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  • 1
    Electronic Resource
    Electronic Resource
    24-Methyl-25-azacycloartanol, an analog of a carbonium ion high-energy intermediate, is a potent inhibitor of (S)-adenosyl-L-methionine: sterol C-24-methyltransferase in higher plant cells (1981)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 103 (1981), S. 2408-2409 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00399a045
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of 2,3-oxidosqualene cyclases (1992)
    s.l. : American Chemical Society
    Biochemistry 31 (1992), S. 7892-7898 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00149a021
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  • 3
    Electronic Resource
    Electronic Resource
    Sterol overproduction is the biochemical basis of resistance to a triazole in calli from a tobacco mutant (1994)
    Springer
    Planta 194 (1994), S. 295-305 
    Details
    ISSN: 1432-2048
    Keywords: Mutant (tobacco calli) ; Nicotiana ; Sterolbiosynthesis inhibitors ; Triazole resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sterol overproduction is shown to be the biochemical basis of resistance to the triazole LAB 170250F (2-(4-chlorophenyl)-3-phenyl-1-(1H-1,2,4-triazol-1-yl)-2,3-oxidopropane), an inhibitor of cytochrome P450-dependent-obtusifoliol-14α-demethylase, in the tobacco (Nicotiana tabacum L. cv. Xanthi) mutant LAB 1-4. Genetic analysis at the callus level indicates that the resistance and the biochemical phenotypes co-segregate during meiotic recombination and therefore result most probably from the same mutation. Analysis of the intracellular distribution of sterols shows that in LAB 1-4 calli containing tenfold the sterol amount of the wild type, the overproduced metabolites, mainly obtusifoliol, are esterified by fatty acids and stored in hyaloplasmic lipid droplets. Thus, the mutant calli maintain a concentration of free sterols in cell membranes, mainly end-products of the sterol-biosynthesis pathway, which corresponds to physiological requirements, whereas the level of free sterols in the wild-type calli treated with the triazole is too low to ensure viability. We also show that sterol overproduction confers resistance to other phytotoxic sterolbiosynthesis inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197528
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  • 4
    Electronic Resource
    Electronic Resource
    Increased sterol biosynthesis in tobacco calli resistant to a triazole herbicide which inhibits demethylation of 14α-methyl sterols (1992)
    Springer
    Planta 187 (1992), S. 315-321 
    Details
    ISSN: 1432-2048
    Keywords: Herbicide resistance ; Mutant (tobacco calli) ; Nicotiana (protoplasts) ; Sterol biosynthesis ; Triazole herbicide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The γ-keto triazole derivative 4,4-dimethyl-1-(2-methoxyphenyl)-1-(1,2,4-triazol-1-yl)-1-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-14α-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 · 1−1) of the γ-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 metaolites, 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).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195654
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  • 5
    Electronic Resource
    Electronic Resource
    Δ7-Sterol-C5-desaturase: molecular characterization and functional expression of wild-type and mutant alleles (1999)
    Springer
    Plant molecular biology 39 (1999), S. 891-906 
    Details
    ISSN: 1573-5028
    Keywords: sterol ; Δ7-sterol-C5(6)-desaturase ; deficient mutant ; complementation ; Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An Arabidopsis thaliana recessive monogenic mutant (ste1-1) presenting a deficiency of the Δ7-sterol-C5(6)-desaturase step in the sterol pathway has been reported previously [12]. To further characterize ste1-1, Arabidopsis, Nicotiana tabacum and Homo sapiens cDNAs encoding Δ7-sterol-C5(6)-desaturases were isolated and identified on the basis of their ability to restore ergosterol synthesis in erg3, a yeast null mutant whose gene encoding the Δ7-sterol-C5(6)-desaturase was disrupted. Overexpression of the Arabidopsis cDNA driven by a 35S promoter in transgenic ste1-1 plants led to full complementation of the mutant. This result demonstrates that STE1 was the impaired component in the desaturation system. Four independent reverse transcriptions of ste1-1 RNA followed by polymerase chain reactions (RT-PCRs), yielded a single product. Alignment of the wild-type ORF with the RT-PCR derived ste1-1 ORF revealed a single amino acid substitution: Thr-114 in the wild-type is changed to Ile in ste1-1. Expression in erg3 resulted in a 6-fold lowered efficiency of the ste1-1 ORF in complementing the yeast biosynthetic pathway when compared to the wild-type ORF. The presence of this mutation in the mutant ste1-1 genomic sequence (and no additional modification between ste1-1 and wild-type genes) demonstrates that the change of the Thr-114 to Ile is necessary and sufficient to create the leaky allele ste1-1. The occurrence of a hydroxylated amino acid (Thr or Ser) at the position corresponding to Thr-114 in the five Δ7-sterol-C5(6)-desaturases identified so far suggests that this amino acid is important for normal enzymatic function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006113919172
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  • 6
    Electronic Resource
    Electronic Resource
    Genetic study and further biochemical characterization of a tobacco mutant that overproduces sterols (1991)
    Springer
    Molecular genetics and genomics 231 (1991), S. 33-40 
    Details
    ISSN: 1617-4623
    Keywords: Tobacco mutant ; Triazole resistance ; Sterol overproduction ; Steryl esters ; Lipid droplets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 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 LAB1-4 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293818
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  • 7
    Electronic Resource
    Electronic Resource
    Metabolism of dietary Δ8-sterols and 9β, 19-cyclopropyl sterols by Locusta migratoria (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 11 (1989), S. 47-62 
    Details
    ISSN: 0739-4462
    Keywords: Triticum sativum ; fenpropimorph ; steryl esters ; ecdysteroids ; 24-methyl pollinastanol ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Adult female locusts were reared on wheat seedlings (experimental wheat) containing more than 97% of 9,10-cyclopropyl sterols and Δ8-sterols and less than 2% of Δ5-sterols. These insects showed a dramatic decrease in their cholesterol, cholestanol and Δ7-cholestanol content compared with control insects. These changes were more dramatic for steryl esters than for free sterols. Similar results were observed in eggs laid by the insects fed on experimental wheat. The decrease in Δ5-, Δ0- and Δ7-sterols in insects reared on experimental wheat was compensated by a marked accumulation of Δ8-sterols and 9β, 19-cyclopropyl sterols in the free sterol fraction and especially in the steryl ester fractions. The ecdysteroid content of eggs laid by experimental female insects was reduced by up to 80% compared with controls. These and other results suggest that the dietary 9β, 19-cyclopropyl sterols and Δ8-sterols cannot be used by Locusta in place of Δ5-sterols for ecdysteroid biosynthesis. To give support to this hypothesis, the experimental wheat was supplemented with various sterols before being presented to the insects immediately after the first egg laying. When cholesterol, sitosterol, or cholestanol were used as supplements, there was a complete recovery of the ecdysteroid titer in the eggs, a disappearance of 9β, 19-cyclopropyl sterols, and a restoration of the cholesterol content in both the animals and the eggs. Stigmasterol, stigmastanol, and ergosterol were much less efficient in reversing the effects of the experimental wheat. As expected, 9β, 19-cyclopropyl sterols were totally ineffective. These results are discussed in the light of our information on the role played by sterols in insect development and on the structural features required by the sterols to fulfill their role.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940110106
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