Uptake and turn-over of glucosinolates sequestered in the sawfly Athalia rosae

Larvae of the sawfly Athalia rosae sequester glucosinolates from their various host plants of the Brassicaceae into their hemolymph for defensive purposes. We found that the glucosinolate concentration in the insect varies in a fluctuating manner during larval development. Analyses of larvae which had been offered diets with different glucosinolate profiles showed that there is an equilibrium between a rapid uptake of glucosinolates into the hemolymph and a continuous turn-over. Injection of glucotropaeolin into the hemolymph and ingestion of the same amount resulted in similar levels of intact glucosinolates recovered from larvae after different periods of time. This indicates that hemolymph glucosinolates are the principal source for glucosinolate degradation. Feeding experiments with [14C]-labeled glucotropaeolin revealed that the majority of the ingested glucosinolate is excreted as one or more unidentified metabolite(s) within 14 h. We found no indication for the presence of an insect myrosinase, or sulfatase in A. rosae, which have been shown to be involved in glucosinolate metabolism in other specialists feeding on Brassicaceae. Furthermore, the metabolism of sinalbin in A. rosae seems to result in different products than its metabolism in the caterpillar Pieris rapae. Obviously, A. rosae has yet another way of coping with the glucosinolates.     

Quantitative trait loci analysis of non-enzymatic glucosinolate degradation rates in Brassica oleracea during food processing

Epidemiological and mechanistic studies show health-promoting effects of glucosinolates and their breakdown products. In literature, differences in non-enzymatic glucosinolate degradation rates during food processing between different vegetables are described, which provide the basis for studying the genetic effects of this trait and breeding vegetables with high glucosinolate retention during food processing. Non-enzymatic glucosinolate degradation, induced by heat, was studied in a publicly available Brassica oleracea doubled haploid population. Data were modeled to obtain degradation rate constants that were used as phenotypic traits to perform quantitative trait loci (QTL) mapping. Glucosinolate degradation rate constants were determined for five aliphatic and two indolic glucosinolates. Degradation rates were independent of the initial glucosinolate concentration. Two QTL were identified for the degradation rate of the indolic glucobrassicin and one QTL for the degradation of the aliphatic glucoraphanin, which co-localized with one of the QTL for glucobrassicin. Factors within the plant matrix might influence the degradation of different glucosinolates in different genotypes. In addition to genotypic effects, we demonstrated that growing conditions influenced glucosinolate degradation as well. The study identified QTL for glucosinolate degradation, giving the opportunity to breed vegetables with a high retention of glucosinolates during food processing, although the underlying mechanisms remain unknown.     

Thermal degradation of glucosinolates

Three glucosinolates (allyl-, benzyl- and 2-phenethyl-) were shown to degrade thermally in a GC column to yield products identical with those obtained conventionally on enzymic decomposition, namely nitriles and isothiocyanates. Nitriles were formed more readily at 125° but the facility for isothiocyanate production varied slightly with the glucosinolate; 2-phenethylglucosinolate was the most labile of those studied yielding isothiocyanate at a column temperature of 150°. Temperature was confirmed as the cause of degradation by isolated heated-tube experiments. The results have significance both with regard to analytical methodology for glucosinolates and their products, and with regard to furthering understanding of the mechanisms of glucosinolate degradation.     

Glucosinolates in Sesamoides canescens and S. pygmaea: Identification of 2-(α-l-arabinopyranosyloxy)-2-phenylethylglucosinolate

A new natural product, 2-(α-l-arabinopyranosyloxy)-2-phenylethylglucosinolate, has been isolated from Sesamoides canescens. This glucosinolate together with 2-hydroxy-2-phenylethylglucosinolate and 2-phenetliylglucosinolate in a 1:1:1 ratio constitutes about 90 % of the total glucosinolate pool in green parts of the plant. Phenethylglucosinolate constitutes about 70 % of the total glucosinolate pool in green parts of S. pygmaea together with minor amounts of the two other glucosinolates. In addition, both plants contain at least seven other glucosinolates. The structure of the new natural product has been confirmed by transformations into d-glucose, l-arabinose, N-(2-(α-l-arabinopyranosyloxy)-2-phenylethyl)thiourea, 3-(α-l-arabinopyranosyloxy)-3-phenylpropionitrile and 3-hydroxy-3-phenylpropionic acid, respectively. The significance of this investigation is briefly discussed in relation to the methods used in glucosinolate analysis, chemotaxonomy and possible catabolic transformation of glucosinolates into amines.     

Variation in the glucosinolate content of vegetative tissues of Chinese lines of Brassica napus L

The glucosinolate content of leaves, stems and roots of a range of Chinese oilseed rape (Brassica napus L.) breeding lines was analysed. Total content and spectrum of individual glucosinolates varied widely, and there was no correlation between seed and vegetative tissue glucosinolate content. Lines with low seed glucosinolates (00) did not necessarily have low glucosinolate content in vegetative tissues; nor did high seed glucosinolate lines always have high vegetative tissue content. There was no correlation between the glucosinolate content of leaf, stem, and root in any given line. It appears that glucosinolate synthesis and accumulation is under tissue-specific control, and the mutation which blocks accumulation of glucosinolates in seeds does not influence other tissues. The responses of these lines to elicitors was also examined. Methyl jasmonate and salicylic acid treatments produced increases in leaf indolyl and aromatic glucosinolates respectively. However, the extent of such increases differed widely between the lines, and there were other, less consistent, effects on other classes of glucosinolate. There seems to be greater variation in glucosinolate accumulation in rape than has previously been reported, and the lines described here have considerable potential for evaluating the effects of manipulating glucosinolate profiles on pest and disease interactions.     

Some glucosinolates of Farsetia aegyptia and Farsetia ramosissima

Air-dried leaves of Farsetia aegyptia and F. ramosissima have been analysed for their glucosinolates; the former was shown to contain at least six but chiefly allylglucosinolate, whilst the latter contains at least five but mainly but-3-enylglucosinolate with some 4-(methylthio)butylglucosinolate. Without the addition of extraneous thioglucosidase enzyme, both species gave predominantly nitrile degradation products of glucosinolates; but if extra enzyme were added, corresponding isothiocyanates became the major products instead. Varying the pH from the natural level for the plant also considerably affected the ratios of glucosinolate products.     

ESP and ESM1 mediate indol-3-acetonitrile production from indol-3-ylmethyl glucosinolate in Arabidopsis

Glucosinolates are plant secondary metabolites that act as direct defenses against insect herbivores and various pathogens. Recent analysis has shown that methionine-derived glucosinolates are hydrolyzed/activated into either nitriles or isothiocyanates depending upon the plants genotype at multiple loci. While it has been hypothesized that tryptophan-derived glucosinolates can be a source of indole-acetonitriles, it has not been explicitly shown if the same proteins control nitrile production from tryptophan-derived glucosinolates as from methionine-derived glucosinolates. In this report, we formally test if the proteins involved in controlling aliphatic glucosinolate hydrolysis during tissue disruption can control production of nitriles during indolic glucosinolate hydrolysis. We show that myrosinase is not sufficient for indol-3-acetonitrile production from indol-3-ylmethyl glucosinolate and requires the presence of functional epithospecifier protein in planta and in vitro to produce significant levels of indol-3-acetonitrile. This reaction is also controlled by the Epithiospecifier modifier 1 gene. Thus, like formation of nitriles from aliphatic glucosinolates, indol-3-acetonitrile production following tissue disruption is controlled by multiple loci raising the potential for complex regulation and fine tuning of indol-3-acetonitrile production from indol-3-ylmethyl glucosinolate.     

Isolation of glucosinolates and the identification of o-(α-l-rhamnopyranosyloxy)benzylglucosinolate from Reseda odorata

A method has been developed for the quantitative isolation of glucosinolates by ion-exchange chromatography and high voltage electrophoresis avoiding strongly alkaline and acidic conditions. The compounds were identified by ¹H and ¹³C NMR spectroscopy and through the products arising from enzymatic, acid and alkaline hydrolysis. The method is well suited for the isolation and identification of glucosinolates containing aglucone parts which produce non-volatile compounds on enzymatic hydrolysis. The method has been used in the isolation and identification of 2-hydroxy-2-methylpropylglucosinolate from Reseda alba, 2-hydroxy-2-phenylethylglucosinolate from R. luteola and a new glucosinolate, o-(α-l-rhamnopyranosyloxy)benzylglucosinolate, occurring in R. odorata. The glucosinolate content in different parts of this plant has been determined and the metabolism of glucosinolates is briefly discussed.     

Root and shoot glucosinolates: a comparison of their diversity, function and interactions in natural and managed ecosystems

The role of glucosinolates in aboveground plant–insect and plant–pathogen interactions has been studied widely in both natural and managed ecosystems. Fewer studies have considered interactions between root glucosinolates and soil organisms. Similarly, data comparing local and systemic changes in glucosinolate levels after root- and shoot-induction are scarce. An analysis of 74 studies on constitutive root and shoot glucosinolates of 29 plant species showed that overall, roots have higher concentrations and a greater diversity of glucosinolates than shoots. Roots have significantly higher levels of the aromatic 2-phenylethyl glucosinolate, possibly related to the greater effectiveness and toxicity of its hydrolysis products in soil. In shoots, the most dominant indole glucosinolate is indol-3-ylglucosinolate, whereas roots are dominated by its methoxyderivatives. Indole glucosinolates were the most responsive after jasmonate or salicylate induction, but increases after jasmonate induction were most pronounced in the shoot. In general, root glucosinolate levels did not change as strongly as shoot levels. We postulate that roots may rely more on high constitutive levels of glucosinolates, due to the higher and constant pathogen pressure in soil communities. The differences in root and shoot glucosinolate patterns are further discussed in relation to the molecular regulation of glucosinolate biosynthesis, the within-tissue distribution of glucosinolates in the roots, and the use of glucosinolate-containing crops for biofumigation. Comparative studies of tissue-specific biosynthesis and regulation in relation to the biological interactions in aboveground and belowground environments are needed to advance investigations of the evolution and further utilization of glucosinolates in natural and managed ecosystems. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Glucosinolate changes in developing pods of single and double low varieties of autumn-sown oilseed rape (B. napus)

Single and double low varieties of oilseed rape were grown in the 1987/88 and 1988/89 seasons to study changes in the concentrations of total and individual glucosinolates within pods during development. Total glucosinolate concentration in seeds of all varieties increased during development when expressed on a fresh weight basis. The levels of the major alkenyl glucosinolates present in the seed; 2–hydroxy-3–butenyl, 3–butenyl and 4–pentenyl had been reduced in the transition from single to double low varieties. The major indole glucosinolates in the seed, 4–hydroxy-3–indolylmethyl and 3–indolylmethyl were present in the same amounts in single and double low varieties but in the latter represented a greater proportion of the total seed glucosinolate content. A decline in the total glucosinolate concentration in the pod walls with time together with the analogous profile of individual glucosinolates in the seeds and pod walls suggests that the pod wall is a major site of seed glucosinolate synthesis. Other plant parts may also have an important role to play in provision of intact glucosinolates or precursors to the pod walls for glucosinolate biosynthesis.     

Piecing together the transport pathway of aliphatic glucosinolates

Glucosinolates are sulfur-rich secondary metabolites characteristic of the Brassicales order. Transport of glucosinolates was suggested more than 30 years ago through a number of studies which indicated that glucosinolates are produced in maternal tissue and subsequently transported to the seed. These observations laid the foundation for numerous studies on glucosinolate transport which have provided a wealth of information on biochemical properties of glucosinolate transport, source–sink relationships between organs and on the transport routes of glucosinolates. However, most of the conclusions and hypotheses proposed in these studies have not been discussed in context of each other to provide a complete overview of the current state of knowledge on glucosinolate transport. In this review, we are thus piecing together the glucosinolate pathway by presenting and critically analyzing all data on glucosinolate research. Furthermore, the data on glucosinolate transport is considered in the light of the newest findings on glucosinolate synthesis and distribution. The aim is to provide a comprehensive and updated set of hypotheses which may prove useful in directing future research on glucosinolate transport.     

拟南芥莲座叶芥子油苷含量对水分胁迫的响应

芥子油苷(glucosinolates)是十字花科植物中一类含氮、含硫的次生代谢产物,与其水解产物在植物防御功能中有重要意义且与环境因子关系密切.通过控制供水的方式对营养生长时期的拟南芥幼苗进行水分胁迫,观察了土壤自然干旱对营养生长时期拟南芥莲座叶芥子油苷含量及组成的影响.结果表明,土壤自然干旱处理下,拟南芥莲座叶的芥子油苷总量从处理3 d起低于对照,且随着处理天数的增加与对照组的差异逐渐增大,脂肪族芥子油苷的响应均比较明显,与芥子油苷总量的变化趋势基本一致,而吲哚族芥子油苷对水分胁迫则不敏感.脂肪族中的4-甲基亚磺酰丁基芥子油苷(4-methylsulphinylbutyl GS,4MSOB)占脂肪族芥子油苷的比例最大,它的含量变化成为影响莲座叶中芥子油苷组合模式的主导因素.     

Genetics of aliphatic glucosinolates. IV. Side-chain modification in Brassica oleracea

The biochemical and genetical relationship between aliphatic glucosinolates which have methylthioalkyl, methylsulphinylalkyl and alkenyl side chains has not been resolved by biochemical studies. In this study, two hypothetical models are tested by the genetic analysis of a backcross population between Brassica drepanensis and B. atlantica. The results support one of the models in which 3-methylthiopropyl glucosinolate is sequentially converted to 3-methylsulphinylpropyl, and then to 2-propenyl glucosinolate, by the action of dominant alleles at two loci. RFLP mapping positioned both loci on the same linkage group homologous to the B. napus N19 linkage group. The implication of the results for the genetic manipulation of glucosinolates in Brassica to improve flavour and nutritional properties, and in order to investigate plant-insect interactions, is discussed.     

Studies on glucosinolate degradation in Lepidium sativum seed extracts

Analysis of Lepidium sativum seeds showed the presence of allyl, 2-phenethyl and benzyl glucosinolates, the first two being reported for the first time from this source. The effects of temperature, pH of the extraction medium and the length of time allowed for autolysis were assessed on the benzyl glucosinolate degradation products in seed extracts. In particulàr benzyl thiocyanate was not produced at higher temperatures but at ambient and lower temperatures it exceeded isothiocyanate. Nitrile was always the major product under the conditions studied, ever at pH levels as high as 7.4. Five new possible benzyl glucosinolate degradation products were detected and evidence is presented that benzaldehyde and benzyl alcohol could be secondary products formed thermally from isothocyanate and thiocyanate, respectively. Benzyl mercaptan and benzyl methyl sulphide also appear to be thermally produced.     

Myzus persicae (green peach aphid) feeding on Arabidopsis induces the formation of a deterrent indole glucosinolate

Cruciferous plants produce a wide variety of glucosinolates as a protection against herbivores and pathogens. However, very little is known about the importance of individual glucosinolates in plant defense and the regulation of their production in response to herbivory. When Myzus persicae (green peach aphid) feeds on Arabidopsis aliphatic glucosinolates pass through the aphid gut intact, but indole glucosinolates are mostly degraded. Although aphid feeding causes an overall decrease in Arabidopsis glucosinolate content, the production of 4-methoxyindol-3-ylmethylglucosinolate is induced. This altered glucosinolate profile is not a systemic plant response, but is limited to the area in which aphids are feeding. Aphid feeding on detached leaves causes a similar change in the glucosinolate profile, demonstrating that glucosinolate transport is not required for the observed changes. Salicylate-mediated signaling has been implicated in other plant responses to aphid feeding. However, analysis of eds5, pad4, npr1 and NahG transgenic Arabidopsis, which are compromised in this pathway, demonstrated that aphid-induced changes in the indole glucosinolate profile were unaffected. The addition of purified indol-3-ylmethylglucosinolate to the petioles of cyp79B2 cyp79B3 mutant leaves, which do not produce indole glucosinolates, showed that this glucosinolate serves as a precursor for the aphid-induced synthesis of 4-methoxyindol-3-ylmethylglucosinolate. In artificial diets, 4-methoxyindol-3-ylmethylglucosinolate is a significantly greater aphid deterrent in the absence of myrosinase than its metabolic precursor indol-3-ylmethylglucosinolate. Together, these results demonstrate that, in response to aphid feeding, Arabidopsis plants convert one indole glucosinolate to another that provides a greater defensive benefit.     

Glucosinolate biochemical diversity and innovation in the Brassicales

Glucosinolates were analysed from herbarium specimens and living tissues from representative of all families of the Brassicales, following the phylogenetic schemes of Rodman et al. (1998) and Hall et al. (2002, 2004), including specimens of Akania, Setchellanthus, Emblingia, Stixis, Forchhammeria and members of the Capparaceae for which glucosinolate content had not previously been reported. The results are reviewed along with additional published data on glucosinolate content of members of the Brassicales. In addition to providing an overview of the evolution of glucosinolate biochemical diversity within the core Brassicales, there were three main findings. Firstly, the glucosinolate content of some 'orphan' taxa of the Brassicales, such as Setchellanthus and Emblingia were consistent with recent phylogentic analyses based upon DNA sequence comparisons, while further analyses of Tirania and Stixis is required. Secondly, methyl glucosinolate is found within the Capparaceae and Cleomaceae, but also, unexpectedly, within Forchhammeria, with implications for the biochemical and evolutionary origin of methyl glucosinolate and the phylogenetic relationships of Forchhammeria. Thirdly, whereas Old World Capparaceae contain methyl glucosinolate, New World Capparaceae, including New World Capparis, either contain methyl glucosinolates or glucosinolates of complex and unresolved structures, indicative of continued innovation in glucosinolate biosynthesis. These taxa may be productive sources of glucosinolate biosynthetic genes and alleles that are not found in the model plant Arabidopsis thaliana.     

Characterization of metabolite quantitative trait loci and metabolic networks that control glucosinolate concentration in the seeds and leaves of Brassica napus

? Glucosinolates are a major class of secondary metabolites found in the Brassicaceae, whose degradation products are proving to be increasingly important for human health and in crop protection. ? The genetic and metabolic basis of glucosinolate accumulation was dissected through analysis of total glucosinolate concentration and its individual components in both leaves and seeds of a doubled-haploid (DH) mapping population of oilseed rape/canola (Brassica napus). ? The quantitative trait loci (QTL) that had an effect on glucosinolate concentration in either or both of the organs were integrated, resulting in 105 metabolite QTL (mQTL). Pairwise correlations between individual glucosinolates and prior knowledge of the metabolic pathways involved in the biosynthesis of different glucosinolates allowed us to predict the function of genes underlying the mQTL. Moreover, this information allowed us to construct an advanced metabolic network and associated epistatic interactions responsible for the glucosinolate composition in both leaves and seeds of B. napus. ? A number of previously unknown potential regulatory relationships involved in glucosinolate synthesis were identified and this study illustrates how genetic variation can affect a biochemical pathway.