Indole Glucosinolates Research Articles

A transcriptome analysis reveals a role for the indole GLS-linked auxin biosynthesis in secondary dormancy in rapeseed (Brassica napus L.)

BackgroundBrassica napus L. has little or no primary dormancy, but exhibits great variation in secondary dormancy. Secondary dormancy potential in oilseed rape can lead to the emergence of volunteer plants that cause genetic contamination, reduced quality and biosafety issues. However, the mechanisms underlying secondary dormancy are poorly understood. In this study, cultivars Huaiyou-WSD-H2 (H) and Huaiyou-SSD-V1 (V), which exhibit low (approximately 5%) and high (approximately 95%) secondary dormancy rate, respectively, were identified. Four samples, before (Hb and Vb) and after (Ha and Va) secondary dormancy induction by polyethylene glycol (PEG), were collected to identify the candidate genes involved in secondary dormancy via comparative transcriptome profile analysis.ResultsA total of 998 differentially expressed genes (DEGs), which are mainly involved in secondary metabolism, transcriptional regulation, protein modification and signaling pathways, were then detected. Among these DEGs, the expression levels of those involved in the sulfur-rich indole glucosinolate (GLS)-linked auxin biosynthesis pathway were markedly upregulated in the dormant seeds (Va), which were validated by qRT-PCR and subsequently confirmed via detection of altered concentrations of indole-3-acetic acid (IAA), IAA conjugates and precursors. Furthermore, exogenous IAA applications to cultivar H enhanced secondary dormancy.ConclusionThis study first (to our knowledge) elucidated that indole GLS-linked auxin biosynthesis is enhanced during secondary dormancy induced by PEG, which provides valuable information concerning secondary dormancy and expands the current understanding of the role of auxin in rapeseed.

Progress and prospects of glucosinolate pathogen resistance in some brassica plants

Plants are constantly defending themselves against an array of assaults by pathogenic organisms. This has led to the evolution of precise and elaborate chemical defense systems involving glucosinolates (GSLs) in cruciferous plants. These GSLs and their hydrolysis products are biologically active and are implicated as enabling formidable plant defense processes in certain economically important members of Brassicaceae like broccoli, cabbage and mustard seed. This review provides a comprehensive report of how indole and aliphatic GSLs mitigate incidents of plant pathogenesis. By evaluating the roles of GSLs in plant-pathogen interaction of some brassica plants, this review highlights the associated mechanism that culminates in disease suppression. Moreover, seven economically important brassica pathogens were reviewed in terms of their ability to disrupt proper plant functioning as well as the mechanisms by which GSLs and their hydrolysis products in Brassica lower the susceptibility to them. Future perspectives of the application of GSLs in plant pathogen resistance using advanced molecular techniques are also discussed.

Comparative analysis of glucosinolate production in hairy roots of green and red kale (Brassica oleracea var. acephala)

Glucosinolates (GSLs) are sulfur- and nitrogen-containing secondary metabolites that function in plant defense and provide benefits to human health. In this study, using Agrobacterium rhizogenes R1000, green and red kale hairy roots were established. The expression levels of GSLs biosynthesis genes and their accumulation in both kale hairy roots were analyzed by quantitative real-time PCR and HPLC. The results showed that the expression of most indolic GSLs biosynthesis genes was higher in the hairy roots of green kale than in that of red kale. In contrast, the expression of BoCYP83A1 and BoSUR1 encoding key enzymes aromatic GSL biosynthesis was significantly higher in red kale hairy root. The HPLC analysis identified six GSLs. The levels of 4-methoxyglucobrassicin, glucobrassicin, and 4-hydroxyglucobrassicin were 6.21, 5.98, and 2 times higher, respectively, in green kale than in red kale, whereas the levels of neoglucobrassicin and gluconasturtiin were 16.2 and 3.48 times higher, respectively, in red kale than in green kale. Our study provides insights into the underlying mechanisms of GSLs biosynthesis in kale hairy roots and can be potentially used as “biological factories” for producing bioactive substances such as GSLs.

Comparative effect of elicitors on the physiology and secondary metabolites in broccoli plants

Elicitation is an economic and sustainable technique for increasing the content of secondary metabolites, mainly bioactive compounds, in plants grown for better human nutrition. The aim of this study was to compare the physiological responses (water relations and mineral nutrition) and the enrichment in glucosinolates (GLSs) and phenolic compounds of broccoli plants (Brassica oleracea L. var. italica) receiving different elicitation treatments. The treatments involved the priming of seeds with KCl and the exposure of plants to elicitors, including K2SO4 and NaCl solutions and foliar sprays of methyl jasmonate (MeJA), salicylic acid (SA), and methionine (Met). The physiological response of the plants in terms of root hydraulic conductance was improved by priming with KCl and elicitation with MeJA or Met. Foliar application of Met significantly increased the plant biomass and enhanced mineral nutrition. In general, all treatments increased the accumulation of indole GLSs, but K2SO4 and MeJA gave the best response and MeJA also favored the formation of a newly described compound, cinnamic-GLS, in the plants. Also, the use of Met and SA as elicitors and the supply of K2SO4 increased the abundance of phenolic compounds; K2SO4 also enhanced growth but did not alter the water relations or the accumulation of mineral nutrients. Therefore, although the response to elicitation was positive, with an increased content of bioactive compounds, regulation of the water relations and of the mineral status of the broccoli plants was critical to maintain the yield.

Comparative transcriptome analyses of genes involved in sulforaphane metabolism at different treatment in Chinese kale using full-length transcriptome sequencing

BackgroundSulforaphane is a natural isothiocyanate available from cruciferous vegetables with multiple characteristics including antioxidant, antitumor and anti-inflammatory effect. Single-molecule real-time (SMRT) sequencing has been used for long-read de novo assembly of plant genome. Here, we investigated the molecular mechanism related to glucosinolates biosynthesis in Chinese kale using combined NGS and SMRT sequencing.ResultsSMRT sequencing produced 185,134 unigenes, higher than 129,325 in next-generation sequencing (NGS). NaCl (75 mM), methyl jasmonate (MeJA, 40 μM), selenate (Se, sodium selenite 100 μM), and brassinolide (BR, 1.5 μM) treatment induced 6893, 13,287, 13,659 and 11,041 differentially expressed genes (DEGs) in Chinese kale seedlings comparing with control. These genes were associated with pathways of glucosinolates biosynthesis, including phenylalanine, tyrosine and tryptophan biosynthesis, cysteine and methionine metabolism, and glucosinolate biosynthesis. We found NaCl decreased sulforaphane and glucosinolates (indolic and aliphatic) contents and downregulated expression of cytochrome P45083b1 (CYP83b1), S-alkyl-thiohydroximatelyase or carbon–sulfur lyase (SUR1) and UDP-glycosyltransferase 74B1 (UGT74b1). MeJA increased sulforaphane and glucosinolates contents and upregulated the expression of CYP83b1, SUR1 and UGT74b1; Se increased sulforaphane; BR increased expression of CYP83b1, SUR1 and UGT74b1, and increased glucosinolates contents. The desulfoglucosinolate sulfotransferases ST5a_b_c were decreased by all treatments.ConclusionsWe confirmed that NaCl inhibited the biosynthesis of both indolic and aliphatic glucosinolates, while MeJA and BR increased them. MeJA and BR treatments, conferred the biosynthesis of glucosinolates, and Se and MeJA contributed to sulforaphane in Chinese kale via regulating the expression of CYP83b1, SUR1 and UGT74b1.

Enhancement of Glucosinolate Production in Watercress ( Nasturtium officinale) Hairy Roots by Overexpressing Cabbage Transcription Factors.

Glucosinolates are secondary metabolites that play important roles in plant defense and human health, as their production in plants is enhanced by overexpressing transcription factors. Here, four cabbage transcription factors (IQD1-1, IQD1-2, MYB29-1, and MYB29-2) affecting genes in both aliphatic and indolic glucosinolates biosynthetic pathways and increasing glucosinolates accumulation were overexpressed in watercress. Five IQD1-1, six IQD1-2, five MYB29-1, six MYB29-2, and one GUS hairy root lines were created. The expression of all genes involved in glucosinolates biosynthesis was higher in transgenic lines than in the GUS hairy root line, in agreement with total glucosinolates contents, determined by high-performance liquid chromatography. In transgenic IQD1-1 (1), IQD1-2 (4), MYB29-1 (2), and MYB29-2 (1) hairy root lines, total glucosinolates were 3.39-, 3.04-, 2.58-, and 4.69-fold higher than those in the GUS hairy root lines, respectively. These results suggest a central regulatory function for IQD1-1, IQD1-2, MYB29-1, and MYB29-2 transcription factors in glucosinolates biosynthesis in watercress hairy roots.

Overexpressing broccoli tryptophan biosynthetic genes BoTSB1 and BoTSB2 promotes biosynthesis of IAA and indole glucosinolates.

Tryptophan is one of the amino acids that cannot be produced in humans and has to be acquired primarily from plants. In Arabidopsis thaliana (Arabidopsis), the tryptophan synthase beta subunit (TSB) genes have been found to catalyze the biosynthesis of tryptophan. Here, we report the isolation and characterization of two TSB genes from Brassica oleracea (broccoli), designated BoTSB1 and BoTSB2. Overexpressing BoTSB1 or BoTSB2 in Arabidopsis resulted in higher tryptophan content and the accumulation of indole-3-acetic acid (IAA) and indole glucosinolates in rosette leaves. Therefore, the transgenic plants showed a series of high auxin phenotypes, including long hypocotyls, large plants and a high number of lateral roots. The spatial expression of BoTSB1 and BoTSB2 was detected by quantitative real-time PCR in broccoli and by expressing the β-glucuronidase reporter gene (GUS) controlled by the promoters of the two genes in Arabidopsis. BoTSB1 was abundantly expressed in vascular tissue of shoots and inflorescences. Compared to BoTSB1, BoTSB2 was expressed at a very low level in shoots but at a higher level in roots. We further investigated the expression response of the two genes to several hormone and stress treatments. Both genes were induced by methyl jasmonate (MeJA), salicylic acid (SA), gibberellic acid (GA), Flg22 (a conserved 22-amino acid peptide derived from bacterial flagellin), wounding, low temperature and NaCl and were repressed by IAA. Our study enhances the understanding of tryptophan biosynthesis and its regulation in broccoli and Arabidopsis. In addition, we provide evidence that TSB genes can potentially be a good tool to breed plants with high biomass and high nutrition.

Biosynthèse des glucosinolates indoliques et rôle écologique de leurs modifications secondaires

Indole glucosinolates are plant secondary metabolites derived from the amino acid tryptophan. They are part of a large group of sulfur-containing molecules almost exclusively found among Brassicales, which include the mustard family (Brassicaceae) with many edible plant species of major nutritional importance. These compounds mediate numerous interactions between these plants and their natural enemies and are therefore of major biological and economical interest. This literature review aims at taking stock of recent advances of our knowledge about the biosynthetic pathways of indole glucosinolates, but also about the defense strategies and ecological processes involving these metabolites.

Variable effects on growth and defense traits for plant ecotypic differentiation and phenotypic plasticity along elevation gradients.

Along ecological gradients, phenotypic differentiation can arise through natural selection on trait diversity and magnitude, and environment‐driven plastic changes. The magnitude of ecotypic differentiation versus phenotypic plasticity can vary depending on the traits under study. Using reciprocal transplant‐common gardens along steep elevation gradients, we evaluated patterns of ecotypic differentiation and phenotypic plasticity of several growth and defense‐related traits for two coexisting but unrelated plant species, Cardamine pratensis and Plantago major. For both species, we observed ecotypic differentiation accompanied by plasticity in growth‐related traits. Plants grew faster and produced more biomass when placed at low elevation. In contrast, we observed fixed ecotypic differentiation for defense and resistance traits. Generally, low‐elevation ecotypes produced higher chemical defenses regardless of the growing elevation. Yet, some plasticity was observed for specific compounds, such as indole glucosinolates. The results of this study may suggest that ecotypic differentiation in defense traits is maintained by costs of chemical defense production, while plasticity in growth traits is regulated by temperature‐driven growth response maximization.

Variations in the glucosinolates of the individual edible parts of three stem mustards (Brassica juncea).

The composition and content of glucosinolates were investigated in the edible parts (petioles, peel and flesh) of tuber mustard, bamboo shoots mustard and baby mustard by high-performance liquid chromatography to reveal the association between the different cooking methods and their glucosinolate profiles. Eight glucosinolates were identified from tuber mustard and baby mustard, including three aliphatic glucosinolates, four indole glucosinolates and one aromatic glucosinolate. Only six of the eight glucosinolates were detected in bamboo shoots mustard. The results show that the distribution and content of glucosinolates varied widely among the different tissues and species. The highest contents of glucosinolates in tuber mustard, bamboo shoots mustard and baby mustard were found in flesh, petioles and peel, respectively. The content of total glucosinolates ranged from 5.21 µmol g–1 dry weight in bamboo shoots mustard flesh to 25.64 µmol g−1 dry weight in baby mustard peel. Aliphatic glucosinolates were predominant in the three stem mustards, followed by indole and aromatic glucosinolates. Sinigrin was the predominant glucosinolate in the three stem mustards. Sinigrin content in tuber mustard was slightly higher than that in baby mustard and much higher than that in bamboo shoots mustard, suggesting that the pungent-tasting stem mustards contained more sinigrin. In addition, a principal components analysis showed that bamboo shoots mustard was distinguishable from the other two stem mustards. A variance analysis indicated that the glucosinolates were primarily influenced by a species × tissue interaction. The correlations among glucosinolates were also analysed.

Divergence in Glucosinolate Profiles between High- and Low-Elevation Populations of Arabidopsis halleri Correspond to Variation in Field Herbivory and Herbivore Behavioral Preferences.

Variation in local herbivore pressure along elevation gradients is predicted to drive variation in plant defense traits. Yet, the extent of intraspecific variation in defense investment along elevation gradients, and its effects on both herbivore preference and performance, remain relatively unexplored. Using populations of Arabidopsis halleri (Brassicaceae) occurring at different elevations in the Alps, we tested for associations between elevation, herbivore damage in the field, and constitutive chemical defense traits (glucosinolates) assayed under common-garden conditions. Additionally, we examined the feeding preferences and performance of a specialist herbivore, the butterfly Pieris brassicae, on plants from different elevations in the Alps. Although we found no effect of elevation on the overall levels of constitutive glucosinolates in leaves, relative amounts of indole glucosinolates increased significantly with elevation and were negatively correlated with herbivore damage in the field. In oviposition preference assays, P. brassicae females laid fewer eggs on plants from high-elevation populations, although larval performance was similar on populations from different elevations. Taken together, these results support the prediction that species distributed along elevation gradients exhibit genetic variation in chemical defenses, which can have consequences for interactions with herbivores in the field.

Simultaneous Quantification of 22 Glucosinolates in 12 Brassicaceae Vegetables by Hydrophilic Interaction Chromatography-Tandem Mass Spectrometry.

Glucosinolates, which are unique to Brassicaceae vegetables, have diverse biological activities, including antimicrobial, antioxidant, and anticancer actions. In this study, we applied hydrophilic interaction chromatography–tandem mass spectrometry (HILIC–MS/MS) to the simultaneous quantification of 22 glucosinolates in 12 Brassicaceae vegetables, including pak choi, choy sum, Chinese cabbage, cauliflower, cabbage, broccoli, Kai Lan, Brussels sprouts, rocket salad, daikon radish, red cherry radish, and watercress. Significant differences in concentration and composition of glucosinolates were observed among these vegetables. Cabbage had the highest level of total glucosinolates (μg/g dry weight: 19 551.2 ± 1317.7), whereas Kai Lan had the lowest level (7611.3 ± 868.4). Aliphatic and indole glucosinolates were the major components in the 12 vegetables ranging from 76 to 100%, except watercress (37%). On the basis of the content of glucosinolates, the 12 vegetables were well distinguishable and classified according to their morphological taxonomy. This study presents a HILIC–MS/MS approach for quantification of glucosinolates, and demonstrates the potential of glucosinolate profiles for Brassicaceae species identification.

Hygienic assessment of indoles in the diet of medical students

A number of studies have shown the relationship between the regular consumption of cruciferous vegetables and the risk of malignant tumors in certain localizations, the activation of mechanisms of alimentary adaptation of the organism under conditions of alien loads, by inducing enzymes of the biotransformation system of xenobiotics. The cruciferous vegetables are distinguished by the presence of minor components, such as indole-3-carbinol, formed during the hydrolysis of glucosinolates. The aim of the investigation was a retrospective study of the content of indoles in students' diet with subsequent quantitative analysis in different comparison groups. The study involved 250 students from a medical university aged 21 to 27 years. To assess the actual nutrition, the developed questionnaires were used, which included the most common products in the Moscow region, sources of indole glucosinolates. It was found that 44% of the respondents didn't include cruciferous vegetables in the diet, and of those who consumed sources of indoles (56% of respondents), only about half received them in the recommended amount. It should also be noted that as in men, in women the most commonly used in the diet product as a source of indoles was cabbage, it was included in the diet of 68% of the respondents who used cruciferous vegetables, rarely pekin cabbage was used (16.3%) and broccoli (16.3%). Cauliflower, radishes, Kale and horseradish was included in the diet of 7.8-14.9% of the students. Less often turnip was consumed - only by 2.1% of the students. No significant differences in the consumption of indoles in the student with deficient, normal or overweight was revealed. Also, there was no correlation between excess weight and the consumption of various indoles sources. The obtained results testify to the extremely low level of alimentary intake of indole-3-carbinol.

Two-tier morpho-chemical defence tactic in Aethionema via fruit morph plasticity and glucosinolates allocation in diaspores.

Fruit dimorphism and the production of glucosinolates (GSLs) are two specific life history traits found in the members of Brassicales, which aid to optimize seed dispersal and defence against antagonists, respectively. We hypothesized that the bipartite dispersal strategy demands a tight control over the production of fruit morphs with expectedly differential allocation of defensive anticipins (GSLs). In dimorphic Aethionema, herbivory by Plutella xylostella at a young stage triggered the production of more dehiscent (seeds released from fruit) than indehiscent fruit morphs (seeds enclosed within persistent pericarp) on the same plant upon maturity. Total GSL concentrations were highest in the mature seeds of dehiscent fruits from Aethionema arabicum and Aethionema saxatile among the different ontogenetic stages of the diaspores. Multivariate analyses of GSL profiles indicated significantly higher concentrations of specific indole GSLs in the diaspores, which require optimal defence after dispersal (i.e., seeds of dehiscent and fruit/pericarp of indehiscent fruit). Bioassays with a potentially coinhabitant fungus, Aspergillus quadrilineatus, support the distinct defensive potential of the diaspores corresponding to their GSL allocation. These findings indicate a two-tier morpho-chemical defence tactic of Aethionema via better protected fruit morphs and strategic provision of GSLs that optimize protection to the progeny for survival in nature.

Functional Characterization of BoaMYB51s as Central Regulators of Indole Glucosinolate Biosynthesis in Brassica oleracea var. alboglabra Bailey.

R2R3-MYB transcription factor MYB51 is known to control indole glucosinolate (indole GSL) biosynthesis in Arabidopsis. Here, two copies of BoaMYB51 have been isolated in Chinese kale (Brassica oleracea var. alboglabra Bailey), designated BoaMYB51.1 and BoaMYB51.2, which exhibit overlapping but distinct expression levels among different organs and respond to signaling molecules in a similar pattern. It has been demonstrated a structural and functional conservation between BoaMYB51s and AtMYB51 by phylogenetic analysis, complementation studies and transient expression assay. To further investigate the transcriptional mechanism, we identified the transcriptional activation domain (TAD) and putative interacting proteins of BoaMYB51s by means of yeast (Saccharomyces cerevisiae) two hybrid. Using tobacco (Nicotiana benthamiana) transient expression assay, we confirmed that the carboxy-end is required for transcriptional activation activity of BoaMYB51s. In addition, several BoaMYB51-interacting proteins have been identified by yeast two-hybrid screening. These results provide important insights into the molecular mechanisms by which MYB51 transcriptionally regulates indole GSL biosynthesis.

Investigation into the removal of glucosinolates and volatiles from anthocyanin-rich extracts of red cabbage.

The aim of the present article was an in-depth characterization of cyanidine-rich red cabbage extracts and the identification of challenges emerging during the purification of their pigments. Two extraction procedures using either hot acidified or temperate water at its genuine pH were compared. LC-MS analyses revealed 20 mostly acylated anthocyanins, five aliphatic glucosinolates, and four indolic glucosinolates as non-volatile constituents. In addition, volatiles were characterized by HS-SPME-GC-MS. Whereas the glycosidic precursors do not impair the sensory properties, their enzymatic degradation products may evoke unpleasant flavors. The crude pigment extract obtained with hot acidified water contained low concentrations of C6 aldehydes, isothiocyanates, nitriles, and sulfides, and was selected for purification experiments. Amberlite XAD 16 HP, polyamide, chitosan, and lignosulfonate were used as adsorbents and flocculants. Particularly, Amberlite and lignosulfonate treatment diminished the content of glucosinolates and volatiles. Interestingly, indolic glucosinolates and acylated anthocyanins showed similar behavior in all purification procedures performed.

Comparative analysis of glucosinolates and metabolite profiling of green and red mustard (brassica juncea) hairy roots.

Here, accumulation of glucosinolates and expression of glucosinolates biosynthesis genes in green and red mustard hairy roots were identified and quantified by HPLC and qRT-PCR analyses. The total glucosinolates content of green mustard hairy root (10.09µg/g dry weight) was 3.88 times higher than that of red mustard hairy root. Indolic glucosinolates (glucobrassicin, 4-methoxyglucobrassicin, and neoglucobrassicin) in green mustard were found at 30.92, 6.95, and 5.29 times higher than in red mustard hairy root, respectively. Conversely, levels of glucotropaeolin (aromatic glucosinolate) was significantly higher in red mustard than in green mustard. Accumulation of glucoraphasatin, an aliphatic glucosinolate, was only observed only in red mustard hairy roots. Quantitative real-time PCR analysis showed that the expression level of genes related to aliphatic and aromatic glucosinolate biosynthesis were higher in red mustard, exception BjCYP83B. The expression of BjCYP79B2, which encodes a key enzyme involved in the indolic glucosinolate biosynthetic pathway, was higher in green mustard than in red mustard. Additionally, to further distinguish between green mustard and red mustard hairy roots, hydrophilic and lipophilic compounds were identified by gas chromatography-mass spectrometry and subjected to principal component analysis. The results indicated that core primary metabolites and glucosinolate levels were higher in the hairy roots of green mustard than in those of red mustard.

Ascorbic Acid and Glucosinolate Levels in New Czech Cabbage Cultivars: Effect of Production System and Fungal Infection

Nutritional value and disease-preventive effects of cabbage are well-known. Levels of the antioxidant compounds ascorbic acid (AA) and glucosinolates (GSL) in new Czech cabbage cultivars were determined in the context of different production systems. The contents of AA and GSLs in cabbage biomass were determined by HPLC. Individual GSLs were identified according to their exact masses with sinigrin used as the external standard. Artificial infection with A. brassicicola generally raised the AA levels. The major GSLs (≥10 mg kg−1) were glucobrassicin, sinigrin, and glucoiberin. Indole and aliphatic GSLs were present, but no aromatic ones were detected. Ecological growth conditions and the artificial fungal infection increased the total content of GSLs and, also, of the methoxylated indole GSLs. Sulforaphane, iberin, indole-3-carbinol, and ascorbigen resulting from the hydrolysis of GSLs were found in both cultivars. The amounts and profiles of GSLs present in the two Czech cultivars demonstrated their good nutritional value. The decomposition products sulforaphane, iberin, indole-3-carbinol, and ascorbigen detected improve its health-promoting qualities and represent a suitable component of the human diet.

β-Lactam Antibiotics Modify Root Architecture and Indole Glucosinolate Metabolism in Arabidopsis thaliana.

The presence of antibiotics in soils could be due to natural production by soil microorganisms or to the effect of anthropogenic activities. However, the impact of these compounds on plant physiology has not been thoroughly investigated. To evaluate the effect of β-lactam antibiotics (carbenicillin and penicillin) on the growth and development of Arabidopsis thaliana roots, plants were grown in the presence of different amounts and we found a reduction in root size, an increase in the size of root hairs as well as an abnormal position closer to the tip of the roots. Those phenomena were dependent on the accumulation of both antibiotics inside root tissues and also correlated with a decrease in size of the root apical meristem not related to an alteration in cell division but to a decrease in cell expansion. Using an RNA sequencing analysis, we detected an increase in the expression of genes related to the response to oxidative stress, which would explain the increase in the levels of endogenous reactive oxygen species found in the presence of those antibiotics. Moreover, some auxin-responsive genes were misregulated, especially an induction of CYP79B3, possibly explaining the increase in auxin levels in the presence of carbenicillin and the decrease in the amount of indole glucosinolates, involved in the control of fungal infections. Accordingly, penicillin-treated plants were hypersensitive to the endophyte fungus Colletotrichum tofieldiae. These results underscore the risks for plant growth of β-lactam antibiotics in agricultural soils, and suggest a possible function for these compounds as fungus-produced signaling molecules to modify plant behavior.

How cadmium affects the fitness and the glucosinolate content of oilseed rape plantlets

Secondary metabolites such as glucosinolates (GSLs) are involved in plant response to biotic stress but can be significantly influenced by abiotic factors as well. Oilseed rape (Brassica napus L.) produces large quantities of several GSLs both in seeds and at the vegetative stage. These sulfur-containing compounds are known to play an important role in cadmium stress tolerance within the Brassicaceae family probably due to specific cross-talk between the S primary and secondary metabolism. Sulfur assimilation is in the middle of multiple metabolic pathways including Cd stress responses at physiological level. Our research focused on the assessment of GSL profiles and content in the roots and shoots of 28-day-old winter oilseed rape plantlets. The study was conducted under in vitro sterile conditions using concentration gradients of 0, 5, 15 and 45 μM of cadmium. A phenotypic analysis was carried out at the end of this experiment in order to evaluate the plantlets’ fitness. Our results described hormetic growth curves for root elongation, root biomass and shoot biomass at Cd concentrations of 5 μM and 15 μM respectively. Our experiment shows that a concentration of 5 μM can be considered as non-toxic, while one of 45 μM represents a lethal dose. Strong relationships were found between Cd accumulated in roots or translocated to shoots and the total sulfur accumulation in the plantlets’ different organs. A decrease of both indole and aliphatic GSL content associated with an increase of Cd accumulation and an increase of total sulfur accumulation was observed in the roots and shoots of the plantlets. It was also further demonstrated that Cd stress has a highly significant effect on roots’ and shoots’ GSL content bringing new insights into GSL’s possible role in the priming of Cd stress.