Stage-specific gene expression during urediniospore germination in Puccinia striiformis f. sp tritici

Yonghong Zhang¹ , Zhipeng Qu¹ , Wenming Zheng² , Bo Liu¹ , Xiaojie Wang¹ , Xiaodan Xue¹ , Liangsheng Xu³ , Lili Huang¹ , Qingmei Han¹ , Jie Zhao¹ and Zhensheng Kang¹

¹College of Plant Protection and Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A&F University, Yangling, Shaanxi, 712100, P.R. China

²College of Life Sciences, Henan Agriculture University, Zhengzhou, Henan, 450002, P.R. China

³College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, P.R. China

author email corresponding author email

BMC Genomics 2008, 9:203doi:10.1186/1471-2164-9-203


Published:	1 May 2008

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 tissues (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.