Cloning and expression analysis of three secreted protein genes from wheat stripe rust fungus Puccinia striiformis f. sp. tritici

Abstract

The Puccinia striiformis f. sp. tritici (Pst) fungus is a biotrophic obligate parasite causing stripe rust, a major disease of wheat worldwide. Pst genes that encode secreted proteins serving as effectors and avirulence genes are thought to be expressed in haustoria. Three putative secreted protein genes from Pst haustoria were characterized in this study. Their full-length cDNAs were obtained using the 5′ rapid amplification of cDNA ends (RACE). Their transcripts were ranged from 769 to 1,094 base pairs (bp), encoding predicted proteins of 93 to 203 amino acids without significant similarities to any accessions in the GenBank protein database, but with some homologies to predicted proteins in P. graminis, the stem rust pathogen. The predicted products of the genes were characterized as secreted proteins and designated as PstSP2C7, PstSP11L10 and PstSP11P10. PstSP11L10 had a much higher expression level in infected leaves than in urediniospores and germinated urediniospores and therefore should be a good candidate for a gene involved in the wheat-Pst interaction.