The regulation of enzyme activities of the nicotine pathway in tobacco

Wagner, Roland; Feth, Friedhelm; Wagner, Karl

doi:10.1111/j.1399-3054.1986.tb03415.x

Cited by 45 publications

(14 citation statements)

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“…After biosynthesis in the tobacco root, nicotine is translocated to the leaf via the xylem and stored in the leaf vacuole with the help of a tonoplast-localized transporter. Nicotine can be demethylated in both leaves and roots, but it is primarily demethylated in senescing leaves (Wagner et al, 1986; Chou and Kutchan, 1998). The accumulation of nicotine in tobacco is affected by environmental factors, culture practices, and plant hormone levels.…”

Section: Introductionmentioning

confidence: 99%

High Temperature Induces Expression of Tobacco Transcription Factor NtMYC2a to Regulate Nicotine and JA Biosynthesis

Yang

et al. 2016

Front. Physiol.

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Environmental stress elevates the level of jasmonic acid (JA) and activates the biosynthesis of nicotine and related pyridine alkaloids in tobacco (Nicotiana tabacum L.) by up-regulating the expression of putrescine N-methyltransferase 1 (NtPMT1), which encodes a putrescine N-methyl transferase that catalyzes nicotine formation. The JA signal suppressor JASMONATE ZIM DOMAIN 1 (NtJAZ1) and its target protein, NtMYC2a, also regulate nicotine biosynthesis; however, how these proteins interact to regulate abiotic-induced nicotine biosynthesis is poorly understood. In this study, we found that high-temperature (HT) treatment activated transcription of NtMYC2a, which subsequently stimulated the transcription of genes associated with JA biosynthesis, including Lipoxygenase (LOX), Allene oxide synthase (AOS), Allene oxide cyclase (AOC), and 12-oxophytodienodate reductase (OPR). Overexpression of NtMYC2a increased nicotine biosynthesis by enhancing its binding to the promoter of NtPMT1. Overexpression of either NtJAZ1 or proteasome-resistant NtJAZ1ΔC suppressed nicotine production under normal conditions, but overexpression only of the former resulted in low levels of nicotine under HT treatment. These data suggest that HT induces NtMYC2a accumulation through increased transcription to activate nicotine synthesis; meanwhile, HT-induced NtMYC2a can activate JA synthesis to promote additional NtMYC2a activity by degrading NtJAZ1 at the post-transcriptional level.

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Section: Introductionmentioning

confidence: 99%

High Temperature Induces Expression of Tobacco Transcription Factor NtMYC2a to Regulate Nicotine and JA Biosynthesis

Yang

et al. 2016

Front. Physiol.

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“…Enzymatic activities for ornithine decarboxylase (ODC), putrescine methyltransferase (PMT), quinolinate phosphoribosyl transferase (QPT), and diamine oxidase (DAO) have been measured in cell-free extracts (Mizusaki et al, 1971(Mizusaki et al, , 1972(Mizusaki et al, , 1973Saunders and Bush, 1979;Wagner et al, 1986). A nicotine synthase activity has been reported in cell-free extracts (Friesen and Leete, 1990).…”

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confidence: 97%

The A and B Loci in Tobacco Regulate a Network of Stress Response Genes, Few of which are Associated with Nicotine Biosynthesis

Kidd

Melillo

et al. 2006

Plant Mol Biol

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Nicotine biosynthesis in Nicotiana tabacum is under genetic control by the A and B loci. Plants containing semi-dominant mutations at both the A and B loci (i.e. aabb genotype) have lower nicotine levels, reduced nicotine biosynthetic enzyme activities, and reduced mRNA levels of the corresponding biosynthetic genes. The A and B loci therefore appear to be coordinate regulators of several nicotine biosynthetic genes and define a group of co-regulated genes called the A-B regulon. To investigate the composition of genes in the A-B regulon, a fluorescent differential display (FDD) screen was used to randomly sample the transcriptomes of wild type and mutant aabb roots. This resulted in the isolation of 64 FDD clones, representing 49 unique genes or gene families. Four genes associated with nicotine biosynthesis were identified, whereas most of the other FDD clones were homologous with an assortment of stress response genes. Thirty-three genes or gene families showed reproducible aabb genotype effects, representing seven distinct mRNA expression patterns in response media treatments that increase the mRNA levels of known alkaloid biosynthetic genes. Thus, the A and B loci regulate the mRNA levels of some target genes differently than others. Eleven genes or gene families showed only treatment-specific effects, representing four mRNA accumulation patterns. These results indicate the A-B regulon is complex network of differentially expressed stress response genes, only a small subset of which are involved in nicotine biosynthesis.

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“…Appreciable DAO activities have been found in tobacco tissues with low nicotine contents; callus (5, 32), leaf (32), and roots of the low-nicotine genotypes (27,32). The biosyntheses of nicotine and tropane alkaloids apparently are not regulated directly by the DAO activities in these species.…”

Section: Purification Of Diamine Oxidasesmentioning

confidence: 99%

Diamine Oxidase from Cultured Roots of Hyoscyamus niger

Hashimoto¹,

Mitani²,

Yamada³

1990

Plant Physiol.

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Diamine oxidase was partially purified from cultured roots of Hyoscyamus niger L. that produce considerable amounts of tropane alkaloids, and then characterized. N-Methylated amines inhibited the activity of the enzyme more strongly than the corresponding primary amines. N-Methylputrescine was the best substrate of those studied, the respective Km values for it and for putrescine and cadaverine being 0.33, 2.85, and 6.25 millimolar. The specificity constants Vmax/Km for putrescine and cadaverine were 11 and 1% of the constant for N-methylputrescine. Marked specificity for the N-methylated diamine would enable the Hyoscyamus enzyme to function specifically in tropane alkaloid biosynthesis.The roots of several solanaceous plants synthesize anticholinergic alkaloids such as hyoscyamine and scopolamine. The tropine moiety of these alkaloids originates from ornithine and/or arginine. In Hyoscyamus albus, the symmetric diamine putrescine derived from these amino acids is first converted to MP' by putrescine N-methyltransferase (EC 2.1.1.53) and then deaminated oxidatively to 4-methylaminobutanal which spontaneously cyclizes to give the N-methylpyrrolinium cation ( Fig. 1) (12,14,15). This oxidative deamination is catalyzed by a DAO (EC 1.4.3.6 Alkaloid-producing, cultured roots of Hyoscyamus albus contain both free putrescine and free MP in their cells (14). But to function specifically in alkaloid biosynthesis, the DAO in Hyoscyamus roots must oxidize MP more efficiently than putrescine and other diamines present. Or, these diamines 'Abbreviations: MP, N-methylputrescine; DAO, diamine oxidase. must be localized in different metabolic compartments in the cells. We here characterize the DAO from cultured Hyoscyamus roots with emphasis on its substrate specificity. MATERIALS AND METHODS Plant MaterialsRoots of Hyoscyamus niger L. have been maintained in vitro in our laboratory since 1984 as described elsewhere (13). Prior to the experiments reported here, samples of these roots were transferred to 300-mL flasks containing 75 mL of auxinfree B5 medium (9) supplemented with 3% (w/v) sucrose, and were then cultured for 6 d. After being harvested with a suction filter, the roots were frozen immediately with liquid nitrogen and then homogenized in a Waring Blendor. The frozen homogenate was kept at -20°C until use.Pea seeds (Pisum sativum cv Alaska) were surface-sterilized and then germinated in moistened vermiculite in the dark for 8 d. The epicotyls of the etiolated pea seedlings were excised and frozen in liquid nitrogen after which they were processed in the same way as Hyoscyamus roots.All the other root, shoot and cell-suspension cultures used had been maintained in our laboratory for several years. The conditions for their culture are described elsewhere ( 14 To study substrate specificity, the ammonia produced by the DAO reaction was measured enzymatically with glutamate dehydrogenase (from beef liver; Oriental Yeast Co., Tokyo) by monitoring the decrease in NADH at 339 nm (18).When purified pea DAO preparati...

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The regulation of enzyme activities of the nicotine pathway in tobacco

Cited by 45 publications

References 15 publications

High Temperature Induces Expression of Tobacco Transcription Factor NtMYC2a to Regulate Nicotine and JA Biosynthesis

High Temperature Induces Expression of Tobacco Transcription Factor NtMYC2a to Regulate Nicotine and JA Biosynthesis

The A and B Loci in Tobacco Regulate a Network of Stress Response Genes, Few of which are Associated with Nicotine Biosynthesis

Diamine Oxidase from Cultured Roots of Hyoscyamus niger

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