Explore the vast range of titles available.

Plants accumulate secondary metabolites to adapt to environmental conditions. These compounds, here exemplified by the purple-colored anthocyanins, are accumulated upon high temperatures, UV-light, drought, and nutrient deficiencies, and may contribute to tolerance to these stresses. Producing compounds is often part of a more broad response of the plant to changes in the environment. Here we investigate how a transcription-factor-mediated program for controlling anthocyanin biosynthesis also has effects on formation of specialized cell structures and changes in the plant root architecture. A systems biology approach was developed in tomato (Solanum lycopersicum) for coordinated induction of biosynthesis of anthocyanins, in a tissue- and development-independent manner. A transcription factor couple from Antirrhinum that is known to control anthocyanin biosynthesis was introduced in tomato under control of a dexamethasone-inducible promoter. By application of dexamethasone, anthocyanin formation was induced within 24 h in vegetative tissues and in undifferentiated cells. Profiles of metabolites and gene expression were analyzed in several tomato tissues. Changes in concentration of anthocyanins and other phenolic compounds were observed in all tested tissues, accompanied by induction of the biosynthetic pathways leading from Glc to anthocyanins. A number of pathways that are not known to be involved in anthocyanin biosynthesis were observed to be regulated. Anthocyanin-producing plants displayed profound physiological and architectural changes, depending on the tissue, including root branching, root epithelial cell morphology, seed germination, and leaf conductance. The inducible anthocyanin-production system reveals a range of phenomena that accompanies anthocyanin biosynthesis in tomato, including adaptions of the plants architecture and physiology.

Aliphatic glucosinolates are compounds which occur in high concentrations in Arabidopsis thaliana and other Brassicaceae species. They are important for the resistance of the plant to pest insects. Previously, the biosynthesis of these compounds was shown to be regulated by transcription factors MYB28 and MYB29. We now show that MYB28 and MYB29 are partially redundant, but in the absence of both, the synthesis of all aliphatic glucosinolates is blocked. Untargeted and targeted biochemical analyses of leaf metabolites showed that differences between single and double knock-out mutants and wild type plants were restricted to glucosinolates. Biosynthesis of long-chain aliphatic glucosinolates was blocked by the myb28 mutation, while short-chain aliphatic glucosinolates were reduced by about 50% in both the myb28 and the myb29 single mutants. Most remarkably, all aliphatic glucosinolates were completely absent in the double mutant. Expression of glucosinolate biosynthetic genes was slightly but significantly reduced by the single myb mutations, while the double mutation resulted in a drastic decrease in expression of these genes. Since the myb28myb29 double mutant is the first Arabidopsis genotype without any aliphatic glucosinolates, we used it to establish the relevance of aliphatic glucosinolate biosynthesis to herbivory by larvae of the lepidopteran insect Mamestra brassicae. Plant damage correlated inversely to the levels of aliphatic glucosinolates observed in those plants: Larval weight gain was 2.6 fold higher on the double myb28myb29 mutant completely lacking aliphatic glucosinolates and 1.8 higher on the single mutants with intermediate levels of aliphatic glucosinolates compared to wild type plants.

The flowering plant Arabidopsis thaliana is an important model system for identifying genes and determining their functions. Here we report the analysis of the genomic sequence of Arabidopsis. The sequenced regions cover 115.4 megabases of the 125-megabase genome and extend into centromeric regions. The evolution of Arabidopsis involved a whole-genome duplication, followed by subsequent gene loss and extensive local gene duplications, giving rise to a dynamic genome enriched by lateral gene transfer from a cyanobacterial-like ancestor of the plastid. The genome contains 25,498 genes encoding proteins from 11,000 families, similar to the functional diversity of Drosophila and Caenorhabditis elegans--the other sequenced multicellular eukaryotes. Arabidopsis has many families of new proteins but also lacks several common protein families, indicating that the sets of common proteins have undergone differential expansion and contraction in the three multicellular eukaryotes. This is the first complete genome sequence of a plant and provides the foundations for more comprehensive comparison of conserved processes in all eukaryotes, identifying a wide range of plant-specific gene functions and establishing rapid systemic ways to identify genes for crop improvement.

Metabolic engineering of terpenoids in plants is a fascinating research topic from two main perspectives. On the one hand, the various biological activities of these compounds make their engineering a new tool for improving a considerable number of traits in crops. These include for example enhanced disease resistance, weed control by producing allelopathic compounds, better pest management, production of medicinal compounds, increased value of ornamentals and fruit and improved pollination. On the other hand, the same plants altered in the profile of terpenoids and their precursor pools make a most important contribution to fundamental studies on terpenoid biosynthesis and its regulation. In this review we describe our recent results with terpenoid engineering, focusing on two terpenoid classes the monoterpenoids and sesquiterpenoids. The emerging picture is that engineering of these compounds and their derivatives in plant cells is feasible, although with some requirements and limitations. For example, in terpenoid engineering experiments crucial factors are the subcellular localisation of both the precursor pool and the introduced enzymes, the activity of endogenous plant enzymes which modify the introduced terpenoid skeleton, the costs of engineering in terms of effects on other pathways sharing the same precursor pool and the phytotoxicity of the introduced terpenoids. Finally, we will show that transgenic plants altered in their terpenoid profile exert novel biological activities on their environment, for example influencing insect behaviour.

Application of new sequencing technology has determined targets of MADS-box transcription factors regulating flower development. The results confirm that the key factors form auto-regulatory networks and regulate many target genes directly.

The defensive effect of endogenous trypsin proteinase inhibitors (NaTPIs) on the herbivore Manduca sexta was demonstrated by genetically altering NaTPI production in M. sexta's host plant, Nicotiana attenuata. To understand how this defense works, we studied the effects of NaTPI on M. sexta gut proteinase activity levels in different larval instars of caterpillars feeding freely on untransformed and transformed plants. Second and third instars larvae that fed on NaTPI-producing (WT) genotypes were lighter and had less gut proteinase activity compared to those that fed on genotypes with either little or no NaTPI activity. Unexpectedly, NaTPI activity in vitro assays not only inhibited the trypsin sensitive fraction of gut proteinase activity but also halved the NaTPI-insensitive fraction in third-instar larvae. Unable to degrade NaTPI, larvae apparently lacked the means to adapt to NaTPI in their diet. However, caterpillars recovered at least part of their gut proteinase activity when they were transferred from NaTPI-producing host plants to NaTPI-free host plants. In addition extracts of basal leaves inhibited more gut proteinase activity than did extracts of middle stem leaves with the same protein content. Although larvae can minimize the effects of high NaTPI levels by feeding on leaves with high protein and low NaTPI activity, the host plant's endogenous NaTPIs remain an effective defense against M. sexta, inhibiting gut proteinase and affecting larval performance.

An essential element of any strategy for non-targeted metabolomics analysis of complex biological extracts is the capacity to perform comparisons between large numbers of samples. As the most widely used technologies are all based on mass spectrometry (e.g. GCMS, LCMS), this entails that we must be able to compare reliably and (semi)automatically large series of chromatographic mass spectra from which compositional differences are to be extracted in a statistically justifiable manner. In this paper we describe a novel approach for the extraction of relevant information from multiple full-scan metabolic profiles derived from LC-MS analyses. Specifically-designed software has made it possible to combine all mass peaks on the basis of retention time and m/z values only, without prior identification, to produce a data matrix output which can then be used for multivariate statistical analysis. To demonstrate the capacity of this approach, aqueous methanol extracts from potato tuber tissues of eight contrasting genotypes, harvested at two developmental stages have been used. Our results showed that it is possible to discover reproducibly discriminatory mass peaks related both to the genetic origin of the material as well as the developmental stage at which it was harvested. In addition the limitations of the approach are explored by a careful evaluation of the alignment quality.[PUBLICATION ABSTRACT]

The use of oats in the human diet has decreased over the past 70 years. This is an unfortunate development from the perspective of human health because oats have a high nutritional value and contain many compounds, including β-glucan, polyphenols, vitamins, and unsaturated fatty acids that are able to maintain or may even improve consumer’s health. In addition, oats fit into a gluten-free diet of celiac disease patients because they lack the T-cell stimulating epitopes from wheat, rye, and barley. We focused on the presence of health-related compounds in oats and how their levels vary among varieties in response to the type of soil. Ten oat varieties were grown in the Netherlands in sandy and clay soil and were analyzed for the presence and concentration of healthy compounds (β-glucan, fatty acids, vitamin E, and antioxidant activity), avenin composition, total protein and starch content, and agronomical characteristics. Principal component analysis showed that genetic background influenced the levels of all analyzed components. Protein, starch, β-glucan, and antioxidants were also affected by the type of soil. The obtained results showed that this kind of analysis can be used to profile oat varieties in general and enables the selection of specific varieties with specific compound characteristics.

Abstract only In 2002, Clavibacter michiganensis subsp. michiganensis (Smith) Davis, the causal organism of bacterial canker of tomato (Lycopersicon esculentum), was isolated from two of six commercial asymptomatic tomato seed lots produced on Java in Indonesia. C. michiganensis subsp. michiganensis has not been reported in Indonesia previously. Methods based on the protocol of the International Seed Health Initiative were used to extract and identify the presence of C. michiganensis subsp. michiganensis in tomato seed. C. michiganensis subsp. michiganensis was isolated with dilution plating on the semiselective media D2ANX and mSCM. The identity of the colonies was confirmed by immunofluorescence microscopy, polymerase chain reaction (2), fatty methyl ester analysis, enzyme-linked immunosorbent assay based on monoclonal antibody 103 (1), and a pathogenicity test in which three replicate tomato plants were stem inoculated with 10 8 cells ml -1 . Within 2 weeks, stripes on stems developed that split and exposed reddish brown cavities (stem cankers). The presence of C. michiganensis subsp. michiganensis poses a direct threat on tomato production, which is one of five economically most important vegetable crops in Indonesia. References: (1) A. Alvarez et al. Phytopathology 83:1405, 1993. (2) M. S. Santos et al. Seed Sci. Technol. 25:581, 1997.