Hideyuki Suzuki

Shikonin, a 1,4-naphthoquinone derivative produced by some limited Boraginaceae species, exhibits unique pharmacological properties and is also used as a natural dye. The regulatory factors of shikonin production have been demonstrated using a cell culture system of Lithospermum erythrorhizon. Among these factors, copper is known to be the strongest enhancer of shikonin production, and the copper-requiring biosynthetic step is shikonin-specific, unlike the byproduct benzoquinones. Despite the long history of shikonin biosynthesis studies for over 40 years, the copper-involved reaction has been still unknown. Here, we explored candidate genes associated with shikonin production using a PCR-select subtraction experiment. Genes encoding PPO, a dicopper-dependent oxidoreductase, was highlighted by the strong synchronous expression with shikonin production. Transcriptome analysis of hairy roots and cultured cells of this plant revealed that, of the five PPO genes expressed in L. erythrorhizon (LePPOs), only LePPO1 showed a close correlation with shikonin production. Then, we generated genome-edited hairy roots of LePPO1 using CRISPR/Cas9-mediated mutagenesis to analyze its impact on shikonin derivative and other specialized metabolite production. The results showed that shikonin content was markedly reduced in all LePPO1-ge lines, while the content of deoxyshikonofuran, a hydroquinone-type shunt product that branches after 3′′-hydroxygeranylhydroquinone in the shikonin biosynthetic pathway, remained unaffected in the LePPO1-ge lines. These findings address the question of why a copper ion is crucial for shikonin biosynthesis and suggest that LePPO1 participates in naphthalene ring formation. Interestingly, LePPO1 is localized in plastids, whereas shikonin accumulates in the apoplast.

Magnolia obovata is renowned for its unique bioactive constituents with medicinal properties traditionally used to treat digestive disorders, anxiety, and respiratory conditions. This study aimed to establish a comprehensive omics resource through untargeted metabolome and transcriptome profiling to explore biosynthesis of pharmacologically active compounds of M. obovata using seven tissues: young leaf, mature leaf, stem, bark, central cylinder, floral bud, and pistil. Untargeted metabolomic analysis identified 6733 mass features across seven tissues and captured chemo-diversity and its tissue-specificity in M. obovata. Through a combination of cheminformatics and manual screening approach, we confirmed the identities of 105 metabolites, including neolignans, such as honokiol and magnolol, which were found to be spatially accumulated in the bark tissue. RNA sequencing generated a comprehensive transcriptome resource, and expression analysis revealed significant tissue-specific expression patterns. Omics dataset integration identified T12 transcript module from WGCNA being correlated with the biosynthesis of magnolol and honokiol in M. obovata. Notably, phylogenetic analysis using transcripts from T12 module identified two laccase (Mo_LAC1 and Mo_LAC2) and three dirigent proteins from the DIR-b/d subfamily as potential candidate genes involved in neolignan biosynthesis. This research established omics resources of M. obovata and laid the groundwork for future studies aimed at optimizing and further understanding the biosynthesis of metabolites of therapeutic potential.

The incidence of internal hernias has recently increased in concordance with the popularization of laparoscopic surgery. Of particular concern are internal hernias occurring in Petersen's space, a space that is surgically created after treatment for gastric cancer and obesity. These hernias cause devastating sequelae, such as massive intestinal necrosis, fatal Roux limb necrosis, and superior mesenteric vein thrombus. In addition, protein-losing enteropathy (PLE) is a rare syndrome involving gastrointestinal protein loss, although its relationship with internal Petersen’s hernias remains unknown. A 75-year-old man with a history of laparotomy for early gastric cancer developed Petersen's hernia 1 year and 5 mo after surgery. He was successfully treated by reducing the incarcerated small intestine and closure of Petersen’s defect without resection of the small intestine. Approximately 3 mo after his surgery for Petersen’s hernia, he developed bilateral leg edema and hypoalbuminemia. He was diagnosed with PLE with an alpha-1 antitrypsin clearance of 733 mL/24 h. Double-balloon enteroscopy revealed extensive jejunal ulceration as the etiology, and it facilitated minimum bowel resection. Pathological analysis showed extensive jejunal ulceration and collagen hyperplasia with nonspecific inflammation of all layers without lymphangiectasia, lymphoma, or vascular abnor malities. His postoperative course was unremarkable, and his bilateral leg edema and hypoalbuminemia improved after 1 mo. There was no relapse over the 5-year follow-up period. PLE and extensive jejunal ulceration may occur after Petersen's hernia. Double-balloon enteroscopy helps identify and resect these lesions.

Mallotus japonicus is a valuable traditional medicinal plant in East Asia for applications as a gastrointestinal drug. However, the molecular components involved in the biosynthesis of bioactive metabolites have not yet been explored, primarily due to a lack of omics resources. In this study, we established metabolome and transcriptome resources for M. japonicus to capture the diverse metabolite constituents and active transcripts involved in its biosynthesis and regulation. A combination of untargeted metabolite profiling with data-dependent metabolite fragmentation and metabolite annotation through manual curation and feature-based molecular networking established an overall metabospace of M. japonicus represented by 2129 metabolite features. M. japonicus de novo transcriptome assembly showed 96.9% transcriptome completeness, representing 226,250 active transcripts across seven tissues. We identified specialized metabolites biosynthesis in a tissue-specific manner, with a strong correlation between transcripts expression and metabolite accumulations in M. japonicus. The correlation- and network-based integration of metabolome and transcriptome datasets identified candidate genes involved in the biosynthesis of key specialized metabolites of M. japonicus. We further used phylogenetic analysis to identify 13 C-glycosyltransferases and 11 methyltransferases coding candidate genes involved in the biosynthesis of medicinally important bergenin. This study provides comprehensive, high-quality multi-omics resources to further investigate biological properties of specialized metabolites biosynthesis in M. japonicus.

Papaya (Carica papaya L.) is widely cultivated in tropical and subtropical countries. While ripe fruit is a popular food item globally, the unripe fruit is only consumed in some Asian countries. To promote the utilization of unripe papaya based on the compositional changes of biological active metabolites, we performed liquid chromatography–Orbitrap–mass spectrometry-based analysis to reveal the comprehensive metabolite profile of the peel and pulp of unripe and ripe papaya fruits. The number of peaks annotated as phenolics and aminocarboxylic acids increased in the pulp and peel of ripe fruit, respectively. Putative carpaine derivatives, known alkaloids with cardiovascular effects, decreased, while carpamic acid derivatives increased in the peel of ripe fruit. Furthermore, the functionality of unripe fruit, the benzyl glucosinolate content, total polyphenol content, and proteolytic activity were detectable after heating and powder processing treatments, suggesting a potential utilization in powdered form as functional material.

Strigolactones (SLs), first identified as germination stimulants for root parasitic weeds, act as endogenous phytohormones regulating shoot branching and as root-derived signal molecules mediating symbiotic communications in the rhizosphere. Canonical SLs typically have an ABCD ring system and can be classified into orobanchol- and strigol-type based on the C-ring stereochemistry. Their simplest structures are 4-deoxyorobanchol (4DO) and 5-deoxystrigol (5DS), respectively. Diverse canonical SLs are chemically modified with one or more hydroxy or acetoxy groups introduced into the A- and/or B-ring of these simplest structures, but the biochemical mechanisms behind this structural diversity remain largely unexplored. Sorgomol in sorghum (Sorghum bicolor [L.] Moench) is a strigol-type SL with a hydroxy group at C-9 of 5DS. In this study, we characterized sorgomol synthase. Microsomal fractions prepared from a high-sorgomol-producing cultivar of sorghum, Sudax, were shown to convert 5DS to sorgomol. A comparative transcriptome analysis identified SbCYP728B subfamily as candidate genes encoding sorgomol synthase. Recombinant SbCYP728B35 catalyzed the conversion of 5DS to sorgomol in vitro. Substrate specificity revealed that the C-8bS configuration in the C-ring of 5DS stereoisomers was essential for this reaction. The overexpression of SbCYP728B35 in Lotus japonicus hairy roots, which produce 5DS as an endogenous SL, also resulted in the conversion of 5DS to sorgomol. Furthermore, SbCYP728B35 expression was not detected in nonsorgomol-producing cultivar, Abu70, suggesting that this gene is responsible for sorgomol production in sorghum. Identification of the mechanism modifying parental 5DS of strigol-type SLs provides insights on how plants biosynthesize diverse SLs.

Lotus japonicus is a model legume that accumulates 8-hydroxyflavonol derivatives, such as gossypetin (8-hydroxyquercetin) 3-O-glycoside, which confer the yellow color to its petals. An enzyme, flavonoid 8-hydroxylase (F8H; LjF8H), is assumed to be involved in the biosynthesis, but the specific gene is yet to be identified. The LjF8H cDNA was isolated as a flavin adenine dinucleotide (FAD)-binding monooxygenase-like protein using flower buds and flower-specific EST data of L. japonicus. LjF8H is a single copy gene on chromosome III consisting of six exons. The conserved FAD- and NAD(P)H-dependent oxidase motifs were found in LjF8H. Phylogenetic analysis suggested that LjF8H is a member of the flavin monooxygenase group but distinctly different from other known flavonoid oxygenases. Analysis of recombinant yeast microsome expressing LjF8H revealed that the enzyme catalyzed the 8-hydroxylation of quercetin. Other flavonoids, such as naringenin, eriodictyol, apigenin, luteolin, taxifolin and kaempferol, also acted as substrates of LjF8H. This broad substrate acceptance was unlike known F8Hs in other plants. Interestingly, flavanone and flavanonol, which have saturated C–C bond at positions 2 and 3 of the flavonoid C-ring, produced 6-hyroxylflavonoids as a by-product of the enzymatic reaction. Furthermore, LjF8H only accepted the 2S-isomer of naringenin, suggesting that the conformational state of the substrates might affect product specificity. The overexpression of LjF8H in Arabidopsis thaliana and Petunia hybrida synthesized gossypetin and 8-hydroxykaempferol, respectively, indicating that LjF8H was functional in plant cells. In conclusion, this study represents the first instance of cloning and identification of F8Hs responsible for gossypetin biosynthesis.

The model land plant Physcomitrella patens synthesizes flavonoids which may act as protectant of ultraviolet-B radiation. We aimed to uncover its flavonoid profile, for which metabolome analysis using liquid chromatography coupled with Ion trap/Orbitrap mass spectrometry was performed. From the 80% methanol extracts, 661 valid peaks were detected. Prediction of the elemental compositions within a mass accuracy of 2 ppm indicated that 217 peaks had single elemental composition. A compound database search revealed 47 peaks to be annotated as secondary metabolites based on the compound database search. Comprehensive substituent search by ShiftedIonsFinder showed there were 13 peaks of potential flavonoid derivatives. Interestingly, a peak having m/z 287.0551, corresponding to that of luteolin, was detected, even though flavone synthase has never been identified in P. patens. Using P. patens labeled with stable isotopes (13C-, 15N-, 18O-, and 34S), we confirmed the elemental composition of the peak as C15H10O6. By a comparison of MS/MS spectra with that of authentic standard, the peak was identified as luteolin or related flavone isomers. This is the first report of luteolin or related flavones synthesis and the possibility of the existence of an unknown enzyme with flavone synthase activity in P. patens.

A unique cytosol-localized geranyl diphosphate synthase supporting a large production of shikonin has evolved from farnesyl diphosphate synthase in Lithospermum