Anthriscus sylvestris Deoxypodophyllotoxin Synthase Involved in the Podophyllotoxin Biosynthesis

Tetrahydrofuran ring formation from dibenzylbutyrolactone lignans is a key step in the biosynthesis of aryltetralin lignans including deoxypodophyllotoxin and podophyllotoxin. Previously, Fe(II)- and 2-oxoglutarate-dependent dioxygenase (2-ODD) from Podophyllum hexandrum (Himalayan mayapple, Berberidaceae) was found to catalyze the cyclization of a dibenzylbutyrolactone lignan, yatein, to give deoxypodophyllotoxin and designated as deoxypodophyllotoxin synthase (DPS). Recently, we reported that the biosynthesis of deoxypodophyllotoxin and podophyllotoxin evolved in a lineage-specific manner in phylogenetically unrelated plant species such as P. hexandrum and Anthriscus sylvestris (cow parsley, Apiaceae). Therefore, a comprehensive understanding of the characteristics of DPSs that catalyze the cyclization of yatein to deoxypodophyllotoxin in various plant species is important. However, for plant species other than P. hexandrum, the isolation of the DPS enzyme gene and the type of the enzyme, e.g. whether it is 2-ODD or another type of enzyme such as cytochrome P-450, have not been reported. In this study, we report the identification and characterization of A. sylvestris DPS (AsDPS). Phylogenetic analysis showed that AsDPS belonged to the 2-ODD superfamily and shared moderate amino acid sequence identity (40.8%) with P. hexandrum deoxypodophyllotoxin synthase (PhDPS). Recombinant protein assay indicated that AsDPS and PhDPS differ in terms of the selectivity of substrate enantiomers. Protein modeling using AlphaFold2 and site-directed mutagenesis indicated that the Tyr305 residue of AsDPS probably contributes to substrate recognition. This study advances our understanding of the podophyllotoxin biosynthetic pathway in A. sylvestris and provides new insight into 2-ODD involved in plant secondary (specialized) metabolism.


Two O-methyltransferases from Phylogenetically Unrelated Cow Parsley (Anthriscus sylvestris) and Hinoki-asunaro (Thujopsis dolabrata var. hondae) as a Signature of Lineage-specific Evolution in Lignan Biosynthesis


Lignocellulose molecular assembly and deconstruction properties of lignin-altered rice mutants


A microscale protocol for alkaline nitrobenzene oxidation of lignins using a readily available reactor


Fractionation and Characterization of Glycol Lignins by Stepwise-pH Precipitation of Japanese Cedar/Poly(ethylene glycol) Solvolysis Liquor


Seed-coat protective neolignans are produced by the dirigent protein AtDP1 and the laccase AtLAC5 in Arabidopsis


Age-dependent and radial sectional differences in the dynamic viscoelastic properties of bamboo culms and their possible relationship with the lignin structures


Plant-specific Dof transcription factors VASCULAR-RELATED DOF1 and VASCULAR-RELATED DOF2 regulate vascular cell differentiation and lignin biosynthesis in Arabidopsis


Effect of heat treatment on the chemical structure and thermal properties of softwood-derived glycol lignin.


Double knockout of OsWRKY36 and OsWRKY102 boosts lignification with altering culm morphology of rice.


Altered lignocellulose chemical structure and molecular assembly in CINNAMYL ALCOHOL DEHYDROGENASE-deficient rice.


OsCAldOMT1 is a bifunctional O-methyltransferase involved in the biosynthesis of tricin-lignins in rice cell walls


De novo transcriptome analysis of needles of Thujopsis dolabrata var. hondae

Podophyllotoxin is a starting material of the semisynthetic anticancer medicines etoposide, teniposide, and etopophos. The major plant source of podophyllotoxin is rhizomes of , which is a Himalayan endangered species; therefore, alternative sources of podophyllotoxin or bioproduction systems have been pursued to avoid exploiting this limited natural resource. In this paper, we report de novo transcriptome analysis of var. , which accumulates the podophyllotoxin derivatives (deoxypodophyllotoxin and β-peltatin A methyl ether) in its needles. We analyzed transcriptomes of the var. young needles to obtain the sequences that putatively encode -methyltransferases, cytochrome P450s, and a 2-oxoglutarate dependent dioxygenase because these protein families are responsible for podophyllotoxin-related compound formation in . The resulting transcriptomes contained considerable numbers of coding sequences classified into the three protein families. Our results are a genetic basis for identifying genes involved in the biosynthesis of podophyllotoxin and related compounds and also for future metabolic engineering of podophyllotoxin in heterologous hosts.


OsMYB108 loss-of-function enriches p-coumaroylated and tricin lignin units in rice cell walls.

The Plant Journal : for Cell and Molecular Biology


Recruitment of specific flavonoid B-ring hydroxylases for two independent biosynthesis pathways of flavone-derived metabolites in grasses

In rice (Oryza sativa), OsF2H and OsFNSII direct flavanones to independent pathways that form soluble flavone C-glycosides and tricin-type metabolites (both soluble and lignin-bound), respectively. Production of soluble tricin metabolites requires CYP75B4 as a chrysoeriol 5'-hydroxylase. Meanwhile, the close homologue CYP75B3 is a canonical flavonoid 3'-hydroxylase (F3'H). However, their precise roles in the biosynthesis of soluble flavone C-glycosides and tricin-lignins in cell walls remain unknown. We examined CYP75B3 and CYP75B4 expression in vegetative tissues, analyzed extractable flavonoid profiles, cell wall structure and digestibility of their mutants, and investigated catalytic activities of CYP75B4 orthologues in grasses. CYP75B3 and CYP75B4 showed co-expression patterns with OsF2H and OsFNSII, respectively. CYP75B3 is the sole F3'H in flavone C-glycosides biosynthesis, whereas CYP75B4 alone provides sufficient 3',5'-hydroxylation for tricin-lignin deposition. CYP75B4 mutation results in production of apigenin-incorporated lignin and enhancement of cell wall digestibility. Moreover, tricin pathway-specific 3',5'-hydroxylation activities are conserved in sorghum CYP75B97 and switchgrass CYP75B11. CYP75B3 and CYP75B4 represent two different pathway-specific enzymes recruited together with OsF2H and OsFNSII, respectively. Interestingly, the OsF2H-CYP75B3 and OsFNSII-CYP75B4 pairs appear to be conserved in grasses. Finally, manipulation of tricin biosynthesis through CYP75B4 orthologues can be a promising strategy to improve digestibility of grass biomass for biofuel and biomaterial production.


Comparative evaluations of lignocellulose reactivity and usability in transgenic rice plants with altered lignin composition


Comparative analysis of lignin chemical structures of sugarcane bagasse pretreated by alkaline, hydrothermal, and dilute sulfuric acid methods


A comparative study of the biomass properties of Erianthus and sugarcane: lignocellulose structure, alkaline delignification rate, and enzymatic saccharification efficiency

Bioscience, Biotechnology, and Biochemistry


Downregulation of p-COUMAROYL ESTER 3-HYDROXYLASE in rice leads to altered cell wall structures and improves biomass saccharification.


Isolation and characterization of polyethylene glycol (PEG)-modified glycol lignin via PEG solvolysis of softwood biomass in a large-scale batch reactor


NMR studies on lignocellulose deconstructions in the digestive system of the lower termite Coptotermes formosanus Shiraki.

Termites represent one of the most efficient lignocellulose decomposers on earth. The mechanism by which termites overcome the recalcitrant lignin barrier to gain access to embedded polysaccharides for assimilation and energy remains largely unknown. In the present study, softwood, hardwood, and grass lignocellulose diets were fed to Coptotermes formosanus workers, and structural differences between the original lignocellulose diets and the resulting feces were examined by solution-state multidimensional nuclear magnetic resonance (NMR) techniques as well as by complementary wet-chemical methods. Overall, our data support the view that lignin polymers are partially decomposed during their passage through the termite gut digestive system, although polysaccharide decomposition clearly dominates the overall lignocellulose deconstruction process and the majority of lignin polymers remain intact in the digestive residues. High-resolution NMR structural data suggested preferential removal of syringyl aromatic units in hardwood lignins, but non-acylated guaiacyl units as well as tricin end-units in grass lignins. In addition, our data suggest that termites and/or their gut symbionts may favor degradation of C-C-bonded β-5 and resinol-type β-β lignin inter-monomeric units over degradation of ether-bonded β-O-4 units, which is in contrast to what has been observed in typical lignin biodegradation undertaken by wood-decaying fungi.


Effects of lignins as diet components on the physiological activities of a lower termite, Coptotermes formosanus Shiraki

We investigated the effects of lignins as diet components on the physiological activities of a lower termite, Coptotermes formosanus Shiraki. Artificial diets composed of polysaccharides with and without purified lignins (milled-wood lignins) from Japanese cedar (softwood), Japanese beech (hardwood), and rice (grass), were fed to C. formosanus workers. The survival and body mass of the workers as well as the presence of three symbiotic protists in the hindguts of the workers were then periodically examined. The survival rates of workers fed on diets containing lignins were, regardless of the lignocellulose diet sources, significantly higher than those of workers fed on only polysaccharides. In addition, it was clearly observed that all the tested lignins have positive effects on the maintenance of two major protists in the hindguts of C. formosanus workers, i.e., Pseudotrichonympha grassii and Holomastigotoides hartmanni. Overall, our data suggest that the presence of lignin is crucial to maintaining the physiological activities of C. formosanus workers during their lignocellulose decomposition. Our data also suggested that some components, possibly minerals and/or non-structural carbohydrates, in grass lignocellulose negatively affect the survival of C. formosanus workers as well as the present rate of the symbiotic protists in their hindguts.


Regulation of CONIFERALDEHYDE 5-HYDROXYLASE expression to modulate cell wall lignin structure in rice

Regulation of a gene encoding coniferaldehyde 5-hydroxylase leads to substantial alterations in lignin structure in rice cell walls, identifying a promising genetic engineering target for improving grass biomass utilization. The aromatic composition of lignin greatly affects utilization characteristics of lignocellulosic biomass and, therefore, has been one of the primary targets of cell wall engineering studies. Limited information is, however, available regarding lignin modifications in monocotyledonous grasses, despite the fact that grass lignocelluloses have a great potential for feedstocks of biofuel production and various biorefinery applications. Here, we report that manipulation of a gene encoding coniferaldehyde 5-hydroxylase (CAld5H, or ferulate 5-hydroxylase, F5H) leads to substantial alterations in syringyl (S)/guaiacyl (G) lignin aromatic composition in rice (Oryza sativa), a major model grass and commercially important crop. Among three CAld5H genes identified in rice, OsCAld5H1 (CYP84A5) appeared to be predominantly expressed in lignin-producing rice vegetative tissues. Down-regulation of OsCAld5H1 produced altered lignins largely enriched in G units, whereas up-regulation of OsCAld5H1 resulted in lignins enriched in S units, as revealed by a series of wet-chemical and NMR structural analyses. Our data collectively demonstrate that OsCAld5H1 expression is a major factor controlling S/G lignin composition in rice cell walls. Given that S/G lignin composition affects various biomass properties, we contemplate that manipulation of CAld5H gene expression represents a promising strategy to upgrade grass biomass for biorefinery applications.


The effects of various lignocelluloses and lignins on physiological responses of a lower termite, Coptotermes formosanus


Disrupting Flavone Synthase II alters lignin and improves biomass digestibility.

Lignin, a ubiquitous phenylpropanoid polymer in vascular plant cell walls, is derived primarily from oxidative couplings of monolignols (-hydroxycinnamyl alcohols). It was discovered recently that a wide range of grasses, including cereals, utilize a member of the flavonoids, tricin (3',5'-dimethoxyflavone), as a natural comonomer with monolignols for cell wall lignification. Previously, we established that cytochrome P450 93G1 is a flavone synthase II (OsFNSII) indispensable for the biosynthesis of soluble tricin-derived metabolites in rice (). Here, our tricin-deficient mutant was analyzed further with an emphasis on its cell wall structure and properties. The mutant is similar in growth to wild-type control plants with normal vascular morphology. Chemical and nuclear magnetic resonance structural analyses demonstrated that the mutant lignin is completely devoid of tricin, indicating that FNSII activity is essential for the deposition of tricin-bound lignin in rice cell walls. The mutant also showed substantially reduced lignin content with decreased syringyl/guaiacyl lignin unit composition. Interestingly, the loss of tricin in the mutant lignin appears to be partially compensated by incorporating naringenin, which is a preferred substrate of OsFNSII. The mutant was further revealed to have enhanced enzymatic saccharification efficiency, suggesting that the cell wall recalcitrance of grass biomass may be reduced through the manipulation of the flavonoid monomer supply for lignification.


MYB-mediated upregulation of lignin biosynthesis in Oryza Sativa towards biomass refinery

Lignin encrusts lignocellulose polysaccharides, and has long been considered an obstacle for the efficient use of polysaccharides during processes such as pulping and bioethanol fermentation. However, lignin is also a potential feedstock for aromatic products and is an important by-product of polysaccharide utilization. Therefore, producing biomass plant species exhibiting enhanced lignin production is an important breeding objective. Herein, we describe the development of transgenic rice plants with increased lignin content. Five (Arabidopsis) and one (rice) MYB transcription factor genes that were implicated to be involved in lignin biosynthesis were transformed into rice ( L. ssp. cv. Nipponbare). Among them, three Arabidopsis MYBs (, , and ) in transgenic rice T lines resulted in culms with lignin content about 1.5-fold higher than that of control plants. Furthermore, lignin structures in -overexpressing rice plants were investigated by wet-chemistry and two-dimensional nuclear magnetic resonance spectroscopy approaches. Our data suggested that heterologous expression of in rice increased lignin content mainly by enriching syringyl units as well as -coumarate and tricin moieties in the lignin polymers. We contemplate that this strategy is also applicable to lignin upregulation in large-sized grass biomass plants, such as , switchgrass, and .


A new O-methyltransferase for monolignol synthesis in Carthamus tinctorius.


Substrate-enantiomer selectivity of matairesinol O-methyltransferases

Previously we reported a cDNA encoding an O-methyltransferase (OMT) responsible for the O-methylation of matairesinol to afford arctigenin in Carthamus tinctorius. However, the regioselectivity and stereoselectivity of its reaction are not yet well understood. In this paper, we report the characterization and comparison of three matairesinol OMTs (MROMTs) encoded by cDNAs isolated from C. tinctorius (CtMROMT), Anthriscus sylvestris (AsMROMT), and Forsythia koreana (FkMROMT). Although they shared matairesinol as a substrate, each recombinant MROMT showed different catalytic behavior. AsMROMT and CtMROMT methylated matairesinol's hydroxyl group at the C4' position giving rise to arctigenin, while FkMROMT methylated the C4 position hydroxyl group giving rise to isoarctigenin. Analysis of the enantiomeric composition of products from racemic matairesinol showed all OMT reactions to be highly selective in terms of the substrate enantiomers and only use the (-)-enantiomer as the substrate.


A novel O-methyltransferase involved in the first methylation step of yatein biosynthesis from matairesinol in Anthriscus sylvestris.


ATL54, a RING-H2 domain protein selected by a gene co-expression network analysis, is associated with secondary cell wall formation in Arabidopsis.


Characterization of 5-hydroxyconiferaldehyde O-methyltransferase in Oryza sativa


A lignan O-methyltransferase catalyzing the regioselective methylation of matairesinol in carthamus tinctorius

Lignans are a group of plant phenolic compounds with various biological activities, including antitumor and antioxidant properties. O-Methylation is a critical step in biosynthesis of these compounds. However, little is known about the O-methyltransferase (OMT) enzymes that catalyze lignan O-methylation. We discovered a highly regioselective OMT activity in safflower (Carthamus tinctorius) seeds that catalyzed the methylation of matairesinol, a dibenzylbutyrolactone lignan, into 4'-O-methylmatairesinol (arctigenin) but not 4-O-methylmatairesinol (isoarctigenin). By examining such OMT activity in correlation with OMT transcript abundances during seed development, we cloned a few putative OMT cDNAs and produced their recombinant proteins in Escherichia coli. Among them, one protein exhibited O-methylation activity for matairesinol with the regioselectivity identical to that of the plant protein, and was named C. tinctorius matairesinol OMT (CtMROMT). CtMROMT did not show any detectable OMT activities towards phenylpropanoid monomers under the reaction conditions tested, while it methylated flavonoid apigenin efficiently into 4'-O-methylapigenin (acacetin). However, quantitative real-time polymerase chain reaction analysis demonstrated that expression of the CtMROMT gene was synchronized with the CtMROMT activity profile and arctigenin accumulation in the plant. These results demonstrated that CtMROMT is a novel plant OMT for lignan methylation.


Characterization of lignocellulose of Erianthus arundinaceus in relation to enzymatic saccharification efficiency.


Microscale thioacidolysis method for the rapid analysis of β-O-4 substructures in lignin


Characterization of Jatropha curcas lignins


Occurrence of guaiacyl/p-hydroxyphenyl lignin in Arabidopsis thaliana T87 cells


Microscale alkaline nitrobenzene oxidation method for high-throughput determination of lignin aromatic components.

The nitrobenzene oxidation method is widely used for structural analysis of lignin. However, the conventional nitrobenzene oxidation method has several drawbacks including the requirement of a sizeable amount of sample material and the rather slow completion of the reaction process. In this paper, we describe a microscale nitrobenzene oxidation method using deuterium-labeled vanillin and syringaldehyde as internal standards. Using this method, we show that the microscale nitrobenzene oxidation method realized high-throughput determination of lignin components using a small amount of sample, i.e. 10 mg per reaction, and high reproducibility. Due to the small sample sizes, the oxidation reaction and extraction steps of a number of samples can be completed in parallel, thus enabling us to process more than 40 samples per day.


Subunit composition of hinokiresinol synthase controls enantiomeric selectivity in hinokiresinol formation

Asparagus officinalis hinokiresinol synthase (HRS) is composed of two subunits, HRSalpha and HRSbeta. Individually, each subunit forms (E)-hinokiresinol (EHR) from 4-coumaryl 4-coumarate, whereas a mixture of both subunits forms (Z)-hinokiresinol (ZHR) from the same substrate. In this study, we analyzed the enantiomeric compositions of ZHR and EHR formed after incubation of 4-coumaryl 4-coumarate with recombinant subunit proteins, recHRSalpha and/or recHRSbeta, and with naturally occurring A. officinalis ZHR. The enantiomeric composition of ZHR formed by the mixture of recHRSalpha and recHRSbeta was (+)-100% enantiomer excess (e.e.), identical to that of A. officinalis ZHR. In contrast, the enantiomeric compositions of EHR formed by recHRSalpha and recHRSbeta, individually, were (-)-20.6 and (-)-9.0% e.e., respectively. These results clearly demonstrate that the subunit composition of A. officinalis HRS controls not only cis/trans isomerism but also enantioselectivity in hinokiresinol formation.


The subunit composition of hinokiresinol synthase controls geometrical selectivity in norlignan formation.

The selective formation of E- or Z-isomers is an important process in natural product metabolism. We show that the subunit composition of an enzyme can alter the geometrical composition of the enzymatic products. Hinokiresinol synthase, purified from Asparagus officinalis cell cultures, is responsible for the conversion of (7E,7'E)-4-coumaryl 4-coumarate to (Z)-hinokiresinol, the first step in norlignan formation. The protein is most likely a heterodimer composed of two distinct subunits, which share identity with members of the phloem protein 2 gene superfamily. Interestingly, each recombinant subunit of hinokiresinol synthase expressed in Escherichia coli solely converted (7E,7'E)-4-coumaryl 4-coumarate to the unnatural (E)-hinokiresinol, the E-isomer of (Z)-hinokiresinol. By contrast, a mixture of recombinant subunits catalyzed the formation of (Z)-hinokiresinol from the same substrate.

Proceedings of the National Academy of Sciences of the United States of America


A heartwood norlignan, (E)-hinokiresinol, is formed from 4-coumaryl 4-coumarate by a Cryptomeria japonica enzyme preparation

An enzyme preparation from the cultured cells of Cryptomeria japonica catalyses the formation of a heartwood norlignan, (E)-hinokiresinol, from two distinct phenylpropanoid monomers: 4-coumaroyl CoA and 4-coumaryl alcohol, and from a dimer: 4-coumaryl 4-coumarate.