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Heavy metals are hazardous pollutants for humans, animals and plants, when their threshold concentration exceeds. Tobacco can accumulate higher concentrations of heavy metals, and the genotypic differences of tobacco in heavy metal uptake and their growth responses have not been clearly examined. In this study, the effects of nickel (Ni) and lead (Pb) on phytoremediation capabilities were tested in four local Oriental tobacco cultivars (Basma, Akhisar, Sanbaglar and Dibek). In two pot experiments, nitrogen (N), phosphorus (P) and potassium (P) were applied in fixed doses, while Pb and Ni were applied at 4 different doses (10, 50, 100 and 150 mg kg(-1)). Plants were harvested after 50 days of growing period, and separated into roots, stems, leaves. The biomass values were measured, and Pb and Ni concentrations were quantified in plant organs. Results revealed that Basma cultivar had the highest total biomass value with 16.63 and 15.92 g pot(-1) for Ni and Pb contents, respectively. While, the lowest total biomass was recorded in Dibek cultivar with 7.09 and 5.71 g pot(-1) for Ni and Pb, respectively. The biomass, Ni and Pb uptake and accumulation capabilities remained in the following order of cultivars Basma > Akhisar > Sanbaglar > Dibek. Depending on the application doses, Ni and Pb concentrations of different plant parts (roots, stems and leaves) of all varieties showed significant (p < 0.01) increases compared to the control treatments. All of the plant parts of Basma variety had higher Ni and Pb concentrations than the Akhisar, Sanbaglar and Dibek variety. Nickel concentrations in the roots, stems and leaves of different cultivars were determined to be the least in the control application and the highest in the NPK+150 mg kg(-1) Ni (Ni-4) application. Lead concentrations in the roots, stems and leaves of different cultivars were determined to be the least in the control application and the highest in the NPK+150 mg kg(-1) Pb (Pb-4) application. Basma variety with higher enrichment factor (EF) and bioaccumulation factor (BAF) values were also found to be more effective than the other varieties for phytoremediation of Ni and Pb. The objective of this study was to examine the Ni and Pb uptake, transport and accumulation properties of oriental tobacco with special emphasis on its different varieties.

Blue mould [Peronospora hyoscyami f. sp. tabacina (Adam) Skalicky 1964] is one of the most important foliar diseases of tobacco that causes significant losses in the Americas, south‐eastern Europe and the Middle East. This review summarizes the current knowledge of the mechanisms employed by this oomycete pathogen to colonize its host, with emphasis on molecular aspects of pathogenicity. In addition, key biochemical and molecular mechanisms involved in tobacco resistance to blue mould are discussed. Taxonomy: Kingdom: Chromista (Straminipila); Phylum: Heterokontophyta; Class: Oomycete; Order: Peronosporales; Family: Peronosporaceae; Genus: Peronospora; Species: Peronospora hyoscyami f. sp. tabacina. Disease symptoms: The pathogen typically causes localized lesions on tobacco leaves that appear as single, or groups of, yellow spots that often coalesce to form light‐brown necrotic areas. Some of the leaves exhibit grey to bluish downy mould on their lower surfaces. Diseased leaves can become twisted, such that the lower surfaces turn upwards. In such cases, the bluish colour of the diseased plants becomes quite conspicuous, especially under moist conditions when sporulation is abundant. Hence the name of the disease: tobacco blue mould. Infection process: The pathogen develops haustoria within plant cells that are thought to establish the transfer of nutrients from the host cell, and may also act in the delivery of effector proteins during infection. Resistance: Several defence responses have been reported to occur in the Nicotiana tabacum–P. hyoscyami f. sp. tabacina interaction. These include the induction of pathogenesis‐related genes, and a correlated increase in the activities of typical pathogenesis‐related proteins, such as peroxidases, chitinases, β‐1,3‐glucanases and lipoxygenases. Systemic acquired resistance is one of the best characterized tobacco defence responses activated on pathogen infection.

The subgenomes of the plant cell, the nuclear genome, the plastome, and the chondriome are known to interact through various types of coevolving macromolecules. The combination of the organellar genome from one species with the nuclear genome of another species often leads to plants with deleterious phenotypes, demonstrating that plant subgenomes coevolve. The molecular mechanisms behind this nuclear–organellar incompatibility have been elusive, even though the phenomenon is widespread and has been known for >70 years. Here, we show by direct and reverse genetic approaches that the albino phenotype of a flowering plant with the nuclear genome of Atropa belladonna (deadly nightshade) and the plastome of Nicotiana tabacum (tobacco) develops as a result of a defect in RNA editing of a tobacco-specific editing site in the plastid ATPase α-subunit transcript. A plastome-wide analysis of RNA editing in these cytoplasmic hybrids and in plants with a tobacco nucleus and nightshade chloroplasts revealed additional defects in the editing of species-specific editing sites, suggesting that differences in RNA editing patterns in general contribute to the pigment deficiencies observed in interspecific nuclear–plastidial incompatibilities.

Apical growth in pollen tubes (PTs) is associated with the presence of tip-focused ion gradients and fluxes, implying polar localization or regulation of the underlying transporters. The molecular identity and regulation of anion transporters in PTs is unknown. Here we report a negative gradient of cytosolic anion concentration focused on the tip, in negative correlation with the cytosolic Ca(2+) concentration. We hypothesized that a possible link between these two ions is based on the presence of Ca(2+)-dependent protein kinases (CPKs). We characterized anion channels and CPK transcripts in PTs and analyzed their localization. Yellow fluorescent protein (YFP) tagging of a homolog of SLOW ANION CHANNEL-ASSOCIATED1 (SLAH3:YFP) was widespread along PTs, but, in accordance with the anion efflux, CPK2/CPK20/CPK17/CPK34:YFP fluorescence was strictly localized at the tip plasma membrane. Expression of SLAH3 with either CPK2 or CPK20 (but not CPK17/CPK34) in Xenopus laevis oocytes elicited S-type anion channel currents. Interaction of SLAH3 with CPK2/CPK20 (but not CPK17/CPK34) was confirmed by Förster-resonance energy transfer fluorescence lifetime microscopy in Arabidopsis thaliana mesophyll protoplasts and bimolecular fluorescence complementation in living PTs. Compared with wild-type PTs, slah3-1 and slah3-2 as well as cpk2-1 cpk20-2 PTs had reduced anion currents. Double mutant cpk2-1 cpk20-2 and slah3-1 PTs had reduced extracellular anion fluxes at the tip. Our studies provide evidence for a Ca(2+)-dependent CPK2/CPK20 regulation of the anion channel SLAH3 to regulate PT growth.

Exposure of crop plants to H2S resulted in an increase in thiol level and a change in the composition of the thiol pool. Non-leguminous species accumulated cysteine and glutathione in the light, whereas in the dark, substantial amounts of gamma-glutamyl-cysteine were also detected. In leguminous species, which contain homoglutathione instead of glutathione, the level of cysteine, gamma-glutamyl-cysteine and homoglutathione increased, both in the light and in the dark. In clover, a species that contains glutathione and homoglutathione, both thiols increased to a high level. Feeding beta-alanine to detached shoots of soybean strongly reduced the accumulation of gamma-glutamyl-cysteine. This suggests that in legumes, the accumulation of gamma-glutamyl-cysteine upon exposure to H2S may result from a limited availability of substrate for homoglutathione synthesis.

The proliferative growth of thin cell layers ofNicotiana tabacum cultured on a rhizogenic medium was markedly disturbed when polyamine biosynthesis was inhibited. Treatments with polyamine inhibitors led to cell expansion, accompanied by thinning of the cell wall and inhibition of cell division, and frequent cases of nucleolar extrusion, mainly in the parenchymal layer in contact with the medium. Nucleolar extrusion was not correlated with cell expansion. The highest incidence of nucleolar extrusion occurred when the pathways of putrescine biosynthesis were inhibited and when spermidine synthesis, via S-adenosylmethionine decarboxylase, was blocked. The duration of the growth phase with nuclear amitotic divisions was prolonged in the presence of the inhibitors and root meristem formation delayed. When polyamines were added with the inhibitors, all reactions proceeded as in the controls.

summary The gene rolB from the T-DNA of Agrobacterium rhizogenes is capable of directing differentiation of roots in transformed plant cells. A detailed histological analysis of the expression of this gene in transgenic tobacco plants is presented here. Gene fusions between the promoter of rolB and the GUS reporter gene (encoding E. coliβ-glucuronidase) were utilized: tissue and cell specific GUS activity as driven by a long (1185 base pairs) and a short (306 bp) version of the rolB promoter was visualized histochemically during different phases of plant development, from embryo to flowering. The extended (1185bp) rolB promoter is under developmental control and is specifically active in the initial cells of all types of meristems and in the vascular system (phloem, phloem parenchyma, xylem parenchyma, pericycle and pericycle-like cells) of mature organs as well as in the central cylinder of the embryo. In contrast, the 306 bp deletion of the promoter is unable to drive expression in menstematic initials but is still active in the vascular system of the seedling.