Poster presentation at the International Seagrass Biology Workshop, Wales, UK, October 16th-21st 2016

1. International Seagrass Biology Workshop, Wales, UK, October 16th
-21st
2016 Alexander-Jueterbock@web.de
Poster PDF
Article link
Transcriptomic adaptation to warm temperatures
in Zostera marina
Jueterbock A.1,∗
, Franssen S.U.2
, Bergmann N.3
, Gu, J.4
, Coyer J.A.5
, Reusch T.B.H. 6
, Bornberg-Bauer E.4
, Olsen J.L.7
1 Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway
2 Institut f¨ur Populationsgenetik, Vetmeduni Vienna, Austria
3 Integrated School of Ocean Sciences (ISOS), Kiel University, Germany
4 Institute for Evolution and Biodiversity, University of M¨unster, Germany
5 Shoals Marine Laboratory, Cornell University, Portsmouth, USA
6 GEOMAR Helmholtz-Centre for Ocean Research Kiel, Evolutionary Ecology of Marine Fishes, Germany
7 Marine Benthic Ecology and Evolution Group, Centre for Ecological and Evolutionary Studies, University of Groningen, The Netherlands
BACKGROUND
Heat waves are a major threat for Zostera marina, the most widely distributed sea-
grass in the northern hemisphere. In previous studies, Z. marina was found to
be more heat tolerant at the southern edge of its European distribution (Mediter-
ranean, [1]). We asked whether inherent heat resistance is a unique characteristic
of Mediterranean seagrass or if Z. marina adapted to warm temperatures in par-
allel along the American and European thermal clines.
METHODS
SAMPLING
North
Atlantic
Current
Gulf
Stream
Northern and southern populations were sampled in Europe (NE, SE) and in the
northeastern USA (NU, SU). Thermally contrasting environments replicated on the
North American and European coasts allowed to test for parallel adaptation to
warm summer temperatures.
Weekly average summer
sea surface temperatures
>25◦C
<25◦C
HEAT STRESS LIBRARIES
Following 20 days of acclimation, living seagrass samples were exposed for 20 days
to a simulated heatwave in a common-garden mesocosm, followed by a 20-day re-
covery period. Samples for transcriptome sequencing (RNAseq) were taken at two
time points under heat stress and at three time points under recovery, resulting in 99
RNAseq libraries with ca. 13,000 uniquely annotated, expressed genes.
2 3 5 7 9
26
19
Temperature(◦
C)
20 40 60 80
Day of experiment
Sampling time points
RNAseq library per pop-
ulation and temperature
treatment
1 2 3
RNAseq (Illumina) + Quality control
Alignment (splice-aware)
Zostera marina genome
Annotation
Filtering reads
Duplicates
Ambiguous mappings
Non-annotated mappings
Expression profiles (rlog transformed)
Gene Library 1 Library 2 Library 3 ...
mRNA1 3.6 5.9 6.4 ...
mRNA2 1.5 0.2 4.0 ...
... ... ... ... ...
RESULTS AND DISCUSSION
HEAT RESPONSE
Hierarchical cluster on the first
five principal components of
heat-responsive gene expression
shows stronger separation
between Atlantic and Mediter-
ranean samples than between
Northern and Southern samples.
Faster recovery of gene expres-
sion in both southern populations
suggests reduced sensitivity to
global warming at the species’
southern edge of distribution.
NEUTRAL DIFFERENTIATION
0.05
1.00
Neighbor-Joining tree based on
Nei’s genetic distances derived
from 139,321 biallelic neutral
SNPs. Notably, the Mediter-
ranean population (SE) was the
most distant from the three At-
lantic populations: a common
pattern associated with virtually
all phylogeographic studies in-
cluding seagrasses [2].
ADAPTIVE DIFFERENTIATION
Differentially expressed genes
(grey numbers) and adaptively
differentially expressed genes
(black numbers). Black dots
indicate adaptive differentiation
(upper dot: A vs. M, lower dot: N
vs. S) under control (C), stress
(S) and/or recovery (R) condi-
tions. Sixteeen of 21 genes that
were likely involved in parallel
adaptation to warm temper-
atures showed also adaptive
expression differences between
Mediterranean and Atlantic
samples. The strong adaptive
differentiation between Atlantic
and Mediterranean populations
at 128 genes suggests that
much of the previously observed
North-South differentiation along
the European coast [e.g. 1]
might be better explained by a
general Mediterranean-Atlantic
differentiation.
CONCLUSION
Although adaptation to warm temperatures is expected to reduce sensitivity to heat-
waves, the continued resistance of seagrass to further anthropogenic stresses
may be impaired by heat-induced downregulation of genes related to photosynthe-
sis, pathogen defence and stress tolerance. Zostera marina has dominated the
North Atlantic through several previous glacial-interglacial periods. Temperature
alone is not the driver, but rather numerous other anthropogenic stressors press
towards a tipping point.
REFERENCES
[1] Franssen SU, Gu J, Bergmann N, Winters G, Klostermeier UC, Rosenstiel P, Bornberg-Bauer E & Reusch, TBH (2011): Transcriptomic
resilience to global warming in the seagrass Zostera marina, a marine foundation species. Proceedings of the National Academy of Sciences
108(48):19276–19281
[2] Olsen JL, Stam WT, Coyer J, Reusch TBH, Billingham M, Bostr¨om C, Calvert E, Christie H, Granger S, la Lumi`ere R, Milchakova N, Oudot-
Le Secq M-P, Procaccini G, Sanjabi B, Serrao E, Veldsink J, Widdicombe S, Wyllie-Echeverria S (2004): North Atlantic phylogeography and
large-scale population differentiation of the seagrass Zostera marina L. Molecular Ecology 13(7):1923–1941