivity. By incubating dehydrosecodine with reductase and oxidase biosynthetic enzymes that act upstream in the pathway, we can access the rare pseudo-aspidosperma alkaloids, pseudo-tabersonine and pseudo-vincadifformine, both in vitro and by reconstitution in the plant Nicotiana benthamiana from an upstream intermediate. We propose a stepwise mechanism to explain the formation of the pseudo-tabersonine scaffold by structurally characterizing enzyme intermediates, and by monitoring the incorporation of deuterium labels. This discovery highlights how plants use redox enzymes to enantioselectively generate new scaffolds from common precursors.

biochemistry↗

bioRxiv2022

Expansion of the Catalytic Repertoire of Alcohol Dehydrogenases in Plant Metabolism

Medium-chain alcohol dehydrogenases (ADHs) comprise a highly conserved enzyme family that catalyse the reversible reduction of aldehydes. However, recent discoveries in plant natural product biosynthesis suggest that the catalytic repertoire of ADHs has been expanded. Here we report the crystal structure of dihydroprecondylocarpine acetate synthase (DPAS), an ADH that catalyses the non-canonical 1,4 reduction of an ,{beta}-unsaturated iminium moiety. Comparison with structures of plant-derived ADHs that catalyse 1,2-aldehyde and 1,2-iminium reductions suggest how the canonical ADH active site can be modified to carry out atypical carbonyl reductions, providing insight into how chemical reactions are diversified in plant metabolism.

biochemistry↗

bioRxiv2021

A beta-glucosidase of an insect herbivore determines both toxicity and deterrence of a dandelion defense metabolite

Gut enzymes can metabolize plant defense metabolites and thereby affect the growth and fitness of insect herbivores. Whether these enzymes also influence herbivore behavior and feeding preference is largely unknown. We studied the metabolization of taraxinic acid {beta}-D-glucopyranosyl ester (TA-G), a sesquiterpene lactone of the common dandelion (Taraxacum officinale) that deters its major root herbivore, the common cockchafer larva (Melolontha melolontha). We demonstrate that TA-G is rapidly deglycosylated and conjugated to glutathione in the insect gut. A broad-spectrum M. melolontha {beta}-glucosidase, Mm_bGlc17, is sufficient and necessary for TA-G deglycosylation. Using plants and insect RNA interference, we show that Mm_bGlc17 reduces TA-G toxicity. Furthermore, Mm_bGlc17 is required for the preference of M. melolontha larvae for TA-G deficient plants. Thus, herbivore metabolism modulates both the toxicity and deterrence of a plant defense metabolite. Our work illustrates the multifacteted roles of insect digestive enzymes as mediators of plant-herbivore interactions.

ecology↗

bioRxiv2020

Two bi-functional cytochrome P450 CYP72 enzymes from olive (Olea europaea) catalyze the oxidative C-C bond cleavage in the biosynthesis of secoxy-iridoids - flavor and quality determinants in olive oil

O_LIOlive (Olea europaea) is an important crop in Europe, with high cultural, economic, and nutritional significance. Olive oil flavor and quality depend on phenolic secoiridoids, but the biosynthetic pathway of these iridoids remains largely uncharacterized. C_LIO_LIWe discovered two novel, bi-functional cytochrome P450 enzymes, catalysing the rare oxidative C-C bond cleavage of 7-epi-loganin to produce oleoside methyl ester (OeOMES) and secoxyloganin (OeSXS), both through a ketologanin intermediary. Although these enzymes are homologous to the previously reported Catharanthus roseus Secologanin Synthase (CrSLS), the substrate and product profiles differ. C_LIO_LIBiochemical assays provided mechanistic insights into the two-step OeOMES and CrSLS reactions. Model-guided mutations of OeOMES changed the product profile in a predictable manner, revealing insights into the molecular basis for this change in product specificity. C_LIO_LIOur results suggest that, in contrast to published hypotheses, in planta production of secoxy-iridoids is secologanin independent. Notably, sequence data of cultivated and wild olives, points to a relation between domestication and OeOMES expression. Thus, the discovery of this key biosynthetic gene suggests a link between domestication and secondary metabolism, and could potentially be used as a genetic marker to guide next-generation breeding programs. C_LI

biochemistry↗

bioRxiv2019

A cytochrome P450 from juvenile mustard leaf beetles hydroxylates geraniol, a key step in iridoid biosynthesis

Juveniles of the leaf beetle Phaedon cochleariae synthesize iridoid via the mevalonate pathway to repel predators. The normal terpenoid biosynthesis is integrated into the dedicated defensive pathway by the {omega}-hydroxylation of geraniol to 8-hydroxygeraniol. Here we identify and characterize the geraniol 8-hydroxylase as a P450 monooxygenase using integrated transcriptomic and proteomic analyses. In the fat body, 73 individual cytochrome P450s were identified. The double stranded RNA (dsRNA)-mediated knock down of CYP6BH5 led to a significant reduction of 8-hydroxygeraniol-glucoside in the hemolymph and, later, of the chrysomelidial in the defensive secretion. Heterologously expressed CYP6BH5 converted geraniol to 8-hydroxygeraniol. In addition to geraniol, CYP6BH5 also catalyzes other monoterpenols, such as nerol and citronellol, into the corresponding , {omega}-dihydroxy compounds.\n\nHighlightsO_LIThe geraniol 8-hydroxylase in Phaedon cochleariae was identified as a cytochrome P450 CYP6BH5.\nC_LIO_LIRNA interference emphasized the importance of CYP6BH5 in iridoid biosynthesis.\nC_LIO_LIIn vitro enzyme assays showed that recombinant CYP6BH5 is a substrate promiscuous enzyme, converting the {omega}-hydroxylation of geraniol, nerol, citronellol but not linalool.\nC_LIO_LIHomology modeling suggested the -OH group of the substrate plays an important role in coordinating the substrates with the enzymes catalytic cavity.\nC_LI

biochemistry↗

bioRxiv2017

Gut microbiota of the pine weevil degrades conifer diterpenes and increases insect fitness

The pine weevil (Hylobius abietis), a major pest of conifer forests throughout Europe, feeds on the bark and cambium, tissues rich in terpenoid resins that are toxic to many insect herbivores. Here we report the ability of the pine weevil gut microbiota to degrade the diterpene acids of Norway spruce. The diterpene acid levels present in ingested bark were substantially reduced on passage through the pine weevil gut. This reduction was significantly less upon antibiotic treatment, and supplementing the diet with gut suspensions from untreated insects restored the ability to degrade diterpenes. In addition, cultured bacteria isolated from pine weevil guts were shown to degrade a Norway spruce diterpene acid. In a metagenomic survey of the insects bacterial community, we were able to annotate several genes of a previously described diterpene degradation (dit) gene cluster. Antibiotic treatment disrupted the core bacterial community of H. abietis guts and eliminated nearly all dit-genes concordant with its reduction of diterpene degradation. Pine weevils reared on an artificial diet spiked with diterpenes, but without antibiotics, were found to lay more eggs with a higher hatching rate than weevils raised on diets with antibiotics or without diterpenes. These results suggest that gut symbionts contribute towards host fitness, but not by detoxification of diterpenes, since these compounds do not show toxic effects with or without antibiotics. Rather the ability to thrive in a terpene rich environment appears to allow gut microbes to benefit the weevil in other ways, such as increasing the nutritional properties of their diet.

evolutionary biology↗