Glucosinolate Profiles Research Articles

Allopolyploidy expanded gene content but not pangenomic variation in the hexaploid oilseed Camelina sativa.

Ancient whole-genome duplications (WGDs) are believed to facilitate novelty and adaptation by providing the raw fuel for new genes. However, it is unclear how recent WGDs may contribute to evolvability within recent polyploids. Hybridization accompanying some WGDs may combine divergent gene content among diploid species. Some theory and evidence suggest that polyploids have a greater accumulation and tolerance of gene presence-absence and genomic structural variation, but it is unclear to what extent either is true. To test how recent polyploidy may influence pangenomic variation, we sequenced, assembled, and annotated twelve complete, chromosome-scale genomes of Camelina sativa, an allohexaploid biofuel crop with three distinct subgenomes. Using pangenomic comparative analyses, we characterized gene presence-absence and genomic structural variation both within and between the subgenomes. We found over 75% of ortholog gene clusters are core in Camelina sativa and <10% of sequence space was affected by genomic structural rearrangements. In contrast, 19% of gene clusters were unique to one subgenome, and the majority of these were Camelina-specific (no ortholog in Arabidopsis). We identified an inversion that may contribute to vernalization requirements in winter-type Camelina, and an enrichment of Camelina-specific genes with enzymatic processes related to seed oil quality and Camelina's unique glucosinolate profile. Genes related to these traits exhibited little presence-absence variation. Our results reveal minimal pangenomic variation in this species, and instead show how hybridization accompanied by WGD may benefit polyploids by merging diverged gene content of different species.

Glucosinolate profile and specifier protein activity determine the glucosinolate hydrolysis product formation in kohlrabi (Brassica oleracea var. gongylodes) in a tissue-specific way

Glucosinolate profile and specifier protein activity determine the glucosinolate hydrolysis product formation in kohlrabi (Brassica oleracea var. gongylodes) in a tissue-specific way

Integrative Analyses of Metabolites and Transcriptome Reveal the Metabolic Pattern of Glucosinolates in Potherb Mustard (Brassica juncea var. multiceps).

Potherb mustard (Brassica juncea var. multiceps) is one of the most commonly consumed leafy vegetable mustards, either fresh or in pickled form. It is rich in glucosinolates, whose hydrolyzed products confer potherb mustard's distinctive flavor and chemopreventive properties. In this study, the composition and content of glucosinolates, as well as the hydrolysis pattern of sinigrin were investigated in potherb mustard leaves of different varieties. Variations in the glucosinolate profile and accumulation were observed among the potherb mustard varieties studied, with sinigrin being the predominant one in all varieties, accounting for 81.55% to 97.27%. Sinigrin tended to be hydrolyzed to isothiocyanate (ITC) rather than epithionitrile (EPN) in potherb mustard, while 3-butenyl nitrile (SIN-NIT) could be hardly detected. Transcriptome analysis revealed a higher expression level of numerous genes involved in aliphatic glucosinolate biosynthesis in X11 compared to X57, corresponding to the higher aliphatic glucosinolate accumulation in X11 (91.07 µmol/g) and lower level in X57 (25.38 µmol/g). ESM1 is known to repress nitrile formation and favor isothiocyanate production during glucosinolate hydrolysis. In this study, all four ESM1s showed a higher expression level in X11 compared to X57, which may determine the hydrolysis pattern of sinigrin in potherb mustard. Altogether, our findings shed light on the glucosinolate metabolic pattern in potherb mustard, which will also facilitate the engineering of metabolic pathways at key checkpoints to enhance bioactive compounds for tailored flavor or pharmaceutical needs.

Cultivated Winter-Type Lunaria annua L. Seed: Deciphering the Glucosinolate Profile Integrating HPLC, LC-MS and GC-MS Analyses, and Determination of Fatty Acid Composition.

Lunaria annua L. (Brassicaceae) is an ornamental plant newly identified in Europe as a promising industrial oilseed crop for its valuable very-long-chain monounsaturated fatty acids (MUFAs), especially erucic acid (EA) and nervonic acid (NA). L. annua seeds were obtained from annual winter-type plants selected and cultivated in Northern France. Using a systematic multiple-method approach, we set out to determine the profile and content of glucosinolates (GSLs), which are the relevant chemical tag of Brassicaceae. Intact GSLs were analyzed through a well-established LC-MS method. Identification and quantification were performed by HPLC-PDA of desulfo-GSLs (dGLs) according to the official EU ISO method. Moreover, GSL structures were confirmed by GC-MS analysis of the related isothiocyanates (ITCs). Seven GSLs were identified, directly or indirectly, as follows: 1-methylethyl GSL, (1S)-1-methylpropyl GSL, (Rs)-5-(methylsulfinyl)pentyl GSL, (Rs)-6-(methylsulfinyl)hexyl GSL, (2S)-2-hydroxy-4-pentenyl GSL, 2-phenylethyl GSL, and 1-methoxyindol-3-ylmethyl GSL. In other respects, the FA composition of the seed oil was determined. Results revealed cultivated L. annua seed to be a source of NA-rich oil, and presscake as a valuable coproduct. This presscake is indeed rich in GSLs (4.3% w/w), precursors of promising bioactive molecules for agricultural and nutraceutical applications.

Metabolomic and Transcriptomic Profiles in Diverse Brassica oleracea Crops Provide Insights into the Genetic Regulation of Glucosinolate Profiles.

Glucosinolates (GSLs) are plant secondary metabolites commonly found in the cruciferous vegetables of the Brassicaceae family, offering health benefits to humans and defense against pathogens and pests to plants. In this study, we investigated 23 GSL compounds' relative abundance in four tissues of five different Brassica oleracea morphotypes. Using the five corresponding high-quality B. oleracea genome assemblies, we identified 183 GSL-related genes and analyzed their expression with mRNA-Seq data. GSL abundance and composition varied strongly, among both tissues and morphotypes, accompanied by different gene expression patterns. Interestingly, broccoli exhibited a nonfunctional AOP2 gene due to a conserved 2OG-FeII_Oxy domain loss, explaining the unique accumulation of two health-promoting GSLs. Additionally, transposable element (TE) insertions were found to affect the gene structure of MAM3 genes. Our findings deepen the understanding of GSL variation and genetic regulation in B. oleracea morphotypes, providing valuable insights for breeding with tailored GSL profiles in these crops.

Turning glucosinolate into allelopathic fate: investigating allyl isothiocyanate variability and nitrile formation in eco-friendly Brassica juncea from South Korea

Leaf mustard (Brassica juncea L.) is explored for its biofumigant properties, derived from its secondary metabolites, particularly allyl isothiocyanate (AITC), produced during the enzymatic breakdown of glucosinolates like sinigrin. The research examines eight leaf mustard cultivars developed in Yeosu city, South Korea, focusing on their genetic characteristics, AITC concentration and nitriles formation rates from glucosinolates. Results indicate that the allelopathic effects, largely dependent on AITC concentration and enzymatic activity, vary across cultivar. Sinigrin and AITC constitute 79% and 36%, respectively, of glucosinolate and its hydrolysis products. The cultivar 'Nuttongii' demonstrates significant potential for inhibiting weeds, exhibiting the highest AITC concentration at 27.47 ± 6.46 µmole g−1 These outcomes highlight the importance of selecting mustard cultivars for biofumigation based on their glucosinolate profiles and hydrolysis product yields. The study also identifies a significant genetic influence on AITC and nitrile formation, suggesting that epithiospecifier protein modulation could enhance both allelopathic and other beneficial effects. Collectively, the research underscores the promise of mustard as a sustainable, environmentally friendly alternative to traditional herbicides.

Glucosinolates in non-Brassicales plant species: Critical literature evaluation and testing of two high chemical quality reports

Glucosinolates (GSLs) are secondary metabolites mainly found in the plant order Brassicales. We critically evaluate reports of GSLs in other orders of flowering plants, propose standards for future reports and subject two cases to rigorous testing. Reports of GSLs in non-Brassicales species should live up to state-of-the-art scientific standards concerning chemical evidence, botanical evidence and biological replication. Occurrence of GSLs in the family Putranjivaceae, order Malpighiales (genera Putranjiva and Drypetes) was reasonably supported, but state-of-the-art confirmation was required. Hence, the taxonomic identity of Putranjiva roxbughii seeds with the previously known GSL profile was confirmed using DNA-based methods. Similarly, good suggestive evidence exist from the family Violaceae, order Malpighiales, but in need of confirmation. No other report of any GSL in a non-Brassicales species meet the proposed scientific standards, but suggestive evidence exists for the family Phytolaccaceae, order Caryophyllales and to a lesser extent family Celastraceae, order Celastrales. A recent report of a GSL in a tropical plant suggested to be a species in the order Sapindales was subjected to a rigorous testing in terms of chemical analysis, biological replication and botanical identification including DNA sequencing. We confirmed the original report concerning chemical structure and reproducibility but revised the botanical identification to a species from the Brassicales order (family Capparidaceae). Hence this paper also reports myrosinase activity, isothiocyanate-type GSL products from roots and stems, and GSL profile of roots, stems, leaves and fruits of Capparis sepiaria L., dominated by Leu-derived 2-methylpropyl GSL in vegetative parts, Val-derived 1-methylethyl GSL and Ile-derived 1-methylpropyl GSL in fruits, and additionally Trp-derived indol-3-ylmethyl GSL and 4-hydroxyindol-3-ylmethyl GSL in immature fruits. Several other GSLs were searched for and conclusively not found above the limit of detection.

Relationship between secondary metabolites and insect loads in cabbage with different leaf shapes and positions.

Secondary metabolites in plants play a crucial role in defense mechanisms against insects, pests, and pathogens. These metabolites exhibit varying distributions within and among plant parts under different biotic and abiotic conditions. Understanding the intricate relationships between secondary metabolites and insect populations can be helpful for elucidating plant defense mechanisms and enhancing agricultural managing efficiencies. To investigate the influence of the glucosinolate profile in the leaves of three cabbage (Brassica oleracea var.capitata L.) varieties on insect loads. Glucosinolate profiles across different leaf positions (such as bottom, middle, and center) and leaf shapes (such as curly and non-curly leaf) of three cabbage varieties (Xiagan [XGA], Xiaguang [XGU], and Qiangxia [QIX]) were analyzed by using high-performance liquid chromatography-mass spectrometry (LC-MS). The insect loads were recorded by visually inspecting the upper and lower layers of each target leaf. Increasing concentrations of four glucosinolates, namely, glucoiberin, progoitrin, glucoraphanin, and glucobrassicin, were positively related to insect loads. While increasing concentrations of the other four glucosinolates, such as neoglucobrassicin, 4-methoxyglucobrassicin, sinigrin, and gluconapin, were negatively related to insect loads. Furthermore, both glucosinolate synthesis and insect loads were significantly higher in the curly-shaped and middle-position leaves than in the non-curly-shaped and bottom- and central-position leaves across the cabbage varieties. Differences in glucosinolate profiles across leaf positions and shapes strongly influenced the insect loads of the three Brassica varieties. This link may further extend our understanding of the real defense power of a particular variety against herbivore damage.

Productive and qualitative profile of unexploited microgreen genotypes from Brassicaceae, Chenopodiaceae, Asteraceae and Portulacaceae families

Microgreens combine visual, taste, flavor and bioactive qualities based on genetic selection, making them a gastronomic novelty. In the present study, ten microgreen genotypes were investigated in terms of biometrical traits (fresh yield, dry matter concentration, and main color indices) alongside compositional analyses, involving cations, nitrate, vitamin C, phenols, and glucosinolate profile. The genotypes were selected from Brassicaceae (five), Chenopodiaceae (one), Portulacaceae (one) and Asteraceae (two) families, according to the availability of unexploited local varieties beyond the commercial ones. The microgreens were cultivated hydroponically in a controlled environment. Distinct genotypic variations were observed for each measured biometric and qualitative trait, with substantial differences noted between and within species. Among the ten genotypes, the underutilized purslane stood out for vitamin C (30 mg 100 g-1 f.w.), Mg (39 mg 100 g-1 f.w.), and the remarkably low nitrate content (7 mg 100 g-1 f.w.). White mustard exhibited the highest levels of glucosinolates (171 mg kg-1 f.w.), phenols (190 mg g.a.e. 100 g-1 f.w), and notable concentrations of cations such as potassium, calcium, and magnesium. From a nutritional perspective, ‘Mugnolo’ (Brassica oleracea var. italica Plenck) proved less suitable as a microgreen due to its highest Na/K ratio (2.28) and generally the low content of other minerals, phenols, vitamin C, and glucosinolates. The findings of this study hold significance for selecting new microgreen species/varieties that align with the preferences and requirements of both consumers and producers.

The Presence of Arbuscular Mycorrhizal Fungi in the Rhizosphere of Transgenic Rapeseed Overexpressing a Trichoderma Thkel1 Gene Improves Plant Development and Yield

Most of the plants belonging to the family of Brassicaceae are non-hosts for arbuscular mycorrhizal fungi (AMF). These plants are known to produce glucosinolates (GSL), a group of allelopathic compounds, with a role in plant defense. The overexpression of the Thkel1 from Trichoderma harzianum in rapeseed (BnKel) plants, this gene encoding a protein that shares similarities with Brassicaceae plant’s nitrile-specifier and epithiospecifier proteins, modified GSL metabolism, reducing the accumulation of toxic isothiocyanates due to hydrolysis of these secondary metabolites. Here, we have analyzed the effect of AMF application on the GSL profiles and the development and yield of BnKel plants. Our results showed that the reduction of GSL compounds on transgenic plants was not enough to allow the formation of arbuscules and vesicles characteristics of an AMF mycorrhizal association. However, the inoculation of transgenic rapeseed plants expressing Thkel1 with AMF improved seed yield and fatty acid composition of the oilseed, showing a beneficial effect of AMF in these plants. The achievement of this effective beneficial association among mycorrhizas and rapeseed plants opens new opportunities in agribiotechnology for the use of AMF as biofertilizers in Brassicaceae crops with potential application in medical, animal and industrial biotechnology.

Glucosinolate hydrolysis in kohlrabi tissues ‐ the influence of glucosinolate profile, specifier protein and myrosinase activity on the outcome of hydrolysis

Glucosinolate hydrolysis in kohlrabi tissues ‐ the influence of glucosinolate profile, specifier protein and myrosinase activity on the outcome of hydrolysis

Chromosome-scale reference genome of broccoli (Brassica oleracea var. italica Plenck) provides insights into glucosinolate biosynthesis.

Broccoli (Brassica oleracea var. italica Plenck) is an important vegetable crop, as it is rich in health-beneficial glucosinolates (GSLs). However, the genetic basis of the GSL diversity in Brassicaceae remains unclear. Here we report a chromosome-level genome assembly of broccoli generated using PacBio HiFi reads and Hi-C technology. The final genome assembly is 613.79Mb in size, with a contig N50 of 14.70Mb. The GSL profile and content analysis of different B. oleracea varieties, combined with a phylogenetic tree analysis, sequence alignment, and the construction of a 3D model of the methylthioalkylmalate synthase 1 (MAM1) protein, revealed that the gene copy number and amino acid sequence variation both contributed to the diversity of GSL biosynthesis in B. oleracea. The overexpression of BoMAM1 (BolI0108790) in broccoli resulted in high accumulation and a high ratio of C4-GSLs, demonstrating that BoMAM1 is the key enzyme in C4-GSL biosynthesis. These results provide valuable insights for future genetic studies and nutritive component applications of Brassica crops.

Characterization of Arabidopsis eskimo1 reveals a metabolic link between xylan O-acetylation and aliphatic glucosinolate metabolism.

Glucuronoxylan is present mainly in the dicot of the secondary cell walls, often O-acetylated, which stabilizes cell structure by maintaining interaction with cellulose and other cell wall components. Some members of the Golgi localized Trichome Birefringence-Like (TBL) family function as xylan O-acetyl transferase (XOAT). The primary XOAT in the stem of Arabidopsis is ESKIMO1/TBL29, and its disruption results in decreased xylan acetylation, stunted plant growth, and collapsed xylem vessels. To elucidate the effect on metabolic reprogramming and identify the underlying cause of the stunted growth in eskimo1, we performed transcriptomic, targeted, and untargeted metabolome analysis, mainly in the inflorescence stem tissue. RNA sequencing analysis revealed that the genes involved in the biosynthesis, regulation, and transport of aliphatic glucosinolates (GSLs) were upregulated, whereas those responsible for indolic GSL metabolism were unaffected in the eskimo1 inflorescence stem. Consistently, aliphatic GSLs, such as 4-methylsulfinylbutyl (4MSOB), were increased in stem tissues and seeds. This shift in the profile of aliphatic GSLs in eskimo1 was further supported by the quantification of the soluble acetate, decrease in accumulation of GSL precursor, i.e., methionine, and increase in the level of jasmonic acid.

An UMAMIT-GTR transporter cascade controls glucosinolate seed loading in Arabidopsis.

Many plant species translocate maternally synthesized specialized metabolites to the seed to protect the developing embryo and later the germinating seedling before it initiates its own de novo synthesis. While the transport route into the seed is well established for primary metabolites, no model exists for any class of specialized metabolites that move from maternal source tissue(s) to embryo. Glucosinolate seed loading in Arabidopsis depends on plasma membrane localized exporters (USUALLY MULTIPLE AMINO ACIDS MOVE IN AND OUT TRANSPORTERs, UMAMITs) and importers (GLUCOSINOLATE TRANSPORTERs, GTRs), but the critical barriers in the seed loading process remain unknown. Here we dissect the transport route of glucosinolates from their source in the reproductive organ to the embryo by re-introducing the transporters at specific apoplastic barriers in their respective mutant backgrounds. We find that UMAMIT exporters and GTR importers form a transporter cascade that is both essential and sufficient for moving glucosinolates across at least four plasma membrane barriers along the route. We propose a model in which UMAMITs export glucosinolates out of the biosynthetic cells to the apoplast, from where GTRs import them into the phloem stream, which moves them to the unloading zone in the chalazal seed coat. From here, the UMAMITs export them out of maternal tissue and ultimately, the GTRs import them into the embryo symplasm, where the seed-specific glucosinolate profile is established by enzymatic modifications. Moreover, we propose that methylsulfinylalkyl glucosinolates are the predominant mobile form in seed loading. Elucidation of the seed loading process of glucosinolates identifies barrier-specific targets for transport engineering strategies to eliminate or over-accumulate a specialized metabolite in seeds with minimal interruption of other cellular processes.

Iberis sempervirens: Antiproliferative Potential from Our Garden

Glucosinolates (GSLs) extracted from various parts of Iberis sempervirens L., including seeds, stems, leaves, and flowers, were qualitatively and quantitatively assessed. The analyses of GSLs were performed by their desulfo counterparts using the UHPLC-DAD-MS/MS technique and by their volatile breakdown products, isothiocyanates, using the GC-MS technique. The GSL profile comprised various types, including those derived from: methionine, represented by methylsulfinylalkyl GSL (glucoiberin), and methylsulfanylalkyl GSL (glucoibervirin and glucoerucin); phenylalanine (glucotropaeolin); and tryptophan (4-methoxyglucobrassicin). Among these, the highest level of glucoiberin was detected in the leaves, reaching 35.37 µmol/g of dry weight (DW), while the highest level of glucoibervirin was detected in the seeds, reaching 18.51 µmol/g DW. To obtain GSL breakdown products, a variety of isolation methods were employed, including hydrodistillation in a Clevenger-type apparatus (HD), CH2Cl2 after myrosinase hydrolysis for 24 h (EXT), microwave-assisted distillation (MAD), and microwave hydrodiffusion and gravity (MHG). Volatile isolates were tested for their antiproliferative activity using an MTT assay against the human lung cancer cell line A549 and the human bladder cancer cell line T24 during an incubation period of 72 h. HD and MAD showed the best activity against T24, with IC50 values of 0.61 µg/mL and 0.62 µg/mL, respectively, while EXT was the most effective against the A549 cell line, with an IC50 of 1.46 µg/mL.

Seed treatment with clothianidin induces changes in plant metabolism and alters pollinator foraging preferences

Neonicotinoids, systemic insecticides that are distributed into all plant tissues and protect against pests, have become a common part of crop production, but can unintentionally also affect non-target organisms, including pollinators. Such effects can be direct effects from insecticide exposure, but neonicotinoids can affect plant physiology, and effects could therefore also be indirectly mediated by changes in plant phenology, attractiveness and nutritional value. Under controlled greenhouse conditions, we tested if seed treatment with the neonicotinoid clothianidin affected oilseed rape’s production of flower resources for bees and the content of the secondary plant products glucosinolates that provide defense against herbivores. Additionally, we tested if seed treatment affected the attractiveness of oilseed rape to flower visiting bumblebees, using outdoor mesocosms. Flowers and leaves of clothianidin-treated plants had different profiles of glucosinolates compared with untreated plants. Bumblebees in mesocosms foraged slightly more on untreated plants. Neither flower timing, flower size nor the production of pollen and nectar differed between treatments, and therefore cannot explain any preference for untreated oilseed rape. We instead propose that this small but significant preference for untreated plants was related to the altered glucosinolate profile caused by clothianidin. Thereby, this study contributes to the understanding of the complex relationships between neonicotinoid-treated crops and pollinator foraging choices, by suggesting a potential mechanistic link by which insecticide treatment can affect insect behavior.

Metabolome and Transcriptome Analyses Provide Insights into Glucosinolate Accumulation in the Novel Vegetable Crop Cardamine violifolia

Cardamine violifolia, a species belonging to the Brassicaceae family, is a novel vegetable crop that is rich in glucosinolates. However, the specific glucosinolate profiles in this species remain unknown. In the present study, four parts of C. violifolia were collected including central leaves (CLs), outer leaves (OLs), petiole (P), and root (R). The highest level of total glucosinolate was observed in the R. A total of 19 glucosinolates were found in C. violifolia. The predominant glucosinolate compounds were 3-methylbutyl glucosinolate, 6-methylsulfinylhexyl glucosinolate, Indol-3-ylmethyl glucosinolate, 4-methoxyglucobrassicin, and neoglucobrassicin. A transcriptome analysis showed that 16 genes, including BCAT1, BCAT3-6, CYP79A2, CYP79B2-3, CYP83A1, CYP83B1, and SOT17-18, and nine metabolites, such as valine, tryptophan, and 1-methylpropyl glucosinolate, were enriched in the glucosinolate biosynthesis pathway. These genes may be involved in the regulation of glucosinolate accumulation among the four parts. A weighted gene co-expression analysis showed that five genes were predicted to regulate glucosinolate accumulation, including ABC transporter G family member 19, 3-ketoacyl-CoA synthase 19, and pyruvate decarboxylase 1. This study deepens our understanding of the nutrient quality of C. violifolia and provides insights into the regulatory mechanism of glucosinolate accumulation in C. violifolia.

Effects of metal amendment and metalloid supplementation on foliar defences are plant accession-specific in the hyperaccumulator Arabidopsis halleri.

Soil pollution by metals and metalloids as a consequence of anthropogenic industrialisation exerts a seriously damaging impact on ecosystems. However, certain plant species, termed hyperaccumulators, are able to accumulate extraordinarily high concentrations of these metal(loid)s in their aboveground tissues. Such hyperaccumulation of metal(loid)s is known to act as a defence against various antagonists, such as herbivores and pathogens. We investigated the influences of metal(loid)s on potential defence traits, such as foliar elemental, organic and mechanical defences, in the hyperaccumulator plant species Arabidopsis halleri (Brassicaceae) by artificially amending the soil with common metallic pollutants, namely cadmium (Cd) and zinc (Zn). Additionally, unamended and metal-amended soils were supplemented with the metalloid silicon (Si) to study whether Si could alleviate metal excess. Individuals originating from one non-/low- and two moderately to highly metal-contaminated sites with different metal concentrations (hereafter called accessions) were grown for eight weeks in a full-factorial design under standardised conditions. There were significant interactive effects of metal amendment and Si supplementation on foliar concentrations of certain elements (Zn, Si, aluminium (Al), iron (Fe), potassium (K) and sulfur (S), but these were accession-specific. Profiles of glucosinolates, characteristic organic defences of Brassicaceae, were distinct among accessions, and the composition was affected by soil metal amendment. Moreover, plants grown on metal-amended soil contained lower concentrations of total glucosinolates in one of the accessions, which suggests a potential trade-off between inorganic defence acquisition and biosynthesis of organic defence. The density of foliar trichomes, as a proxy for the first layer of mechanical defence, was also influenced by metal amendment and/or Si supplementation in an accession-dependent manner. Our study highlights the importance of examining the effects of co-occurring metal(loid)s in soil on various foliar defence traits in different accessions of a hyperaccumulating species.

The allotetraploid horseradish genome provides insights into subgenome diversification and formation of critical traits

Polyploidization can provide a wealth of genetic variation for adaptive evolution and speciation, but understanding the mechanisms of subgenome evolution as well as its dynamics and ultimate consequences remains elusive. Here, we report the telomere-to-telomere (T2T) gap-free reference genome of allotetraploid horseradish (Armoracia rusticana) sequenced using a comprehensive strategy. The (epi)genomic architecture and 3D chromatin structure of the A and B subgenomes differ significantly, suggesting that both the dynamics of the dominant long terminal repeat retrotransposons and DNA methylation have played critical roles in subgenome diversification. Investigation of the genetic basis of biosynthesis of glucosinolates (GSLs) and horseradish peroxidases reveals both the important role of polyploidization and subgenome differentiation in shaping the key traits. Continuous duplication and divergence of essential genes of GSL biosynthesis (e.g., FMOGS-OX, IGMT, and GH1 gene family) contribute to the broad GSL profile in horseradish. Overall, the T2T assembly of the allotetraploid horseradish genome expands our understanding of polyploid genome evolution and provides a fundamental genetic resource for breeding and genetic improvement of horseradish.

Glucosinolate Catabolism Maintains Glucosinolate Profiles andTransport inSulfur-Starved Arabidopsis.

Glucosinolates (GSLs) are sulfur (S)-rich specialized metabolites present in Brassicales order plants. Our previous study found that GSL can function as a S source in Arabidopsis seedlings via its catabolism catalyzed by two β-glucosidases (BGLUs), BGLU28 and BGLU30. However, as GSL profiles in plants vary among growth stages and organs, the potential contribution of BGLU28/30-dependent GSL catabolism at the reproductive growth stage needs verification. Thus, in this study, we assessed growth, metabolic and transcriptional phenotypes of mature bglu28/30 double mutants grown under different S conditions. Our results showed that compared to wild-type plants grown under -S, mature bglu28/30 mutants displayed impaired growth and accumulated increased levels of GSL in their reproductive organs and rosette leaves of before-bolting plants. In contrast, the levels of primary S-containing metabolites, glutathione and cysteine decreased in their mature seeds. Furthermore, the transport of GSL from rosette leaves to the reproductive organs was stimulated in the bglu28/30 mutants under -S. Transcriptome analysis revealed that genes related to other biological processes, such as ethylene response, defense response and plant response to heat, responded differentially to -S in the bglu28/30 mutants. Altogether, these findings broadened our understanding of the roles of BGLU28/30-dependent GSL catabolism in plant adaptation to nutrient stress.