Haplopappus gracilis

Flavanone 3 -hydroxylase (F3 H ECl.14.13.21 CYP75B) activity was initially identified in microsomal preparations of golden weed (Haplopappus gracilis) [110]. E3 H from irradiated parsley cell cultures was later biochemically analyzed and characterized as a cytochrome P450 having an absolute requirement for NADPH and molecular oxygen as cofactors [111]. The enzyme has been shown to have activity with flavanones, flavones, dihydroflavonols, and flavonols, but does not appear to have activity with anthocyanidins [111]. The first cDNA clone for E3 H was isolated from Petunia [112]. It has been suggested that E3 H may serve as an anchor for the proposed flavonoid multi-enzyme complex on the cytosolic surface of the endoplasmic reticulum [44]. 

Aminouracil produces a block in the mitotic cycle of various plants. For example, cessation of mitosis occurred in Vida faba roots incubated 24 h with this compound [392—394]. Depending on different experimental conditions, thymidine or thymidylic acid may or may not alleviate these effects [392—394]. It was concluded that 5-aminouracil depressed the rate of DNA synthesis, which led to an accumulation of cells in the S phase. After removal of the agent, DNA synthesis resumed. Similar results have been observed with Allium cepa and Haplopappus gracilis [395, 396]. Inhibition of guanosine incorporation into RNA of meristematic cells in Vida faba by 5-aminouracil was also reported [397]. 

This enzyme was first reported in the microsomal fractions of Haplopappus gracilis cell cultures,33 studied in more detail in parsley,34 and later shown to occur in the flowers of several species.7 F3 H catalyzes the hydroxylation of naringenin and dihydrokaempferol (DHK), as well as of apigenin or kaempferol to their respective 3 -hydroxy derivatives, eriodictyol, dihydroquercetin (DHQ), luteolin, and quercetin, but does not accept the flavan 3,4-diols or anthocyanidins as substrates,34 indicating that B-ring hydroxylation of the latter is determined at the dihydroflavonol level. It was more than two decades later that the first cDNA clone encoding F3 H was isolated and characterized from the flowers of Petunia hybridal Arabidopsis thaliana,36 and Perilla frutescens.37 Their recombinant proteins were shown to... 

FRITSCH, H., GRISEBACH, H., Biosynthesis of cyanidin in cell cultures of Haplopappus gracilis. Phytochemistry, 1975,14,2437-2442. 

Table 5.9. Cytoplasmic labelling distribution over the various cytoplasmic components of the tips of primary roots of germinated Haplopappus gracilis from electron microscope autoradiographs...

Haplopappus gracilis 171 Hazel see Corylus avellana Hedera helix 10 Helianthus annuus (sunflower) 2,9,20,34-36,... 

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