Elicitor-induced transcription factors for metabolic reprogramming of secondary metabolism in Medicago truncatula

<p>Abstract</p> <p>Background</p> <p>Exposure of <it>Medicago truncatula </it>cell suspension cultures to pathogen or wound signals leads to accumulation of various classes of flavonoid and/or triterpene defense molecules, orchestrated via a complex signalling network in which transcription factors (TFs) are essential components.</p> <p>Results</p> <p>In this study, we analyzed TFs responding to yeast elicitor (YE) or methyl jasmonate (MJ). From 502 differentially expressed TFs, <it>WRKY </it>and <it>AP2/EREBP </it>gene families were over-represented among YE-induced genes whereas <it>Basic Helix-Loop-Helix </it>(<it>bHLH</it>) family members were more over-represented among the MJ-induced genes. Jasmonate ZIM-domain <it>(JAZ</it>) transcriptional regulators were highly induced by MJ treatment. To investigate potential involvement of <it>WRKY </it>TFs in signalling, we expressed four <it>Medicago WRKY </it>genes in tobacco. Levels of soluble and wall bound phenolic compounds and lignin were increased in all cases. <it>WRKY W109669 </it>also induced tobacco <it>endo-1,3-β-glucanase </it>(<it>NtPR2</it>) and enhanced the systemic defense response to tobacco mosaic virus in transgenic tobacco plants.</p> <p>Conclusion</p> <p>These results confirm that <it>Medicago WRKY </it>TFs have broad roles in orchestrating metabolic responses to biotic stress, and that they also represent potentially valuable reagents for engineering metabolic changes that impact pathogen resistance.</p

A combined functional and structural genomics approach identified an EST-SSR marker with complete linkage to the Ligon lintless-2 genetic locus in cotton (Gossypium hirsutum L.)

<p>Abstract</p> <p>Background</p> <p>Cotton fiber length is an important quality attribute to the textile industry and longer fibers can be more efficiently spun into yarns to produce superior fabrics. There is typically a negative correlation between yield and fiber quality traits such as length. An understanding of the regulatory mechanisms controlling fiber length can potentially provide a valuable tool for cotton breeders to improve fiber length while maintaining high yields. The cotton (<it>Gossypium hirsutum </it>L.) fiber mutation Ligon lintless-2 is controlled by a single dominant gene (<it>Li₂</it>) that results in significantly shorter fibers than a wild-type. In a near-isogenic state with a wild-type cotton line, <it>Li₂</it>is a model system with which to study fiber elongation.</p> <p>Results</p> <p>Two near-isogenic lines of Ligon lintless-2 (<it>Li₂</it>) cotton, one mutant and one wild-type, were developed through five generations of backcrosses (BC₅). An F₂population was developed from a cross between the two <it>Li₂</it>near-isogenic lines and used to develop a linkage map of the <it>Li₂</it>locus on chromosome 18. Five simple sequence repeat (SSR) markers were closely mapped around the <it>Li₂</it>locus region with two of the markers flanking the <it>Li₂</it>locus at 0.87 and 0.52 centimorgan. No apparent differences in fiber initiation and early fiber elongation were observed between the mutant ovules and the wild-type ones. Gene expression profiling using microarrays suggested roles of reactive oxygen species (ROS) homeostasis and cytokinin regulation in the <it>Li₂</it>mutant phenotype. Microarray gene expression data led to successful identification of an EST-SSR marker (NAU3991) that displayed complete linkage to the <it>Li₂</it>locus.</p> <p>Conclusions</p> <p>In the field of cotton genomics, we report the first successful conversion of gene expression data into an SSR marker that is associated with a genomic region harboring a gene responsible for a fiber trait. The EST-derived SSR marker NAU3991 displayed complete linkage to the <it>Li₂</it>locus on chromosome 18 and resided in a gene with similarity to a putative plectin-related protein. The complete linkage suggests that this expressed sequence may be the <it>Li₂</it>gene.</p

Analysis of cDNA libraries from developing seeds of guar (<it>Cyamopsis tetragonoloba </it>(L.) Taub)

<p>Abstract</p> <p>Background</p> <p>Guar, <it>Cyamopsis tetragonoloba </it>(L.) Taub, is a member of the <it>Leguminosae </it>(<it>Fabaceae</it>) family and is economically the most important of the four species in the genus. The endosperm of guar seed is a rich source of mucilage or gum, which forms a viscous gel in cold water, and is used as an emulsifier, thickener and stabilizer in a wide range of foods and industrial applications. Guar gum is a galactomannan, consisting of a linear (1→4)-β-linked D-mannan backbone with single-unit, (1→6)-linked, α-D-galactopyranosyl side chains. To better understand regulation of guar seed development and galactomannan metabolism we created cDNA libraries and a resulting EST dataset from different developmental stages of guar seeds.</p> <p>Results</p> <p>A database of 16,476 guar seed ESTs was constructed, with 8,163 and 8,313 ESTs derived from cDNA libraries I and II, respectively. Library I was constructed from seeds at an early developmental stage (15–25 days after flowering, DAF), and library II from seeds at 30–40 DAF. Quite different sets of genes were represented in these two libraries. Approximately 27% of the clones were not similar to known sequences, suggesting that these ESTs represent novel genes or may represent non-coding RNA. The high flux of energy into carbohydrate and storage protein synthesis in guar seeds was reflected by a high representation of genes annotated as involved in signal transduction, carbohydrate metabolism, chaperone and proteolytic processes, and translation and ribosome structure. Guar unigenes involved in galactomannan metabolism were identified. Among the seed storage proteins, the most abundant contig represented a conglutin accounting for 3.7% of the total ESTs from both libraries.</p> <p>Conclusion</p> <p>The present EST collection and its annotation provide a resource for understanding guar seed biology and galactomannan metabolism.</p

Metabolomics and Gene Identification in Plant Natural Product Pathways

Book chapter on metabolomics and gene identification in plant natural product pathways

A functional genomics approach to (iso)flavonoid glycosylation in the model legume Medicago truncatula

Article on a functional genomics approach to (iso)flavonoid glycosylation in the model legume Medicago truncatula

Genome-wide analysis of phenylpropanoid defence pathways

Article on genome-wide analysis of phenylpropanoid defence pathways

Integrated Metabolite and Transcript Profiling Identify a Biosynthetic Mechanism for Hispidol in Medicago truncatula Cell Cultures1[C][W][OA]

Metabolic profiling of elicited barrel medic (Medicago truncatula) cell cultures using high-performance liquid chromatography coupled to photodiode and mass spectrometry detection revealed the accumulation of the aurone hispidol (6-hydroxy-2-[(4-hydroxyphenyl)methylidene]-1-benzofuran-3-one) as a major response to yeast elicitor. Parallel, large-scale transcriptome profiling indicated that three peroxidases, MtPRX1, MtPRX2, and MtPRX3, were coordinately induced with the accumulation of hispidol. MtPRX1 and MtPRX2 exhibited aurone synthase activity based upon in vitro substrate specificity and product profiles of recombinant proteins expressed in Escherichia coli. Hispidol possessed significant antifungal activity relative to other M. truncatula phenylpropanoids tested but has not been reported in this species before and was not found in differentiated roots in which high levels of the peroxidase transcripts accumulated. We propose that hispidol is formed in cell cultures by metabolic spillover when the pool of its precursor, isoliquiritigenin, builds up as a result of an imbalance between the upstream and downstream segments of the phenylpropanoid pathway, reflecting the plasticity of plant secondary metabolism. The results illustrate that integration of metabolomics and transcriptomics in genetically reprogrammed plant cell cultures is a powerful approach for the discovery of novel bioactive secondary metabolites and the mechanisms underlying their generation

Genomic and Coexpression Analyses Predict Multiple Genes Involved in Triterpene Saponin Biosynthesis in Medicago truncatula[C][W]

This study sought to identify genes involved in the biosynthesis of the triterpene skeleton in Medicago truncatula using a comprehensive gene expression clustering analysis. The UGT73F3 gene was shown to function as a uridine diphosphate glycosyltransferase in the biosynthesis of triterpene saponins