epigenetic regulation ataee

Epigenetic Regulationof Transposable Elements

in Plants

Presented by: Elham Ataee

Shiraz university

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Contents

1. TRANSPOSON DEFINITION2. TYPES OF TRANSPOSABLE ELEMENTS3. SILENCING MECHANISMS THAT SUPPRESS TEs

Transposon Recognition and Initiation of Silencing Post-transcriptional silencing of TEs by RNAi Chromatin modifications Maintenance and Memory

4 .TRANSPOSON REACTIVATION

5 .TE SPECIFICITIES AND REGULATION

6. TEs CONTRIBUTE TO CHROMOSOME FORM AND FUNCTION

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Transposable elements

DNA sequences that can change their genomic location intragenomically either autonomously or non-autonomously are called transposable elements.

4 Types of transposable elements

5 Types of transposable elements

6 Types of transposable elements

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Transposon Recognition and Initiation of Silencing

Post-transcriptional silencing of TEs by RNAi

Chromatin modifications Maintenance and Memory

Silencing Mechanisms That Suppress TEs

8 Transposon Recognition and Initiation of Silencing

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Potential aberrant transcripts produced by transposons.

Transposon Recognition and Initiation of Silencing

ds RNA

PTGS:Posttranscriptionalgene silencing 21-22 nt

TGS: Transcriptional geneSilencing 24-26 nt

Dicer siRNA

10 Post-transcriptional silencing of TEs by RNAi

AGO

RISC: RNA-induced silencing complexAGO: Argonaute

11Chromatin modifications

Methylation of histone H3 at lysine 9 (H3K9)

DNA methylation on cytosine residues

Proteins that modify chromatin structure

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(PolIVa) RNA polymerase IVa (DCL3) DICER-LIKE 3 (AGO4) ARGONAUTE4(CMT3) CHROMOMETHYASE 3(KYP) KRYPTONITE(RDR2) RNA-DEPENDENT RNA POLYMERASE 2(DRD1) DEFECTIVE IN RNA-DIRECTED DNA METHYLATION 1(DRM2) DOMAINS REARRANGED METHYLTRANSFERASE 2

Maintenance and Memory

24-26 nt

13 Transposon Reactivation

A variety of conditions induce transposon activation.

Tissue culture A source of epigenetic variation

Biotic and abiotic agents Extracts from fungi and bacteria Temperature Stress

Synthetic hybrids Changes in patterns of DNA methylation

TE specificities and regulation14

A heat map showing the distributions of genes and different classes of TEs in a typical grass genome. High concentrations of a particular sequence feature are indicated by red and low concentrations by blue.

Copy number inversely correlates with genic insertion bias

Low-copy-number TEs Insertion into open chromatin

Centromere

LTR retrotransposons

DNA elements

Insert near genes

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Epigenetic status (predominantly DNA methylation) of telomeric and sub-telomeric repeats

Role in regulating telomereelongation in mammalian cells

Centromere, Telomere

TEs, and the epigenetic silencing Role In centromere function

TEs Contribute To Chromosome Form And Function