02538nas a2200241   4500008004100000022001400041245015600055210006900211260001600280300000700296490000700303520174800310100001802058700002202076700002102098700002002119700002602139700002702165700001602192700002102208700001802229856004902247       2015                        eng d  a1471-216400aInvolvement of a citrus meiotic recombination TTC-repeat motif in the formation of gross deletions generated by ionizing radiation and MULE activation.0 aInvolvement of a citrus meiotic recombination TTCrepeat motif in  c2015 Feb 13  a690 v163 aBACKGROUND: Transposable-element mediated chromosomal rearrangements require the involvement of two transposons and two double-strand breaks (DSB) located in close proximity. In radiobiology, DSB proximity is also a major factor contributing to rearrangements. However, the whole issue of DSB proximity remains virtually unexplored. RESULTS: Based on DNA sequencing analysis we show that the genomes of 2 derived mutations, Arrufatina (sport) and Nero (irradiation), share a similar 2 Mb deletion of chromosome 3. A 7 kb Mutator-like element found in Clemenules was present in Arrufatina in inverted orientation flanking the 5’ end of the deletion. The Arrufatina Mule displayed "dissimilar" 9-bp target site duplications separated by 2 Mb. Fine-scale single nucleotide variant analyses of the deleted fragments identified a TTC-repeat sequence motif located in the center of the deletion responsible of a meiotic crossover detected in the citrus reference genome. CONCLUSIONS: Taken together, this information is compatible with the proposal that in both mutants, the TTC-repeat motif formed a triplex DNA structure generating a loop that brought in close proximity the originally distinct reactive ends. In Arrufatina, the loop brought the Mule ends nearby the 2 distinct insertion target sites and the inverted insertion of the transposable element between these target sites provoked the release of the in-between fragment. This proposal requires the involvement of a unique transposon and sheds light on the unresolved question of how two distinct sites become located in close proximity. These observations confer a crucial role to the TTC-repeats in fundamental plant processes as meiotic recombination and chromosomal rearrangements.1 aTerol, Javier1 aIbañez, Victoria1 aCarbonell, José1 aAlonso, Roberto1 aEstornell, Leandro, H1 aLicciardello, Concetta1 aGut, Ivo, G1 aDopazo, Joaquín1 aTalon, Manuel  uhttp://www.biomedcentral.com/1471-2164/16/69