Partial Self-Fertility in a Theoretical Amphiploid Progenitor of N. tabacum

Burk, L. G.

doi:10.1093/oxfordjournals.jhered.a108438

Cited by 29 publications

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“…These seeds germinated well (> 95%) and recovered plants were fertile. Adult plants of ≈ 2–3 m tall look phenotypically normal as observed in the S 0 generation (Burk, 1973); were without morphological abnormalities; and had little plant‐to‐plant variability. The white‐pink flowers closely resembled N. tabacum .…”

Section: Methodsmentioning

confidence: 93%

“…The observed heterozygosity at the rDNA locus is in accord with this supposition (Skalická et al ., 2003). As only two or three viable seeds per capsule were recovered from the S 0 plant (Burk, 1973), we can speculate that meiosis predominantly generates infertile gametes or abortive zygotes. Increased fertility of S 1 and subsequent generations suggests that two, possibly three, distinctive and relatively stable genotypes were selected.…”

Section: Discussionmentioning

confidence: 99%

“…From known genetic variation in natural tobacco analysed to date, a single ancestral polyploid origin seems the most likely hypothesis, based on the following factors. (1) There are very high levels of lethality in artifical interspecific Nicotiana hybrids (Burk, 1973; Tezuka & Marubashi, 2004). Also, our F 1 plants are completely sterile even after chromosome doubling (K.S., unpublished results).…”

Section: Discussionmentioning

confidence: 99%

“…The synthetic hybrid Th37 tobacco line was obtained from the US National Plant Germplasm System (NPGS, USDA, North Carolina State University, USA) as a kind gift from Professor Verne A. Sissons (USDA, Agricultural Research Station, North Carolina State University). The plants were made from the cross ♀ N. sylvestris (2 n = 24) × ♂ N. tomentosiformis (2 n = 24) and converted to a fertile amphidiploid by in vitro callus culture ( S 0 , Burk, 1973). Selfed seeds were obtained from a single regenerated plant ( S 1 ).…”

Section: Methodsmentioning

confidence: 99%

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Preferential elimination of repeated DNA sequences from the paternal, Nicotiana tomentosiformis genome donor of a synthetic, allotetraploid tobacco

et al. 2005

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Summary• Nicotiana tabacum (tobacco, 2 n = 4 x = 48) is a natural allotetraploid combining two ancestral genomes closely related to modern Nicotiana sylvestris and Nicotiana tomentosiformis . Here we examine the immediate consequences of allopolyploidy on genome evolution using 20 S 4 -generation plants derived from a single synthetic, S 0 plant made by Burk in 1973 (Th37).• Using molecular and cytogenetic methods we analysed 14 middle and highly repetitive sequences that together total ≈ 4% of the genome.• Two repeats related to endogenous geminiviruses (GRD5) and pararetroviruses ( Nto EPRV), and two classes of satellite repeats (NTRS, A1/A2) were partially or completely eliminated at variable frequency (25 -60%). These sequences are all from the N. tomentosiformis parent. Genomic in situ hybridization revealed additivity in chromosome numbers in two plants (2 n = 48), while a third was aneuploid for an N. tomentosiformis -origin chromosome (2 n = 49). Two plants had homozygous translocations between chromosomes of the S-and T-genomes.• The data demonstrate that genetic changes in synthetic tobacco were fast, targeted to the paternal N. tomentosiformis -donated genome, and some of the changes showed concordance with changes that presumably occurred during evolution of natural tobacco.

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Section: Methodsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Preferential elimination of repeated DNA sequences from the paternal, Nicotiana tomentosiformis genome donor of a synthetic, allotetraploid tobacco

et al. 2005

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“…Modern tobacco is an amphidiploid, containing both ancestral Nicotiana tomentosiformis and Nicotiana sylvestris genomes (Burk, 1973). To clone the MTHFR fulllength cDNAs of W38 as well as of the two progenitor species, reverse transcription PCR with a pair of primers (NtMF/NtMR) targeting specifically the 1,788-bp coding region (Fig.…”

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confidence: 99%

Alteration of the Alkaloid Profile in Genetically Modified Tobacco Reveals a Role of Methylenetetrahydrofolate Reductase in Nicotine N-Demethylation

et al. 2012

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Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme of the tetrahydrofolate (THF)-mediated one-carbon (C1) metabolic network. This enzyme catalyzes the reduction of 5,10-methylene-THF to 5-methyl-THF. The latter donates its methyl group to homocysteine, forming methionine, which is then used for the synthesis of S-adenosyl-methionine, a universal methyl donor for numerous methylation reactions, to produce primary and secondary metabolites. Here, we demonstrate that manipulating tobacco (Nicotiana tabacum) MTHFR gene (NtMTHFR1) expression dramatically alters the alkaloid profile in transgenic tobacco plants by negatively regulating the expression of a secondary metabolic pathway nicotine N-demethylase gene, CYP82E4. Quantitative real-time polymerase chain reaction and alkaloid analyses revealed that reducing NtMTHFR expression by RNA interference dramatically induced CYP82E4 expression, resulting in higher nicotine-tonornicotine conversion rates. Conversely, overexpressing NtMTHFR1 suppressed CYP82E4 expression, leading to lower nicotine-to-nornicotine conversion rates. However, the reduced expression of NtMTHFR did not affect the methionine and Sadenosyl-methionine levels in the knockdown lines. Our finding reveals a new regulatory role of NtMTHFR1 in nicotine Ndemethylation and suggests that the negative regulation of CYP82E4 expression may serve to recruit methyl groups from nicotine into the C1 pool under C1-deficient conditions. Tetrahydrofolate (THF)-mediated one-carbon (C1) metabolism generates and provides C1 units in different oxidation states for various anabolic pathways, including alkaloid biosynthesis in plants (Hanson et al., 2000). Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylene-THF into the most reduced C1 derivative, 5-methyl-THF (Guenther et al., 1999;Roje et al., 1999;Gelling et al., 2004). The latter then serves as the methyl group donor for Met synthesis from homocysteine (Guenther et al., 1999;Hanson et al., 2000). More than 80% of synthesized Met is further converted to S-adenosyl-methionine (AdoMet), which is the universal methyl group donor in reactions leading to modifications of various primary and secondary metabolites (Giovanelli et al., 1985;Hanson et al., 2000;Roje, 2006). In plants, MTHFRs have been cloned and characterized from Arabidopsis (Arabidopsis thaliana) and maize (Zea mays; Roje et al., 1999). In contrast to the mammalian enzymes, which are NADPH dependent and inhibited by AdoMet, plant MTHFRs are NADH dependent and AdoMet insensitive. In addition, the reaction that they catalyze is likely reversible in the cytosol (Roje et al., 1999). To 1 This work was supported by the Golden LEAF Foundation (a startup fund to the Biomanufacturing Research Institute & Technology Enterprise), the National Institute of General Medical Sciences (grant no. SC3GM088084 to J.X.), the National Science Foundation of China and the Yunnan Tobacco Company (grant nos. 31060046 and 2011YN04 to B.X.), and the National Science Foundation (grant nos. MCB-04...

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Pollen Heteromorphism inNicotiana tabacum (Solanaceae)

Till–Bottraud

Mignot

Paepe

et al. 1995

American J of Botany

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Pollen heteromorphism is defined as the production by a single plant of different fertile pollen types in all its anthers, and thus all flowers, throughout its life cycle. Eight cultivars of Nicotiana tabacum, as well as its ancestors (N. tabacum is an amphiploid hybrid 4 × from a cross between N. sylvestris and N. tomentosiformis) and recent hybrids were analyzed. Most cultivars and the hybrids are heteromorphic (producing 3‐ and 4‐aperturate pollen grains), whereas both parent species are homomorphic (3‐aperturate). Heteromorphism is a common consequence of polyploidization and these results agree with this interpretation. There is a significant variation in the proportions of the two pollen types among cultivars (genetic component), but also (with a much lower component of variance) within each cultivar, between plants (genets), flowers of a plant, and even anthers of a flower. This is interpreted as a release of the selective pressure: the cultivars of N. tabacum were obtained after several generations of selfing and are themselves selfers. Selfing, by removing pollen mixtures on a stigma, removes pollen competition, which is the drive for heteromorphism, and allows for a large variation of the proportions of the different pollen types.

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Partial Self-Fertility in a Theoretical Amphiploid Progenitor of N. tabacum

Cited by 29 publications

References 0 publications

Preferential elimination of repeated DNA sequences from the paternal, Nicotiana tomentosiformis genome donor of a synthetic, allotetraploid tobacco

Preferential elimination of repeated DNA sequences from the paternal, Nicotiana tomentosiformis genome donor of a synthetic, allotetraploid tobacco

Alteration of the Alkaloid Profile in Genetically Modified Tobacco Reveals a Role of Methylenetetrahydrofolate Reductase in Nicotine N-Demethylation

Pollen Heteromorphism inNicotiana tabacum (Solanaceae)

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