Links, Matthew G., Holub, E. B., Jiang, Rays H. Y., Sharpe, Andrew G., Hegedus, Dwayne, Beynon, Elena, Sillito, Dean, Clarke, Wayne E., Uzuhashi, Shihomi and Borhan, Mohammad Hossein (2011) De novo sequence assembly of Albugo candida reveals a small genome relative to other biotrophic oomycetes. BMC Genomics, Vol.12 (No.1). Article No. 503. doi:10.1186/1471-2164-12-503

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Abstract

Background: Albugo candida is a biotrophic oomycete that parasitizes various species of Brassicaceae, causing a
disease (white blister rust) with remarkable convergence in behaviour to unrelated rusts of basidiomycete fungi.
Results: A recent genome analysis of the oomycete Hyaloperonospora arabidopsidis suggests that a reduction in
the number of genes encoding secreted pathogenicity proteins, enzymes for assimilation of inorganic nitrogen and
sulphur represent a genomic signature for the evolution of obligate biotrophy. Here, we report a draft reference
genome of a major crop pathogen Albugo candida (another obligate biotrophic oomycete) with an estimated
genome of 45.3 Mb. This is very similar to the genome size of a necrotrophic oomycete Pythium ultimum (43 Mb)
but less than half that of H. arabidopsidis (99 Mb). Sequencing of A. candida transcripts from infected host tissue
and zoosporangia combined with genome-wide annotation revealed 15,824 predicted genes. Most of the
predicted genes lack significant similarity with sequences from other oomycetes. Most intriguingly, A. candida
appears to have a much smaller repertoire of pathogenicity-related proteins than H. arabidopsidis including genes
that encode RXLR effector proteins, CRINKLER-like genes, and elicitins. Necrosis and Ethylene inducing Peptides
were not detected in the genome of A. candida. Putative orthologs of tat-C, a component of the twin arginine
translocase system, were identified from multiple oomycete genera along with proteins containing putative tatsecretion
signal peptides.
Conclusion: Albugo candida has a comparatively small genome amongst oomycetes, retains motility of sporangial
inoculum, and harbours a much smaller repertoire of candidate effectors than was recently reported for H.
arabidopsidis. This minimal gene repertoire could indicate a lack of expansion, rather than a reduction, in the
number of genes that signify the evolution of biotrophy in oomycetes.

Item Type:	Journal Article
Subjects:	Q Science > QR Microbiology
Divisions:	Faculty of Science > Life Sciences (2010- )
Library of Congress Subject Headings (LCSH):	Albugo candida -- Genetics
Journal or Publication Title:	BMC Genomics
Publisher:	BioMed Central Ltd.
ISSN:	1471-2164
Official Date:	13 October 2011
Dates:	Date Event 13 October 2011 Published
Volume:	Vol.12
Number:	No.1
Page Range:	Article No. 503
DOI:	10.1186/1471-2164-12-503
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	Canada. Agriculture and Agri-Food Canada, NCBI
Grant number:	56025 (NCBI)

Data sourced from Thomson Reuters' Web of Knowledge

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