Mendelian and non mendelian epigenetics What is epigenetics? Mendelian and non mendelian epigenetics Why fungi?

1500 MY Hedges et al., 2004

Blair et al., 2005

Ascomycota Saccharomycotina, Hemiascomycotina Archiascomycotina, Taphrinomycotina Pezizomycotina 330-420 MY Ascomycota

w+ w- su wv e

su wv Su(var)205 HP1

Homology silencing Dosage compensation (XX-XY ) Post-transcriptional Imprinting Transvection Paramutation Rip and Mip Homology silencing Post-transcriptional Gene silencing Co-suppression RNAi Silencing in ciliates Quelling Meiotic silencing by unpaired DNA

Dikaryon DNA replication Caryogamy, synapsis First division Second division

Caryogamy, synapsis First division 6:2 segregation

Dikaryon DNA replication Caryogamy, synapsis First division Second division

4:4 segregation Dikaryon DNA replication Caryogamy, synapsis First division Second division

0:8 segregation Dikaryon DNA replication Caryogamy, synapsis First division Second division

Sau3A GATC not GATC* MboI GATC and GATC* HpaII CCGG not CC*GG MspI CCGG and CC*GG

Ascobolus immersus

met2+t…met2+ r met2+t…met2+ r revertant from 7 met2+tmet2+ r Sau3A GATC not GATC* MboI GATC and GATC*

Two general models for premeiotic phenomena ?

Two putative DNA methylases in Ascobolus immersus

b2 X

Masc1 are they methylases? RID

There is a fundamental conceptual difference between RIP and MIP: MIP is a genuine epigentic phenomenon, RIP is directed mutation!

Unsolved problems of RIPand MIP: Are there other premeiotic phenomena? What is the nature of the homology recognition system? Can a transcript be involved? How does (in RIP) mutation trigger methylation? Why and how is methylation (in MIP) triggered in the absence of mutation? How general is the phenomenon? Archeological evidence for RIP in organisms without methylation and/or without sexual cycle.

qde-1 RNA dependent RNA-polymerase: ego1 and rrf1 in qde-1 RNA dependent RNA-polymerase: ego1 and rrf1 in Cænorhabditis elegans, SD1/SGS2 in Arabidopsis thaliana, RprA in Dictyostelium discoideum qde-3 Rec Q-like helicase: ? qde2 argonaute family: rde1 of C. elegans, AGO1 in A.thaliana, aubergine and piwi in D. melanogaster

QDE3 QDE3+ TOP aRNA, hpRNA QDE1 gene transcript QDE2 dsRNA Dicer

par-1, a Gene Required for Establishing Polarity in C par-1, a Gene Required for Establishing Polarity in C. elegans Embryos Encodes a putative Ser/Thr Kinase that is Asymmetrically Distributed Su Gou and Keneth J. Kemphues, Cell, Vol 81, 611-620 1995

mir172 apl2 Wt apetala2 mir172 overexpressed

Gene silencing Anti-transcript Gene (DNA) Transcript Transcript (RNA) Double stranded RNA RNAi Machinery Transcript (RNA) Protein Gene silencing

QDE3 QDE3+ TOP aRNA, hpRNA QDE1 gene transcript QIP QDE2 (argonaut) dsRNA Dicer

Transvection model Lonely gene model

Transvection model Lonely gene model

Sad: a RNA dependent RNA polymerase similar to QDE1 SMS2: a protein of the argonaut family

aRNA ? gene transcript dsRNA SAD-1 SMS-2 Dicer SML3, (DCL-1)

How general is post-transcriptional silencing?

“Q” pathway “M” pathway RNA pol. QDE-1 SAD-1 absent RrpB Dicer DCL-2 (M. grisea) DCL-1(SML3) DclB DclA Argonaute QDE-2 SML2 RsdA PpdB

RNAi is almost universal What about quelling? and MSUD?