Expressed Sequence Tags from the oomycete Plasmopara halstedii, an obligate parasite of the sunflower.
BACKGROUND
Sunflower downy mildew is a major disease caused by the obligatory biotrophic oomycete Plasmopara halstedii. Little is known about the molecular mechanisms underlying its pathogenicity. In this study we used a genomics approach to gain a first insight into the transcriptome of P. halstedii.


RESULTS
To identify genes from the obligatory biotrophic oomycete Plasmopara halstedii that are expressed during infection in sunflower (Helianthus annuus L.) we employed the suppression subtraction hybridization (SSH) method from sunflower seedlings infected by P. halstedii. Using this method and random sequencing of clones, a total of 602 expressed sequence tags (ESTs) corresponding to 230 unique sequence sets were identified. To determine the origin of the unisequences, PCR primers were designed to amplify these gene fragments from genomic DNA isolated either from P. halstedii sporangia or from Helianthus annuus. Only 145 nonredundant ESTs which correspond to a total of 373 ESTs (67.7%) proved to be derived from P. halstedii genes and that are expressed during infection in sunflower. A set of 87 nonredundant sequences were identified as showing matches to sequences deposited in public databases. Nevertheless, about 7% of the ESTs seem to be unique to P. halstedii without any homolog in any public database.


CONCLUSIONS
A summary of the assignment of nonredundant ESTs to functional categories as well as their relative abundance is listed and discussed. Annotation of the ESTs revealed a number of genes that could function in virulence. We provide a first glimpse into the gene content of P. halstedii. These resources should accelerate research on this important pathogen.
Bouzidi
Mohamed Fouad
MF
UMR 1095 INRA-UBP "Amélioration et Santé des Plantes", Université Blaise Pascal, 24, Avenue des Landais 63177 Aubière Cedex, France. m-fouad.bouzidi@univ-bpclermont.fr
Parlange
Francis
F
Nicolas
Paul
P
Mouzeyar
Said
S
D000595:Amino Acid Sequence; D000818:Animals; D020224:Expressed Sequence Tags / Q000737:chemistry; D005658:Fungi / Q000235:genetics / Q000472:pathogenicity; D020869:Gene Expression Profiling; D006368:Helianthus / Q000382:microbiology*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization / Q000379:methods; D009868:Oomycetes / Q000235:genetics* / Q000472:pathogenicity*; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000382:microbiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D037521:Virulence Factors / Q000032:analysis / Q000235:genetics
D037521:Virulence Factors