Transposition in plants: a molecular model

Saedler, Heinz; Nevers, Patricia

doi:10.1002/j.1460-2075.1985.tb03670.x

Cited by 223 publications

(115 citation statements)

References 27 publications

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“…This footprint can also be explained by the model if it is assumed that in this case the staggered nicks that initiated excision were misplaced and occurred five bases to the left of the left set of duplicated bases and one base to the right of the right set of duplicated bases. While the footprint data presented above are entirely consistent with the model of Saedler and Nevers (1985), and as interpreted provide strong support for it, other interpretations are possible, and the data do not necessarily preclude other models.…”

Section: Footprints Found In M a + Revertants Of Crh22 Are Similar Tosupporting

confidence: 60%

“…Analysis of footprints has inspired several transposition models in plants, including one by Saedler and Nevers (1985) that invokes participation of the cell's DNA repair system in excision to explain the alterations of target site duplications that are commonly observed. One such class of alterations consists of the addition of extra nucleotides that represent partial inversions of one or both copies of the target site duplication, accounted for in the model by template switching at one or both termini of the element during excision.…”

Section: Footprints Found In M a + Revertants Of Crh22 Are Similar Tomentioning

confidence: 99%

“…One footprint contained two copies of the CCT inversion. These 10 footprints fall neatly into the two subclasses predicted by the model of Saedler and Nevers (1985) to occur with template switching, the first nine (CCTAGG) when switching occurs at one end of the transposon and the last (CCTCCTAGG) when switching occurs at both ends. The remaining footprint (found in CRH22-Rll) is more complex; in this case, the inverse of the eight base pairs of nitA sequence immediately adjacent to the left end of the insertion site plus the inverse of the four base pairs immediately adjacent to the right end of the insertion site were inserted between the sets of bases duplicated during the insertion event.…”

Section: Footprints Found In M a + Revertants Of Crh22 Are Similar Tomentioning

confidence: 99%

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Jordan, an active Volvox transposable element similar to higher plant transposons.

1993

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We have isolated a 1595-bp transposable element from the multicellular green alga Volvox carteri following its insertion into the nitrate reductase (nitA) locus. This element, which we have named Jordan, has short (12-bp) terminal inverted repeats and creates a 3-bp target site duplication, like some higher plant transposons of the classic type. Contained within the first 200 bp of one end of the element are 55-bp inverted repeats, one of which begins with the terminal inverted repeat. Revertants of the transposon insertion into the nitA locus were obtained at a rate of . u~O -~ per Volvox embryo per generation. In each revertant examined, all transposon sequences were completely excised, but footprints containing both sets of duplicated bases, in addition to three to nine extra bases, were left behind. Jordan contains no significant open reading frames and so appean to be nonautonomous. DNA gel blot analysis indicates that Jordan is a member of a large family of homologous elements in the Volvox genome. We have isolated and characterized several of these homologs and found that they contain termini very similar to those of Jordan. Efforts to utilize Jordan and its homologs as tools to tag and clone developmentally interesting genes of Volvox are discussed.

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Section: Footprints Found In M a + Revertants Of Crh22 Are Similar Tosupporting

confidence: 60%

Section: Footprints Found In M a + Revertants Of Crh22 Are Similar Tomentioning

confidence: 99%

Section: Footprints Found In M a + Revertants Of Crh22 Are Similar Tomentioning

confidence: 99%

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Jordan, an active Volvox transposable element similar to higher plant transposons.

1993

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“…For band 6, 2,369 bp of Ac were deleted, but two Ac regions were duplicated following the breakpoint (100% identity to Ac bases 2116 to 2125 and 2118 to 2136). Surprisingly, two events (bands 5 and 7) contained typical excision footprints (52,54) in the Waxy host duplication (data not shown) in addition to the deletions and insertions described above.…”

Section: Resultsmentioning

confidence: 87%

“…Errors in this process would lead to the replacement of the excised element by a mutated copy, i.e., a new Ds element. We therefore conclude that, typically, Ds formation occurs through homologous recombination between the broken donor site and its homologous region, and we rule out DSB repair mechanisms that do not involve DNA synthesis, such as the single strand annealing (SSA) model (31) or end-joining of broken ends at the donor site (52,54).…”

Section: Discussionmentioning

confidence: 99%

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

Rubin

Levy

1997

Molecular and Cellular Biology

114

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The mechanism by which the maize autonomous Ac transposable element gives rise to nonautonomous Ds elements is largely unknown. Sequence analysis of native maize Ds elements indicates a complex chimeric structure formed through deletions of Ac sequences with or without insertions of Ac-unrelated sequence blocks. These blocks are often flanked by short stretches of reshuffled and duplicated Ac sequences. To better understand the mechanism leading to Ds formation, we designed an assay for detecting alterations in Ac using transgenic tobacco plants carrying a single copy of Ac. We found frequent de novo alterations in Ac which were excision rather than sequence dependent, occurring within Ac but not within an almost identical Ds element and not within a stable transposase-producing gene. The de novo DNA rearrangements consisted of internal deletions with breakpoints usually occurring at short repeats and, in some cases, of duplication of Ac sequences or insertion of Ac-unrelated fragments. The ancient maize Ds elements and the young Ds elements in transgenic tobacco showed similar rearrangements, suggesting that Ac-Ds elements evolve rapidly, more so than stable genes, through deletions, duplications, and reshuffling of their own sequences and through capturing of unrelated sequences. The data presented here suggest that abortive Ac-induced gap repair, through the synthesis-dependent strand-annealing pathway, is the underlying mechanism for Ds element formation.Dissociation, or Ds, is the first discovered transposable element (TE). It was identified as a maize locus on chromosome 9, where breaks occur in the presence of Activator (Ac), a second gene found at a separate locus (33,34). Subsequent studies showed that Ac can transpose autonomously whereas Ds moves only in the presence of Ac (35,36). In addition, Ac activity can turn into a Ds type of instability, while no occurrences were found of Ds turning into Ac (37, 38). On the basis of these observations, McClintock proposed that Ds nonautonomous elements are derived from Ac through mutations (39). The proposal that Ac and Ds are phylogenetically related has been supported by molecular analysis, as described below, but the mechanism responsible for the conversion of Ac into Ds is still unknown.Ac is a 4.6-kb-long element flanked by 11-bp terminal inverted repeats (TIRs) (12). It encodes an 807-amino-acid protein, the transposase, necessary for both Ac and Ds transposition (28). Ds elements, on the other hand, do not encode a functional transposase but retain regions which are essential for their transposition (6). There are six fully sequenced Ds elements, all of which share with Ac nearly identical TIRs and fall into the following four categories: (i) those with nearly no similarity to Ac, like Ds1 (57); (ii) elements with highly similar subterminal regions but with internal deletions, like Ds9 (46); (iii) double Ds elements where one internally deleted Ds is inserted into another identical Ds in an inverted orientation (9); and (iv) Ds elements that contain bot...

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Mobile Elements in Maize

Petérson

1986

Plant Breeding Reviews

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Transposition in plants: a molecular model

Abstract: A molecular model for transposition of plant transposable elements is described. This process may occur via excision and re‐integration of the element. Excision generates DNA sequence diversity which suggests the participation of DNA repair enzymes in the healing of the donor molecule.

Cited by 223 publications

References 27 publications

Jordan, an active Volvox transposable element similar to higher plant transposons.

Jordan, an active Volvox transposable element similar to higher plant transposons.

Abortive Gap Repair: Underlying Mechanism for Ds element Formation

Mobile Elements in Maize

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