An extracellular arabinogalactan-protein from Nicotiana tabacum

An extracellular arabinogalactan-protein was obtained from suspension-cultured tobacco cells. It seemed to be a homogeneous preparation from the results of gel-filtration, ultracentrifugation and disc gel electrophoresis. Its MW was estimated to be 2.24 × 10⁵ and its sedimentation coefficient (S_20,w) was calculated to be 5.07 S. It consisted of arabinose (40.0%), galactose (36.2%), rhamnose (0.8 %), glucuronic acid (10.0 %), glucosamine (0.2 %), galactosamine (0.1%) and protein (5.5 %). The sugar moiety appeared to be a typical arabino-3,6-galactan. A d-glucuronic acid residue was present as the non-reducing terminal group and was attached to C(O)-6 of a d-galactosyl residue by β-linkage.     

Affinity chromatography of Nicotiana tabacum ribonucleases

The purification of tobacco ribonuclease by affinity chromatography is described. 5′-(4-amino-phenylphosphoryl)-guanosine 2′, (3′) phosphate, a ribonuelease inhibitor, has been synthesized and insolubilized onto agarose beads. The resulting adsorbent binds tobacco and some other plant ribonucleases strongly but reversibly at pH 5.4. The bound enzyme can be eluted by changing the pH or ionic strength of the eluting buffer, or by specific elution with substrate or inhibitor. Binding is not due to simple ion-exchange properties of the adsorbent.     

Partial purification and characterization of two Nicotiana tabacum leaf ribonucleases

Two enzymes with similar properties that degrade RNA but not DNA have been partially purified from tobacco leaves. They differ in sub-cellular localization and in ability to hydrolyse ribonucleoside 2′,3′-cyclic phosphates.     

Changes in the chlorophylls and carotenoids of leaves of Nicotiana tabacum during senescence

In addition to chlorophylls a and b, β-carotene, lutein, violaxanthin and neoxanthin, leaves of tobacco (Nicotiana tabacum L. cv. Virginia Gold) contain antheraxanthin in some harvests. In lower leaves, chlorophylls decreased more rapidly than carotenoids during senescence, but both types of pigment decreased at equal rates in upper leaves. The chlorophyll a:b ratio decreased only in post-mature leaves. Total carotenoid decreased with age, with the relative proportion of β-carotene increasing in lower leaves. Seasonal influences rather than age of leaf determines whether antheraxanthin is present. No esterified xanthophylls were found in senescent leaves.     

Ribonucleases in Nicotiana tabacum leaf extracts treated with phenol

When tobacco leaf extracts are treated with phenol, ca 20% of the ribonuclease (RNase) activity survives and can be measured when the phenol is removed. After purification, the resistant RNase is inactivated by phenol; this suggests that tobacco leaves contain material that protects the RNase. Phenol-resistant RNase may be one of the TMV-RNA inactivating systems present in phenol extracts of tobacco leaves.     

In vivo synthesis of stigmasterol in Nicotiana tabacum

Six-day-old tobacco seedlings rapidly incorporated and metabolized exogenously supplied [4-¹⁴C]-sitosterol, but none of the radioactivity was recovered from stigmasterol. However, exogenously supplied [2-¹⁴C]-mevalonic acid was incorporated into both sitosterol and stigmasterol. Based on these results it is suggested that the biosynthetic pathway of stigmasterol is not via sitosterol but that both sterols have a common precursor.     

Enzymes of starch metabolism in Nicotiana tabacum callus

Activities of enzymes of starch metabolism were determined in tobacco callus grown in light or darkness and in the presence or absence of gibberellic acid. There was a higher rate of starch turnover in light-grown cultures, as judged by the activities of synthetic and degradative enzymes. Gibberellic acid-treated tissues contained a lower level of starch than the corresponding control tissue. This decrease could be correlated with the activity of phosphorylase. Cultured tissue and seedling material were found to have comparable levels of activity for the starch metabolizing enzymes.     

Methylation analysis of extracellular polysaccharides from suspension-cultured cells of Nicotiana tabacum

The soluble extracellular polysaccharides (ECP) of suspension-cultured tobacco cells were fractionated by DEAE-Sephadex CC into seven sub-fractions. Su     

Aliphatic and aromatic amines during development of Nicotiana tabacum

Putrescine, spermidine, spermine, tyramine and phenethylamine have been analysed in the apical parts, leaves, stems, flowers and roots of the tobacco p     

Extracellular phosphohydrolases from suspension cultures of Nicotiana tabacum

Several phosphohydrolase activities were detected in the medium after growth of suspension cultures of tobacco cells. A rapid rate of hydrolysis was observed with DNA, RNA, 3′-nucleotides, phosphoric anhydrides, p-nitrophenyl phosphate, and synthetic phosphodiesters. A fractionation of some of these phosphohydrolase activities was achieved by gel chromatography.     

RNA from callus cultures and leaves of Nicotiana tabacum

MAK column chromatography has been used to analyse RNA from normal and crown gall callus cultures and leaves of Nicotiana tabacum. To determine the elution behaviour of well-defined DNA-like RNAs with different GC content, complementary RNAs (c-RNA) synthesized on Agrobacterium tumefaciens DNA and crown gall DNA were used. The elution profile of the RNA from all three tissues followed a similar pattern. By salt gradient elution the RNA in the tRNA region showed a remarkably high CMP content which was significantly higher for the normal tissues than for crown gall tissue. RNA from the callus cultures contained more DNA-like RNA (D-RNA) with a higher turnover rate than RNA from leaves. Because of its relatively low poly A content, measured as RNase A + T₁ resistance, as well as its high turnover rate, the salt-eluted D-RNA is thought to be heterogeneous nuclear RNA (Hn-RNA) and not mRNA. RNA molecules that might represent the mRNA population, having intramolecular poly A tracts, were subsequently eluted by a salt gradient, a low salt buffer and with the chaotropic agent guanidine thiocyanate, which removed tenaciously bound (TB-RNA) in two fractions, α and β. Crown gall RNA showed both a different labelling behaviour and a higher poly A content in the α and β fractions compared to the normal tissues. c-RNAs may be eluted at different salt concentrations because of their different GC content. They give rise to a considerable fraction of TB-RNA which in the presence of tobacco leaf RNA was split into fractions similar to α and β. No fraction was found amongst these RNAs which did have intramolecular poly A tracts.     

A galactoglucomannan from extracellular polysaccharides of suspension-cultured cells of Nicotiana tabacum

A polysaccharide containing d-xylose, l-arabinose, d-mannose, d-galactose and d-glucose residues in the molar ratio of 0.07:0.16:1.     

Carbohydrate oxidation during Nicotiana tabacum callus growth

Tobacco callus was cultured in light or dark, with or without giberellic acid, and with various carbon sources in the medium, and the growth rate and activities of some enzymes of the Embden-Meyerhof-Parnas and pentose phosphate pathway were determined. No changes in the specific activities of enzymes of either pathway could be correlated with growth but there was a light-dependent stimulation of the pentose phosphate pathway enzymes examined.     

Biosynthesis of azetidine-2-carboxylic acid from methionine in Nicotiana tabacum

The administration of dl-methionine-[1¹⁴C] to Nicotia tabacum resulted in the formation of radioactive azetidine-2-carboxylic acid (isolated by dilution) which was specifically labelled on its carboxyl group. This result and other evidence strongly indicates that this imino acid is a normal component of tobacco.     

Development of aminoacyl tRNA synthetases in cultured Nicotiana tabacum cells

Changes in the activity of aminoacyl tRNA synthetases during growth of tobacco XD cells in suspension culture have been determined by the pyrophosphate exchange assay. Alanyl, arginyl, glutamyl, glutaminyl and seryl tRNA synthetases showed the lowest activity, whilst lysyl, histidyl, leucyl, isoleucyl, phenylalanyl threonyl and valyl tRNA synthetases were most active. Most synthetases, and total protein, increased to a maximum, at around 7 days, just before mid-exponential phase, and then fell.     

The biosynthesis of feruloyltyramine in Nicotiana tabacum

The biosynthesis of feruloyltyramine in Nicotiana tabacum Xanthi n.c. leaves is achieved through the action of the enzyme feruloyl-CoA tyramine N-feruloyl-CoA transferase. Its activity is increased 5- to 8-fold following infection by tobacco mosaic virus at 20°. The enzyme is soluble, its MW is 45 000, and it can synthesize a wide range of amides due to its low specificity for cinnamoyl-CoA thioesters and aromatic amines. Its affinity for feruloyl-CoA fragments is also described.     

An arabinoglucuronomannan from suspension-cultured cells of Nicotiana tabacum

From the soluble polysaccharides of suspension-cultured, tobacco cells (Nicotiana tabacum), an arabinoglucuronomannan (AGM) was isolated from the extract with phosphate buffer. Application of partial hydrolysis with acid, carboxyl reduction, methylation analysis, and ¹H- and ¹³C-n.m.r. spectroscopy indicated AGM to consist of the tetrasaccharide repeating-unit

.     

Sesquiterpenoid stress compounds from Nicotiana species

Solavetivone, 3-hydroxysolavetivone, solanascone, phytuberin and phytuberol were identified as stress compounds in leaves of Nicotiana tabacum cv Samsun NN. N. sylvestris, which is the maternal progenitor of N. tabacum, produced all the above compounds except 3-hydroxysolavetivone. In the F₁, hybrid of N. tabacum and N. glutinosa, all the stress compounds produced by N. tabacum and N. glutinosa, respectively, were accumulated.     

Ornithine decarboxylase activity and the hypersensitive reaction to tobacco mosaic virus in Nicotiana tabacum

The activity of ornithine decarboxylase (ODC) is increased 20 fold in leaves of Nicotiana tabacum cv. Xanthi n.c. following infection with tobacco mosaic virus at 20°. The activity reaches its maximum when localized necrotic lesions appear. There is little or no increase in plants kept at 32° when infection is systemic. However, if the infected plants are transferred to 20°, a marked and rapid increase in ODC activity occurs in the upper leaves, which collapse seven to nine hours after the transfer. ODC activity therefore parallels the activity of phenylalanine ammonia lyase during the hypersensitive reaction. Tyrosine decarboxylase was found to be activated in the same conditions. By contrast no increase in arginine decarboxylase activity could be detected. Temperature has a much greater effect on the polyamine and tyramine content of Xanthi n.c. leaves than does infection with TMV.     

Two labdane diterpenoids from Nicotiana raimondii

Two new labdanoids from Nicotiana raimondii have been identified as (12E) - 7β - hydroxylabda - 8(20),12,14 - triene and 7β - hydroxy - labda - 8(20),13(16),14 - triene.