Genus Nicotiana Research Articles

Nicotiana tabacum, or the Letter "Aleph" with 22 Flowers.

My work in diagnostics development has led me into some unusual and unexpected projects. One such project required the development of a PCR-based test for the purpose of distinguishing between commercial and ornamental species of the genus Nicotiana : Nicotiana tabacum and Nicotiana sylvestris. After initially pursuing assays based on differences …

Homologs of the rolC gene of naturally transgenic toadflaxes Linaria vulgaris and Linaria creticola are expressed in vitro

Agrobacterium mediated transformation is the most common way for obtaining transgenic plants in laboratory conditions. At the same time, there are species inside the genera Nicotiana, Linaria and Ipomoea that contain homologs of agrobacterial T-DNA genes as a result of genetic transformation of their ancestral forms in natural conditions. Such plants are called naturally transgenic plants, and T-DNA in their genomes is called cellular (cT-DNA). It is proposed that in the evolution of these genera, the introduced sequences played an important role. This idea is confirmed by the data on the expression of some T-DNA genes in Nicotiana and Ipomoea. Until the last moment, the expression of cT-DNA genes in Linaria has not been documented. However, the analysis of the nucleotide sequence indicates the functionality of rolC gene in L. vulgaris Mill., L. acutiloba Fisch. ex Rchb., L. genistifolia (L.) Mill. In this research work, we have sequenced the rolC homolog in one more toadflax species (Linaria creticola Kuprian). The in silico analysis of this gene has shown that it can encode a full-length peptide. Using the real time RT-PCR method, we have demonstrated that the rolC homolog is expressed in vitro in shoots, roots and calli of L. vulgaris Mill., as well as in shoots of L. creticola Kuprian. The results obtained are an important argument in favor of the fact that cT-DNA is functional and that its fixation in genomes played a certain role in the evolutionary process. However, the level of expression of the gene studied is quite low. A similar trend was observed in other naturally transgenic species. This can explain the absence of explicit morphological differences of species containing cT-DNA from their non-transgenic relatives.

Biologically active components in seeds of three Nicotiana species

Tobacco seeds, available as an untitilized byproduct of the commercial leaf production in many countries around the world, can be a valuable source of natural products with biological activity. The genus Nicotiana (Solanaceae) includes more than 65 species, but the most economically important and commercially cultivated is Nicotiana tabacum L. (common tobacco) and to a much lesser degree N. rustica L. (Aztec tobacco). The objective of this study was to evaluate tobacco seed oil and cakes of three tobacco species: two genotypes of N. alata Link & Otto (jasmine tobacco), N. rustica, and N. tabacum, with respect to their potential uses. The glyceride seed oil content was 37.6% and 40.9% for the two genotypes of N. alata, 37.5% for N. rustica, and 30.9% for N. tabacum. Overall, the content of phospholipids was 0.2–0.3% in the oils. Total sterol amount in the oils was 0.35–0.48%. The main component was β-sitosterol, followed by cholesterol and Δ5-avenasterol (in N. alata, white petals), cholesterol and campesterol (in N. alata, pink petals), campesterol and Δ5-avenasterol (in N. rustica), and campesterol and stigmasterol (in N. tabacum). In the tocopherol fraction (101, 117, 178, and 106 mgkg−1 in N. alata white and pink forms, N. rustica, and N. tabacum, respectively in the oils) the most predominant (higher than 97%) was the γ-tocopherol. Overall, the main fatty acids (FA) in the three Nicotiana species were linoleic (61.7–67.6% range), oleic (15.5–19.0%), and palmitic (9.1–12.5%). The remaining seed cakes (after Soxhlet extraction of glyceride oil), potentially valuable nutrient by-products, were characterized with regard to their content of minerals, cellulose, proteins, and amino acids. Seed cake cellulose content varied between 32.5 and 45.2%, and protein content was 26.7–34.1%. Seed cakes were rich in mineral macro- and micronutrients, with some differences between the species. Highest content of total nitrogen and protein were found in N. rustica (5.5% and 34.1%, respetively), and highest content of cellulose was found in N. alata (white petals genotype). Potassium concentration was higher in N. tabacum and N. rustica cakes, whereas the concentrations of iron and zinc were highest in N. alata (pink petals genotype). Amino acid composition was dominated by aspartic acid, arginine, and threonine in N. alata, and by arginine, aspartic acid, and histidine in N. rustica. The results suggest potential alternative uses of tobacco seeds and cake as animal feed, and possibly as feedstock for new consumer human health products. The concentration of amino acids important for animal nutrition (lysine, methionine, and cysteine) in tobacco seed cakes was low, implying a need for careful combination with other animal diet ingredients.

Agrobacterium-Mediated Transformation in the Evolution of Plants.

In most cases, the genetic engineering of plants uses Agrobacterium-mediated transformation to introduce novel genes. In nature, insertion of T-DNA into the plant genome and its subsequent transfer via sexual reproduction have been shown for several species in the genera Nicotiana, Ipomoea , and Linaria . A sequence homologous to T-DNA of the Ri plasmid of Agrobacterium rhizogenes was found in the genome of wild-type Nicotiana glauca (section Noctiflorae) more than 30years ago and was named "cellular T-DNA" (cT-DNA). It comprises an imperfect inverted repeat and contains homologs of several T-DNA oncogenes (NgrolB, NgrolC, Ngorf13, Ngorf14) and an opine synthesis gene (Ngmis). Multiple cT-DNAs have also been found in species of the sections Tomentosae and Nicotiana of the genus Nicotiana. These ancient cT-DNA genes are still expressed, indicating that they may play a role in the evolution of these plants. In 2012-2013, cT-DNA was detected and characterized in Linaria vulgaris and L. genistifolia ssp. dalmatica. Their cT-DNA is present in two copies and organized as an imperfect direct tandem repeat, containing LvORF2, LvORF3, LvORF8, LvrolA, LvrolB, LvrolC, LvORF13, LvORF14, and the Lvmis genes. In 2015, cT-DNA was found in Ipomoea. Two types of T-DNA-like sequences were described within this genera, and their distribution varied among cultured hexaploid, tetraploid, and wild diploid forms. Thus, several independent T-DNA integration events occurred in the genomes of these three plant genera. We propose that the events of T-DNA insertion in the plant genome might have affected their evolution, resulting in the creation of new plant species. In this chapter, we focus on the structure and functions of cT-DNA in Linaria, Nicotiana, and Ipomoea and discuss their possible evolutionary role.

Wild tobacco genomes reveal the evolution of nicotine biosynthesis

Nicotine, the signature alkaloid of Nicotiana species responsible for the addictive properties of human tobacco smoking, functions as a defensive neurotoxin against attacking herbivores. However, the evolution of the genetic features that contributed to the assembly of the nicotine biosynthetic pathway remains unknown. We sequenced and assembled genomes of two wild tobaccos, Nicotiana attenuata (2.5 Gb) and Nicotiana obtusifolia (1.5 Gb), two ecological models for investigating adaptive traits in nature. We show that after the Solanaceae whole-genome triplication event, a repertoire of rapidly expanding transposable elements (TEs) bloated these Nicotiana genomes, promoted expression divergences among duplicated genes, and contributed to the evolution of herbivory-induced signaling and defenses, including nicotine biosynthesis. The biosynthetic machinery that allows for nicotine synthesis in the roots evolved from the stepwise duplications of two ancient primary metabolic pathways: the polyamine and nicotinamide adenine dinucleotide (NAD) pathways. In contrast to the duplication of the polyamine pathway that is shared among several solanaceous genera producing polyamine-derived tropane alkaloids, we found that lineage-specific duplications within the NAD pathway and the evolution of root-specific expression of the duplicated Solanaceae-specific ethylene response factor that activates the expression of all nicotine biosynthetic genes resulted in the innovative and efficient production of nicotine in the genus Nicotiana Transcription factor binding motifs derived from TEs may have contributed to the coexpression of nicotine biosynthetic pathway genes and coordinated the metabolic flux. Together, these results provide evidence that TEs and gene duplications facilitated the emergence of a key metabolic innovation relevant to plant fitness.

Nectar sugars and amino acids in day- and night-flowering Nicotiana species are more strongly shaped by pollinators' preferences than organic acids and inorganic ions.

Floral nectar contains mainly sugars but also amino acids, organic acids, inorganic ions and secondary compounds to attract pollinators. The genus Nicotiana exhibits great diversity among species in floral morphology, flowering time, nectar compositions, and predominant pollinators. We studied nectar samples of 20 Nicotiana species, composed equally of day- and night-flowering plants and attracting different groups of pollinators (e.g. hummingbirds, moths or bats) to investigate whether sugars, amino acids, organic acids and inorganic ions are influenced by pollinator preferences. Glucose, fructose and sucrose were the only sugars found in the nectar of all examined species. Sugar concentration of the nectar of day-flowering species was 20% higher and amino acid concentration was 2-3-fold higher compared to the nectar of night-flowering species. The sucrose-to-hexose ratio was significantly higher in night-flowering species and the relative share of sucrose based on the total sugar correlated with the flower tube length in the nocturnal species. Flowers of different tobacco species contained varying volumes of nectar which led to about 150-fold higher amounts of total sugar per flower in bat- or sunbird-pollinated species than in bee-pollinated or autogamous species. This difference was even higher for total amino acids per flower (up to 1000-fold). As a consequence, some Nicotiana species invest large amounts of organic nitrogen for certain pollinators. Higher concentrations of inorganic ions, predominantly anions, were found in nectar of night-flowering species. Therefore, higher anion concentrations were also associated with pollinator types active at night. Malate, the main organic acid, was present in all nectar samples but the concentration was not correlated with pollinator type. In conclusion, statistical analyses revealed that pollinator types have a stronger effect on nectar composition than phylogenetic relations. In this context, nectar sugars and amino acids are more strongly correlated with the preferences of predominant pollinators than organic acids and inorganic ions.

19. ニコチアナ属植物の種間雑種の葯培養(昭和53年度 年次講演会要旨)

19. ニコチアナ属植物の種間雑種の葯培養(昭和53年度 年次講演会要旨)

Non-host Resistance Induced by the Xanthomonas Effector XopQ Is Widespread within the Genus Nicotiana and Functionally Depends on EDS1.

Most Gram-negative plant pathogenic bacteria translocate effector proteins (T3Es) directly into plant cells via a conserved type III secretion system, which is essential for pathogenicity in susceptible plants. In resistant plants, recognition of some T3Es is mediated by corresponding resistance (R) genes or R proteins and induces effector triggered immunity (ETI) that often results in programmed cell death reactions. The identification of R genes and understanding their evolution/distribution bears great potential for the generation of resistant crop plants. We focus on T3Es from Xanthomonas campestris pv. vesicatoria (Xcv), the causal agent of bacterial spot disease on pepper and tomato plants. Here, 86 Solanaceae lines mainly of the genus Nicotiana were screened for phenotypical reactions after Agrobacterium tumefaciens-mediated transient expression of 21 different Xcv effectors to (i) identify new plant lines for T3E characterization, (ii) analyze conservation/evolution of putative R genes and (iii) identify promising plant lines as repertoire for R gene isolation. The effectors provoked different reactions on closely related plant lines indicative of a high variability and evolution rate of potential R genes. In some cases, putative R genes were conserved within a plant species but not within superordinate phylogenetical units. Interestingly, the effector XopQ was recognized by several Nicotiana spp. lines, and Xcv infection assays revealed that XopQ is a host range determinant in many Nicotiana species. Non-host resistance against Xcv and XopQ recognition in N. benthamiana required EDS1, strongly suggesting the presence of a TIR domain-containing XopQ-specific R protein in these plant lines. XopQ is a conserved effector among most xanthomonads, pointing out the XopQ-recognizing RxopQ as candidate for targeted crop improvement.

Conversion of nornicotine to 6-hydroxy-nornicotine and 6-hydroxy-myosmine by Shinella sp. strain HZN7.

Nornicotine is a natural alkaloid produced by plants in the genus Nicotiana and is structurally related to nicotine. Importantly, nornicotine is the direct precursor of tobacco-specific nitrosamine N'-nitrosonornicotine, which is a highly potent human carcinogen. Microbial detoxification and degradation of nicotine have been well characterized; however, until now, there has been no information on the molecular mechanism of nornicotine degradation. In this study, we demonstrate the transformation of nornicotine by the nicotine-degrading strain Shinella sp. HZN7. Three transformation products were identified as 6-hydroxy-nornicotine, 6-hydroxy-myosmine, and 6-hydroxy-pseudooxy-nornicotine by UV spectroscopy, high-resolution mass spectrometry, nuclear magnetic resonance, and Fourier transform-infrared spectroscopy analyses. The two-component nicotine dehydrogenase genes nctA1 and nctA2 were cloned, and their product, NctA, was confirmed to be responsible for the conversion of nornicotine into 6-hydroxy-nornicotine as well as nicotine into 6-hydroxy-nicotine. The 6-hydroxy-nicotine oxidase, NctB, catalyzed the oxidation of 6-hydroxy-nornicotine to 6-hydroxy-myosmine, and it spontaneously hydrolyzed into 6-hydroxy-pseudooxy-nornicotine. However, 6-hydroxy-pseudooxy-nornicotine could not be further degraded by strain HZN7. This study demonstrated that nornicotine is partially transformed by strain HZN7 via nicotine degradation pathway.

Complete Chloroplast Genome of Nicotiana otophora and its Comparison with Related Species.

Nicotiana otophora is a wild parental species of Nicotiana tabacum, an interspecific hybrid of Nicotiana tomentosiformis and Nicotiana sylvestris. However, N. otophora is least understood as an alternative paternal donor. Here, we compared the fully assembled chloroplast (cp) genome of N. otophora and with those of closely related species. The analysis showed a cp genome size of 156,073 bp and exhibited a typical quadripartite structure, which contains a pair of inverted repeats separated by small and large single copies, containing 163 representative genes, with 165 microsatellites distributed unevenly throughout the genome. Comparative analysis of a gene with known function across Nicotiana species revealed 76 protein-coding sequences, 20 tRNA sequences, and 3 rRNA sequence shared between the cp genomes. The analysis revealed that N. otophora is a sister species to N. tomentosiformis within the Nicotiana genus, and Atropha belladonna and Datura stramonium are their closest relatives. These findings provide a valuable analysis of the complete N. otophora cp genome, which can identify species, elucidate taxonomy, and reconstruct the phylogeny of genus Nicotiana.

Significance and determinants of tobacco use: A brief review

Tobacco is a plant product derived from a variety of plants belonging to the genus Nicotiana. The alkaloid nicotine present in the plant leafs is a stimulant and has an addictive effect. The tobacco plants have been historically grown and used for recreational purposes by the American local population. The dried tobacco leaves are consumed as chewing tobacco, snuff, and smoked in a variety of dispensations. Tobacco use (TU) has an adverse effect on various body systems and is a determinant for different diseases ranging from cancers to atherosclerosis. TU is a modifiable environmental risk factor for various diseases. Hence, with public health education and behavior modification, its burden can be reduced in a given society. Thus, the understanding of the incidence and prevalence of its use is necessary. This review attempts to sum up the significance and determinants of TU.

Laser-Induced Breakdown Spectroscopy (LIBS) Quality Control and Origin Identification of Handmade Manufactured Cigars.

Tobacco is an agricultural product originating in America that is obtained by processing the leaves of various plants of the genus Nicotiana tabacum. It is the inedible product occupying the most plantings in the world, according to a recent report from the United Nations Food and Agriculture Organization. It is consumed in various ways, but the most popular form of consumption is, undoubtedly, by smoking cigarettes. A particular segment of the tobacco industry is the manufacturing of handmade cigars, which for some third-world countries is an important source of income. There are different qualities of cigars, and a major problem is the adulteration that occurs, for example, when authentic high-quality leaves are replaced by lower quality leaves. A factor that influences the quality of the cigars is the smoke combustion process, which depends on several factors, particularly the composition of the leaves. We present a simple and quick technique for the quality control and origin identification of handmade cigars that measures the Mg/Ca ratios in the tobacco leaves and wrappers of the cigars using laser-induced breakdown spectroscopy.

Editorial: "Agrobacterium biology and its application to transgenic plant production".

Editorial: "Agrobacterium biology and its application to transgenic plant production".

Characterization of hybrid seedlings from crosses of <i>Nicotiana stocktonii</i> Brandegee×<i>N. tabacum</i> L. and <i>N. stocktonii</i>×progenitors of <i>N. tabacum</i>

Hybrid lethality is one of the sexual barriers preventing wide hybridization. In the genus Nicotiana, hybrid lethality is observed in some interspecific cross combinations. Interspesific hybridization of Nicotiana stocktonii×N. tabacum has not been carried out from the viewpoint of expression of lethality. N. tabacum has an S subgenome derived from N. sylvestris and a T subgenome derived from N. tomentosiformis. In this study, hybrid seedlings from the cross N. stocktonii×N. tabacum, were obtained by ovule culture. The hybrid seedlings were classified as normal seedlings, tumorous types and vitrified plants, and they did not express lethality. Hybrid seedlings from the cross N. stocktonii×N. sylvestris expressed lethality. Moreover, hybrid seedlings from N. stocktonii×N. tomentosiformis also expressed lethality. This suggests that both the S genome of N. sylvestris and the T genome of N. tomentosiformis have factors causing lethality in hybrids with N. stocktonii. However, hybrid seedlings from N. stocktonii×N. tabacum did not express lethal symptoms in this study. We suggested that the factors responsible for lethality in N. tabacum must have been lost or no longer expressed during the process of speciation, probably due to reorganization and modification of the genomes.

Alkaloid production and capacity for methyljasmonate induction by hairy roots of two species in Tribe Anthocercideae, family Solanaceae.

In addition to producing medicinally important tropane alkaloids, some species in the mainly Australian Solanaceous tribe Anthocercideae, sister to genus Nicotiana, are known to also contain substantial levels of the pyridine alkaloids nicotine and nornicotine. Here, we demonstrate that axenic hairy root cultures of two tribe Anthocercideae species, Cyphanthera tasmanica Miers and Anthocercis ilicifolia ssp. ilicifolia Hook, contain considerable amounts of both nicotine and nornicotine (~0.5-1% DW), together with lower levels of the tropane alkaloid hyoscyamine (<0.2% DW). Treatment of growing hairy roots of both species with micromolar levels of the wound stress hormone methyl-jasmonate (MeJa) led to significant increases (P<0.05) in pyridine alkaloid concentrations but not of hyoscyamine. Consistent with previous studies involving Nicotiana species, we also observed that transcript levels of key genes required for pyridine alkaloid synthesis increased in hairy roots of both Anthocercideae species following MeJa treatment. We hypothesise that wound-associated induction of pyridine alkaloid synthesis in extant species of tribe Anthocercideae and genus Nicotiana was a feature of common ancestral stock that existed before the separation of both lineages ~15million years ago.

Identification of expressed resistance gene analogs (RGA) and development of RGA-SSR markers in tobacco

Tobacco is an important cash crop and an ideal experimental system for studies of plant-pathogen interactions. Identification of tobacco resistance (R) genes and resistance gene analogs (RGAs) is propitious to elucidate the underlying resistant mechanisms. In recent years, the public tobacco EST (expressed sequence tags) data set, which provides a rich source for identifying expressed RGAs, has enlarged substantially. In this study, 149606 Uni-ESTs were assembled from 412325 tobacco ESTs available in GenBank, scanned with 112 published plant R-genes protein sequences, and 1113 Nicotiana (tobacco) RGAs (NtRGAs) were identified. The majority of them comprised the common R-genes domains, such as NBS-LRR, LRR-PK, LRR, PK and Mlo, while we were unable to identify 109 RGAs using published domains of R-genes. Upon sequence alignment, 1079 NtRGAs were allocated on 712 loci within the Nicotiana benthamiana genome. A total of 78 simple sequence repeats (SSRs) were identified from 72 NtRGAs, and out of 64 newly designed primer pairs, 54 primer pairs generated clear bands upon PCR amplification using tobacco genomic DNA. Only nine primer pairs displayed polymorphism in 24 varieties of tobacco, with 2-4 alleles per locus (2.56 alleles on average), while 41 primer pairs were able to detect polymorphisms in six wild species of genus Nicotiana, with 2-4 alleles per locus (2.61 alleles on average).

The evolutionary fate of the horizontally transferred agrobacterial mikimopine synthase gene in the genera Nicotiana and Linaria.

Few cases of spontaneously horizontally transferred bacterial genes into plant genomes have been described to date. The occurrence of horizontally transferred genes from the T-DNA of Agrobacterium rhizogenes into the plant genome has been reported in the genus Nicotiana and in the species Linaria vulgaris. Here we compare patterns of evolution in one of these genes (a gene encoding mikimopine synthase, mis) following three different events of horizontal gene transfer (HGT). As this gene plays an important role in Agrobacterium, and there are known cases showing that genes from pathogens can acquire plant protection function, we hypothesised that in at least some of the studied species we will find signs of selective pressures influencing mis sequence. The mikimopine synthase (mis) gene evolved in a different manner in the branch leading to Nicotiana tabacum and N. tomentosiformis, in the branch leading to N. glauca and in the genus Linaria. Our analyses of the genus Linaria suggest that the mis gene began to degenerate soon after the HGT. In contrast, in the case of N. glauca, the mis gene evolved under significant selective pressures. This suggests a possible role of mikimopine synthase in current N. glauca and its ancestor(s). In N. tabacum and N. tomentosiformis, the mis gene has a common frameshift mutation that disrupted its open reading frame. Interestingly, our results suggest that in spite of the frameshift, the mis gene could evolve under selective pressures. This sequence may still have some regulatory role at the RNA level as suggested by coverage of this sequence by small RNAs in N. tabacum.

Deep sequencing of the ancestral tobacco species Nicotiana tomentosiformis reveals multiple T-DNA inserts and a complex evolutionary history of natural transformation in the genus Nicotiana.

Nicotiana species carry cellular T-DNA sequences (cT-DNAs), acquired by Agrobacterium-mediated transformation. We characterized the cT-DNA sequences of the ancestral Nicotiana tabacum species Nicotiana tomentosiformis by deep sequencing. N. tomentosiformis contains four cT-DNA inserts derived from different Agrobacterium strains. Each has an incomplete inverted-repeat structure. TA is similar to part of the Agrobacterium rhizogenes 1724 mikimopine-type T-DNA, but has unusual orf14 and mis genes. TB carries a 1724 mikimopine-type orf14-mis fragment and a mannopine-agropine synthesis region (mas2-mas1-ags). The mas2' gene codes for an active enzyme. TC is similar to the left part of the A. rhizogenes A4 T-DNA, but also carries octopine synthase-like (ocl) and c-like genes normally found in A. tumefaciens. TD shows a complex rearrangement of T-DNA fragments similar to the right end of the A4 TL-DNA, and including an orf14-like gene and a gene with unknown function, orf511. The TA, TB, TC and TD insertion sites were identified by alignment with N. tabacum and Nicotiana sylvestris sequences. The divergence values for the TA, TB, TC and TD repeats provide an estimate for their relative introduction times. A large deletion has occurred in the central part of the N. tabacum cv. Basma/Xanthi TA region, and another deletion removed the complete TC region in N. tabacum. Nicotiana otophora lacks TA, TB and TD, but contains TC and another cT-DNA, TE. This analysis, together with that of Nicotiana glauca and other Nicotiana species, indicates multiple sequential insertions of cT-DNAs during the evolution of the genus Nicotiana.

Horizontal gene transfer from Agrobacterium to plants.

Most genetic engineering of plants uses Agrobacterium mediated transformation to introduce novel gene content. In nature, insertion of T-DNA in the plant genome and its subsequent transfer via sexual reproduction has been shown in several species in the genera Nicotiana and Linaria. In these natural examples of horizontal gene transfer from Agrobacterium to plants, the T-DNA donor is assumed to be a mikimopine strain of A. rhizogenes. A sequence homologous to the T-DNA of the Ri plasmid of Agrobacterium rhizogenes was found in the genome of untransformed Nicotiana glauca about 30 years ago, and was named “cellular T-DNA” (cT-DNA). It represents an imperfect inverted repeat and contains homologs of several T-DNA oncogenes (NgrolB, NgrolC, NgORF13, NgORF14) and an opine synthesis gene (Ngmis). A similar cT-DNA has also been found in other species of the genus Nicotiana. These presumably ancient homologs of T-DNA genes are still expressed, indicating that they may play a role in the evolution of these plants. Recently T-DNA has been detected and characterized in Linaria vulgaris and L. dalmatica. In Linaria vulgaris the cT-DNA is present in two copies and organized as a tandem imperfect direct repeat, containing LvORF2, LvORF3, LvORF8, LvrolA, LvrolB, LvrolC, LvORF13, LvORF14, and the Lvmis genes. All L. vulgaris and L. dalmatica plants screened contained the same T-DNA oncogenes and the mis gene. Evidence suggests that there were several independent T-DNA integration events into the genomes of these plant genera. We speculate that ancient plants transformed by A. rhizogenes might have acquired a selective advantage in competition with the parental species. Thus, the events of T-DNA insertion in the plant genome might have affected their evolution, resulting in the creation of new plant species. In this review we focus on the structure and functions of cT-DNA in Linaria and Nicotiana and discuss their possible evolutionary role.

Investigations of possible horizontal gene transfer from Agrobacterium to some representatives of the family Solanaceae

The development of methods of genetic engineering of plants poses in modern society the question of the safety of transgenic plants. Transformation of plants has been criticized as artificial process performed only in the laboratory. At the same time there is evidence that some members of the genus Nicotiana and Linaria contain sequences homologous to the T-DNA of Agrobacterium rhizogenes in their genomes. The question: whether there are other examples of horizontal gene transfer from Agrobacterium to the plant among the representatives of the family. Solanaceae, is still actual. We performed screening of representatives of four genera of the family Solanaceae for the presence of sequences homologous to oncogeniclike genes rolB, rolC, ORF13, ORF14. New examples of horizontal gene transfer were not detected. Apparently, the presence of sequences homologous to oncogenes of A. rhizogenes in the genome of nontransformed plants is not common to the whole family Solanaceae and is characteristic only of the some species of the genus Nicotiana.