Balancing Retrospection and Visions: The Cytogenetics Group of the Society of Plant Breeding (GPZ) Came Together in Dresden - Karger Publishers
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Meeting Report
Cytogenet Genome Res 2019;159:163–168 Accepted: November 29, 2019
Published online: January 14, 2020
DOI: 10.1159/000505280
Balancing Retrospection and Visions: The
Cytogenetics Group of the Society of Plant
Breeding (GPZ) Came Together in Dresden
Tony Heitkam
Faculty of Biology, Technical University Dresden, Dresden, Germany
From September 26th to 27th, 2019, the Cytogenetics the cytogenetics community needs both (1) an under-
group of the Society of Plant Breeding (GPZ) met in a re- standing of the unresolved research questions still push-
laxed atmosphere near Dresden (Germany). This year’s ing the field, and (2) good grasps on the strengths and
meeting focused on “Chromosome Biology, Genome limitations of the modern methods. We positioned the
Evolution, and Modern Cytogenetics in the Context of Cytogenetics group meeting at this intersection and
Plant Breeding” and was attended by 41 members from wanted to have a small-scale meeting, during which in-
academia and industry (Fig. 1). teraction and conversation would be easy and rewarding.
Therefore, we decided on the beautiful park setting on the
outskirts of Dresden, left room for discussions and strolls
Balancing Retrospection and Visions for the Future through the gardens, as well as organized two joint meals
of Cytogenetics and a guided city tour.
The scope and also the venue of the GPZ Cytogenetics
Although the first reports of mitotic cell divisions were meeting has been chosen by Prof. Dr. Thomas Schmidt,
already published over a century ago [Schneider, 1873], former group leader of TU Dresden’s research group
cytogenetics continuously offers new insights into the bi- “Plant Cell and Molecular Biology,” and initiator of the
ology and the evolution of chromosomes and genomes. meeting. In the light of his very recent, tragic, and abso-
Molecular approaches introduced in the 1980s to 1990s lutely unpredictable death, the meeting was dedicated to
have thoroughly rebuilt the field and made it possible to his memory.
support plant breeding with unmet precision, e.g., by the That we met the balance between retrospection and
generation of karyotypes or the dissection of the species’ the future can – to no small part – be attributed to Pat
contributions to introgressions [Jiang and Gill, 2006]. Heslop-Harrison (University of Leicester, UK, and South
Now that germplasm collections have arrived in the ge- China Botanical Garden, Guangzhou, China) and his
nomics age [Milner et al., 2019] and wild crop relatives thoughtful keynote. He initially submitted an abstract en-
can be domesticated by a few gene edits [Zsögön et al., titled “Genomes and Crops: Domestication and Now Su-
2018], also the cytogenetics field is being re-positioned perdomestication,” starting with: “It has never been a
again. To be able to successfully integrate big data, next-/ more exciting time to work on genome evolution, chro-
third-generation sequencing, oligo- and CRISPR-FISH, mosomes, and crops […]”. As former mentor and long-
© 2020 S. Karger AG, Basel Tony Heitkam
Faculty of Biology, Technical University Dresden
Zellescher Weg 20b
E-Mail karger@karger.com
DE–01062 Dresden (Germany)
www.karger.com/cgr
E-Mail tony.heitkam @ tu-dresden.deFig. 1. Science in a relaxed environment. The GPZ Cytogenetics meeting near Dresden assembled 41 attendants.
Photograph taken by Gerhard Menzel.
standing close friend to Thomas Schmidt, he rewrote his An update on wheat (Triticum aestivum) genomics
lecture to pay tribute to Thomas’ scientific achievements. was provided by Hana Šimková (Institute of Experimen-
Pat found the right words to lead us through Thomas’ life tal Botany of the Academy of Sciences of the Czech Re-
in biology, starting from his doctorate and postdoc years public). She informed about the progress of single-chro-
in Halle, the time in Norwich and Kiel, and the science mosome optical mapping, a technique already established
coming from his lab at TU Dresden. in the group [Staňková et al., 2016]. To provide a realistic
guide for wheat genome assembly, DNA molecules with
lengths between 150 kb and 1 Mb were imaged using the
Integration of Cytogenetics with *omics Bionano Genomics technology. As an example for a prac-
Technologies tical application, she demonstrated how optical mapping
has helped to pin down a locus conferring resistance
How *omics technologies may influence and expand against Russian wheat aphids [Tulpová et al., 2019].
the scope of cytogenetics was the topic of the first session, Next, Phoung Hoang and Ingo Schubert (IPK Gater-
chaired by Andreas Houben (IPK Gatersleben, Germa- sleben, Germany) described how integration of third-
ny). We jumped in with computer scientist Amanda Sou- generation genome sequencing and comparative multi-
za Câmara (IPK Gatersleben, Germany) introducing us color FISH helped to produce the most current duckweed
to polymer simulations and how they can help to under- (Spirodela sp.) genome maps [Hoang et al., 2019]. They
stand the folded structure of mitotic chromosomes. Us- laid out how map discrepancies were resolved and how
ing fluorescent in situ hybridization (FISH) with oligo- these results provided a more complete picture of karyo-
nucleotide probes (oligo-FISH) spanning a defined length type evolution in duckweeds.
along barley (Hordeum vulgare) chromosomes, she The progress on the integration of genetic and physical
showed how in situ methods may help to support her sim- maps of Phalaenopsis orchid was presented by Yi-Tzu
ulations. Combining both analyses, she argued that the Kuo (National Taiwan University, Taiwan). She ex-
mitotic chromosome may be formed by nested loops ar- plained that for the generation of a molecular cytogenet-
ranged side by side in a dynamical helical scaffold. ic map, 22 linkage groups were hybridized onto the or-
164 Cytogenet Genome Res 2019;159:163–168 Heitkam
DOI: 10.1159/000505280chid’s 19 pachytene chromosomes. The resulting map group to hypothesize that pentaploid dogroses originated
showed high consistency with all linkage group-specific by independent and reciprocal hybridization events.
DNA markers. This high-quality genome sequence al- Tony Heitkam (TU Dresden, Germany) presented
lowed for example to trace the duplication events in the how multi-color FISH helped to trace the origin of saf-
evolutionary history of the chalcone synthase gene family fron crocus (Crocus sativus) [Schmidt et al., 2019]. She
[Kuo et al., 2019]. explained how the project group used whole-genome se-
Vildana Suljevic (University of Vienna, Austria) and quencing reads of low coverage to identify tandem re-
André Marques (Max Planck Institute for Plant Breeding peats, which served as landmark probes for saffron
Research, Germany) explained how they used low-cover- karyotyping. Comparative FISH uncovered an autotrip-
age sequencing to determine the repeat composition of loidy of different cytotypes from the wild Crocus cart-
their genomes of interest: Vildana Suljevic first intro- wrightianus. Corroborating this, Frank Blattner’s group
duced us to genomes of the highly pungent chili peppers at IPK Gatersleben used genotyping by sequencing and
(Capsicum sp.) and showed that some of the very abun- independently arrived at the same conclusion [Nemati et
dant satellite DNA families presumably derived from al., 2019].
spacer regions of functional rDNAs. Similar to the pep-
pers, the white lupin (Lupinus albus) genome is also oc-
cupied by a high amount of satellite DNAs. André Special Chromosome Types
Marques showed that most of its satellite DNA families
are associated with CENH3-immunoprecipitated chro- Pat Heslop-Harrison chaired the third session on spe-
matin. Nevertheless, it has been possible to develop chro- cial chromosome types. Andreas Houben started by giv-
mosomal landmark probes for the identification of most ing an overview why we should pay attention to holocen-
chromosome pairs. tric chromosomes. As holocentricity evolved indepen-
dently at least 13 times (4 times in plants), he dived into
the question whether holocentromeres resembled each
Meiosis, Gamete Formation, and Polyploidy other across the plant kingdom. Focusing on Poales mod-
els, he presented distinct holocentromere types, differing
The second session was chaired by Christiane Ritz in sequence organization and dynamics.
(Senckenberg Museum Görlitz, Germany) and targeted Bimodal karyotypes combine chromosomes which
the development of polyploids, gamete formation, and are either very small or very large. Mariana Báez (Fed-
meiosis. Anna Nowicka (Institute of Experimental Bota- eral University of Pernambuco, Recife, Brazil, and IPK
ny of the Academy of Sciences of the Czech Republic) Gatersleben, Germany) introduced Eleutherine bulbosa
started the session and focused on endoreduplication with a very large chromosome pair complementing the
processes in the developing barley seed. She and her proj- 5 much smaller pairs. She posed the question whether
ect group studied the nuclear ploidy of the embryo, endo- repetitive DNA fractions vary between both chromo-
sperm, and pericarp during seed development from pol- some sets. Indeed, retrotransposons differed in their dis-
lination until full maturity. They found that endoredupli- tribution, pointing to a different organization of the bi-
cation is an essential process during grain development modal subgenomes, which probably evolved by repeat
mainly occurring in the endosperm. accumulation on the large chromosome pair [Báez et al.,
An intriguing plant model for the investigation of 2019].
polyploidy was presented by Aleš Kovařík (Czech Acad- Jörg Fuchs (IPK Gatersleben, Germany) addressed
emy of Science, Institute of Biophysics, Czech Republic). why dispensable B chromosomes not only survive, but are
The dogroses (members of the genus Rosa, section Cani- even preferentially inherited. He used flow cytometry to
nae) with ploidies of 4, 5, and 6 are marked by a meiosis sort pollen nuclei according to their vegetative or genera-
with asymmetric distribution of genetic material in the tive origin. At the same time, the number of B chromo-
gametes [Herklotz et al., 2018]. To understand the genet- somes was quantified [Wu et al., 2019]. This allowed to
ic origin of the unusual pentaploid dogrose, 5 dogrose measure an accumulation of B chromosomes in genera-
species were comparatively sequenced in low coverage. tive nuclei during the first pollen mitosis and represents
Characterization of the repeat landscapes gave rise to a set an accurate estimate of the strength of the B chromosome
of tandem repeat probes, serving as cytogenetic land- drive in Aegilops speltoides.
marks for comparative karyotyping. This led the project
GPZ Cytogenetics Meeting in Dresden Cytogenet Genome Res 2019;159:163–168 165
DOI: 10.1159/000505280Genome Stability and Nucleus Architecture “Can you magnify nuclei prior to microscopy?,” asked
Ivona Kubalova (IPK Gatersleben, Germany). She pre-
Chaired by Ingo Schubert, the fourth session targeted sented how chromatin can be physically expanded with
the stability of the genome and the architecture of the a polyelectrolyte hydrogel, which causes the sample to
nucleus. Kateřina Perničková, David Kopecký, and Mah- swell – a new method that she transferred from mamma-
moud Said (Institute of Experimental Botany of the Acad- lian [Wassie et al., 2019] to plant tissue. Wide-field mi-
emy of Sciences of the Czech Republic) reported on the croscopy showed that the treated barley nuclei retained
processes following alien introgressions. Kateřina Per- their general structure, whereas super-resolution micros-
ničková asked why introgressed chromosomes were of- copy revealed a loss of the chromatin ultrastructure. Nev-
ten eliminated during meiosis [Perničková et al., 2019]. ertheless, the chromatin position of expanded nuclei was
Using 3D-FISH and confocal microscopy, she found that maintained, as for example shown for the iconic Rabl
abnormal positioning of alien chromosomes may not configuration.
only occur during meiosis but also in somatic nuclei. Updates on oligo-FISH in banana (Musa acuminata)
When observing alien rye (Secale cereale) chromosomes were presented by Eva Hribova (Institute of Experimental
in a wheat background, the project group frequently de- Botany of the Academy of Sciences of the Czech Repub-
tected incorrectly positioned rye telomeres. This abnor- lic). She showed how chromosome painting probes were
mal telomere arrangement may reduce the rye chromo- designed from the reference genome sequence and how
somes’ potential to reach the meiotic bouquet, and thus their use may shed light on chromosomal rearrangements
may lead to their elimination. in banana species [Šimoníková et al., 2019].
On broader terms, David Kopecký divided hybrids
with introgressed material into 2 types based on their
meiotic behavior: in meiosis, chromosomes of type I hy- A Look at the Posters
brids pair exclusively between homologs, whereas type II
hybrids also allow homoeologous chromosome pairing. The meeting hosted 11 posters, which were vividly dis-
The observed meiotic behavior may indicate the evolu- cussed. Alžběta Němečková (Institute of Experimental
tionary trajectory of the hybrid, e.g., the degree of genome Botany of the Academy of Sciences of the Czech Repub-
dominance or a potential elimination of chromosomes lic) asked whether chromatin arrangements in interphase
[Kopecký et al., 2019]. nuclei correlate with genome size. Using the root tip mer-
Then, Mahmoud Said argued for the importance of istem of 7 grasses, she found that interphase nuclei of spe-
synteny between homoeologous loci in interspecific hy- cies with relatively small genomes (Brachypodium, rice
brids. He focused on 2 Aegilops species important for and maize) contained dense chromatin in few, small re-
wheat improvement and localized 44 single-gene probes gions. In contrast, interphase nuclei of species with large
from wheat along the Aegilops chromosomes. The detect- genomes (barley, wheat, rye, and oat) had many and more
ed structural rearrangements provide insights into the ge- dispersed loci of compacted chromatin.
nome evolution of grasses and may support Aegilops use In 11 duckweeds, Phoung Hoang and Ingo Schubert
in wheat breeding. investigated the inverse relationship between genome
size and leaf area. So far, genome sizes, cell and nuclear
volume were correlated. The karyotypes varied depend-
New Tools, Perspectives, and Applications ing on the species, but without being directly associated
with genome size.
Veit Schubert (IPK Gatersleben, Germany) chaired Veronika Kapustová (Institute of Experimental Bota-
the final session covering a range of new tools and meth- ny of the Academy of Sciences of the Czech Republic)
ods advancing the cytogenetics field. Takayoshi Ishii built on the reports of apparent 18S-5.8S-26S rDNA relo-
(Tottori University, Japan) presented a CRISPR/Cas9- cation along the chromosomes of several grasses during
based approach to allow visualization of defined genomic their evolution [Dubcovsky and Dvorák, 1995]. To ad-
sequences in fixed nuclei. The RNA-guided endonuclease dress this nomad-like behavior of rDNA loci in Triticeae
in situ labeling (RGEN-ISL) method does not require de- grasses, she presented how new technologies including
naturation steps and hence better preserves the chroma- Bionano optical maps and Hi-C data may help to define
tin structure compared to conventional FISH [Ishii et al., the exact positions and arrangements of rDNA loci.
2019; Nemeckova et al., 2019].
166 Cytogenet Genome Res 2019;159:163–168 Heitkam
DOI: 10.1159/000505280Antonia Simon (University of Vienna, Austria) pre- bedded in highly compacted, repetitive regions, poten-
sented how tandem repeats from 2 Capsicum species were tially providing safe havens preserving the EPRV ele-
used for the identification of all chromosome pairs. Com- ments.
parative karyotyping revealed intraspecific polymor- Finally, Tony Heitkam traced the evolution of the al-
phism and allowed to trace genomic restructuring events lotetraploid crop quinoa (Chenopodium quinoa) starting
during speciation and domestication. from potential A- and B-genome precursor species [Heit-
Ludmila Cristina Oliveira (Biology Center Academy kam et al., 2019]. For this, she used comparative whole-
of Sciences of the Czech Republic) informed us about the genome sequencing data in low coverage, Southern and
genus Cuscuta, comprising species with mono- and holo- in situ hybridization to identify and characterize the tan-
centric chromosomes. She compared the centromeric dem repeat profiles of all 3 species. The diploid A- and
histone H3 variant CENH3 among those species, finding B-genomes were marked by unequal satDNA amplifica-
large differences across the subgenera. Whereas species tion and subgenome-specific occurrence. She suggested
with monocentric chromosomes contained canonical ac- scenarios for the evolution of the satellite DNAs before
tive centromeres made up of satellite DNA and CRM- and after allopolyploidization and could exclude C. pal-
type chromoviruses [Neumann et al., 2011], some holo- lidicaule as quinoa’s parental species.
centric species were unusually depleted of CENH3. This
raises the question if the CENH3 function even plays a
role in Cuscuta holocentromeres [Oliveira et al., 2019]. Outlook
Lastly, Thomas Schmidt’s group (TU Dresden, Ger-
many) presented much of the ongoing work on which The Cytogenetics working group will meet again in
Thomas had a direct impact: 2021, with a venue and date yet to be specified (see www.
Ludwig Mann and Kathrin Seibt showcased their new facebook.com/GPZcytogenetic or https://gpz-online.de/
softwares for the analysis of extrachromosomal DNA as arbeitsgebiete/3-cytogenetik-chromosomenanalyse).
well as the FlexiDot software to generate visually attrac-
tive dotplots [Seibt et al., 2018].
Kathrin Seibt also presented her work on short inter- Acknowledgement
spersed nuclear elements (SINEs), more specifically the
The conference organizers Tony Heitkam and Andreas Houben
Angio-SINE superfamily [Seibt et al., 2019]. These usu-
wish to thank the staff of TU Dresden’s “Plant Cell and Molecular
ally diverse transposable elements harbor a surprisingly Biology” lab for help in all aspects of the meeting organization.
conserved 3′ module and occur in at least 46 plant ge- Similarly, the IPK Gatersleben supported us on many levels, and
nomes of 13 orders. SINEs with this domain are frequent- pragmatically jumped in, if anything was unclear. Regarding this
ly enriched in and nearby genes, potentially impacting meeting report, T. Heitkam sincerely thanks Kathrin Seibt and An-
dreas Houben for critical proofreading of this manuscript.
their expression or splicing.
Using the sugar beet (Beta vulgaris) genome, Beatrice
Weber showed that tandem repeats and retrotransposons
Disclosure Statement
have more in common than previously thought. She pre-
sented sugar beet’s uniquely mixed tandem repeat/ret- The author has no conflicts of interest to declare.
rotransposon landscape, with at least 8 retrotransposon
families harboring different tandem repeats in their 3′
untranslated regions. To better understand whether the Funding Sources
internal repeats invaded or emerged within the ret-
rotransposons, she characterized 2 selected tandem re- We gratefully received financial support from the Society for
peat-retrotransposon partnerships. Plant Breeding (GPZ), the KWS SAAT SE & Co. KGaA, and the
Technische Universität Dresden (“Flexibler Fördertopf Interna-
How remnants of pararetroviral infections in the past tionalisierung,“ grant number Flx1909_125).
may escape elimination was explained by Nicola Schmidt.
Also working on the sugar beet genome, she identified 3
endogenous pararetrovirus (EPRV) families. Whereas 2
families still included intact copies, the third family was
much more degenerated. Based on molecular and cyto-
genetic methods, she concluded that the EPRVs are em-
GPZ Cytogenetics Meeting in Dresden Cytogenet Genome Res 2019;159:163–168 167
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