Hilhorst, H.W.M.

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Sleeping Beauties, dormancy and resistance in harsh environments: molecular, proteomic and metabolomic aspects - Berlin, Germany, 18-20 May 2008

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MEETING REPORT
Sleeping Beauties, dormancy and resistance in harsh
environments: molecular, proteomic and metabolomic
aspects – Berlin, Germany, 18–20 May 2008
Dormancy, diapause, rest and quiescence are all terms
that are in use to indicate a state of (temporary)
lowered metabolic activity (‘hypometabolic state’) in
living organisms. Dormancy occurs in many orga-
nisms from all kingdoms, ranging from bears to mice
and frogs, from fish to buds and seeds, and from
crustaceans to yeast and bacteria. Oddly enough,
interaction among the research groups studying the
phenomenon in the various systems has been rare. The
aim of the Sleeping Beauties Workshop was to bring
these groups together, to discover similarities among
the systems under study and to initiate discussions
and collaborations. The Sleeping Beauties Workshop
attracted some 70 participants from all over the world
at the Max Planck Institute in Dahlem-Berlin. The
pleasant surroundings and inspiring history of this
location were very conducive to a lively meeting.
An excellent keynote lecture was delivered by
Kenneth Storey (Carleton University, Ottawa,
Canada), in his characteristic and animated idiosyn-
cratic style, in which he addressed mechanisms
of metabolic suppression during hibernation of
mammals. During hibernation only 1–2% of the
genes are turned on, protein synthesis is reduced to
c. 1% and energy production to 5%. The hiber-
nation-related pathways appear to be controlled
by phosphorylation/dephosphorylation, e.g. via
eukaryotic initiation factor-2a (eIF2a) and eukary-
otic elongation factor-2 (eEF-2), as well as epigenetic
inhibition. The few genes that are ‘switched on’
during hibernation are mitochondrial genes, genes
encoding antioxidant and stress proteins, and
transcription factors.
In his keynote address, Felix Franks (BioUpdate
Foundation, London, UK) discussed the importance
of the physical properties of water in water stress
responses of living organisms. For example, did you
know that chilling increases the pH of water from 7 to
8 and that this may uncouple metabolic pathways in
living cells? Also, freezing damage of cells is not
usually the result of growth of ice crystals but of an
increase in solute concentration, as in drying. From
these two keynote lectures, it already became clear
that dormancy and stress responses are intimately
intertwined, a feature that seems obvious, but which is
not commonly addressed in seed research.
The 30 or so shorter talks were devoted to such
themes as Dormant forms, Quiescence and hiber-
nation, Survival in harsh and extreme environments,
LEA proteins and dormant forms, Ecological aspects
of dormancy and germination, and Exit from
dormancy. These themes were addressed in a limited
number of model systems. The model systems
reported on for dormancy research from other
kingdoms included the tardigrades (or waterbears),
a fascinating phylum of approximately 750 species.
Tardigrades are cryptobiotic multicellular organisms
(size 0.3–0.5 mm) with precise muscle control, which
move like higher animals. In the dry state, they
survive acid and solvent attack, very high and very
low temperatures, high pressure and radioactive
radiation. They have been found under layers of ice
5 m thick, in oceans 6000 m below the surface and on
6000 m high mountains (www.tardigrades.com). Like
the tardigrades, the rotifers are multicellular animals.
They have specialized organ systems and a complete
digestive tract that includes both a mouth and anus.
Most species of rotifers are about 0.2–0.5 mm long.
Of the three classes of the Rotifera phylum, the
Bdelloidea can survive drying for extended periods
(http://www.ucmp.berkeley.edu/phyla/rotifera/
rotifera.html).
Other speakers discussed the killifish, which are
mostly 2.5–5 cm long, are oviparous and may produce
diapause embryos that are resistant to drying and
anoxia. In this way, they survive their sometimes
harsh habitats, such as shallow lakes that may remain
inundated for several weeks and subsequently dry up
for months. The killifish are considered an excellent
model to study effects of hypoxia and anoxia in
vertebrates.
Seed Science Research (2008) 18, 185–187 doi:10.1017/S0960258508042207
Suspended animation in insects (arctic springtail,
an arctic species tolerant of freezing desiccation),
Artemia franciscana (brine shrimp) cysts, cyanobacteria
and yeast was also discussed. The plant contingent of
the meeting was well represented by talks devoted
to seed dormancy (Julia Buitink, Marc Cohn, William
Finch-Savage, Henk Hilhorst, Dirk Hincha, Olivier
Leprince, Gerhard Leubner, David Macherel and Peter
Toorop) and bud dormancy (James Anderson).
Despite the substantial phylogenetic distances
among these organisms, as the meeting progressed
striking similarities became apparent among the
dormant and/or dry states. Since many of these
organisms are now being studied with the aid of
modern molecular ‘-omics’ technology, we are able
to compare complete transcriptomes or extensive
expressed sequence tag (EST) libraries across species.
Also high-resolution protein structure and binding
properties of proteins, as well as metabolic aspects,
were among the presented results. So, what were the
similarities?
As mentioned, dormancy and stress responses
are closely associated. Many of the above organisms
become dormant before they are exposed to stress
conditions. The timing of this may depend on
developmental phase (e.g. sexual versus asexual),
seasonal rhythms, environmental cues and food
supply, among others. The common denominators
appear to be (epigenetically) controlled reduction of
metabolic activity, arrest of the cell cycle and the
initiation of protective mechanisms. Most of the
presentations addressed aspects of these key events.
Several examples were given of metabolic control
mediated by AMP-activated protein kinase (AMPK), a
highly conserved eukaryotic protein serine/threonine
kinase. It controls energy homeostasis and is activated
by metabolic stresses in mammals. In Medicago seeds,
the AMPK analogue MtSNF4b is a subunit of the
SnRK1 (sucrose-non-fermenting-related kinase) com-
plex and is activated by energy deprivation. It is
associated with both dormancy and protection of
seeds against adverse conditions. Many of the
protective mechanisms among various organisms
include late-embryogenesis abundant (LEA) (-like)
proteins and heat-shock proteins (HSP). Although the
functions of LEAs may appear undisputed from a
superficial scan of the literature (i.e. stabilizers of
proteins and membranes, antioxidants, ion sinks
and hydration buffers), there is very little conclusive
evidence for these functions in vivo. However, in a
fascinating presentation, Alan Tunnacliffe (Cambridge
University, UK) showed that a group 3 LEA protein,
which is expressed in mammalian cells, ameliorates
formation of inclusion bodies by aggregation-prone
proteins.
A number of lectures discussed the induction and
release from dormancy on the level of the transcrip-
tome. Both in bud and seed dormancy, co-expression
analysis of dormant and non-dormant transcriptomes
is being attempted to identify ‘super-nodes’ within
regulatory networks in order to pinpoint the key genes
in the regulation of dormancy. Although these in silico
experiments should be approached with caution, they
may yield valuable information that can be verified by
‘wet’ experiments. In his presentation, Seed Science
Research Editor, Marc Cohn, gave valuable information
as to how this could be done in a less ambiguous way.
It is clear that systems biology is here to stay.
One of the sessions included a number of talks
on the ecology of some of the model organisms.
Again, some stunning similarities among organisms
became apparent. For example, the dynamics of
dormant egg banks of the water flea in underwater
LEA summit (left to right): David Macherel, Dirk Hincha,
Olivier Leprince and Alan Tunnacliffe. Photo by M.A. Cohn. Esther Lubzens. Photo by M.A. Cohn.
H. Hilhorst186
sediment layers seem almost congruent with that of
soil seed banks.
From the above examples, it should be clear that
dormancy, and its regulation and mechanisms, is a
common feature of many extremophiles across all
the kingdoms of life. Bringing together researchers
of the different organisms and disciplines in the
Sleeping Beauties Workshop was a splendid initiat-
ive of Professor Esther Lubzens (National Institute of
Oceanography, Haifa, Israel). The Sleeping Beauties
Project website is http://www.gmm.gu.se/SB/,
where most of the PowerPoint slides from the oral
presentations, as well as photographs from the
meeting, will be posted in due course. I am certain
that this meeting was an inspiration to all of us and
will hopefully stimulate ‘across borders’ collabor-
ations. The next Sleeping Beauties is planned in
Israel in 2010.
Henk Hilhorst
Laboratory of Plant Physiology,
Wageningen University,
Arboretumlaan 4,
6703 BD Wageningen, The Netherlands
E-mail: Henk.Hilhorst@wur.nl.
q 2008 Cambridge University Press
Meeting Report: dormancy and resistance in harsh environments 187


Sleeping Beauties, dormancy and resistance in harsh environments: molecular, proteomic and metabolomic aspects - Berlin, Germany, 18-20 May 2008

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