John McCallum

John McCallum

orcid

Research Focus & Metrics

Academic Career Length

36Years (1991-Present)

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

Representative Publications

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3 December 2013 in Nature Communications
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RLRobyn Lee
Robyn Lee
SBSamantha Baldwin
Samantha Baldwin
FKFernand Kenel
Fernand Kenel
JMJohn McCallum
John McCallum
RMRichard Macknight
Richard Macknight

16 April 2018 in BMC Genomics
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Journal Article
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SPSarah M. Pilkington
Sarah M. Pilkington
RCRoss Crowhurst
Ross Crowhurst
EHElena Hilario
Elena Hilario
SNSimona Nardozza
Simona Nardozza
LFLena Fraser
Lena Fraser
RSRobert J Schaffer
Robert J Schaffer
Most published genome sequences are drafts, and most are dominated by computational gene prediction. Draft genomes typically incorporate considerable sequence data that are not assigned to chromosomes, and predicted genes without quality confidence measures. The current Actinidia chinensis (kiwifruit) ‘Hongyang’ draft genome has 164 Mb of sequences unassigned to pseudo-chromosomes, and omissions have been identified in the gene models. A second genome of an A. chinensis (genotype Red5) was fully sequenced. This new sequence resulted in a 554.0 Mb assembly with all but 6 Mb assigned to pseudo-chromosomes. Pseudo-chromosomal comparisons showed a considerable number of translocation events have occurred following a whole genome duplication (WGD) event some consistent with centromeric Robertsonian-like translocations. RNA sequencing data from 12 tissues and ab initio analysis informed a genome-wide manual annotation, using the WebApollo tool. In total, 33,044 gene loci represented by 33,123 isoforms were identified, named and tagged for quality of evidential support. Of these 3114 (9.4%) were identical to a protein within ‘Hongyang’ The Kiwifruit Information Resource (KIR v2). Some proportion of the differences will be varietal polymorphisms. However, as most computationally predicted Red5 models required manual re-annotation this proportion is expected to be small. The quality of the new gene models was tested by fully sequencing 550 cloned ‘Hort16A’ cDNAs and comparing with the predicted protein models for Red5 and both the original ‘Hongyang’ assembly and the revised annotation from KIR v2. Only 48.9% and 63.5% of the cDNAs had a match with 90% identity or better to the original and revised ‘Hongyang’ annotation, respectively, compared with 90.9% to the Red5 models. Our study highlights the need to take a cautious approach to draft genomes and computationally predicted genes. Our use of the manual annotation tool WebApollo facilitated manual checking and correction of gene models enabling improvement of computational prediction. This utility was especially relevant for certain types of gene families such as the EXPANSIN like genes. Finally, this high quality gene set will supply the kiwifruit and general plant community with a new tool for genomics and other comparative analysis.

1 January 2004 in The Plant Cell
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Journal Article
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JKJoseph C. Kuhl
Joseph C. Kuhl
FCFoo Cheung
Foo Cheung
QYQiaoping Yuan
Qiaoping Yuan
WMWilliam Martin
William Martin
YZYayeh Zewdie
Yayeh Zewdie
MHMichael Havey
Michael Havey
Enormous genomic resources have been developed for plants in the monocot order Poales; however, it is not clear how representative the Poales are for the monocots as a whole. The Asparagales are a monophyletic order sister to the lineage carrying the Poales and possess economically important plants such as asparagus, garlic, and onion. To assess the genomic differences between the Asparagales and Poales, we generated 11,008 unique ESTs from a normalized cDNA library of onion. Sequence analyses of these ESTs revealed microsatellite markers, single nucleotide polymorphisms, and homologs of transposable elements. Mean nucleotide similarity between rice and the Asparagales was 78% across coding regions. Expressed sequence and genomic comparisons revealed strong differences between the Asparagales and Poales for codon usage and mean GC content, GC distribution, and relative GC content at each codon position, indicating that genomic characteristics are not uniform across the monocots. The Asparagales were more similar to eudicots than to the Poales for these genomic characteristics.

9 December 2016 in Frontiers in Plant Science
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Journal Article
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KSKathy E. Schwinn
Kathy E. Schwinn
HNHanh Ngo
Hanh Ngo
FKFernand Kenel
Fernand Kenel
DBDavid A. Brummell
David A. Brummell
NANick W. Albert
Nick W. Albert
KDKevin Davies
Kevin Davies
Bulb colour is an important consumer trait for onion (Allium cepa L., Allioideae, Asparagales). The bulbs accumulate a range of flavonoid compounds, including anthocyanins (red), flavonols (pale yellow) and chalcones (bright yellow). Flavonoid regulation is poorly characterised in onion and in other plants belonging to the Asparagales, despite being a major plant order containing many important crop and ornamental species. R2R3-MYB transcription factors associated with the regulation of distinct branches of the flavonoid pathway were isolated from onion. These belonged to sub-groups (SGs) that commonly activate anthocyanin (SG6, MYB1) or flavonol (SG7, MYB29) production, or repress phenylpropanoid/flavonoid synthesis (SG4, MYB4, MYB5). MYB1 was demonstrated to be a positive regulator of anthocyanin biosynthesis by the induction of anthocyanin production in onion tissue when transiently overexpressd and by reduction of pigmentation when transiently repressed via RNAi. Furthermore, ectopic red pigmentation was observed in garlic (A. sativum L.) plants stably transformed with a construct for co-overexpression of MYB1 and a bHLH partner. MYB1 also was able to complement the acyanic petal phenotype of a defined R2R3-MYB anthocyanin mutant in Antirrhinum majus of the asterid clade of eudicots. The availability of sequence information for flavonoid-related MYBs from onion enabled phylogenetic groupings to be determined across monocotyledonous and dicotyledonous species, including the identification of characteristic amino acid motifs. This analysis suggests that divergent evolution of the R2R3-MYB family has occurred between Poaceae/Orchidaceae and Allioideae species. The DNA sequences identified will be valuable for future analysis of classical flavonoid genetic loci in Allium crops and will assist the breeding of these important crop species.

1 January 1998 in Theoretical and Applied Genetics
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JKJ. J. King
J. J. King
JBJ. M. Bradeen
J. M. Bradeen
OBO. Bark
O. Bark
JMJohn McCallum
John McCallum
MHM. J. Havey
M. J. Havey

15 July 2005 in Molecular Genetics and Genomics
Verified
Journal Article
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WMWilliam J. Martin
William J. Martin
JMJohn McCallum
John McCallum
Masayoshi ShigyoMasayoshi Shigyo
Masayoshi Shigyo
Jernej JakseJernej Jakse
Jernej Jakse
JKJoseph C. Kuhl
Joseph C. Kuhl
MHMichael Havey
Michael Havey