Dirk de Graaf

Prof. Dr. Dirk de Graaf

Ghent University, Belgium
orcid

Research Focus & Metrics

Academic Career Length

33Years (1994-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2014 in BMC Genomics
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Journal Article
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CEChristine G Elsik
Christine G Elsik
KWKim C Worley
Kim C Worley
ABAnna K Bennett
Anna K Bennett
MBMartin Beye
Martin Beye
FCFrancisco Camara
Francisco Camara
OCon behalf of Honey Bee Genome Sequencing Consortium
on behalf of Honey Bee Genome Sequencing Consortium
The first generation of genome sequence assemblies and annotations have had a significant impact upon our understanding of the biology of the sequenced species, the phylogenetic relationships among species, the study of populations within and across species, and have informed the biology of humans. As only a few Metazoan genomes are approaching finished quality (human, mouse, fly and worm), there is room for improvement of most genome assemblies. The honey bee (Apis mellifera) genome, published in 2006, was noted for its bimodal GC content distribution that affected the quality of the assembly in some regions and for fewer genes in the initial gene set (OGSv1.0) compared to what would be expected based on other sequenced insect genomes. Here, we report an improved honey bee genome assembly (Amel_4.5) with a new gene annotation set (OGSv3.2), and show that the honey bee genome contains a number of genes similar to that of other insect genomes, contrary to what was suggested in OGSv1.0. The new genome assembly is more contiguous and complete and the new gene set includes ~5000 more protein-coding genes, 50% more than previously reported. About 1/6 of the additional genes were due to improvements to the assembly, and the remaining were inferred based on new RNAseq and protein data. Lessons learned from this genome upgrade have important implications for future genome sequencing projects. Furthermore, the improvements significantly enhance genomic resources for the honey bee, a key model for social behavior and essential to global ecology through pollination.

24 April 2015 in Genome Biology
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Journal Article
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BSBen M Sadd
Ben M Sadd
SBSeth Barribeau
Seth Barribeau
Guy BlochGuy Bloch
Guy Bloch
Dirk de GraafDirk de Graaf
Dirk de Graaf
PDPeter Dearden
Peter Dearden
KWKim C Worley
Kim C Worley
Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation.

1 April 2008 in Journal of Insect Science
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BSBieke Scharlaken
Bieke Scharlaken
Dirk de GraafDirk de Graaf
Dirk de Graaf
KGKaren Goossens
Karen Goossens
MBMarleen Brunain
Marleen Brunain
LPLuc Peelman
Luc Peelman
FJFrans J. Jacobs
Frans J. Jacobs
In this study an important and often neglected aspect of gene expression studies in insects, the validation of appropriate reference genes with stabl

15 January 2010 in Insect Molecular Biology
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Journal Article
Open access
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Dirk de GraafDirk de Graaf
Dirk de Graaf
MAM. Aerts
M. Aerts
MBM. Brunain
M. Brunain
CDC. A. Desjardins
C. A. Desjardins
FJF. J. Jacobs
F. J. Jacobs
BDBart Devreese
Bart Devreese
With the Nasonia vitripennis genome sequences available, we attempted to determine the proteins present in venom by two different approaches. First, we searched for the transcripts of venom proteins by a bioinformatic approach using amino acid sequences of known hymenopteran venom proteins. Second, we performed proteomic analyses of crude N. vitripennis venom removed from the venom reservoir, implementing both an off‐line two‐dimensional liquid chromatography matrix‐assisted laser desorption/ ionization time‐of‐flight (2D‐LC‐MALDI‐TOF) mass spectrometry (MS) and a two‐dimensional liquid chromatography electrospray ionization Founer transform ion cyclotron resonance (2D‐LC‐ESI‐FT‐ICR) MS setup. This combination of bioinformatic and proteomic studies resulted in an extraordinary richness of identified venom constituents. Moreover, half of the 79 identified proteins were not yet associated with insect venoms: 16 proteins showed similarity only to known proteins from other tissues or secretions, and an additional 23 did not show similarity to any known protein. Serine proteases and their inhibitors were the most represented. Fifteen nonsecretory proteins were also identified by proteomic means and probably represent so‐called ‘venom trace elements’. The present study contributes greatly to the understanding of the biological diversity of the venom of parasitoid wasps at the molecular level.

8 May 2018 in Journal of Apicultural Research
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Journal Article
Open access
RBRobert Brodschneider
Robert Brodschneider
Alison GrayAlison Gray
Alison Gray
NANoureddine Adjlane
Noureddine Adjlane
ABAlexis Ballis
Alexis Ballis
VBValters Brusbardis
Valters Brusbardis
JDJiří Danihlík
Jiří Danihlík
In this short note we present comparable loss rates of honey bee colonies during winter 2016/2017 from 27 European countries plus Algeria, Israel and Mexico, obtained with the COLOSS questionnaire. The 14,813 beekeepers providing valid loss data collectively wintered 425,762 colonies, and reported 21,887 (5.1%, 95% confidence interval 5.0–5.3%) colonies with unsolvable queen problems and 60,227 (14.1%, 95% CI 13.8–14.4%) dead colonies after winter. Additionally we asked for colonies lost due to natural disaster, which made up another 6,903 colonies (1.6%, 95% CI 1.5–1.7%). This results in an overall loss rate of 20.9% (95% CI 20.6–21.3%) of honey bee colonies during winter 2016/2017, with marked differences among countries. The overall analysis showed that small operations suffered higher losses than larger ones (p < 0.001). Overall migratory beekeeping had no significant effect on the risk of winter loss, though there was an effect in several countries. A table is presented giving detailed results from 30 countries. A map is also included, showing relative risk of colony winter loss at regional level.

30 May 2019 in Journal of Apicultural Research
Verified
Journal Article
Open access
Alison GrayAlison Gray
Alison Gray
RBRobert Brodschneider
Robert Brodschneider
NANoureddine Adjlane
Noureddine Adjlane
ABAlexis Ballis
Alexis Ballis
VBValters Brusbardis
Valters Brusbardis
VSVictoria Soroker
Victoria Soroker
This short article presents loss rates of honey bee colonies over winter 2017/18 from 36 countries, including 33 in Europe, from data collected using the standardized COLOSS questionnaire. The 25,363 beekeepers supplying data passing consistency checks in total wintered 544,879 colonies, and reported 26,379 (4.8%, 95% CI 4.7–5.0%) colonies with unsolvable queen problems, 54,525 (10.0%, 95% CI 9.8–10.2%) dead colonies after winter and another 8,220 colonies (1.5%, 95% CI 1.4–1.6%) lost through natural disaster. This gave an overall loss rate of 16.4% (95% CI 16.1–16.6%) of honey bee colonies during winter 2017/18, but this varied greatly from 2.0 to 32.8% between countries. The included map shows relative risks of winter loss at regional level. The analysis using the total data-set confirmed findings from earlier surveys that smaller beekeeping operations with at most 50 colonies suffer significantly higher losses than larger operations (p < .001). Beekeepers migrating their colonies had significantly lower losses than those not migrating (p < .001), a different finding from previous research. Evaluation of six different forage sources as potential risk factors for colony loss indicated that intensive foraging on any of five of these plant sources (Orchards, Oilseed Rape, Maize, Heather and Autumn Forage Crops) was associated with significantly higher winter losses. This finding requires further study and explanation. A table is included giving detailed results of loss rates and the impact of the tested forage sources for each country and overall.