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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Dark germinated Arabidopsis thaliana Ler seedlings grown on medium with the commonly used imidazole-type fungicide imazalil (IMA) resemble de-etiolated (det) brassinosteroid-deficient mutants. IMA hampers cell elongation in the hypocotyl, but stimulates radial expansion during dark growth. This phenotype could partially be restored by simultaneous addition of 24-epibrassinolide (EBR). A complete restoration of the hypocotyl length could only be achieved by combining EBR and gibberellic acid. As Arabidopsis thaliana etr1-3 de-etiolates on IMA containing medium in the dark, in the same dose-dependent manner as the wild type, its effects cannot be attributed to the induction of extra ethylene production. Studies with A. thaliana seedlings expressing CPD::GUS show that IMA up-regulates the expression of CPD, which encodes a key cytochrome P450 enzyme in the brassinosteroid (BR)-biosynthesis pathway. This effect is reverted by EBR, indicating that the up-regulation of CPD by IMA might result from the lack of end product brassinolide. Together these data suggest that, in Arabidopsis, one of the effects of IMA is an inhibition of BR-biosynthesis. IMA is an available and cheap agrochemical that might be a valuable tool for future brassinosteroid research.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Key words: 1-Aminocyclopropane-1-carboxylate synthase – Differential gene expression – Ethylene – Indole-3-acetic acid –Lupinus (ethylene) – Multigene family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. 1-Aminocyclopropane-1-carboxylate (ACC) synthase (ACS; EC 4.4.1.14) is the key regulatory enzyme of the ethylene biosynthetic pathway and is encoded by a multigene family in Arabidopsis thaliana, tomato, mung bean and other plants. Southern blot analysis revealed the existence of at least five ACS genes in white lupin (Lupinus albus L.) genome. Four complete and one partial sequences representing different ACS genes were cloned from the lupin genomic library. The levels of expression of two of the genes, LA-ACS1 and LA-ACS3, were found to increase after hypocotyl wounding. Apparently, these two genes were up-regulated by exogenous IAA treatment of seedlings. The LA-ACS3 mRNA levels were also elevated in the apical part of hypocotyl, which is reported to contain a high endogenous auxin concentration. This gene may be involved in the auxin- and ethylene-controlled apical hook formation. The expression of the LA-ACS4 gene was found to be almost undetectable. This gene may represent a “silent” twin of LA-ACS5 as these two genes share a considerable level of homology in coding and non-coding regions. The LA-ACS5 mRNA is strongly up-regulated in the embryonic axis of germinating seeds at the time of radicle emergence, and was also found in roots and hypocotyls of lupin seedlings.
    Type of Medium: Electronic Resource
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