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ΑΝΙΥΝΕΤ΢Η ΓΟΝΙΔΙΑΚΩΝ ΣΟΠΩΝ ΠΟ΢ΟΣΙΚΩΝ ΙΔΙΟΣΗΣΩΝ (QTL)
΢ΣΗΝ Σ΢ΙΠΟΤΡΑ (Sparus aurata L.)
Λοσκοβίηες Δ.1,4*, Σαρροπούλοσ Ε.2, Μπαηαργιάς Κ.3, Αποζηολίδες Α.4, Κωηούλας
Γ.2, Τζιγγενόποσλος Κ.2, Χαηδεπλής Δ.1
1
2
3
4
Αιεμάλδξεην Τερλνινγηθό Δθπαηδεπηηθό Ίδξπκα Θεζζαινλίθεο (Α.Τ.Δ.Η.Θ.), Σρνιή Τερλνινγίαο
Γεωπνλίαο, Τκήκα Εωηθήο Παξαγωγήο, Τ.Θ. 141, 57400, Σίλδνο
Διιεληθό Κέληξν Θαιαζζίωλ Δξεπλώλ, Ηλζηηηνύην Θαιάζζηαο Βηνινγίαο θαη Γελεηηθήο, Τ.Θ. 2214,
Γνύξλεο Πεδηάδνο, 715 00 Ζξάθιεην Κξήηεο
Τερλνινγηθό Δθπαηδεπηηθό Ίδξπκα Μεζνινγγίνπ, Τκήκα Υδαηνθαιιηεξγεηώλ θαη Αιηεπηηθήο
Γηαρείξηζεο, Νέα Κηίξηα, 30200, Μεζνιόγγη
Αξηζηνηέιεην Παλεπηζηήκην Θεζζαινλίθεο, Γεωπνληθή Σρνιή, Τνκέαο Εωηθήο Παξαγωγήο,
Δξγαζηήξην Ηρζπνθνκίαο-Αιηείαο, Λεωθόξνο Γεωξγηθήο Σρνιήο, Θεζζαινλίθε
Περίληψη
Ζ ηζηπνύξα απνηειεί έλα νηθνλνκηθήο ζεκαζίαο είδνο ζηελ Μεζνγεηαθή πδαηνθαιιηέξγεηα.
Πξαγκαηνπνηήζακε κία αλάιπζε κέξνπο ηνπ γνληδηώκαηνο γηα ηελ ραξηνγξάθεζε γνληδηαθώλ ηόπωλ
πνζνηηθώλ ηδηνηήηωλ (QTL) πνπ επεξεάδνπλ ην ζωκαηηθό βάξνο θαη ην θύιν ζε απηό ην εξκαθξόδηην
είδνο. Πξνεγνύκελε εξεπλεηηθή κειέηε έδεημε ηελ ύπαξμε δύν ζηαηηζηηθά ζεκαληηθώλ QTL ζηελ νκάδα
ζύλδεζεο 21 (LG21). Σηελ παξνύζα εξγαζία πξνζζέζακε πεξηζζόηεξε πιεξνθνξία ζηα γνλνηππηθά
δεδνκέλα καο ώζηε λα δηεμάγνπκε κηα εθηελέζηεξε κειέηε ηεο γελεηηθήο βάζεο ηωλ παξαπάλω
ηδηνηήηωλ. Γηα ην ζθνπό απηό ρξεζηκνπνηήζεθαλ δείγκαηα από δέθα παηξνγνληθέο εηεξνζαιείο
νηθνγέλεηεο ηζηπνύξαο θαη ζπλνιηθά 74 πιεξνθνξηαθνί κηθξνδνξπθνξηθνί δείθηεο γηα ηελ θαηαζθεπή
ελλέα νκάδωλ ζύλδεζεο, ζπλνιηθνύ κήθνπο 495,3 cM θαη κέζε απόζηαζε δεηθηώλ 8,2 cM.
Δθαξκόζζεθαλ νη ζηαηηζηηθέο κέζνδνη ηεο αλάιπζεο δηαζηήκαηνο θαη γξακκηθήο παιηλδξόκεζεο, αιιά
θαη ηεο αλάιπζεο πνιιαπιώλ QTL ώζηε λα απμεζεί ε δπλαηόηεηα ραξηνγξάθεζεο. Σπλνιηθά
εληνπίζηεθαλ ηέζζεξα QTL γηα βάξνο θαζώο θαη έμε QTL γηα θύιν (ηξία δεπγάξηα ζε ηξεηο δηαθνξεηηθέο
νκάδεο ζύλδεζεο) ζύκθωλα κε ην κνληέιν ηωλ δύν ζπλδεδεκέλωλ QTL. Τν πνζνζηό ηεο θαηλνηππηθήο
παξαιιαθηηθόηεηαο πνπ εμεγείηαη από ηα QTL γηα βάξνο θπκάλζεθε από 9,3% κέρξη 17,2%,
ππνγξακκίδνληαο έηζη ηελ δπλαηόηεηα γηα ρξεζηκνπνίεζή ηνπο ζηελ ‘ππνβνεζνύκελε από δείθηεο’
επηινγή (MAS). Τξεηο νκάδεο ζύλδεζεο παξνπζίαζαλ ζηαηηζηηθή ζεκαληηθόηεηα γηα ηελ ύπαξμε QTL
πνπ επεξεάδνπλ ηόζν ην βάξνο όζν θαη ην θύιν, γεγνλόο πνπ δείρλεη ηελ γελεηηθή ζπζρέηηζε ζε έλα
βαζκό ηωλ δύν απηώλ ηδηνηήηωλ ζηελ ηζηπνύξα. Δπίζεο, ε κειέηε ηνπ κνξηαθνύ κεραληζκνύ πνπ νδεγεί
ζηελ αιιαγή ηνπ θύινπ κπνξεί λα πξνζθέξεη λέα γλώζε ζην πνιύπινθν ζύζηεκα θαζνξηζκνύ ηνπ
θύινπ αιιά θαη ηεο εμέιημεο απηνύ.
Λέξεις κλειδιά: QTL, Sparus aurata, σδατοκαλλιέργειες
* Σπγγξαθέαο επηθνηλωλίαο: Λνπθνβίηεο Γεκήηξηνο ([email protected])
QUANTITATIVE TRAIT LOCI FOR BODY GROWTH AND SEX
DETERMINATION IN THE HERMAPHRODITE TELEOST FISH Sparus
aurata L.
Loukovitis D.1,4*, Sarropoulou E.2, Batargias C.3, Apostolidis A.P.4, Kotoulas G.2,
Tsigenopoulos C.S.2, Chatziplis D.1
1
2
Αlexander Technological Educational Institute of Thessaloniki (A.T.E.I.Th), School of Agricultural
Technology, Department of Animal Production, Laboratory of Animal Breeding and Genetics, Sindos,
57400, Greece
Hellenic Center for Marine Research, Institute of Marine Biology and Genetics, Gournes Pediados,
Heraklion, 71003, Crete, Greece
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3
Technological Educational Institute of Messolonghi, School of Agricultural Technology, Department of
Aquaculture and Fisheries, Laboratory of Molecular Population and Quantitative Genetics,
Messolonghi, 30200, Greece
4
Aristotle University of Thessaloniki, Faculty of Agriculture, Department of Animal Production,
Laboratory of Ichthyology and Fisheries, Thessaloniki, 54124, Greece
Abstract
Gilthead seabream (Sparus aurata L.) is an important marine foodfish in the Mediterranean aquaculture.
A partial-genome scan was conducted to map quantitative trait loci (QTL) affecting body weight and sex
in this sequential hermaphrodite species. Fish from ten paternal half-sib families were included and 47
informative microsatellite markers were used to construct five linkage groups (2, 3, 6, 9 and 21) of S.
aurata genome with a total sex-average length of 237.5 cM (Kosambi) and mean marker interval of 5.9
cM. Interval mapping by linear regression was applied and extended to a multiple-QTL analysis approach
to increase mapping power. In total, two growth-related QTL were found and four sex-linked QTL (two
pairs in two different LGs) were detected under the two-QTL model of analysis. The proportion of
phenotypic variation explained by the two body weight QTL was 9.3 and 17.2 %, revealing their potential
for use in marker-assisted selection (MAS). In conclusion, two out of five examined linkage groups
showed significant evidence for QTL affecting both growth and sex, suggesting that the two traits are
genetically correlated to some extent in seabream. Studying the molecular mechanism of sex reversal may
also elucidate the complex mechanistic of the sex determination process and its evolution.
Keywords: QTL, Sparus aurata, aquaculture.
*Corresponding author: Loukovitis Dimitrios ([email protected])
1. Introduction
Quantitative genetic variation characterizes most traits of economic importance
in livestock, including growth-related traits and disease resistance. Variation in such
complex traits is often controlled by a number of different loci, named Quantitative
Trait Loci (QTL), as well as environmental factors. The identification of QTL in nonmodel species like the gilthead seabream (Sparus aurata) is of importance in order to
unravel specific biological questions which cannot be addressed in model-organisms. In
addition, by identifying QTL in commercial important species will enhance the
application of marker-assisted breeding for genetic improvement of productive traits.
Simulation studies have shown that the utilization of marker information might be
extremely helpful toward time- and cost-efficient breeding programs by increasing the
accuracy of selection and decreasing the generation interval, compared to selection
based only upon records of individuals and their relatives (Smith and Simpson 1986,
Lande and Thomson 1990). In the present study, we used the seabream genetic map
(Franch et al. 2006) to conduct a partial genome scan for the identification of possible
QTL affecting body weight and sex.
2. Materials and Methods
Ten paternal half-sib families were used to search for body weight- and sexassociated QTL. Pedigree structure was obtained after parentage analysis with nine
microsatellite markers. Overall, 10 male and 48 female brooders contributed to the
population structure having a total number of 409 offspring, with 360 (88%) being
males and 49 (12%) being females. Genomic DNA was isolated from fin clips, by
standard proteinase K digestion, following the salting out procedure as described in
Miller et al. (1988). Forty-seven (47) informative microsatellite markers were chosen
from the published genetic linkage map (Franch et al. 2006) of S. aurata, to cover five
linkage groups totally (2, 3, 6, 9 and 21). These were genotyped on all samples (parents
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and offspring) using an ABI PRISM® 3700 DNA analyzer (Applied Biosystems, CA,
USA). The construction of the linkage groups, the order and the distance between the
genotyped microsatellite markers was done from the data using the CRIMAP 3.0
software (Green et al. 1990). Given the seabream family structure in our study, the QTL
detection method was based on half-sib interval mapping analysis through a linear
regression approach (Knott et al. 1996), testing also for the existence of multiple QTL
on the same linkage group by fitting a two-QTL model to the analysis. The web-based
software GridQTL 1.3.2 was used to perform the analysis. Furthermore, an estimation
of the percentage of within-family variance explained (PVE) by the QTL was also
calculated.
3. Results
The 47 microsatellites were used to construct five linkage groups of S. aurata
genome with a total sex-average length of 237.5 cM (Kosambi) and mean marker
interval of 5.9 cM. Mapping of markers was consistent with the existing LG map of
seabream, although their order and distance were not totally preserved. QTL analysis for
body weight revealed one genome-wide significant QTL and one chromosome-wide
significant QTL on linkage groups 21 and 9, respectively (Table 1). The percentage of
within-family variance explained (PVE across all 10 families) by the QTL on LG21 was
17.2%. On the other hand, fitting one-QTL model in the analysis for sex failed to detect
significant QTL on any of the linkage groups tested. When assuming a two-QTL model,
however, two linkage groups (LG9 and LG21) showed chromosome-wide significant
evidence for the presence of two linked QTL affecting the trait of sex (Table 2).
Table 1. Estimates of location, significance and percentage of within-family variation explained (PVE)
for body weight-related QTL in Sparus aurata.
5% significance threshold
LG
Position (cM)
F ratio
Chromosome-wide
Genome-wide
PVE (%)
9
35
2.31
2.20
3.03
9.3
21
20
3.42
2.19
3.03
17.2
Table 2. Estimates of location, significance
for sex-related QTL in Sparus aurata.
Position (cM)
F ratio
2 QTL
LG
QTLA
QTLB
vs.
0 QTL
9
17
49
3.14
21
6
20
3.45
and percentage of within-family variation explained (PVE)
5% significance threshold
2 QTL
vs.
1 QTL
4.43
4.33
Chromosome-wide
Genome-wide
2.81
2.86
4.0
4.0
PVE (%)
11.7
19.3
4. Discussion
Body weight was significantly associated at a genome-wide scale with one QTL
positioned on linkage group 21. The fraction of phenotypic variance explained by this
QTL was 17.2 %, showing clearly its potential for use in marker-assisted selection
(MAS). In addition, preliminary results from ANOVA revealed that allelic substitution
at the microsatellite markers located near the QTL had large effects on body weight.
Certain allelic combinations showed significantly improved performances of this
commercially important trait.
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Previous data in the sequential hermaphrodite fish Sparus aurata suggest that the
mechanism of sex reversal is controlled by social activities and group dynamics (Zohar
et al. 1978). In our study, however, we found for the first time linkage between sex and
four loci (two pairs) located on LGs 9 and 21. Moreover, these linkage groups showed
also significant evidence for QTL affecting growth, suggesting either the linkage
between QTL (in each LG) or possibly the existence of a single QTL on each linkage
group with pleiotropic effects. Whatever the case is, we give evidence that the two traits
are genetically correlated to some extent in seabream. Consequently, based on our
results, we believe that there might be a genetic component involved in S. aurata sex
change apart from environmental factors.
5. Acknowledgments
This research has been co-financed by the European Union (European Social
Fund – ESF) and Greek national funds through the Operational Program "Education and
Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research
Funding Program: Heracleitus II. Investing in knowledge society through the European
Social Fund.
References
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Green P., Falls K., Crooks S. (1990) Documentation for CRIMAP, Version 2.4.
Washington University School of Medicine, St. Louis, pp 70.
Knott S. A., Elsen J.M., Haley C.S. (1996) Methods for multiple marker mapping of
quantitative trait loci in half-sib populations. Theoretical and Applied Genetics,
93: 71-80.
Lande R., Thomson R. (1990) Efficiency of MAS in the improvement of quantitative
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Miller S. A., Dykes D.D., Polesky H.F. (1988) A simple salting out procedure for
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This research has been co-financed by the European Union (European
Social Fund – ESF) and Greek national funds through the Operational
Program "Education and Lifelong Learning" of the National Strategic
Reference Framework (NSRF) - Research Funding Program: Heracleitus
II. Investing in knowledge society through the European Social Fund.
European Union
European Social Fund
4th International Symposium “Hydrobiology – Fisheries”, Volos 9-11 June 2011