Basic HTML Version
International Journal of Marine Science 2014, Vol.4, No.50, 1-22
http://ijms.biopublisher.ca
5
Figure 4 VTE:
Symbiodinium
gene expression.
nrt2
(A) and
hsp70
(B) gene expression from
Symbiodinium
within
Seriatopora hystrix
nubbins from Houbihu (“upwelling” site
[UWS]) or Houwan (“non-upwelling” site [NUWS]) exposed
to either a stable (hollow squares) or variable (filled diamonds)
temperature treatment for seven days. Please see the text or
Tables A1-3 for full gene names. Gene expression data were
normalized as described in the text and presented as unit-less.
Error bars represent standard error of the mean in all panels
(
n
=3 replicates [6 pseudo-replicates] per treatment-site of
origin), and in panel B only, the letters adjacent to icons denote
Tukey’s honestly significant difference groups (
p
<0.05) for the
temperature effect only.
1.4 VTE: host coral gene expression
Expression of the stress-targeted gene
hsp70
(Figure
5A), four cytoskeleton-targeted genes;
actb
(Figure
5C),
trp1
(Figure 5D),
tuba
(Figure 5E), and
ezrin
(Figure 5F), and three osmoregulation-targeted genes;
cplap2
(Figure 5G),
oatp
(Figure 5H), and
trcc
(Figure 5I), were normalized to both recovery of the
Solaris spike (data not shown) and the host GCP; the
latter of which was shown to be stable between sites
of origin and temperature treatments (data not shown).
Although host
hsp70
expression was found at
significantly higher (~3.5-fold) levels in samples
exposed to the stable temperature regime (Figure 5A),
there was neither site of origin nor interaction effects
(Table A3). There was also no significant correlation
between
Symbiodinium
and host
hsp70
expression
(Figure 5B; linear regression
t
-test,
t
=2.1,
p
>0.05).
The expression of both
actb
(Figure 5C) and
cplap2
(Figure 5G) was affected by the experimental
treatments (Table A3); the former was found to be 30%
higher in samples exposed to the variable temperature
regime.
cplap2
was characterized by an interaction
effect in which corals from the NUWS exposed to the
variable temperature regime expressed 2.1-fold higher
levels than corals from the UWS exposed to this same
temperature profile. Of the 14 target genes assessed
across both compartments, 2 (host
actb
and
tuba
; 14%)
were significantly affected by temperature in the ETE,
whereas 7 (
Symbiodinium rbcL
,
psI
,
pgpase
[from
Mayfield et al., 2012a], and
hsp70
and host coral
hsp70
,
actb
, and
cplap2
; 50%) demonstrated
significant differences between temperature regimes
in the VTE. This difference in the overall proportion
of target genes demonstrating a significant difference
across the two experiments was marginally significant
(
X
2
=3.9,
p
=0.05).
1.5 VTE: host coral genotyping
With the exception of Sh4-001, all microsatellite loci
were polymorphic (Table 2); the former was excluded
from the calculations. The number of alleles (N
A
),
observed heterozygosity (H
o
), and expected
heterozygosity (H
e
) for each remaining locus ranged
from 1 to 7 (mean=3.9), 0 to 0.83 (mean=0.53), and 0
to 0.89 (mean=0.63), respectively. Deviations from
Hardy-Weinberg equilibrium and heterozygote
deficiencies were suggested by inbreeding coefficient
(F
IS
) values, which were significant for samples from
the UWS (F
IS
=0.24,
p
<0.05), but not the NUWS
(F
IS
=0.099,
p
=0.20). The overall F
IS
value of 0.16 was
statistically significant (
p
<0.05), suggesting that
inbreeding may
exist within these two populations.
There were no null alleles across the seven loci (data
not shown). Finally, no significant genetic
differentiation was found between the Houbihu and
Houwan samples (fixation index [F
ST
]=-0.012,
p
>0.05), though this could be partially attributed to
the small sample size (
n
=6 for each site of origin).