Inhibitors of sterol biosynthesis and growth in plants and fungi

Burden, Raymond S.; Cooke, David T.; Carter, Geoffrey A.

doi:10.1016/s0031-9422(00)97862-2

Cited by 113 publications

(55 citation statements)

References 104 publications

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“…This accumulation resulted in a decreased amount of D 5 -sterols such as campesterol, sitosterol, and stigmasterol. The sterol biosynthetic pathway inferred from the sterol profile of cyp51A2-3 is shown in Figure 7 and is fully in accordance with the previous work in which plants were treated with triazole derivatives, inhibitors of obtusifoliol 14a-demethylase (Burden et al, 1989;Schaller et al, 1993). The results shown in Table I indicate that cyp51A2-3 is depleted of the pathway end products such as brassicasterol, cholesterol, 24-methylene cholesterol, campesterol, isofucosterol, sitosterol, and stigmasterol, when compared to the wild type.…”

Section: Cyp51a2-3 Mutants Accumulate Obtusifoliol and 14a-methyl Stesupporting

confidence: 87%

Arabidopsiscyp51Mutant Shows Postembryonic Seedling Lethality Associated with Lack of Membrane Integrity

et al. 2005

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CYP51 exists in all organisms that synthesize sterols de novo. Plant CYP51 encodes an obtusifoliol 14a-demethylase involved in the postsqualene sterol biosynthetic pathway. According to the current gene annotation, the Arabidopsis (Arabidopsis thaliana) genome contains two putative CYP51 genes, CYP51A1 and CYP51A2. Our studies revealed that CYP51A1 should be considered an expressed pseudogene. To study the functional importance of the CYP51A2 gene in plant growth and development, we isolated T-DNA knockout alleles for CYP51A2. Loss-of-function mutants for CYP51A2 showed multiple defects, such as stunted hypocotyls, short roots, reduced cell elongation, and seedling lethality. In contrast to other sterol mutants, such as fk/hydra2 and hydra1, the cyp51A2 mutant has only minor defects in early embryogenesis. Measurements of endogenous sterol levels in the cyp51A2 mutant revealed that it accumulates obtusifoliol, the substrate of CYP51, and a high proportion of 14a-methyl-D 8 -sterols, at the expense of campesterol and sitosterol. The cyp51A2 mutants have defects in membrane integrity and hypocotyl elongation. The defect in hypocotyl elongation was not rescued by the exogenous application of brassinolide, although the brassinosteroid-signaling cascade is apparently not affected in the mutants. Developmental defects in the cyp51A2 mutant were completely rescued by the ectopic expression of CYP51A2. Taken together, our results demonstrate that the Arabidopsis CYP51A2 gene encodes a functional obtusifoliol 14a-demethylase enzyme and plays an essential role in controlling plant growth and development by a sterol-specific pathway.Sterols are ubiquitous among most eukaryotic organisms. Bulk sterols, such as cholesterol in animals, ergosterol in yeast (Saccharomyces cerevisiae), and sitosterol in plants, serve to regulate membrane fluidity and permeability and indirectly affect the activity and distribution of integral membrane proteins, including enzymes, ion channels, and signal transduction components (Hartmann, 1998). These sterols also serve as precursors for bioactive molecules, such as mammalian steroid hormones, plant brassinosteroid (BR) hormones, and insect ecdysteroids to control developmental processes (Clouse, 2000). BRs are plant hormones that have important roles in plant development, including cell elongation, division, vascular differentiation, senescence, and stress responses (Clouse and Sasse, 1998). Plant sterols are also substrates for the synthesis of a wide range of secondary metabolites (Hartmann, 1998). Recently, the implication of sitosterol glucoside in the synthesis of cellodextrins has been proposed (Peng et al., 2002), and a link between sterol biosynthesis and cellulose production has been further documented (Schrick et al., 2004a).Plant sterols derive from cycloartenol via a series of reactions, including methylation, reduction, isomerization, and desaturation. The molecular genetic and biochemical analyses using Arabidopsis (Arabidopsis thaliana) mutants for genes encoding sterol biosynthe...

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Section: Cyp51a2-3 Mutants Accumulate Obtusifoliol and 14a-methyl Stesupporting

confidence: 87%

Arabidopsiscyp51Mutant Shows Postembryonic Seedling Lethality Associated with Lack of Membrane Integrity

et al. 2005

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“…In summary, the identification of phytosterols in P. carinii is significant because it provides further evidence for classifying the organism as a fungus and could be used diagnostically to indicate the presence of the organism. Furthermore, the plant-like character of the sterols suggests possible new targets for drug development on the basis of differences in sterol biosynthetic pathways between plants and fungi (5). Finally, given the difficulties associated with growing this organism in vitro, this information may provide insight into nutritional supplements that could enhance growth in culture.…”

Section: Resultsmentioning

confidence: 99%

Phytosterols are present in Pneumocystis carinii

Furlong

Samia

Rose

et al. 1994

Antimicrob Agents Chemother

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Although originally classified as a protozoan, Pneumocystis carinii is now considered to have fungal characteristics. Drugs typically used for the treatment of fungal infections target ergosterol. Because P. carinii is an important pathogen in AIDS and other immunocompromised patients, knowledge of the sterol content of this organism may be useful as a basis for developing new treatment strategies or for improving diagnosis. P. carinii organisms were harvested from infected rat lungs and were purified by filtration. Control preparations from uninfected animals were identically prepared. Lipids were extracted from the organisms and control preparations and were separated into neutral lipid, glycolipid, and phospholipid fractions by silicic acid chromatography. The neutral lipid fraction was further treated by alkaline hydrolysis and was analyzed by reversed-phase high-pressure liquid chromatography (HPLC), gas chromatography (GC), and GC-mass spectrometry (GC-MS). As shown by HPLC, the neutral lipid fraction from infected rats contained a minimum of six peaks, while in control preparations a single peak with a retention time identical to that of cholesterol was observed. The predominant sterol in these preparations was positively identified by GC-MS as cholesterol and constituted 80 to 90% of the total. The remaining peaks had relative retention times similar to those of phytosterols by both HPLC and GC, and the similarity of these sterols to those derived from plants and fungi was confirmed by MS. Ergosterol, however, was not present. These results provide further evidence for a close phylogenetic relationship between P. carinii and fungi and suggest that these sterols could be used as targets for drug development and for improving diagnosis.Pneumocystis carinii is one of the leading causes of opportunistic infection in AIDS patients (30). Despite the importance of this microorganism as an opportunistic pathogen, much basic information about the parasite is lacking. While originally classified phylogenetically as a protozoan, analyses of P. carinii DNA and mitochondrial and rRNA sequences have generally shown a higher degree of homology to the mitochondrial and rRNA sequences of fungi (yeasts) than to those of protozoa (9,13,27,31,34,35). The exact relationship remains to be determined. Analyses of 5S RNA have suggested a somewhat close phylogenetic relationship to members of the Rhizopoda-Myxomycota-Zygomycota group of "protista fungi." Other studies have suggested similarities to Saccharomyces, Candida, and Neurospora spp. and "red yeast" fungi. In general, the arguments in favor of classifying P. carinii as a protozoan are the amoeboid appearance of the trophic form, susceptibility to antiprotozoal drugs such as pentamidine isethionate or trimethoprim-sulfamethoxazole, insusceptibility to antifungal drugs such as amphotericin B, and the lack of ergosterol in Pneumocystis cell membranes. Arguments in favor of including P. carinii among the fungi include similarities of the sporogenous state to ascospore format...

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“…It is also possible that some growth can occur independently of GAs. The complete inhibition of growth at 100 uM tetcyclacis may partially be due to the inhibition of other processes than GA biosynthesis, such as sterol biosynthesis, which is known to be inhibited by high concentrations of both tetcyclacis and triapenthenol (3,16). Since the retardants also block the oxidation of abscisic acid to phaseic acid (25), at least part ofthe growth inhibition could conceivable be due to accumulation of abscisic acid.…”

Section: A-amylase Productionmentioning

confidence: 99%

ent-Kaurene Biosynthesis in Germinating Barley (Hordeum vulgare L., cv Himalaya) Caryopses and Its Relation to α-Amylase Production

Großelindemann¹,

Je²,

Stöckl³

et al. 1991

Plant Physiol.

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ent-Kaurene biosynthesis as a prerequisite for gibberellin (GA) biosynthesis was studied in germinating Hordeum vulgare L., cv Himalaya caryopses and correlated, in time, with the appearance of a-amylase activity. The rate of ent-kaurene biosynthesis was estimated by inhibiting its further metabolism with plant growth retardants (triapenthenol or tetcyclacis) and measuring its accumulation by isotope dilution using combined gas chromatographymass spectrometry. In the inhibitor-treated caryopses, ent-kaurene accumulation began approximately 24 hours after imbibition and proceeded at a rate of about I to 2 picomoles per hour per caryopsis, depending on the batch of seeds. In the absence of inhibitor, ent-kaurene did not accumulate, indicating that it is normally turned over rapidly, presumably to further intermediates of the GA biosynthesis pathway and eventually to GAs. entKaurene accumulation occurred almost exclusively in the shoot, which is, therefore, probably the site of biosynthesis. a-Amylase production began between 30 and 36 hours after imbibition and, thus, correlated well with de novo GA biosynthesis, as estimated from ent-kaurene accumulation. However, inhibition of ent-kaurene oxidation by plant growth retardants did not reduce the aamylase production significantly, although it did reduce shoot elongation. We conclude that ent-kaurene is produced in the shoot and is continuously converted to GA, which is essential for normal shoot elongation, but not for the production of a-amylase in the aleurone layer.Paleg (15) and Yomo (23) discovered independently that GA3 could substitute for the embryo in initiating a-amylase formation in germinating barley grains. This finding and the demonstration by Chrispeels and Varner (4) that isolated aleurone layers produced a-amylase in response to added GA3 led to the well-known hypothesis that GA3 produced in the embryo diffuses to the aleurone tissue where it induces the formation of a-amylase and other hydrolytic enzymes. The induction of a-amylase in the aleurone layer in response to XSupported by grants from the Deutsche Forschungsgemeinschaft. 2Present address: Instand e.V., Johannes-Weyer-Str.

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Inhibitors of sterol biosynthesis and growth in plants and fungi

Cited by 113 publications

References 104 publications

Arabidopsiscyp51Mutant Shows Postembryonic Seedling Lethality Associated with Lack of Membrane Integrity

Arabidopsiscyp51Mutant Shows Postembryonic Seedling Lethality Associated with Lack of Membrane Integrity

Phytosterols are present in Pneumocystis carinii

ent-Kaurene Biosynthesis in Germinating Barley (Hordeum vulgare L., cv Himalaya) Caryopses and Its Relation to α-Amylase Production

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