Developmental Regulation of Methyl Benzoate Biosynthesis and Emission in Snapdragon Flowers

Caffeine is synthesized through sequential three-step methylation of xanthine derivatives at positions 7-N, 3-N, and 1-N. However, controversy exists as to the number and properties of the methyltransferases involved. Using primers designed on the basis of conserved amino acid regions of tea caffeine synthase and Arabidopsis hypothetical proteins, a particular DNA fragment was amplified from an mRNA population of coffee plants. Subsequently, this fragment was used as a probe, and four independent clones were isolated from a cDNA library derived from coffee young leaves. Upon expression in Escherichia coli, one of them was found to encode a protein possessing 7-methylxanthine methyltransferase activity and was designated as CaMXMT. It consists of 378 amino acids with a relative molecular mass of 42.7 kDa and shows similarity to tea caffeine synthase (35.8%) and salicylic acid methyltransferase (34.1%). The bacterially expressed protein exhibited an optimal pH for activity ranging between 7 and 9 and methylated almost exclusively 7-methylxanthine with low activity toward paraxanthine, indicating a strict substrate specificity regarding the 3-N position of the purine ring. K m values were estimated to be 50 and 12 M for 7-methylxanthine and S-adenosyl-L-methionine, respectively. Transcripts of CaMXMT could be shown to accumulate in young leaves and stems containing buds, and green fluorescent protein fusion protein assays indicated localization in cytoplasmic fractions. The results suggest that, in coffee plants, caffeine is synthesized through three independent methylation steps from xanthosine, in which CaMXMT catalyzes the second step to produce theobromine.

show abstract

“…flowers (22). In addition, we found several related sequences in the expressed sequence tag of Arabidopsis.…”

Section: -Methylxanthine Methyltransferase Of Coffee Plantsbelow)mentioning

confidence: 89%

7-Methylxanthine Methyltransferase of Coffee Plants

Ogawa

Herai

Koizumi

et al. 2001

Journal of Biological Chemistry

130

114

View full text Add to dashboard Cite

show abstract

“…JA and MeJA levels in other transgenic lines (2 through 5) were similar to that of line 1 plants within experimental errors. encodes a protein homologous to a new class of carboxyl methyltransferases, such as the B. campestris f loral nectaryspecific NTR1 (20), the C. breweri SAMT (21), and the A. majus BAMT (27) (Fig. 1).…”

Section: Discussionmentioning

confidence: 99%

“…In particular, the JMT protein showed 85, 43, and 40% amino acid sequence similarities with B. campestris NTR1, an orthologue of JMT (20), Clarkia breweri SAMT, a SAM:salicylic acid carboxyl methyltransferase (21), and Antirrhinum majus BAMT, a SAM:benzoic acid carboxyl methyltransferase (27), respectively. The SAM-binding motifs of JMT and NTR1 occur in the N-terminal portion of the protein, instead of C-terminal side as observed in other Omethyltransferases.…”

Section: Structural Features Of Jmtmentioning

confidence: 99%

See 1 more Smart Citation

Jasmonic acid carboxyl methyltransferase: A key enzyme for jasmonate-regulated plant responses

Seo

Song

Cheong

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

668

457

View full text Add to dashboard Cite

Methyl jasmonate is a plant volatile that acts as an important cellular regulator mediating diverse developmental processes and defense responses. We have cloned the novel gene JMT encoding an S-adenosyl-L-methionine:jasmonic acid carboxyl methyltransferase (JMT) from Arabidopsis thaliana. Recombinant JMT protein expressed in Escherichia coli catalyzed the formation of methyl jasmonate from jasmonic acid with K m value of 38.5 M. JMT RNA was not detected in young seedlings but was detected in rosettes, cauline leaves, and developing flowers. In addition, expression of the gene was induced both locally and systemically by wounding or methyl jasmonate treatment. This result suggests that JMT can perceive and respond to local and systemic signals generated by external stimuli, and that the signals may include methyl jasmonate itself. Transgenic Arabidopsis overexpressing JMT had a 3-fold elevated level of endogenous methyl jasmonate without altering jasmonic acid content. The transgenic plants exhibited constitutive expression of jasmonate-responsive genes, including VSP and PDF1.2. Furthermore, the transgenic plants showed enhanced level of resistance against the virulent fungus Botrytis cinerea. Thus, our data suggest that the jasmonic acid carboxyl methyltransferase is a key enzyme for jasmonate-regulated plant responses. Activation of JMT expression leads to production of methyl jasmonate that could act as an intracellular regulator, a diffusible intercellular signal transducer, and an airborne signal mediating intra-and interplant communications.

show abstract

“…They are involved in the biosynthesis of floral scent substances exemplified by snapdragon (Antirrhinum sp.) 5 and roses (Rosa spp.). 6 The monoterpenes found were trans-β-ocimene, linalool, cis-linalool oxide, α-terpineol, myrtenol and trans-carveol, common chemicals in floral scents.…”

Section: Resultsmentioning

confidence: 99%

Zizyphus mauritiana Lam. (Rhamnaceae) and the chemical composition of its floral fecal odor

Alves

Pinto

Costa

et al. 2005

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

As flores de Zizyphus mauritiana Lam. (Rhamnaceae) exalam um forte odor fecal, e sua análise por micro-extração em fase sólida (SPME) associada a cromatografia gasosa-espectrometria de massas (CG-EM), co-injeção de padrões e índices de retenção revelou o benzaldeído como constituinte majoritário. Foram observados ainda benzenóides, ácidos carboxílicos, aldeídos, hidrocarbonetos alifáticos e monoterpenóides. A avaliação olfatométrica do SPME realizada por CG-olfatometria em sniffing port indicou o escatol (3-metil-indol) como o responsável pelo odor fecal das flores e a vanilina pelo seu odor adocicado.When in blossom, jujube (Zizyphus mauritiana Lam., Rhamnaceae) emanates a strong fecal odor. The substances responsible for this scent were analysed by headspace solid-phase microextraction and gas chromatography-mass spectrometry (SPME-GC-MS) associated to standard co-injection and retention indexes, which showed benzaldehyde as major constituent. Minor benzenoids, aliphatic carboxylic acids, aldehydes, hydrocarbons and oxygenated monoterpenes were also observed. Olfactometric evaluation of the SPME using GC-sniffing port indicated skatole (3-methyl-indole) as responsible for the fecal odor and vanillin for the sweety odor. Keywords:Zizyphus mauritiana, Rhamnaceae, aroma, skatole, headspace solid-phase microextraction IntroductionAround 170 tropical and subtropical species of Zizyphus Mill. are known. Z. mauritiana Lam. is popularly known as Aprin, Ber, Dunks or Indian jujube and belongs to the family Rhamnaceae. The plants vary from bushy shrubs 1.2-1.8 m tall to trees up to 12 m and about five yellowish-green flowers with 4-5 petals are borne on short inflorescences at the leaf axils. During the week of blossom, the thousands of flowers emanate a strong scent reminiscent of human excrement, which is detectable over 30 m from the tree, attracting hundreds of flies. We have seen small green dung-beetles visiting the flowers as well.Many publications deal with the varieties, cultivars, cultivation, propagation and analyses of the constituents present on Z. mauritiana, 1 and more rarely with pollination of the Indian jujube.2 However, we were unable to find any mention of the strong fecal odor of the flowers and vegetative parts of any Zizyphus species, and decided to study the chemical constituents responsible for this notable character. Materials and Methods Plant materialFlowers were collected from a single specimen of Zizyphus mauritiana Lam. cultivated at the Botanical Orchard of the Museu Nacional, Rio de Janeiro, during 2 successive blossoms. A voucher specimen (R. J. V. Alves, 6990), was deposited in the herbarium of Museu Nacional. InstrumentationAn Agilent 6890 gas chromatograph was used coupled to an Agilent 5973 quadrupole mass spectrometer with electron ionization mode (EI) generated at 70 eV (ion source at 230 °C and transfer line at 280 °C). GC was performed on , where it was held for 20 min. At the end of the column, the effluent was split 1:1 (by volume) into the mass detector and the sniffing port,...

show abstract

Developmental Regulation of Methyl Benzoate Biosynthesis and Emission in Snapdragon Flowers

Cited by 51 publications

References 0 publications

7-Methylxanthine Methyltransferase of Coffee Plants

7-Methylxanthine Methyltransferase of Coffee Plants

Jasmonic acid carboxyl methyltransferase: A key enzyme for jasmonate-regulated plant responses

Zizyphus mauritiana Lam. (Rhamnaceae) and the chemical composition of its floral fecal odor

Contact Info

Product

Resources

About