Construction and characterization of a full-length cDNA library for the wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici)

A full-length cDNA library, consisting of 42,240 clones with an average cDNA insert of 1.9 kb, was constructed using urediniospores of race PST-78 of P. striiformis f. sp. tritici. From 196 sequenced cDNA clones, we determined functions of 73 clones (37.2%). In addition, 36 clones (18.4%) had significant homology to hypothetical proteins, 37 clones (18.9%) had some homology to genes in other fungi, and the remaining 50 clones (25.5%) did not produce any hits. From the 73 clones with functions, we identified 51 different genes encoding protein products that are involved in amino acid metabolism, cell defense, cell cycle, cell signaling, cell structure and growth, energy cycle, lipid and nucleotide metabolism, protein modification, ribosomal protein complex, sugar metabolism, transcription factor, transport metabolism, and virulence/infection.The full-length cDNA library is useful in identifying functional genes of P. striiformis.Puccinia striiformis Westend., a fungus in Pucciniacea, Uredinales, Basidiomycotina, Eumycota, causes stripe (yellow) rust. Based on specific pathogenicity on cereal crops and grasses, the fungal species consists of various formae speciales, such as P. striiformis f. sp. tritici on wheat (Triticum aestivum), P. striiformis f. sp. hordei on barley (Hordeum vulgare), P. striiformis f. sp. poae on bluegrass (Poa pratensis) and P. striiformis f. sp. dactylidis on orchard grass (Dactylis glomerata) [9,32]. Among the various formae speciales, the wheat and barley stripe rust pathogens are most economically important. Wheat stripe rust has been reported in more than 60 countries and all continents except Antarctica [6]. Devastating epidemics of wheat stripe rust often occur in many countries in Africa, Asia, Australia, Europe, North America and South America [6,32]. In the U. S., stripe rust of wheat has existed for more than 100 years [19,25]. The disease had been primarily a major problem in western US before 2000, but has become increasingly impo