Molecular 'pharming' with plant P450s.
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Cytochrome P-450 Enzyme System↗
Biomedical subjects
C Chapple
Publications and source records attributed to C Chapple.
Modified lignin in tobacco and poplar plants over-expressing the Arabidopsis gene encoding ferulate 5-hydroxylase.
Ferulate 5-hydroxylase (F5H) is a cytochrome P450-dependent monooxygenase that catalyses the hydroxylation of ferulic acid, coniferaldehyde and coniferyl alcohol in the pathways leading to sinapic acid and syringyl lignin biosynthesis. Earlier studies in Arabidopsis have demonstrated that F5H over-expression increases lignin syringyl monomer content and abolishes the tissue-specificity of its deposition. To determine whether this enzyme has a similar regulatory role in plants that undergo secondary growth, we over-expressed the F5H gene in tobacco and poplar. In tobacco, over-expression of F5H under the control of the cauliflower mosaic virus 35S promoter increased lignin syringyl monomer content in petioles, but had no detectable effect on lignification in stems. By contrast, when the cinnamate 4-hydroxylase (C4H) promoter was used to drive F5H expression, there was a significant increase in stem lignin syringyl monomer content. Yields of thioglycolic acid and Klason lignin in C4H-F5H lines were lower than in the wild-type, suggesting that F5H over-expression leads to a reduced deposition or an altered extractability of lignin in the transgenic plants. Histochemical analysis suggested that the novel lignin in C4H-F5H transgenic lines was altered in its content of hydroxycinnamyl aldehydes. Transgenic poplar trees carrying the C4H-F5H transgene also displayed enhanced lignin syringyl monomer content. Taken together, these data show that hydroxylation of guaiacyl-substituted lignin precursors controls lignin monomer composition in woody plants, and that F5H over-expression is a viable metabolic engineering strategy for modifying lignin biosynthesis in forest species.
Arabidopsis↗
NMR characterization of lignins in Arabidopsis altered in the activity of ferulate 5-hydroxylase.
Nuclear magnetic resonance (NMR) of isolated lignins from an Arabidopsis mutant deficient in ferulate 5-hydroxylase (F5H) and transgenic plants derived from the mutant by overexpressing the F5H gene has provided detailed insight into the compositional and structural differences between these lignins. Wild-type Arabidopsis has a guaiacyl-rich, syringyl-guaiacyl lignin typical of other dicots, with prominent beta-aryl ether (beta-O-4), phenylcoumaran (beta-5), resinol (beta-beta), biphenyl/dibenzodioxocin (5-5), and cinnamyl alcohol end-group structures. The lignin isolated from the F5H-deficient fah1-2 mutant contained only traces of syringyl units and consequently enhanced phenylcoumaran and dibenzodioxocin levels. In fah1-2 transgenics in which the F5H gene was overexpressed under the control of the cauliflower mosaic virus 35S promoter, a guaiacyl-rich, syringyl/guaiacyl lignin similar to the wild type was produced. In contrast, the isolated lignin from the fah1-2 transgenics in which F5H expression was driven by the cinnamate 4-hydroxylase promoter was almost entirely syringyl in nature. This simple lignin contained predominantly beta-aryl ether units, mainly with erythro-stereochemistry, with some resinol structures. No phenylcoumaran or dibenzodioxocin structures (which require guaiacyl units) were detectable. The overexpression of syringyl units in this transgenic resulted in a lignin with a higher syringyl content than that in any other plant we have seen reported.
Arabidopsis↗
New routes for lignin biosynthesis defined by biochemical characterization of recombinant ferulate 5-hydroxylase, a multifunctional cytochrome P450-dependent monooxygenase.
The enzymes and genes of the lignin biosynthetic pathway have been studied for several decades, but the gene encoding ferulate 5-hydroxylase (F5H) was cloned only 3 years ago by T-DNA tagging in Arabidopsis. To characterize the enzyme in detail, we have expressed F5H in yeast. According to current models of the phenylpropanoid pathway, F5H catalyzes the hydroxylation of ferulate to 5-hydroxyferulate; however, our studies indicate that the enzyme also uses coniferaldehyde and coniferyl alcohol as substrates. Unexpectedly, the K(m) values measured for the latter two substrates are three orders of magnitude lower than that measured for ferulic acid, suggesting that in lignifying tissues, syringyl monomers may be derived from their guaiacyl counterparts by hydroxylation and subsequent methylation. Thus, F5H may function later in the lignin biosynthetic pathway than was originally proposed. To further test this model, recombinant F5H was incubated together with ferulic acid, coniferaldehyde, or coniferyl alcohol in the presence of native or recombinant Arabidopsis caffeic acid/5-hydroxyferulic acid O-methyltransferase and [(14)C]S-adenosylmethionine. In all cases, the corresponding radiolabeled sinapyl derivatives were synthesized, indicating that the necessary enzymes required for this pathway are present in Arabidopsis. Taken together, these data suggest that the previously accepted pathway for lignin biosynthesis is likely to be incorrect.
Arabidopsis↗
The pharmacological treatment of urinary incontinence.
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Adrenergic alpha-Antagonists↗
The responsiveness of the ICSmale questionnaire to outcome: evidence from the ICS-'BPH' study.
OBJECTIVE: To evaluate the responsiveness of the ICSmale questionnaire to the outcome of treatments for lower urinary tract symptoms (LUTS). PATIENTS AND METHODS: Consecutive men aged >45 years attending 23 urology centres in 12 countries, with symptoms suggestive of bladder outlet obstruction secondary to benign prostatic hyperplasia (BPH), were recruited to Phase I of the International Continence Society (ICS)-'BPH' study. In Phase II of the ICS-'BPH' study, 355 men in 15 centres in nine countries were followed up, having proceeded to treatment according to clinical practice. All men completed the ICS-'BPH' study questionnaire at baseline and follow-up, including the ICSmale which concerns LUTS and related problems. RESULTS: Patients included in Phase II were similar to those in Phase I according to age and levels of baseline symptoms. Patients received a range of treatments: 32% TURP, 29% drug therapies, 20% watchful waiting, 9% minimally invasive therapies and 10% 'others' (including open prostatectomy). For patients who underwent TURP, most LUTS, including voiding and filling symptoms, were highly statistically significantly better at follow-up than at baseline (P<0.0001). For drug, minimally invasive and 'other' treatments, fewer LUTS were highly statistically significantly better. For those undergoing watchful waiting, no symptoms were significantly different between baseline and follow-up. CONCLUSION: The ICSmale questionnaire, in addition to being psychometrically valid and reliable, is responsive to change in outcome.
Age Factors↗
Factors involved in the success of antimuscarinic treatment.
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Attitude to Health↗
Regulation of ferulate-5-hydroxylase expression in Arabidopsis in the context of sinapate ester biosynthesis.
Sinapic acid is an intermediate in syringyl lignin biosynthesis in angiosperms, and in some taxa serves as a precursor for soluble secondary metabolites. The biosynthesis and accumulation of the sinapate esters sinapoylglucose, sinapoylmalate, and sinapoylcholine are developmentally regulated in Arabidopsis and other members of the Brassicaceae. The FAH1 locus of Arabidopsis encodes the enzyme ferulate-5-hydroxylase (F5H), which catalyzes the rate-limiting step in syringyl lignin biosynthesis and is required for the production of sinapate esters. Here we show that F5H expression parallels sinapate ester accumulation in developing siliques and seedlings, but is not rate limiting for their biosynthesis. RNA gel-blot analysis indicated that the tissue-specific and developmentally regulated expression of F5H mRNA is distinct from that of other phenylpropanoid genes. Efforts to identify constructs capable of complementing the sinapate ester-deficient phenotype of fah1 mutants demonstrated that F5H expression in leaves is dependent on sequences 3' of the F5H coding region. In contrast, the positive regulatory function of the downstream region is not required for F5H transcript or sinapoylcholine accumulation in embryos.
Alleles↗
Role of alpha1-adrenoceptors in the future treatment of urological diseases.
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Adrenergic alpha-1 Receptor Antagonists↗
Lignin monomer composition is determined by the expression of a cytochrome P450-dependent monooxygenase in Arabidopsis.
The phenylpropanoid pathway provides precursors for the biosynthesis of soluble secondary metabolites and lignin in plants. Ferulate-5-hydroxylase (F5H) catalyzes an irreversible hydroxylation step in this pathway that diverts ferulic acid away from guaiacyl lignin biosynthesis and toward sinapic acid and syringyl lignin. This fact led us to postulate that F5H was a potential regulatory step in the determination of lignin monomer composition. To test this hypothesis, we have used Arabidopsis to examine the impact of F5H overexpression. Arabidopsis is a useful model system in which to study lignification because in wild-type plants, guaiacyl and syringyl lignins are deposited in a tissue-specific fashion, while the F5H-deficient fah1 mutant accumulates only guaiacyl lignin. Here we show that ectopic overexpression of F5H in Arabidopsis abolishes tissue-specific lignin monomer accumulation. Surprisingly, overexpression of F5H under the control of the lignification-associated cinnamate-4-hydroxylase promoter, but not the commonly employed cauliflower mosaic virus 35S promoter, generates a lignin that is almost entirely comprised of syringylpropane units. These experiments demonstrate that modification of F5H expression may enable engineering of lignin monomer composition in agronomically important plant species.
Journal Article↗
Plant cell walls as targets for biotechnology.
Plants are the sources of major food, feed, and fiber products that are used globally. This past year has seen advances in our understanding of the enzymes that modify wall architecture, the cloning of the first cellulose synthase gene, and revisions to the lignin biosynthetic pathway. These discoveries have facilitated the development of new strategies to alter cell wall properties in transgenic plants.
Biotechnology↗
Latest developments in the field of neurotransmitters.
Receptors involved in neurotransmission are an important target for drug therapy and the identification and development of receptor-specific compounds is an essential part of contemporary drug development. Antagonists acting at detrusor muscarinic receptors and prostatic adrenergic receptors are now established therapies for the treatment of bladder instability and benign prostatic hyperplasia, respectively. Future developments await the results of basic pathophysiological studies to establish the role of classical and nonadrenergic, noncholinergic neurotransmission in the development and maintenance of diseases of the lower urinary tract. With the development of better pharmacological tools and molecular biological techniques, receptor properties are likely to be found to be tissue-specific, making the development of drugs with true tissue specificity and fewer side effects a reality.
Female↗
Mutants of Arabidopsis thaliana with altered cell wall polysaccharide composition.
To analyze the synthesis, structure and function of the plant cell wall by a genetic approach, 5200 chemically mutagenized Arabidopsis plants were screened for changes in the monosaccharide composition of hydrolyzed cell wall material by gas chromatography of alditol acetates This screening procedure identified 23 mutant lines representing 11 different loci designated mur1 to mur11. The mur lines fall into essentially three groups: (1) complete absence of a monosaccharide, (2) significant reduction in the amount of a single monosaccharide, and (3) complex alterations in the relative amounts of several monosaccharides. All mutants in the first category represent alleles of the mur1 locus, and are deficient in the de novo synthesis of fucose. Mutants with reductions in a single monosaccharide have been identified for fucose (mur2, mur3), arabinose (mur4, mur5, mur6, mur7), and rhamnose (mur8). Mutants with complex changes in monosaccharide composition are represented by the mur9, mur10 and mur11 loci. Most of the mutant lines did not show obvious morphological or physiological alterations; however, lines mur1, mur9 and mur10 co-segregated with reduced vigor or dwarfism of the plants. These results demonstrate the feasibility of identifying plants with altered cell wall compositions via a biochemical screening procedure. The availability of these mutants provides novel opportunities to study the functions of cell wall polysaccharides, gain insight into the biosynthesis of cell wall material, and clone cell wall-related genes.
Arabidopsis↗
Prolonged survival of human spermatozoa when co-incubated with epididymal cell cultures.
Human epididymal tissue was recovered from 11 patients undergoing orchidectomy without anti-androgen treatment. Everted epithelial fragments from the caput and corpus epididymis of six patients were successfully cultured in a modified RPMI 1640 medium supplemented with HEPES and androgens for up to 110 days (mean 56 +/- 28) in 5% CO(2) in air at 37 degrees C. Epithelial cells from human oviduct and non-reproductive tract cells (breast epithelial cells, fibroblasts) were also cultured for comparison. The proportion of epididymal epithelial cells in primary cultures assessed by immunofluorescent localization using a cytokeratin monoclonal antibody was shown to be >70% for the first 6-8 weeks of culture. Light and electron microscopy indicated that epithelial cells maintained polarity and some normal morphology during the culture period. Washed epididymal or ejaculated spermatozoa prepared by a 'swim-up' procedure were co-incubated (i) directly with epididymal cells in culture wells, (ii) in 12 mm Millicell inserts within culture wells, thereby preventing contact of spermatozoa with culture cells; and (iii) in culture medium alone. A significant proportion of spermatozoa in direct contact with culture cells or in Millicell inserts were viable after 6 days of co-incubation (30-45%) and exhibited progressive motility, while all spermatozoa in medium alone were non-motile by 3 days. Using computer-assisted sperm analysis it was shown that the progressive motility of viable spermatozoa decreased gradually for the first 5 days in culture and then remained constant (approximately 30 microm/s, average path velocity). After 12 days of co-incubation, 15 +/- 4% of spermatozoa in direct contact with epithelial cells remained motile; in one experiment, a few spermatozoa (<1%) were motile at 17 days. Light and electron microscope observations indicated that prolonged sperm survival was associated with close apposition of spermatozoa (by equatorial segment) to the apical membrane of epithelial cells. Oviductal epithelial cells were also beneficial for sperm survival, but other cell types had no effect.
Adult↗
Cinnamate-4-hydroxylase expression in Arabidopsis. Regulation in response to development and the environment.
Cinnamate-4-hydroxylase (C4H) is the first Cyt P450-dependent monooxygenase of the phenylpropanoid pathway. To study the expression of this gene in Arabidopsis thaliana, a C4H cDNA clone from the Arabidopsis expressed sequence tag database was identified and used to isolate its corresponding genomic clone. The entire C4H coding sequence plus 2.9 kb of its promoter were isolated on a 5.4-kb HindIII fragment of this cosmid. Inspection of the promoter sequence revealed the presence of a number of putative regulatory motifs previously identified in the promoters of other phenylpropanoid pathway genes. The expression of C4H was analyzed by RNA blot hybridization analysis and in transgenic Arabidopsis carrying a C4H-beta-glucuronidase transcriptional fusion. C4H message accumulation was light-dependent, but was detectable even in dark-grown seedlings. Consistent with these data, C4H mRNA was accumulated to light-grown levels in etiolated det1-1 mutant seedlings. C4H is widely expressed in various Arabidopsis tissues, particularly in roots and cells undergoing lignification. The C4H-driven beta-glucuronidase expression accurately reflected the tissue-specificity and wound-inducibility of the C4H promoter indicated by RNA blot hybridization analysis. A modest increase in C4H expression was observed in the tt8 mutant of Arabidopsis.
Amino Acid Sequence↗
Antisense suppression of 4-coumarate:coenzyme A ligase activity in Arabidopsis leads to altered lignin subunit composition.
The phenylpropanoid enzyme 4-coumarate:coenzyme A ligase (4CL) is considered necessary to activate the hydroxycinnamic acids for the biosynthesis of the coniferyl and sinapyl alcohols subsequently polymerized into lignin. To clarify the role played by 4CL in the biosynthesis of the guaiacyl (G) and syringyl (S) units characteristic of angiosperm lignin, we generated 4CL antisense Arabidopsis lines having as low as 8% residual 4CL activity. The plants had decreases in thioglycolic acid-extractable lignin correlating with decreases in 4CL activity. Nitrobenzene oxidation of cell walls from bolting stems revealed a significant decrease in G units in 4CL-suppressed plants; however, levels of S lignin units were unchanged in even the most severely 4CL-suppressed plants. These effects led to a large decrease in the G/S ratio in these plants. Our results suggest that an uncharacterized metabolic route to sinapyl alcohol, which is independent of 4CL, may exist in Arabidopsis. They also demonstrate that repression of 4CL activity may provide an avenue to manipulate angiosperm lignin subunit composition in a predictable manner.
Arabidopsis↗
The ICS-'BPH' Study: the psychometric validity and reliability of the ICSmale questionnaire.
OBJECTIVE: To assess the validity and reliability of the ICSmale questionnaire developed for the International Continence Society-'Benign Prostatic Hyperplasia' (ICS-'BPH') study. PATIENTS AND METHODS: Urology departments in 12 countries recruited 1271 consecutive men > 45 years old, with lower urinary tract symptoms and possible benign prostatic obstruction, to the ICS-'BPH' study (the clinical group); 423 ambulent men were recruited from a general practice in the UK to provide a community group. Each individual was asked to complete the wide-ranging ICSmale questionnaire, comprising questions concerned with urinary symptoms, the bother they cause, and issues of quality of life and sexual function. Content, construct and criterion validity of the symptom and problem questions were assessed by interviews with patients and urologists, testing hypotheses within sub-studies, and in relation to frequency-volume diaries and uroflowmetry. Reliability was assessed by measures of internal consistency and a test-retest analysis. RESULTS: The ICSmale questionnaire was easy to complete. It was clearly able to differentiate between men in clinical and community populations, and detected the expected positive age gradient for most symptoms in the community group. There was reasonable agreement between relevant parts of the questionnaire and frequency-volume charts when a relatively flexible approach was taken, but there was a very poor relationship between questions assessing strength of stream and the results of uroflowmetry. Internal consistency was high, and overall the questionnaire demonstrated good test-retest reliability. CONCLUSION: The self-completed ICSmale questionnaire had high levels of psychometric validity and reliability.
Aged↗
Sinapic acid ester metabolism in wild type and a sinapoylglucose-accumulating mutant of arabidopsis.
Sinapoylmalate is one of the major phenylpropanoid metabolites that is accumulated in the vegetative tissue of Arabidopsis thaliana. A thin-layer chromatography-based mutant screen identified two allelic mutant lines that accumulated sinapoylglucose in their leaves in place of sinapoylmalate. Both mutations were found to be recessive and segregated as single Mendelian genes. These mutants define a new locus called SNG1 for sinapoylglucose accumulator. Plants that are homozygous for the sng1 mutation accumulate normal levels of malate in their leaves but lack detectable levels of the final enzyme in sinapate ester biosynthesis, sinapoylglucose:malate sinapoyltransferase. A study of wild-type and sng1 seedlings found that sinapic acid ester biosynthesis in Arabidopsis is developmentally regulated and that the accumulation of sinapate esters is delayed in sng1 mutant seedlings.
Arabidopsis↗