Showing papers on "Chalcone synthase published in 2004"
TL;DR: The results give further support for the protective role of flavonoids and hydroxy cinnamic acids against high solar radiation in plants.
Abstract: The effect of solar radiation on flavonoid biosynthesis was studied in bilberry ( Vaccinium myrtillus L.) leaves. Expression of flavonoid pathway genes of bilberry was studied in the upper leaves of bilberry, exposed to direct sunlight, in the shaded leaves growing lower in the same plants and in fruits. Bilberry-specific digoxigenin-dUTP-labeled cDNA fragments of five genes from the general phenylpropanoid pathway coding phenylalanine ammonia-lyase and from the flavonoid pathway coding chalcone synthase, flavanone 3-hydroxylase, dihydroflavonol 4-reductase, and anthocyanidin synthase were used as probes in gene expression analysis. Anthocyanins, catechins, proanthocyanidins, flavonols and hydroxycinnamic acids from the leaves and fruits were identified and quantified using high-performance liquid chromatography combined with a diode array detector. An increase in the expression of the studied flavonoid pathway genes was observed in leaves growing under direct sun exposure. Also, the concentrations of anthocyanins, catechins, flavonols and hydroxycinnamic acids were higher in the leaves exposed to direct sunlight. However, the concentration of polymeric procyanidins was lower in sun-exposed leaves, whereas that of prodelphinidins was slightly increased. The results give further support for the protective role of flavonoids and hydroxy cinnamic acids against high solar radiation in plants. Also, the roles of different flavonoid compounds as a defense against stress caused by sun exposure is discussed.
262 citations
TL;DR: This work presents the first STS crystal structure and identifies, by mutagenic conversion of alfalfa CHS into a functional stilbene synthase, the structural basis for the evolution of STS cyclization specificity in type III polyketide synthase (PKS) enzymes.
239 citations
TL;DR: Increase in pigmentation in the black seed coats was associated with release of the silencing effect specifically on CHS7/CHS8, which occurred at all stages of seed coat development.
Abstract: Chalcone synthase, a key regulatory enzyme in the flavonoid pathway, constitutes an eight-member gene family in Glycine max (soybean). Three of the chalcone synthase (CHS) gene family members are arranged as inverted repeats in a 10-kb region, corresponding to the I locus (inhibitor). Spontaneous mutations of a dominant allele (I or ii) to a recessive allele (i) have been shown to delete promoter sequences, paradoxically increasing total CHS transcript levels and resulting in black seed coats. However, it is not known which of the gene family members contribute toward pigmentation and how this locus affects CHS expression in other tissues. We investigated the unusual nature of the I locus using four pairs of isogenic lines differing with respect to alleles of the I locus. RNA gel blots using a generic open reading frame CHS probe detected similar CHS transcript levels in stems, roots, leaves, young pods, and cotyledons of the yellow and black isolines but not in the seed coats, which is consistent with the dominant I and ii alleles mediating CHS gene silencing in a tissue-specific manner. Using real-time RT-PCR, a variable pattern of expression of CHS genes in different tissues was demonstrated. However, increase in pigmentation in the black seed coats was associated with release of the silencing effect specifically on CHS7/CHS8, which occurred at all stages of seed coat development. These expression changes were linked to structural changes taking place at the I locus, shown to encompass a much wider region of at least 27 kb, comprising two identical 10.91-kb stretches of CHS gene duplications. The suppressive effect of this 27-kb I locus in a specific tissue of the G. max plant represents a unique endogenous gene silencing mechanism.
201 citations
TL;DR: The cloning and coexpression in Escherichia coli of phenylalanine ammonia lyase, cinnamate‐4‐hydroxylase, 4‐coumarate:CoA ligase, and chalcone synthase from the model plant Arabidopsis thaliana are reported, with high‐level production of the flavanone naringenin observed for the first time.
Abstract: Flavonoids are important plant-specific secondary metabolites synthesized from 4-coumaroyl coenzyme A (CoA), derived from the general phenylpropanoid pathway, and three malonyl-CoAs. The synthesis involves a plant type III polyketide synthase, chalcone synthase. We report the cloning and coexpression in Escherichia coli of phenylalanine ammonia lyase, cinnamate-4-hydroxylase, 4-coumarate:CoA ligase, and chalcone synthase from the model plant Arabidopsis thaliana. Simultaneous expression of all four genes resulted in a blockage after the first enzymatic step caused by the presence of nonfunctional cinnamate-4-hydroxylase. To overcome this problem we fed exogenous 4-coumaric acid to induced cultures. We observed high-level production of the flavanone naringenin as a result. We were also able to produce phloretin by feeding cultures with 3-(4-hydroxyphenyl)propionic acid. Feeding with ferulic or caffeic acid did not yield the corresponding flavanones. We have also cloned and partially characterized a new tyrosine ammonia lyase from Rhodobacter sphaeroides. Tyrosine ammonia lyase was substituted for phenylalanine ammonia lyase and cinnamate-4-hydroxylase in our E. coli clones and three different growth media were tested. After 48 h induction, high-level production (20.8 mg L(-1)) of naringenin in metabolically engineered E. coli was observed for the first time.
171 citations
TL;DR: The results indicate the value of VIGS with tandem constructs containing CHS as reporter and a target gene as a tool for examining the function of floral-associated genes.
Abstract: Agrobacterium-mediated infection of petunia (Petunia hybrida) plants with tobacco rattle virus (TRV) bearing fragments of Petunia genes resulted in systemic infection and virus-induced gene silencing (VIGS) of the homologous host genes. Infection with TRV containing a phytoene desaturase (PDS) fragment resulted in reduced abundance of PDS transcripts and typical photobleaching of photosynthetic tissues. Infection with TRV containing a chalcone synthase (CHS) fragment resulted in silencing of anthocyanin production in infected flowers. The silencing phenotype ranged from scattered white spots on the normal purple background to entirely white flowers. Symptoms in the V26 cultivar were a diffuse mosaic, but infection of some purple-flowered commercial cultivars resulted in large white sectors and even entirely white flowers. Abundance of CHS transcripts in the white flowers was less than 4% of that in purple flowers on the same plant. Infection with TRV containing a tandem construct of PDS and CHS resulted in leaf photobleaching and white patterns on the flowers. Transcripts of CHS and PDS were reduced both in leaves and in flowers confirming simultaneous silencing of both genes by the tandem construct. We tested the effects of infection with TRV containing CHS and a fragment of a petunia gene encoding for 1aminocyclopropane-1-carboxylate oxidase (ACO4) Abundance of transcripts encoding ACO4 and ACO1 were reduced (by 5% and 20%, respectively) in infected flowers. Whether the flowers were treated with ACC or pollinated, the white (silenced) flowers or flower sectors produced less ethylene and senesced later than purple (non-silenced) tissues. These results indicate the value of VIGS with tandem constructs containing CHS as reporter and a target gene as a tool for examining the function of floral-associated genes. Abbreviations: ACO, 1-aminocyclopropane-1-carboxylate oxidase; CHS, chalcone synthase; PDS, phytoene desaturase; PTGS, post-transcriptional gene silencing; PVX, potato virus X; TGMV, tomato golden mosaic virus; TMV, tobacco mosaic virus; TRV, tobacco rattle virus; VIGS, virus-induced gene silencing
171 citations
TL;DR: The genetic approach confirms that NO is an important regulatory component in the signaling network of plant defense responses and possibly functions in incompatible plant-pathogen interactions by inhibiting the plant antioxidative machinery and thereby ensuring locally prolonged H2O2 levels.
Abstract: Recent experiments indicate that nitric oxide (NO) plays a pivotal role in disease resistance and several other physiological processes in plants. However, most of the current information about the function of NO in plants is based on pharmacological studies, and additional approaches are therefore required to ascertain the role of NO as an important signaling molecule in plants. We have expressed a bacterial nitric oxide dioxygenase (NOD) in Arabidopsis plants and/or avirulent Pseudomonas syringae pv tomato to study incompatible plant-pathogen interactions impaired in NO signaling. NOD expression in transgenic Arabidopsis resulted in decreased NO levels in planta and attenuated a pathogen-induced NO burst. Moreover, NOD expression in plant cells had very similar effects on plant defenses compared to NOD expression in avirulent Pseudomonas. The defense responses most affected by NO reduction during the incompatible interaction were decreased H2O2 levels during the oxidative burst and a blockage of Phe ammonia lyase expression, the key enzyme in the general phenylpropanoid pathway. Expression of the NOD furthermore blocked UV light-induced Phe ammonia lyase and chalcone synthase gene expression, indicating a general signaling function of NO in the activation of the phenylpropanoid pathway. NO possibly functions in incompatible plant-pathogen interactions by inhibiting the plant antioxidative machinery, and thereby ensuring locally prolonged H2O2 levels. Additionally, albeit to a lesser extent, we observed decreases in salicylic acid production, a diminished development of hypersensitive cell death, and a delay in pathogenesis-related protein 1 expression during these NO-deficient plant-pathogen interactions. Therefore, this genetic approach confirms that NO is an important regulatory component in the signaling network of plant defense responses.
166 citations
TL;DR: It is demonstrated that naturally occurring PTGS plays a key role in expression of a distinctive phenotype in plants and is presented as a simple clear example of the elucidation of the molecular mechanism for viral symptom induction.
Abstract: Most commercial Glycine max (soybean) varieties have yellow seeds because of loss of pigmentation in the seed coat. It has been suggested that inhibition of seed coat pigmentation in yellow G. max may be controlled by homology-dependent silencing of chalcone synthase (CHS) genes. Our analysis of CHS mRNA and short-interfering RNAs provide clear evidence that the inhibition of seed coat pigmentation in yellow G. max results from posttranscriptional rather than transcriptional silencing of the CHS genes. Furthermore, we show that mottling symptoms present on the seed coat of G. max plants infected with some viruses can be caused by suppression of CHS posttranscriptional gene silencing (PTGS) by a viral silencing suppressor protein. These results demonstrate that naturally occurring PTGS plays a key role in expression of a distinctive phenotype in plants and present a simple clear example of the elucidation of the molecular mechanism for viral symptom induction.
138 citations
TL;DR: There is a complex relationship between antioxidant capacity and flavonoids content, suggesting the great participation of other compounds in the antioxidant potential of the plants.
Abstract: The main goal of this study was to generate potato tubers with increased levels of flavonoids and thus modified antioxidant capacities. To accomplish this, the vector carrying multigene construct was prepared and several transgenic plants were generated, all overexpressing key biosynthesis pathway enzymes. The single-gene overexpression or simultaneous expression of genes encoding chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR) resulted in a significant increase of measured phenolic acids and anthocyanins. The increase in phenolic compounds synthesis is accompanied by decreases in starch and glucose levels in transgenic plants. The flavonoids-enriched plants showed improved antioxidant capacity; however, there is a complex relationship between antioxidant capacity and flavonoids content, suggesting the great participation of other compounds in the antioxidant potential of the plants. These other compounds are not yet recognized.
136 citations
TL;DR: In this article, the authors used RNA interference against a gene of chalcone synthase (CHS), a key enzyme for anthocyanin and flavonoid biosynthesis.
107 citations
TL;DR: The fungus induced significantly different lesion lengths in the two clones, indicating that one clone was more resistant to the fungus than the other, and the more resistant clone contained higher starch concentrations before infection that were reduced more quickly after infection before returning to original values.
Abstract: Polyphenolic parenchyma cells (PP cells) in Norway spruce (Picea abies (L.) Karst.) stem phloem play important roles in constitutive and inducible defenses. To determine whether anatomical and molecular changes in PP cells are correlated with tree resistance, we infected two Norway spruce clones with the pathogenic fungus Ceratocystis polonica (Siem.) C. Moreau. The fungus induced significantly different lesion lengths in the two clones, indicating that one clone was more resistant to the fungus (short lesions) than the other (long lesions). After infection, the cross-sectional area of PP cells and their vacuolar polyphenol bodies increased in the three most recent annual rings of PP cells in both clones. The more resistant clone had larger PP cells with denser polyphenol bodies than the less resistant clone, whereas the less resistant clone accumulated relatively more polyphenols after infection. Compared with the less resistant clone, the more resistant clone contained higher starch concentrations before infection that were reduced more quickly after infection before returning to original values. Low transcript levels of chalcone synthase were detected in uninfected tissues of both clones, but the levels increased dramatically after infection. Transcript levels were higher and peaked 6 days earlier in the more resistant clone than in the less resistant clone. The activity of at least one highly basic peroxidase isoform was greatly enhanced after infection, and this increase occurred earlier in the more resistant clone.
97 citations
TL;DR: Results indicate that flavonoid biosynthesis genes from tea are differentially regulated in the developmental stages, and the subtractive cDNA library and EST database described in this study represent a valuable resource for future research aimed at improving economically important secondary metabolic characteristics in crops.
TL;DR: Chimeric ESTs were identified that may represent read-through transcription from a flanking truncated gene into a CHS cluster, generating aberrant CHS RNA molecules that could play a role in CHS gene silencing.
Abstract: The I locus in soybean (Glycine max) corresponds to a region of chalcone synthase (CHS) gene duplications affecting seed pigmentation. We sequenced and annotated BAC clone 104J7, which harbors a dominant i(i) allele from Glycine max 'Williams 82', to gain insight into the genetic structure of this multigenic region in addition to examining its flanking regions. The 103-kb BAC encompasses a gene-rich region with 11 putatively expressed genes. In addition to six copies of CHS, these genes include: a geranylgeranyltransferase type II beta subunit (E.C.2.5.1.60), a beta-galactosidase, a putative spermine and (or) spermidine synthase (E.C.2.5.1.16), and an unknown expressed gene. Strikingly, sequencing data revealed that the 10.91-kb CHS1, CHS3, CHS4 cluster is present as a perfect inverted repeat separated by 5.87 kb. Contiguous arrangement of CHS paralogs could lead to folding into multiple secondary structures, hypothesized to induce deletions that have previously been shown to effect CHS expression. BAC104J7 also contains several gene fragments representing a cation/hydrogen exchanger, a 40S ribosomal protein, a CBL-interacting protein kinase, and the amino terminus of a subtilisin. Chimeric ESTs were identified that may represent read-through transcription from a flanking truncated gene into a CHS cluster, generating aberrant CHS RNA molecules that could play a role in CHS gene silencing.
TL;DR: Using sensitive methods of sequence comparison and fold recognition, genes homologous to chalcone isomerase are identified in all completely sequenced fungi, in slime molds, and in many gammaproteobacteria.
Abstract: Chalcone isomerase, an enzyme in the isoflavonoid pathway in plants, catalyzes the cyclization of chalcone into (2S)-naringenin. Chalcone isomerase sequence family and three-dimensional fold appeared to be unique to plants and has been proposed as a plant-specific gene marker. Using sensitive methods of sequence comparison and fold recognition, we have identified genes homologous to chalcone isomerase in all completely sequenced fungi, in slime molds, and in many gammaproteobacteria. The residues directly involved in the enzyme's catalytic function are among the best conserved across species, indicating that the newly discovered homologs are enzymatically active. At the same time, fungal and bacterial species that have chalcone isomerase-like genes tend to lack the orthologs of the upstream enzyme chalcone synthase, suggesting a novel variation of the pathway in these species.
TL;DR: The full-length cDNA clones for 18 glucosyltransferase (GT) genes were isolated from petal tissue of carnation (Dianthus caryophyllus) bearing various flower colors and three of the 18 were characterized as 3-GT possessing different substrate specificities for flavonoids and anthocyanidin.
Abstract: Yellow petals of carnations contain chalcone 2′-O-glucoside. The glucosylation occurs after the p-coumaroyl CoA and malonyl-CoA condensation reaction by chalcone synthase (CHS), but the enzyme(s) transferring glucose from UDP-glucose to the 2′-OH position of chalcone has not been identified. The full-length cDNA clones for 18 glucosyltransferase (GT) genes were isolated from petal tissue of carnation (Dianthus caryophyllus) bearing various flower colors. The 18 GTs encoded in the cDNAs were enzymatically characterized in an E. coli expression system using chalcone, flavanone, flavone, flavonol and anthocyanidin as substrates. Three of the 18 were characterized as 3-GT possessing different substrate specificities for flavonoids and anthocyanidin and another two GTs catalyzed the transfer of glucose to the 2′-hydroxyl group of chalcone. In addition, these two enzymes glucosylated flavonol (3-OH and 7-OH), flavanone (7-OH), flavone (7-OH) and anthocyanidin (3-OH and 7-OH).
TL;DR: The catalytic diversities of the enzymes provided further mechanistic insights into the type III PKS reactions, and suggested involvement of the CHS-superfamily enzymes in the biosynthesis of long-chain alkyl polyphenols such as urushiol and ginkgolic acid in plants.
TL;DR: It is shown that transcription of the flavonoid 3′-hydroxylase was coordinately regulated with that of chalcone synthase and dihydroflavonol reductase, and expression of these genes was induced within the first 24 h of fungal challenge.
TL;DR: The co-segregation of markers and red color were observed in F2 segregating populations, supporting the conclusion that color difference in red and yellow onions is likely to be due to the lack of an active DFR gene.
Abstract: Anthocyanin, one of the flavonoids, is a primary determinant of red color in onions. Inheritance studies indicate that a single gene determines the color difference between yellow and red onions. In order to establish which gene might be responsible for this color difference, full-length cDNAs of five structural genes: chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and flavonol synthase (FLS) were cloned using degenerate PCR and RACE (Rapid Amplification of cDNA Ends). RT-PCR was carried out for these five genes to examine differential expression between yellow and red colored bulbs. Accumulation of the DFR gene transcript only occurred in red onions. In F3 populations which originated from the cross between yellow and red parents, DFR transcript was detected only in red F3 lines. To design molecular markers for selection of yellow and red DFR alleles, the DFR gene was sequenced from genomic DNA isolated from both types of onions. The genomic DNA sequence revealed the DFR gene consists of six exons and five introns. A PCR-RFLP marker was designed based on 2% polymorphic nucleotide sequence of the DFR gene between yellow and red onions. The co-segregation of markers and red color were observed in F2 segregating populations, supporting the conclusion that color difference in red and yellow onions is likely to be due to the lack of an active DFR gene.
TL;DR: To elucidate gene regulation of flower colour formation, the gene expressions of the enzymes involved in flavonoid biosynthesis were investigated in correlation with their product during floral development in lisianthus.
Abstract: To elucidate gene regulation of flower colour formation, the gene expressions of the enzymes involved in flavonoid biosynthesis were investigated in correlation with their product during floral development in lisianthus. Full-length cDNA clones of major responsible genes in the central flavonoid biosynthetic pathway, including chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoid 3',5'-hydroxylase (F3'5'H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and flavonol synthase (FLS), were isolated and characterized. In lisianthus, the stage of the accumulation of flavonols and anthocyanins was shown to be divided clearly. The flavonol content increased prior to anthocyanin accumulation during floral development and declined when anthocyanin began to accumulate. CHS, CHI, and F3H were necessary for both flavonol and anthocyanin biosynthesis and were coordinately expressed throughout all stages of floral development; their expressions were activated independently at the stages corresponding to flavonol accumulation and anthocyanin accumulation, respectively. Consistent with flavonol and anthocyanin accumulation patterns, FLS, a key enzyme in flavonol biosynthesis, was expressed prior to the expression of the genes involved in anthocyanin biosynthesis. The genes encoding F3'5'H, DFR, and ANS were expressed at later stages, just before pigmentation. The genes responsible for the flavonoid pathways branching to anthocyanins and flavonols were strictly regulated and were coordinated temporally to correspond to the biosynthetic order of their respective enzymes in the pathways, as well as in specific organs. In lisianthus, FLS and DFR, at the position of branching to flavonols and anthocyanins, were supposed to play a critical role in regulation of each biosynthesis.
TL;DR: It was for the first time demonstrated that the diketide-NAC was also a substrate for recombinant polyketide reductase (PKR) from Glycyrrhiza echinata, and converted to the corresponding beta-ketohemithioester.
TL;DR: Nitric oxide acts as a key signal in plant resistance to incompatible pathogens by triggering resistance‐associated hypersensitive cell death and could play a role in pathways leading to systemic acquired resistance.
Abstract: Nitric oxide (NO), first characterized as an endothelium-derived relaxation factor, is involved in diverse cellular processes including neuronal signaling, blood pressure homeostasis, and immune response. Recent studies have also revealed a role for NO as a signaling molecule in plants. As a developmental regulator, NO promotes germination, leaf extension and root growth, and delays leaf senescence and fruit maturation. Moreover, NO acts as a key signal in plant resistance to incompatible pathogens by triggering resistance-associated hypersensitive cell death. In addition, NO activates the expression of several defense genes (e.g. pathogenesis-related genes, phenylalanine ammonialyase, chalcone synthase) and could play a role in pathways leading to systemic acquired resistance.
TL;DR: Control of anthocyanin biosynthesis in anthurium spathe differs from that described for flowers of other species, with DFR a key regulatory point and a complex mix of developmental and environmental control signals.
Abstract: The expression of anthocyanin biosynthesis genes during flower colour development in Anthurium andraeanum (anthurium) was studied. A cDNA library was constructed from mRNA from the anthurium spathe, and full-length cDNA clones identified for the flavonoid biosynthetic enzymes chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS). These were used to measure transcript levels in the spathe during flower development, in cultivars with different flower colours, over the diurnal cycle, and in the spadix. CHS, F3H and ANS were expressed at all stages of spathe and spadix development. However, DFR transcript levels varied significantly between stages, and DFR may represent a key point of regulation. A diurnal rhythm of DFR transcript abundance in the spathe was also observed, with transcript levels high at dawn and dusk and low at noon. Control of anthocyanin biosynthesis in anthurium spathe differs from that described for flowers of other species, with DFR a key regulatory point and a complex mix of developmental and environmental control signals.
TL;DR: The enzyme activities encoded in five cDNAs for chalcone synthase (CHS) homologs from hop showed both naringenin-chalcone and phlorisovalerophenone forming activity, so it is highly possible that flavonoid depends mainly on CHS_H1, while bitter acid biosynthesis depends mostly on VPS and CHS-H1.
Abstract: The enzyme activities encoded in five cDNAs for chalcone synthase (CHS) homologs from hop were investigated Only valerophenone synthase (VPS) and CHS_H1 showed both naringenin-chalcone and phlorisovalerophenone forming activity Narigenin-chalcone production by VPS was much lower than by CHS_H1 Therefore, it is highly possible that flavonoid depends mainly on CHS_H1, while bitter acid biosynthesis depends mainly on VPS and CHS_H1
TL;DR: An Agrobacterium-mediated method was developed to transform pCHS (a pBI121-based expression vector which the β-glucuronidase, GUS, reporter gene in this vector was substituted by the Petunia chalcone synthase, CHS, cDNA) into Echinacea purpurea, the first published study on genetic transformation inEchinacea plants.
TL;DR: There is a need for a complete brassinosteroid pathway in UV-B signalling in plants, as shown in Arabidopsis thaliana, where three mutants deficient in the biosynthetic pathway of brassinolide were attacked and showed reduced levels of mRNA transcripts.
TL;DR: A polyketide synthase was suggested to catalyze the first step of cannabinoid biosynthesis, leading to olivetolic acid, which was detected in the protein extract of Cannabis sativa flowering top.
TL;DR: The focus was diverted to the enzymes mMDH and mCS for further molecular characterization as potentially important determinants of fruit flavour via regulation of the sugar : acid balance and citrate synthase and malate dehydrogenase activities increased substantially during ripening.
Abstract: Salt-extractable proteins from the cell walls of immature and ripe strawberry (Fragaria x ananassa Duch. cv. Elsanta) fruit were separated using two-dimensional polyacrylamide gel electrophoresis. Seven polypeptides (enzymes) were characterized from their N-terminal sequences: (1) glyceraldhyde-3-phosphate dehydrogenase (EC 1.2.1.12); (2) triose phosphate isomerase (TPI; EC 5.3.1.1); (3) mitochondrial malate dehydrogenase (mMDH; EC 1.1.1.37); (4) NADH glutamate dehydrogenase (EC 1.4.1.3); (5) chalcone synthase (ChS; EC 2.3.1.74); (6) mitochondrial citrate synthase (mCS; EC 4.1.3.7); and (7) UDP glucose:flavonoid 3-O-glucosyltransferase (UDPG:FGT; EC 2.4.1.91). The sequenced polypeptides identified only cytosolic proteins, two of which (ChS and UDPG:FGT) had already been identified as being up-regulated in ripening (strawberry) fruit and important contributors to ripe fruit character. Our focus was therefore diverted to the enzymes mMDH and mCS for further molecular characterization as potentially important determinants of fruit flavour via regulation of the sugar : acid balance. Citrate synthase (CS) and malate dehydrogenase (MDH) enzyme activities increased substantially during ripening, as did citrate and malate contents. The increase in CS activity is supported by western blot analysis. One strawberry mCS (Fa-mCS-I) and two mMDH (Fa-mMDH-I and -II) cDNAs were cloned that were 77, 82 and 53% identical (respectively) to sequences from other plant sources. Northern analysis showed that CS and MDH expression did not correlate with enzyme activities and these findings are discussed.
TL;DR: A polyketide synthase has been suggested to play an important role in cannabinoid biosynthesis in Cannabis sativa L. sativa and over-expression of the construct in Escherichia coli M15 resulted in a 45 kDa protein, which has chalcone synthase activity as well as valerophenone synth enzyme activity, a chal cone synthase-like activity.
Patent•
14 Apr 2004TL;DR: In particular, the present invention relates to the combinatorial expression of chalcone synthase (CHS) and/or dihydroflavonol 4-reductase (BAN) in plants to modify the content of condensed tannins.
Abstract: The present invention relates to nucleic acid fragments encoding amino acid sequences for flavonoid biosynthetic enzymes in plants, and the use thereof for the modification of, for example, flavonoid biosynthesis in plants, and more specifically the modification of the content of condensed tannins. In particularly preferred embodiments, the invention relates to the combinatorial expression of chalcone synthase (CHS) and/or dihydroflavonol 4-reductase (BAN) and/or leucoanthocyanidine reductase (LAR) in plants to modify, for example, flavonoid biosynthesis or more specifically the content of condensed tannins.
TL;DR: Chalcononaringenin 2′- O -glucoside (Ch2′G) was found to be the major pigment molecule in the petals of carnations bearing yellow flowers, and probable factors caused to the variation include the amount of substrates supplying the flavonoid biosynthetic pathway, spontaneous isomerization flowing over the CHI step producing flavonol derivatives, and chalcone 2-glucOSyltransferase activity.
TL;DR: Positive Darwinian selection appears to have promoted the divergence of subfamily ABC and subfamily DE and is at least partially responsible for a rate increase following gene duplication in morning glories.
Abstract: Chalcone synthase (CHS) is a key enzyme in the biosynthesis of flavonoides, which are important for the pigmentation of flowers and act as attractants to pollinators. Genes encoding CHS constitute a multigene family in which the copy number varies among plant species and functional divergence appears to have occurred repeatedly. In morning glories (Ipomoea), five functional CHS genes (A–E) have been described. Phylogenetic analysis of the Ipomoea CHS gene family revealed that CHS A, B, and C experienced accelerated rates of amino acid substitution relative to CHS D and E. To examine whether the CHS genes of the morning glories underwent adaptive evolution, maximum-likelihood models of codon substitution were used to analyze the functional sequences in the Ipomoea CHS gene family. These models used the nonsynonymous/synonymous rate ratio (ω = d
N
/d
S
) as an indicator of selective pressure and allowed the ratio to vary among lineages or sites. Likelihood ratio test suggested significant variation in selection pressure among amino acid sites, with a small proportion of them detected to be under positive selection along the branches ancestral to CHS A, B, and C. Positive Darwinian selection appears to have promoted the divergence of subfamily ABC and subfamily DE and is at least partially responsible for a rate increase following gene duplication.