Tnt1 elements are a superfamily of LTR-retrotransposons distributed in the Solanaceae plant family and represent good model systems for studying regulatory and evolutionary controls established between hosts and transposable elements. Tnt1 retrotransposons tightly control their activation, by restricting expression to specific conditions. The Tnt1A element, originally discovered in tobacco, is expressed in response to stress, and its activation by microbial factors is followed by amplification, demonstrating that factors of pathogen origin can generate genetic diversity in plants. The Tnt1A promoter has the potential to be activated by various biotic and abiotic stimuli but a number of these are specifically repressed in tobacco and are revealed only when the LTR promoter is placed in a heterologous context. We propose that a tobacco- and stimulus-specific repression has been established in order to minimize activation in conditions that might generate germinal transposition. In addition to tight transcriptional controls, Tnt1A retrotransposons self-regulate their activity through gradual generation of defective copies that have reduced transcriptional activity. Tnt1 retrotransposons found in various Solanaceae species are characterized by a high level of variability in the LTR sequences involved in transcription, and have evolved by gaining new expression patterns, mostly associated with responses to diverse stress conditions. Tnt1A insertions associated with genic regions are initially favored but seem subsequently counter-selected, while insertions in repetitive DNA are maintained. On the other hand, amplification and loss of insertions may result from more brutal occurrences, as suggested by the large restructuring of Tnt1 populations observed in tobacco compared to each of its parental species. The distribution of Tnt1 elements thus appears as a dynamic flux, with amplification counterbalanced by loss of insertions. Tnt1 insertion polymorphisms are too high to reveal species relationships in the Nicotiana genus, but can be used to evaluate species relationships in the Lycopersicon and Capsicum genera. This also demonstrates that the behavior of Tnt1 retrotransposons differs between host species, most probably in correlation to differences in expression conditions and in the evolutionary and environmental history of each host.   

Araujo PG, Casacuberta JM, Costa APP, Hashimoto RY, Grandbastien M-A, Van Sluys M-A: Retrolyc1 subfamilies defined by different U3 regulatory regions in the Lycopersicon genus. Mol Gen Genom 266:35–41 (2001).
Arnaud P, Goubely C, Pélissier T, Deragon JM: SINE retroposons can be used in vivo as nucleation centers for de novo methylation. Mol Cell Biol 20:3434–3441 (2000).
Beguiristain T, Grandbastien M-A, Puigdomenech P, Casacuberta JM: Three Tnt1 subfamilies show different stress-associated patterns of expression in tobacco. Consequences for retrotransposon control and evolution in plants. Plant Physiol 127:212–221 (2001).
Bennetzen JL: Mechanisms and rates of genome expansion and contraction in flowering plants. Genetica 115:29–36 (2002).
Brosius J: Genomes were forged by massive bombardments with retroelements and retrosequences. Genetica 107:209–238 (1999).
Capy P: Classification of transposable elements, in Capy P, et al. (eds): Dynamics and Evolution of Transposable Elements, pp 37–52 (Landes Bioscience, Austin 1998).
Casacuberta JM, Grandbastien M-A: Characterisation of LTR sequences involved in the protoplast specific expression of the tobacco Tnt1 retrotransposon. Nucleic Acids Res 21:2087–2093 (1993).
Casacuberta JM, Santiago N: Plant LTR-retrotransposons and MITEs: control of transposition and impact on the evolution of plant genes and genomes. Gene 311:1–11 (2003).
Casacuberta JM, Vernhettes S, Grandbastien M-A: Sequence variability within the tobacco retrotransposon Tnt1 population. EMBO J 14:2670–2678 (1995).
Casacuberta JM, Vernhettes S, Audéon C, Grandbastien M-A: Quasispecies in retrotransposons: a role for sequence variability in Tnt1 evolution. Genetica 100:109–117 (1997).
Chase MW, Cox AV, Clarkson J, Knapp S, Marshall JA, Parokonny AS: Molecular systematics, GISH and the origin of hybrid taxa in Nicotiana (Solanaceae). Ann Botany 92:107–127 (2003).
Comai L: Genetic and epigenetic interactions in allopolyploid plants. Plant Mol Biol 43:387–399 (2000).
Costa APP, Scortecci KC, Hashimoto RY, Araujo PG, Grandbastien M-A, Van Sluys M-A: Retrolyc1-1, a member of the Tnt1 retrotransposon super-family in the Lycopersicon peruvianum genome. Genetica 107:65–72 (1999).
Courtial B, Feurbach F, Eberhard S, Rohmer L, Chiapello H, Camilleri C, Lucas H: Tnt1 transposition events are induced by in vitro transformation of Arabidopsis thaliana, and transposed copies integrate into genes. Mol Genet Genomics 265:32–42 (2001).
Dellaporta SL, Chomet PS, Mottinger JP, Wood JA, Yu SM, Hicks JB: Endogenous transposable element associated with virus infection in maize. Cold Spring Harbor Symp Quant Biol 49:321–328 (1984).
Domingo E, Martina-Salas E, Sobrino F, de la Torre JC, Portela A, Ortin J, Lopez-Galindez C, Perez-Brena P, Villanueva N, Najera R, VandePol S, Steinhauer S, DePolo N, Holland JJ: The quasispecies (extremely heterogeneous) nature of viral RNA genome populations: biological relevance – a review. Gene 40:1–8 (1985).
d’Erfuhrth I, Cosson V, Eschstruth A, Lucas H, Kondorosi A, Ratet P: Efficient transposition of the Tnt1 tobacco retrotransposon in the model legume Medicago truncatula. Plant J 33:1–12 (2003).
Eugelm T, Rushton PJ, Robatzek S, Somssich IE: The WRKY superfamily of plant transcription factors. Trends Plant Sci 5:199–206 (2000).
Ganko EW, Bhattacharjee V, Schliekelman P, McDonald JF: Evidence for the contribution of LTR retrotransposons to C. elegans gene evolution. Mol Biol Evol, online (http://mbeoupjournalsorg/cgi/reprint/msg200v1) Mol Biol Evol 20:1925–1931 (2003).
Garreton V, Carpinelli J, Jordana X, Holuigue L: The as-1 promoter element is an oxydative stress-responsive element and salicylic acid activated it via oxidative species. Plant Physiol 130: 1516–1526 (2002).
Goldsbrough AP, Albrecht H, Stratford R: Salicylic acid inducible binding of a tobacco nuclear protein to a 10 bp sequence which is highly conserved among stress-inducible genes. Plant J 3:563–571 (1993).
Goodspeed TH: The genus Nicotiana. (Chronica Botanica Company, Massachusetts 1954).
Grandbastien M-A: Activation of plant retrotransposons under stress conditions. Trends Plant Sci 3:181–187 (1998).
Grandbastien M-A, Spielmann A, Caboche M: Tnt1, a mobile retroviral-like transposable element of tobacco isolated via plant cell genetics. Nature 337:376–380 (1989).
Grandbastien M-A, Lucas H, Mhiri C, Morel J-B, Vernhettes S, Casacuberta JM: The expression of the tobacco Tnt1 retrotransposon is linked to the plant defense response. Genetica 100:241–252 (1997).
Grimmig B, Gonzalez-Perez MN, Leubner-Metzger G, Vogeli-Lange R, Meins F Jr, Hain R, Penuelas J, Heidenreich B, Langebartels C, Ernst D, Sandermann H Jr: Ozone-induced gene expression occurs via ethylene-dependent and -independent signalling. Plant Mol Biol 51:599–607 (2003).
Hart CM, Nagy F, Meins FJ: A 61 bp enhancer element of the tobacco 1,3 glucanase B gene interacts with one or more regulated nuclear proteins. Plant Mol Biol 21:121–131 (1993).
Hirochika H: Activation of plant retrotransposons by stress, in Oono K, Takaiwa F (eds): Modification of Gene Expression and Non-Mendelien Inheritance, pp 15–21 (National Institute of Agrobiological Resources, Tsukuba 1995).
Hirochika H, Okamoto H, Kakutani T: Silencing of retrotransposons in Arabidopsis and reactivation by the ddm1 mutation. Plant Cell 12:357–368 (2000).
Hoeren FU, Dolferus R, Wu Y, Peacock WJ, Dennis ES: Evidence for a role for AtMYB2 in the induction of the Arabidopsis alcohol dehydrogenase gene (ADH1) by low oxygen. Genetics 149:479–490 (1998).
IHGSC (International Human Genome Sequencing Consortium): Initial sequencing and analysis of the human genome. Nature 409:860–921 (2001).
Johns MA, Mottinger J, Freeling M: A low copy number, copia-like transposon in maize. EMBO J 4:1093–1102 (1985).
Jordan IK, Rogozin IB, Glazko GV, Koonin EV: Origin of a substantial fraction of human regulatory sequences from transposable elements. Trends Genet 19:68–72 (2003).
Kalendar R, Tanskanen J, Immonen S, Nevo E, Schulman A: Genome evolution of wild barley (Hordeum spontaneum) by BARE-1 retrotransposon dynamics in response to sharp microclimati divergence. Proc Natl Acad Sci USA 97:6603–6607 (2000).
Kashkush K, Feldman M, Levy AA: Transcriptional activation of retrotransposons alters the expression of adjacent genes in wheat. Nat Genet 33:102–106 (2003).
Korfhage U, Trezzini GF, Meier I, Hahlbrock K, Somssich IE: Plant homeodomain protein involved in transcriptional regulation of a pathogen defense-related gene. Plant Cell 6:695–708 (1994).
Kovalchuk I, Kovalchuk O, Kalk V, Boyko V, Filkowski J, Heinlein M, Hohn B: Pathogen-induced systemic plant signal triggers DNA rearrangements. Nature 423:760–762 (2003).
Kumar A, Bennetzen JL: Plant retrotransposons. Annu Rev Genet 33:479–532 (1999).
Labrador M, Farré M, Utzet F, Fontdevila A: Interspecific hybridization increases transposition rates of Osvaldo. Mol Biol Evol 16:931–937 (1999).
Landry J-R, Mager D, Wilhelm BT: Complex controls: the role of alternative promoters in mammalian genomes. Trends Genet 19:640–648 (2003).
Lenoir A, Lavie L, Prieto J-L, Goubely C, Côté J-C, Pélissier T, Deragon J-M: The evolutionary origin and genomic organization of SINEs in Arabidopsis thaliana. Mol Biol Evol 18:2315–2322 (2001).
Leprince AS, Grandbastien M-A, Meyer C: Retrotransposons of the Tnt1B family are mobile in Nicotiana plumbaginifolia and can induce alternative splicing of the host gene upon insertion. Plant Mol Biol 47:533–541 (2001).
Levy AA, Feldman M: The impact of polyploidy on grass genome evolution. Plant Physiol 130:1587–1593 (2002).
Liu B, Wendel JF: Retrotransposon activation followed by rapid repression in introgressed rice plants. Genome 43:874–880 (2000).
Loake GJ, Faktor O, Lamb CJ, Dixon RA: Combination of H-box and G-box cis elements is necessary for feedforward stimulation of a chalcone synthase promoter by the phenylpropanoid-pathway intermediate p-coumaric acid. Proc Natl Acad Sci USA 89:9230–9234 (1992).
Lönnig W-E, Saedler H: Chromosome rearrangements and transposable elements. Annu Rev Genet 36:389–410 (2002).
Marillonnet S, Wessler SR: Retrotransposon insertion into the maize waxy gene results in tissue-specific RNA processing. Plant Cell 1997 9:967–978 (1997).
Medstrand P, van de Lagemaat LN, Mager DL: Retroelement distributions in the human genome: variations associated with age and proximity to genes. Genome Res 12:1483–1495 (2002).
Melayah D, Bonnivard E, Chalhoub B, Audéon C, Grandbastien M-A: The mobility of the tobacco Tnt1 retrotransposon correlates with its transcriptional activation by fungal factors. Plant J 28:159–168 (2001).
Melayah D, Lim KY, Bonnivard E, Chalhoub B, Dorlhac de Borne F, Mhiri C, Leitch AR, Grandbastien M-A: Distribution of the Tnt1 retrotransposon family in the amphidiploid tobacco (Nicotiana tabacum) and its wild Nicotiana relatives. Biol J Linnean Soc, in press (2004).
Mhiri C, Morel J-B, Vernhettes S, Casacuberta P, Lucas H, Grandbastien M-A: The promoter of the tobacco Tnt1 retrotransposon is induced by wounding and by abiotic stress. Plant Mol Biol 33:257–266 (1997).
Mhiri C, De Wit PJGM, Grandbastien M-A: Expression of the Tnt1 retrotransposon in tomato after inoculation with the fungal pathogen Cladosporium fulvum. Mol Plant-Microbe Interact 12:592–603 (1999).
Moreau-Mhiri C, Morel J-B, Audéon C, Ferault M, Grandbastien M-A, Lucas H: Regulation of the tobacco Tnt1 retrotransposon in heterologous species following pathogen-related stress. Plant J 9:409–419 (1996).
Okamoto H, Hirochika H: Silencing of transposable elements in plants. Trends Plant Sci 6:527–534 (2001).
Pauls PK, Kunert K, Huttner E, Grandbastien M-A: Expression of the tobacco Tnt1 retrotransposon promoter in heterologous species. Plant Mol Biol 26:393–402 (1994).
Pourtau N, Lauga B, Audéon C, Grandbastien M-A, Goulas P, Salvado J-C: The promoter of the Tnt1A retrotransposon is activated by ozone air pollution in tomato, but not in its natural host tobacco. Plant Sci 165:983–992 (2003).
Pouteau S, Huttner E, Grandbastien M-A, Caboche M: Specific expression of the tobacco Tnt1 retrotransposon in protoplasts. EMBO J 10:1911–1918 (1991).
Pouteau S, Grandbastien M-A, Boccara M: Microbial elicitors of plant defense responses activate transcription of a retrotransposon. Plant J 5:535–542 (1994).
Romero I, Fuertes A, Benito MJ, Malpica JM, Leyva A, Paz-Ares J: More than 80R2R3-MYB regulatory genes in the genome of Arabidopsis thaliana. Plant J 14:273–284 (1998).
Ruiz-Lara S, Tapia G, Yanez M, Verdugo I, Ahumada I, Gonzalez E: Ethylene involvement in stress-induced expression of the TLC1.1 retrotransposon from Lycopersicon chilense. 7th International Congress of Plant Molecular Biology, June 23–28, Barcelona, Spain, Abstract W01–20 (2003).
Schramke V, Allshire R: Hairpin RNAs and retrotransposon LTRs effect RNAi and chromatin-based gene silencing. Science 301:1069–1074 (2003).
Shinozaki K, Yamaguchi-Shinozaki K, Seki M: Regulatory network of gene expression in the drought and cold stress responses. Curr Opin Plant Biol 6:410–417 (2003).
Simpson SD, Nakashima K, Narusaka Y, Seki M, Shinozaki K, Yamaguchi-Shinozaki K: Different novel cis-acting elements of erd1, a clpA homologous Arabidopsis gene function in induction by dehydration stress and dark-induced senescence. Plant J 33:259–270 (2003).
Steward N, Ito M, Yamaguchi Y, Koizumi N, Sano H: Periodic DNA methylation in maize nucleosomes and demethylation by environmental stress. J Biol Chem 277:37741–37746 (2002).
Takeda S, Sugimoto K, Otsuki H, Hirochika H: A 13-bp cis-regulatory element in the LTR promoter of the tobacco retrotransposon Tto1 is involved in responsiveness to tissue culture, wounding, methyl jasmonate and fungal elicitors. Plant J 18:383–393 (1999).
Takeda S, Sugimoto K, Kakutani T, Hirochika H: Linear DNA intermediates of the Tto1 retrotransposon in Gag particles accumulated in stressed tobacco and Arabidopsis thaliana. Plant J 28:307–317 (2001).
Tikhonov AP, SanMiguel PJ, Nakajima Y, Gorenstein NM, Bennetzen JL, Avramova Z: Colinearity and its exceptions in orthologous adh regions of maize and sorghum. Proc Natl Acad Sci USA 96:7409–7414 (1999).
van de Lagemaat LN, Landry JR, Mager DL, Medstrand P: Transposable elements in mammals promote regulatory variation and diversification of genes with specialized functions. Trends Genet 19:530–536 (2003).
Varagona MJ, Purugganan M, Wessler SR: Alternative splicing induced by insertion of retrotransposons into the maize waxy gene. Plant Cell 4:811–820 (1992).
Vernhettes S, Grandbastien M-A, Casacuberta JM: In vivo characterization of transcriptional regulatory sequences involved in the defence-associated expression of the tobacco retrotransposon Tnt1. Plant Mol Biol 35:673–679 (1997).
Vernhettes S, Grandbastien M-A, Casacuberta JM: The evolutionary analysis of the Tnt1 retrotransposon in Nicotiana species reveals the high plasticity of its regulatory sequences. Mol Biol Evol 15:827–836 (1998).
Waugh R, McLean K, Flavell AJ, Pearce SR, Kumar A, Thomas BBT, Powel W: Genetic distribution of Bare-1-like retrotransposable elements in the barley genome revealed by sequence-specific amplification polymorphisms (SSAP). Mol Gen Genet 253:687–694 (1997).
Waugh O’Neill RJ, O’Neill MJ, Marshall Graves JA: Undermethylation associated with retroelement activation and chromosome remodelling in an interspecific mammalian hybrid. Nature 393:68–72 (1998).
Wendel JF, Cronn RC, Johnston JS, Price HJ: Feast and famine in plant genomes. Genetica 115:37–47 (2002).
Wessler SR: Plant retrotransposons: turned on by stress. Curr Biol 6:959–961 (1996).
Wessler SR, Bureau TE, White SE: LTR-retrotransposons and MITEs: important players in the evolution of plant genomes. Curr Opin Genet Dev 5:814–21 (1995).
White SE, Habera LF, Wessler SR: Retrotransposons in the flanking regions of normal plant genes: a role for copia-like elements in the evolution of gene structure and expression. Proc Natl Acad Sci USA 91:11792–11796 (1994).
Wohlgemuth H, Mittelstrass K, Kschieschan S, Bender J, Weigel HJ, Overmyer K, Kangasjarvi J, Sandermann H, Langebartels C: Activation of an oxidative burst is a general feature of sensitive plants exposed to the air pollutant ozone. Plant Cell Environ 25:717–726 (2002).
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.