| Abstract: BACKGROUND : Puccinia striiformis f . sp . tritici is an obligate biotrophic pathogen that causes leaf stripe rust on wheat .
Although it is critical to understand molecular mechanisms of pathogenesis in the wheat stripe rust fungus for developing novel disease management strategies , little is known about its genome and gene functions due to difficulties in molecular studies with this important pathogen .
To identify genes expressed during early infection stages , in this study we constructed a cDNA library with RNA isolated from urediniospores of P striiformis f . sp . tritici germinated for 10 h .
RESULTS : A total of 4798 ESTs were sequenced from the germinated urediniospore library and assembled into 315 contigs and 803 singletons .
About 23 . 9% and 13 . 3% of the resulting 1118 unisequences were homologous to functionally characterized proteins and hypothetical proteins , respectively .
The rest 62 . 8% unisequences had no significant homologs in GenBank .
Several of these ESTs shared significant homology with known fungal pathogenicity or virulence factors , such as HESP767 of the flax rust and PMK1 , GAS1 , and GAS2 of the rice blast fungus .
We selected six ESTs ( Ps28 , Ps85 , Ps87 , Ps259 , Ps261 , and Ps159 ) for assaying their expression patterns during urediniospore germination and wheat infection by quantitative real-time PCR .
All of them had the highest transcript level in germinated urediniospores and a much less transcript level in un-germinated urediniospores and infected wheat it issues ( 1-7 dpi ) .
The transcript level of Ps159 increased at later infection stages ( 6-7 dpi ) .
Our data indicated that these genes were highly expressed in germinated urediniospores and may play important roles in fungal-plant interactions during early infection stages in the wheat stripe rust fungus .
CONCLUSION : Genes expressed in germinated urediniospores of P striiformis f . sp . tritici were identified by EST analysis .
Six of them were confirmed by quantitative real-time PCR assays to be highly expressed in germinated urediniospores .
|
