Epigenetic Interactions among Three dTph1 Transposons in Two Homologous Chromosomes Activate a New Excision-Repair Mechanism in Petunia

Houwelingen, Adèle van; Souer, Erik; Mol, J.G.J.; Koes, Ronald

doi:10.2307/3870752

Cited by 11 publications

(13 citation statements)

References 4 publications

(6 reference statements)

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“…Figure 7A shows that the Ϫ1-and ϩ4-bp frameshift mutations can be explained, consistent with existing models for footprint formation, by two independent excisions of the same Activator-like transposon. However, in our analyses of footprints produced by dTph1 elements, we never found the relatively large deletions in the target site duplication inferred in Figure 7A, suggesting that these may be rare events (van Houwelingen et al, 1999).…”

Section: The Role Of Transposons In the Generation Of An2 ϫ Allelesmentioning

confidence: 62%

Molecular Analysis of the anthocyanin2 Gene of Petunia and Its Role in the Evolution of Flower Color

et al. 1999

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The shape and color of flowers are important for plant reproduction because they attract pollinators such as insects and birds. Therefore, it is thought that alterations in these traits may result in the attraction of different pollinators, genetic isolation, and ultimately, (sympatric) speciation. Petunia integrifolia and P. axillaris bear flowers with different shapes and colors that appear to be visited by different insects. The anthocyanin2 ( an2 ) locus, a regulator of the anthocyanin biosynthetic pathway, is the main determinant of color differences. Here, we report an analysis of molecular events at the an2 locus that occur during Petunia spp evolution. We isolated an2 by transposon tagging and found that it encodes a MYB domain protein, indicating that it is a transcription factor. Analysis of P. axillaris subspecies with white flowers showed that they contain an2 Ϫ alleles with two alternative frameshifts at one site, apparently caused by the insertion and subsequent excision of a transposon. A third an2 ؊ allele has a nonsense mutation elsewhere, indicating that it arose independently. The distribution of polymorphisms in an2 ؊ alleles suggests that the loss of an2 function and the consequent changes in floral color were not the primary cause for genetic separation of P. integrifolia and P. axillaris. Rather, they were events that occurred late in the speciation process, possibly to reinforce genetic isolation and complete speciation. INTRODUCTIONFlowers are the structures containing the male and female sex organs of angiosperms. Flowers of diverse species display a wide range of different morphologies and pollination strategies. For instance, flowers of wind-pollinated species usually possess small and inconspicuous petals or no petals at all, whereas flowers of insect-pollinated plants usually possess large, brightly colored, and patterned petals that serve as visual signals and a landing site for visiting insects.Recent experiments suggest that the wide variety of plant and flower morphologies may have depended on the evolution of a relatively small number of genes. First, mutations at single loci, usually isolated by breeders or researchers, are sufficient to cause fundamental alterations in inflorescence architecture (Doebley et al., 1997;Souer et al., 1998). Similarly, the different shapes, colors, and color patterns of naturally occurring Mimulus (monkeyflower) spp are due to alterations at only a few (major) loci (Bradshaw et al., 1995).Second, even very different inflorescence and flower architectures appear to be determined by genes that often encode conserved proteins but that differ in their expression patterns (reviewed in Doebley and Lukens, 1998).The isolation of key regulatory loci and analysis of the molecular alterations that have taken place in them will provide new insights into the evolution and diversification of flower morphology. The biosynthesis of anthocyanin flower pigments is particularly suited for such studies, because it is a well-defined biochemical pathway that is being...

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Section: The Role Of Transposons In the Generation Of An2 ϫ Allelesmentioning

confidence: 62%

Molecular Analysis of the anthocyanin2 Gene of Petunia and Its Role in the Evolution of Flower Color

et al. 1999

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“…Features are shared with trans-silencing phenomena in Drosophila (Henikoff and Comai 1998) and fungi (Colot et al 1996;van West et al 1999) (McClintock 1965;Krebbers et al 1987;Martienssen 1996). Also, allele interactions between transposons alter the excision-repair mechanism (van Houwelingen et al 1999). An eventual understanding of mechanisms underlying paramutation should reveal how alleles and other homologous sequences interact in the nucleus to influence the regulation of each other, and how heritable expression states are established, maintained through numerous cell divisions, and transmitted to the next generation.…”

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confidence: 99%

Differential chromatin structure within a tandem array 100 kb upstream of the maize b1 locus is associated with paramutation

Stam¹,

Belele²,

Dorweiler³

et al. 2002

Genes Dev.

255

280

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Recombination mapping defined a 6-kb region, 100 kb upstream of the transcription start site, that is required for B-I enhancer activity and paramutation-a stable, heritable change in transcription caused by allele interactions in maize (Zea mays). In this region, B-I and B (the only b1 alleles that participate in paramutation) have seven tandem repeats of an 853-bp sequence otherwise unique in the genome; other alleles have one. Examination of recombinant alleles with different numbers of tandem repeats indicates that the repeats are required for both paramutation and enhancer function. The 6-kb region is identical in B-I and B, showing that epigenetic mechanisms mediate the stable silencing associated with paramutation. This is the first endogenous gene for which sequences required for paramutation have been defined and examined for methylation and chromatin structure. The tandem repeat sequences are more methylated in B-I (high expressing) relative to B (low expressing), opposite of the typical correlation. Furthermore, the change in repeat methylation follows establishment of the B epigenetic state. B-I has a more open chromatin structure in the repeats relative to B. The nuclease hypersensitivity differences developmentally precede transcription, suggesting that the repeat chromatin structure could be the heritable imprint distinguishing the two transcription states.

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“…Meyer et al, 1993;Patterson et al, 1993;Hollick et al, 2000;Mittelsten Scheid et al, 2003), but it can also affect other processes, such as transposition (Harrison and Carpenter, 1973;vanHouwelingen et al, 1999) or recombination (Rassoulzadegan et al, 2002). In this review, for simplicity, the term 'gene expression' will be used to indicate the affected process.…”

Section: Transcriptional Gene Silencingmentioning

confidence: 99%

“…In most paramutation phenomena repeated sequences are required for the paramutation process English and Jones, 1998;Luff et al, 1999;vanHouwelingen et al, 1999;Walker and Panavas, 2001;Stam et al, 2002). Repeated sequences are a major trigger for the formation of silenced chromatin (Grewal and Jia, 2007;Zaratiegui et al, 2007).…”

Section: Sequence Features: Repeated Sequencesmentioning

confidence: 99%

“…Two dTph1 transposons organized in an IR are necessary for a paramutation-like trans-interaction that results in a novel transposition mechanism in petunia plants (vanHouwelingen et al, 1999). Furthermore, all examined paramutable r1 alleles (16) contain two r1 genes in an IR organization (Walker and Panavas, 2001).…”

Section: Sequence Features: Repeated Sequencesmentioning

confidence: 99%

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Paramutation: Heritable in TransEffects

Stam

Louwers

Handbook of Maize

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Paramutation is the heritable transfer of epigenetic information from one allele of a gene to another allele of the same gene. In general, the consequence of this trans-communication is a change in gene expression. Paramutation has been observed in plants, fungi and mammals, but is most extensively studied in maize thanks to the long-standing history of maize genetics. For decades, paramutation has been a mystery, but recent progress has shed light on the mechanisms underlying this phenomenon. The identification of MOP1 as an RNA-dependent RNA polymerase shows that RNA plays a crucial role in the trans-inactivation process. RNA however appears not the only player in the paramutation process. In this chapter, potential mechanisms will be discussed in light of characteristics that the various paramutation phenomena have in common.

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Epigenetic Interactions among Three dTph1 Transposons in Two Homologous Chromosomes Activate a New Excision-Repair Mechanism in Petunia

Cited by 11 publications

References 4 publications

Molecular Analysis of the anthocyanin2 Gene of Petunia and Its Role in the Evolution of Flower Color

Molecular Analysis of the anthocyanin2 Gene of Petunia and Its Role in the Evolution of Flower Color

Differential chromatin structure within a tandem array 100 kb upstream of the maize b1 locus is associated with paramutation

Paramutation: Heritable in TransEffects

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