This document summarizes a seminar presentation on the initiation of meiotic recombination and conservation across eukaryotes. It introduces key concepts like Spo11 and double-strand breaks. It then discusses studies in organisms like mice, Arabidopsis, and rice on the different types of Spo11 and associated proteins. The document reviews methods to detect double-strand breaks and examines the control and regulation of break formation, including factors like chromosome structure and histone modifications. Finally, it presents two case studies on characterization of Spo11 in C. elegans and the synaptonemal complex protein ZYP1 in Arabidopsis and concludes with discussing open questions and future perspectives in the field.

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WELCOME

2. Initiation of Meiotic Recombination : Conservation
and Specificities among Eukaryotes
UNIVERSITY OF AGRICULTURAL SCIENCES, BENGALURU
COLLEGE OFAGRICULTURE, V C FARM, MANDYA
SEMINAR - I
2
SURESH YADAV
I.D. No. PALM-6005
Department of Genetics and Plant Breeding

3. Introduction
Key role of Spo11 in DSBs
Control and regulation of DSBs
Case Studies
Conclusion
Future perspectives
CONTENTS
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TERMINOLOGY

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 Synaptonemal complex :-
 Crossing over (CO) :-

6. Cont…
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 Pseudo-autosomal region (PAR) :-
 Chiasma:-

7. Role of meiosis :-
Essential for fertility in most of the sexually propagated
species
Genome evolution
Helps in maintaining the immortality of the germ line
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Eijpe et al.,(1999)

9. Spo11: The Catalytic Activity for Double-Strand
Break formation
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Bergerat et al., (1997)

10. Domains of Spo 11:
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Nicholas et al., (1999)
DNA-binding core TOPRIM domain
Spo 11

11. Different types of Spo11:
Eukaryotes Type of Spo11
Mice and Humans SPO11α , SPO11β
Arabidopsis thaliana SPO11-1, SPO11- 2, SPO11-3
Oryza sativa OsSPO11-1, OsSPO11-4 (Mainly)
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Hartung et al., (2007)

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Spo11-Associated Proteins
Ski8, a WD
(tryptophan–aspartic
acid) repeat protein
Rec102, Rec104 Rec114, Mei4, Mer2
Miyoshi et al., (2012)

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Maleki et al., (2007)
Saccharomyces cerevisiae Schizosaccharomyces pombe
Mus musculus Arabidopsis thaliana

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DETECTION OF DOUBLE STRAND BREAKS
SOUTHERN
BLOTTING
END
LABELING
AND RADIO
LABEL
ChIP OF
RECOMBINA
TION
PROTEINS
USE OF
MUTANTS
SEQUENCING
Saski et al., (2011)

15. Chromosome structure and organization
Chromosome axis: HORMA domain– containing
proteins
 The Hop1-Red1 complex: regulate the choice
between interhomolog and inter sister
recombination
E.g. In M. musculus, two hop1 orthologs have been
identified: HORMAD1 and HORMAD2
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CONTROLAND REGULATION OF DNA DOUBLE-STRAND
BREAK FORMATION:
Kleckner, (2006)

16. Linking DNA double-strand break sites to
chromosome axes:-
• Nucleosome depleted regions (NDRs) :-
• Histone H3 trimethylated lysine 4 (H3K4me3):
• This modification is known to be enriched in accessible
chromatin, often near transcription start sites and some
transcription enhancers
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Shilatifard, (2008)

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Acquaviva et al., (2013)
Saccharomyces cerevisiae Schizosaccharomyces pombe Mus musculus

18. Condensin:-
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Protein complex that plays
roles in chromosome
organization and Compaction
and required for efficient
homologue pairing and proper
processing of double strand
breaks
Mets et al., (2009)

19. Axis length:-
Correlations between axis length and Crossing over
activity ?
Pseudoautosomal region (PAR): region on a sex
chromosome that is homologous between the X and the Y
chromosomes
Eg. PAR region in M. musculus
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Kauppi et al., (2011)

20. Coordination Between Formation and Repair of DNA
Double-Strand Breaks:-
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Chin et al., (2001)

21. Where are Double-strand Breaks Formed ?
Recombination events are not randomly distributed
i.e. hotspots and cold spots for recombination
Double-Strand Break Maps in Saccharomyces cerevisiae:
 Sequencing Spo11-oligos led to the identification of
DSB hotspots, twofold higher than the genome-wide
average
21Pan et al., (2011)

22. Double-Strand Break Map in Mus musculus:-
22Baudt et al., (2007)

23. Cont…
23
Brick et al., (2012)

24. Progeny analysis Genotyping
High-throughput
sequencing
Drouaud et al., (2006)
Crossover and Non-crossover Hotspots in Arabidopsis thaliana:-
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25. Meiotic Recombination at Specific Genomic Regions:-
• Proper repair of all DSBs with a minimum of deleterious
events
• Centromeres:-
25Sasaki et al., (2010)

26. Cont….
• Telomeres:-
Other Repeats:- eg. rDNA genes
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Mieczkowski et al., (2007)

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Case Studies…

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Functional characterization of the meiosis-specific DNA double-
strand break inducing factor SPO-11 from C. elegans
Yi yeh et al., (2017)Taiwan

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30. Results:- Monomeric nature of SPO-11
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31. Cont…
SPO-11 possesses thermal labile DNA binding activity :-
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32. Cont…
• DNA binding properties of SPO-11 :-
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33. Cont….
• SPO-11 lacks DNA cleavage activity :-
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34. Cont….
• Characterization of the SPO-11 G290D mutant :-
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The Arabidopsis synaptonemal complex protein ZYP1
is required for chromosome synapsis and normal fidelity
of crossing over
Birmingham (United Kingdom) Higgins et al., (2005)

36. Results:-
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Identification of ZYP1a and ZYP1b:-

37. Cont…
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ZYP1a and ZYP1b localization :-

38. Cont…
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ZYP1 localization requires initiation of recombination :-
Identical distribution of ZYP1a and ZYP1b :-

39. Cont…
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Depletion of ZYP1 results in a delay in progression through meiotic
prophase I :-

40. Cont…
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Prophase I progression is delayed in the absence of ZYP 1 :-

41. Cont…
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Loss of ZYP1 results in aberrant associations and recombination
between nonhomologous chromosomes :-

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43. The molecular machinery for DSB formation remains to be
characterized.
How DSB formation is regulated in time and space still remains
to be understood.
Ideally new strategies should be developed to follow the
dynamics of DSB formation and the interaction of DSB sites
with the chromosome axis.
The consequences of hotspot localization for genome evolution
remain unclear.
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Future perspectives

44. Cont…
The evolutionary consequences of having stable or
dynamic DSB sites remain to be understood.
It has been difficult to evaluate the impact of gene
conversion events on genome dynamics because of the
limited data available documenting NCO events in most
species.
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THANK YOU