Papers by Pierre Benveniste
European journal of biochemistry, Aug 26, 2004
During a search for cDNAs encoding plant sterol acyltransferases, we isolated four full-length cD... more During a search for cDNAs encoding plant sterol acyltransferases, we isolated four full-length cDNAs from Arabidopsis thaliana that encode proteins with substantial identity with animal lecithin : cholesterol acyltransferases (LCATs). The expression of one of these cDNAs, AtLCAT3 (At3g03310), in various yeast strains resulted in the doubling of the triacylglycerol content. Furthermore, a complete lipid analysis of the transformed wild-type yeast showed that its phospholipid content was lower than that of the control (void plasmid-transformed) yeast whereas lysophospholipids and free fatty acids increased. When microsomes from the AtLCAT3-transformed yeast were incubated with di-[1-14C]oleyl phosphatidylcholine, both the lysophospholipid and free fatty acid fractions were highly and similarly labelled, whereas the same incubation with microsomes from the control yeast produced a negligible labelling of these fractions. Moreover when microsomes from AtLCAT3-transformed yeast were incubated with either sn-1- or sn-2-[1-14C]acyl phosphatidylcholine, the distribution of the labelling between the free fatty acid and the lysophosphatidylcholine fractions strongly suggested a phospholipase A1 activity for AtLCAT3. The sn-1 specificity of this phospholipase was confirmed by gas chromatography analysis of the hydrolysis of 1-myristoyl, 2-oleyl phosphatidylcholine. Phosphatidylethanolamine and phosphatidic acid were shown to be also hydrolysed by AtLCAT3, although less efficiently than phosphatidylcholine. Lysophospatidylcholine was a weak substrate whereas tripalmitoylglycerol and cholesteryl oleate were not hydrolysed at all. This novel A. thaliana phospholipase A1 shows optimal activity at pH 6-6.5 and 60-65 degrees C and appears to be unaffected by Ca2+. Its sequence is unrelated to all other known phospholipases. Further studies are in progress to elucidate its physiological role.
Journal of the Chemical Society, 1983
Plant Physiology, Jun 1, 1989
Maize (Zea mays L.) caryopses were grown in the presence of fenpropimorph, a systemic fungicide, ... more Maize (Zea mays L.) caryopses were grown in the presence of fenpropimorph, a systemic fungicide, for 7 days in the dark. Membrane fractions enriched, respectively, in endoplasmic retic- ulum, plasma membrane, and mitochondria were isolated from control and treated maize roots and analyzed for their free sterol, phospholipid, and fatty acid composition. In treated plants, the intracellular distribution of free sterols was dramatically modified both qualitatively and quantitatively. The normally occurring A5sterols disappeared almost completely and were replaced by 9,B,19-cyclopropyl sterols, mainly cycloeucalenol and 24-methyl pollinastanol. These new compounds were found to accumulate in all the membrane fractions in such a way that the endoplasmic reticulum-rich fraction became the richest one in free sterols instead of the plasma membrane. In contrast, the fenpropimorph treatment of maize roots was shown not to affect either the relative proportions or the amounts of the individual phospholipids, but an increase in the unsaturation index of phospholipidfatty acyl chains of the endoplasmic reticulum-rich fraction was observed. The present data suggest that, in higher plant mem- branes, cyclopropyl sterols could play a structural role similar to that of the bulk of A5-sterols. Whereas animal and fungal cells generally contain one major sterol, respectively, cholesterol (1)1 and ergosterol (17), ' Chemical nomenclature: cholesterol (1), cholest-5-en-3,B-ol; 24- methyl cholesterol (2), (24r)-24-methylcholest-5-en-3(3-ol; stigmas- terol (3), (24S)24-ethylcholesta-5,22E-dien-33-ol; sitosterol (4), (24R)-24-ethylcholest-5-en-3f3-ol; isofucosterol (5), stigmasta-5,24 (28)Z-dien-3f-ol; 24-methyl pollinastanol ( ), (24r)-24,14a-di- methyl-9fl, 19-cyclo-5a-cholestan-3#-ol; 24-methylene pollinastanol (7), 14a-methyl-9f,19-cyclo-5a-ergost-24(28)-en-33-ol; 24-ethyl pollinastanol (8), 14a-methyl-9j3, 19-cyclo-5a-stigmastan-3f-ol; obtusi- foliol (9), 4a, 14a-dimethyl-5a-ergosta-8,24(28)-dien-3 (-ol; cycloeucalenol (10), 4a, 14a-dimethyl-9(, 19-cyclo-5a-ergost-24(28)-en-3(-ol; 24-dihydrocycloeucalenol (11), (24R)-24,4a, 14a-trimethyl-9,B, 19-cyclo-5a-cholestan-3,B-ol; 31-norcyclobranol (12), 4a,14a-dimethyl-9,3,19-cyclo-5a-ergost-24(25)-en-3fl-ol; cyclofuntumienol (13), 4a, 14a-dimethyl-93,19-cyclo-5a-stigmast-24(28)Z-en-3,3-ol; cycloar- tenol (14), 4,4,14a-trimethyl-9,B, 19-cyclo-5a-cholest-24-en-3,-ol; 24- methylene cycloartanol (15), 4,4,14a-trimethyl-93, 19-cyclo-5a-ergost-24(28)-en-33-ol; f-amyrin (16), olean-12-en-3,B-ol; ergosterol (17), (24R)-24-methylcholesta-5,7,22E-trien-3,B-ol; fenpropimorph, (R,S)-4-[3-(4-tert-butylphenyl)-2-methyl-propyl]-2,6-dimethylmorpholine.
Over the past 20 years, an increasing number of sterol biosynthesis inhibitors (SBI’s) have been ... more Over the past 20 years, an increasing number of sterol biosynthesis inhibitors (SBI’s) have been developed as fungicides widely used in crop protection or medicine, but also as potential hypocholesterolemic agents in mammals. In common with most eukaryotic organisms, higher plants also possess sterols and here too interference with their biosynthesis have profound biological effects which may lead to the development of new herbicides. Moreover, little is known about the impact of agricultural fungicides on plant sterol biosynthesis and the understanding of the mechanisms controlling their selective toxicity towards the fungus and relative safeness to the plant. Until recently most of SBI’s have been discovered from extensive screening programmes and only a few inhibitors have been rationally designed, particularly in the case of enzymes involved in plant sterol biosynthesis |1,2|.
Plant Science Letters, Apr 1, 1983
The plasma membrane-bound uridine-diphosphate-glucose-sterol-~-D-glucosyltransferase (UDPGSGT) of... more The plasma membrane-bound uridine-diphosphate-glucose-sterol-~-D-glucosyltransferase (UDPGSGT) of etiolated maize coleoptiles is activated by low concentrations (close to the critical micellar concentration (CMC)) of Triton X-100. Treatment of plasma membrane (PM) vesicles with hydroxyl ions or with phospholipase A: resulted in a stimulation of the enzymatic activity and in an elimination of the capacity of the enzyme to be activated by Triton X-100. The action of the phospholipase A2 resulted also in a strong inhibition of the incorporation of uridine diphosphate (UDP) glucose into 6'-acyl steryl-~-D-glucosides (ASG). The results obtained lead to the conclusion that hydroxyl ions and phospholipase A~ can be used in place of detergents to reveal latent enzymatic sites. They bring some further insights into the knowledge of the topology of the UDPGSGT in the transverse plane of the PM vesicles.
Molecular Genetics And Genomics, Dec 1, 1991
A genetic and biochemical characterization is presented of a tobacco mutant that was previously s... more A genetic and biochemical characterization is presented of a tobacco mutant that was previously shown to have an increased sterol content with an accumulation of biosynthetic intermediates. We first show that a precise regulation of the membrane sterol composition occurs in this mutant, via a selective esterification process. Indeed, sterols representing the usual end-products of the biosynthetic pathway are preferably integrated into the membranes as free sterols, whereas most of the intermediates pool is esterified and stored in cytoplasmic lipid droplets. It is further demonstrated that overproduction of sterols by the LABIa4 mutant is due to a single nuclear and semi-dominant mutation. Finally, increase of biosynthesis and esterification of unusual sterols are shown to be responsible for the resistance of LAB1-4 calli to LAB170 250F, the triazole pesticide used to select this mutant. However, differentiated LAB1-4 tissues do not express the resistance trait, suggesting that sterol biosynthesis might not be the only site of action for the triazole at the plant level.
European journal of biochemistry, Jun 1, 1997
Two methyl transfers are involved in the course of plant sterol biosynthesis and responsible for ... more Two methyl transfers are involved in the course of plant sterol biosynthesis and responsible for the formation of 24-alkyl sterols (mainly 24-ethyl sterols) which play major roles in plant growth and development. The first methyl transfer applies to cycloartenol, the second one to 24-methylene lophenol. Five cDNA clones encoding two Arabidopsis thalianu, two Nicotiana tabacum and one Ricinus communis S-adenosyl-L-methionine (AdoMet) sterol methyltransferases (SMT) were isolated. The deduced amino acid sequences of A. thaliana and N. tabacum SMT are about 80% identical in all possible combinations. In contrast they are about 40% identical with the deduced amino acid sequence of R. communis SMT and the published Glycine max sequence. Both A. thaliana and one N. tabacum SMT cDNAs were expressed in a yeast null mutant erg6, deficient in AdoMet zymosterol C24-methyltransferase and containing C24-non-alkylated sterols. In all cases, several 24-ethylidene sterols were synthesized. A thorough study of the sterolic composition of erg6 expressing the A. thaliana cDNA 411 (erg6-4118-pYeDP60) showed 24-methylene and 24-ethylidene derivatives of 4-desmethy1, 4a-methyl and 4,4-dimethyl sterols as well as 24-methyl and 24-ethyl derivatives of 4-desmethyl sterols. The structure of 5a-stigmasta-8, Z-24(24')-dien-3P-o1, the major sterol of transformed yeasts, was demonstrated by 400 MHz 'H NMR. Microsomes from erg-6-42 18-pYeDP60 were shown to possess AdoMet-dependent sterol-C-methyltransferase activity. Delipidated preparations of these microsomes converted cycloartenol into 24-methylene cycloartanol and 24-methylene lophenol into 24-ethylidene lophenol, thus allowing the first identification of a plant sterol-C-methyltransferase cDNA. The catalytic efficiency of the expressed SMT was 17-times higher with 24-methylene lophenol than with cycloartenol. This result provides evidence that the A. thuliana cDNA 41 1 (and most probably the 3 plant SMT cDNAs presenting 80% identity with it) encodes a 24-methylene lophenol-C-24l methyltransferase catalyzing the second methylation step of plant sterol biosynthesis.
Steryl glucosides and acylated steryl glucosides are present with free and esterified sterols in ... more Steryl glucosides and acylated steryl glucosides are present with free and esterified sterols in all plant tissues investigated so far, most probably as components of membrane structures1. The glucosylation of sterols is catalyzed by UDP-glucose sterol s-D-glucosyl transferase (UDPG-SGTase), a plasma membrane bound enzyme of plant cells2. The reaction consists of a glucose transfer from UDP-glucose to a phytosterol with formation of a s-glucosidic linkage between the anomeric carbon of glucose and the 3-hydroxyl group of the sterol1: $$Sterol\,+\,UDP-glucose\,\to \,steryl\,glucoside\,+\,UDP$$ Studies in other laboratories1 and ours3 indicate clearly that UDPG-SGTase is specific for UDP-glucose and natural 4-demethyl sterols.
Biochemical Society Transactions, Feb 1, 1990
Phytochemistry, Oct 1, 1972
Abstract Tissues of Jerusalem Artichoke grown in vitro were incubated in the presence of sodium a... more Abstract Tissues of Jerusalem Artichoke grown in vitro were incubated in the presence of sodium acetate 1- 14 C in the dark and under far red light. Phytosterols were isolated and purified and their specific radio-activities measured. A reproducible increase of the specific radioactivity of sterols was observed for tissues subjected to far red light.
Planta, Jun 1, 1992
The ~,-keto triazole derivative 4,4-dimethyl-1-(2-methoxyphenyl)-l-(1,2,4-triazol-l-yl)-l-penten-... more The ~,-keto triazole derivative 4,4-dimethyl-1-(2-methoxyphenyl)-l-(1,2,4-triazol-l-yl)-l-penten-3-one is toxic to Nicotiana tabacum L. cv. Xanthi plants or cell cultures. Analysis of the sterol composition of treated wild-type plant material demonstrates that this herbicide is an inhibitor of the C-14or-methyl demethylation process in sterol biosynthesis. Selection experiments, consisting of screening large populations of microcalli derived from UV-mutagenized tobacco protoplasts for resistance to a lethal dose (1 mg 9 1-1) of the 7-keto triazole, have resulted in the recovery of two groups of resistant calli. In the first group, selected calli show a sterol composition in the absence or presence of the inhibitor very similar to that of wild-type sensitive calli, whereas in the second group the main feature of the selected calli is a new sterol profile. These calli present an overproduction of sterols with a concomitant esterification of overproduced metabolites, just as it was demonstrated for calli previously selected in our laboratory for resistance to LAB 170250F, a triazole fungicide (Maillot-Vernier et al., 1991, Mol. Gen. Genet. 231, 33-40).
Biochemical Society Transactions, Dec 1, 2000
acid (capric acid) both were good acyl acceptors; there was no difference in incorporation betwee... more acid (capric acid) both were good acyl acceptors; there was no difference in incorporation between the two exogenous substrates. On the other hand, in the absence of added DAG the activity was not reduced, indicating that our microsomal preparation had endogenous saturating DAG and probably the added diolein had no access to the enzyme. However, DAG dependency of the enzyme activity could be demonstrated when enzyme preparations had a small amount of endogenous DAG or were in the presence of detergents [9]. Triton X-100, a non-ionic form detergent, was tested for inhibition of microsomal DAGAT, and when added to the reaction mixture (0.1-0.2%) it reduced about half of the original enzyme activity. With CHAPS (7.5 mM), a zwitterionic detergent, the enzyme was not denatured; at this concentration Wiberg et al. [19] obtained an optimal activity, but a higher concentration of CHAPS (16.2mM) decreased the T A G formation. Nevertheless, CHAPS was found to be the least inhibitory for DAGAT activity, as also reported by Kwanyuen and Wilson [20], and thus it may be useful for enzyme solubilization.
Plant Journal, Mar 1, 1996
A yeast null mutant (erg 3) defective in ERG 3, the gene encoding the C‐5 sterol desaturase requi... more A yeast null mutant (erg 3) defective in ERG 3, the gene encoding the C‐5 sterol desaturase required for ergosterol synthesis was transformed with an Arabidopsis thaliana cDNA library inserted in a yeast vector. Transformants (4×105) were screened for cycloheximide (CH) resistance and 400 possible clones were analyzed to determine their sterol profile. Low levels of ergosterol in addition to Δ7‐ and Δ8‐sterols normally present in erg3 were isolated in three yeast transformants. Characterization of one transformant indicated a cDNA of 1141 bp. Transformation of an erg 3 strain with this plasmid led to CH resistance, nystatin sensitivity and an ergosterol profile. After subcloning in a pBluescript vector and subsequent sequencing, an ORF of 843 bp encoding a possible 281 amino acid polypeptide was deduced. Three histidine‐rich motifs (HX3H, HX2HH and HX2HH) were found in the A. thaliana ORF which are also present in the yeast ERG 3 gene. These histidine‐rich motifs are also characteristic of many membrane‐bound fatty acid desaturases from higher plants. These data strongly suggest that the A. thaliana cDNA encodes Δ7‐sterol‐C‐5‐desaturase.
Plant Journal, May 1, 1995
Nicotiana tabacum protoplasts have been transformed by Agrobacterium tumefaciens containing a T-D... more Nicotiana tabacum protoplasts have been transformed by Agrobacterium tumefaciens containing a T-DNA in which the gene CYP51A1 encoding lanosterol-14-demethylase (LAN14DM) from Saccharomyces cerevisiae is under the control of a cauliflower mosaic virus (CaMV) 35S promoter. Two transformants strongly expressed the LAN14DM as shown by Northern and Western experiments. These transgenic calli were killed by LAB 170250F (LAB) (a phytotoxic fungicide inhibiting both plant obtusifoliol-14-demethylase (OBT14DM) and LAN14DM) but were resistant to gamma-ketotriazole (gamma-kt), a herbicide which has been shown to inhibit OBT14DM but not LAN14DM at a concentration that was lethal to control calli. However, these transgenic calli were killed by mixtures of gamma-kt plus fungicide inhibitors of LAN14DM such as ketoconazole, itraconazole or flusilazole which alone were not effective. Further analysis of the transgenic calli grown in the presence of gamma-kt showed that their delta 5-sterol content was close to that of untreated control calli obtained from protoplasts transformed with control plasmid; this is in agreement with evidence that the LAN14DM expressed from the transgene could bypass the blocked OBT14DM by using the plant substate obtusifoliol. In contrast, control calli when treated with gamma-kt, displayed a sterol content strongly enriched in 14 alpha-methyl sterols and depressed in physiological delta 5-sterols. When the transgenic calli were cultured in mixtures of gamma-kt and LAN14DM inhibitors sterol compositions enriched in 14 alpha-methyl sterols were obtained, reflecting a strong inhibition of both &#39;endogenous&#39; OBT14DM and &#39;exogenous&#39; LAN14DM. Taken together these results show that in tobacco calli transformed with CYP51A1, resistance to a triazole herbicide arises from expression of a functional LAN14DM enzyme; its activity in transgenic tissues creates a bypass of the sterol biosynthetic pathway at the 14-demethylase level when this latter is blocked by an OBT14DM herbicide inhibitor.
Phytochemistry, 1982
Abstract In addition to the previously found ergosta-5, E -23-dien-3β-ol and 5α-ergosta-7, E -23-... more Abstract In addition to the previously found ergosta-5, E -23-dien-3β-ol and 5α-ergosta-7, E -23-dien-3β-ol, the following Δ 23 sterols have been identified in etiolated maize coleoptiles: cyclosadol, 4α, 14α-dimethyl-5α-ergosta-8, E -23-dien-3β-ol, 4α, 14α-dimethyl-9β, 19-cyclo-5α-ergosta-8, E -23-dien-3β-ol and 4α-methyl-5α-ergosta-7, E -23-dien-3β-ol. The incubation of maize coleoptile microsomes in the presence of cycloartenol and of [ 14 C-methyl] S -adenosyl methionine gave a mixture of labelled 24-methylene cycloartanol and cyclosadol. No trace of cyclolaudenol could be detected in these conditions. It is suggested that Δ 23 sterols are products of the C-24 methyltransferase reaction and they probably do not arise from a Δ 24 → Δ 23 isomerization occurring at a later stage of the biosynthesis. The Δ 13 -sterols may play an intermediary role in the biosynthesis of 24-methyl sterols in this plant material.
Lipids, Mar 1, 2000
Higher plant cells contain a mixture of 24-desmethyl, 24-methyl(ene), and 24-ethyl(idene) sterols... more Higher plant cells contain a mixture of 24-desmethyl, 24-methyl(ene), and 24-ethyl(idene) sterols in given proportions according to species but also to cell type. As a first step to investigate the function of such sterol compositions in the physiology of a plant, we have illustrated in the present work the coexistence of two distinct (S)-adenosyl-L-methionine sterol-C24-methyltransferases (SMT) in transgenic Nicotiana tabacum L. Indeed, modulation of the expression of the tobacco gene SMT1-1, which encodes a cycloartenol-C24-methyltransferase, results in variations of the proportion of cycloartenol and a concomitant effect on the proportion of 24-ethyl sterols. Overexpression in tobacco of the Arabidopsis thaliana (L.) Heynh. gene SMT2-1 which encodes a 24-methylene lophenol-C24(1)-methyltransferase, results in a dramatic modification of the ratio of 24-methyl cholesterol to sitosterol associated with a reduced growth, a topic discussed in the present work.
Journal of Biological Chemistry, Oct 1, 2005
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Papers by Pierre Benveniste