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Transcriptional activation of retrotransposons alters the expression of adjacent genes in wheat

Transcriptional activation of retrotransposons alters the expression of adjacent genes in wheat. Khalil Kashkush, Moshe Feldman & Avraham A. Levy. Department of Plant Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel. Kim Tae Hyung 2005. 01. 08.

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Transcriptional activation of retrotransposons alters the expression of adjacent genes in wheat

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  1. Transcriptional activation of retrotransposons alters the expression of adjacent genes in wheat Khalil Kashkush, Moshe Feldman & Avraham A. Levy Department of Plant Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel Kim Tae Hyung 2005. 01. 08

  2.   HERVs Expression and Structure Analysis System

  3. Alternative promoter of intergenic

  4. TransposonsWe are focusing on the Ac/Ds elements; on their origin, on their regulation and on the intermediates of transposition. DSB repair We have studied the repair of DSBs generated by transposons, and we showed that these breaks can be repaired by homologous recombination between ectopic sequences. We have studied the repair of breaks done in vitro and characterized the end joining products. In general, we found the DSB repair in plants is error-prone. Accurate repair via homologous recombination is a less prominent DSB repair pathway in plants than non-homologous end-joining. Polyploidy-induced DNA rearrangements We have shown, in collaboration with Prof. Moshe Feldman, that certain DNA sequences that were isolated by microdissection of wheat chromosomes undergo rapid elimination as a result of polyploidy. We are currently investigating the underlying mechanism of this polyploidy-induced sequence elimination. Genetic tools We have developed a miniature tomato cultivar with a rapid growth cycle as a model system for forward and reverse genetics in tomato (Meissner et al., 1997; Meissner et al. 2000). We are using this cultivar for large scale mutagenesis via transposon, EMS andfast-neutron. This work was initiated under the auspices of the Israeli plant genome center. We have shown that the bacterial genes, RuvC stimulates homologous recombination in plants. We have isolated hyper-recombinogenic mutants and we are testing whether these mutants and plants expressing bacterial genes can be used for improving the efficiency of gene targteting. Levy lab’s research interests

  5. Analysis of the Wis2-1A retrotransposon activation T.monococcum ssp. aegilopodes (AmAm) Amphiploid (BBAA) Ae. Sharonensis (SlSI) Internal Wis 2-1A fragment (RT) More than 1000 sites cDNA-AFLP Northern Control (18S rDNA probe) Southern 8kb band

  6. cDNA-retrotransposon display Amphiploid vs Diploids 360 transcripts Putative activation Putative silencing Negative control 26/360  7% 10 of 26 only appeared in the amphiploid 16 of 26 were only present in both parents

  7. Molecular characterization of chimeric transcripts 22/26 (gel purified & sequenced) In most cases, the LTR was positioned in the 3’UTR downstream of the neighboring gene Similarity to Psal 8 new transcripts (Wis23, 29, 30, 31, 35, 36, 37, 39) were unknown sequence. 6 (Wis38, 40, 24, 28, 43, 44) corresponded to wheat or barley ESTs with no known homology. 6 ( Wis25, 34, 41, 42, 26, 32) were similar to previously characterized genes.

  8. Expression of transcripts flanking LTRs RNase treatment silencing activation Promoter activity of the 5’LTR with TSS in U3 region Quantitative RT-PCR (12 cycles)

  9. Induction of the iojap-like antisense transcript from the 5’ LTR Quantitative RT-PCR (12 cycles) The level of expression was 156 times higher in the amphiploid than in the diploid parents

  10. Disruption of normal gene expression Generate new patterns of gene expression Generate antisense RNA for neighboring elements Help maintain silence of the gene family Alternative promoter Intragenic analysis Effective of Coding capacity Tissue specificity Discussions

  11. >50kb

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