title: Generation of a wheat leaf rust, Puccinia triticina, EST database from stage-specific cDNA libraries.
abstract: Thirteen cDNA libraries constructed from small amounts of leaf rust mRNA using optimized methods served as the source for the generation of 25 558 high-quality DNA sequence reads. Five life-cycle stages were sampled: resting urediniospores, urediniospores germinated over water or plant extract, compatible, interactive stages during appressorium or haustorium formation just before sporulation, and an incompatible interaction. mRNA populations were subjected to treatments such as full-length cDNA production, subtractive and normalizing hybridizations, and size selection methods combined with PCR amplification. Pathogen and host sequences from interactive libraries were differentiated in silico using cereal and fungal sequences, codon usage analyses, and by means of a partial prototype cDNA microarray hybridized with genomic DNAs. This yielded a non-redundant unigene set of 9760 putative fungal sequences consisting of 6616 singlets and 3144 contigs, representing 4.7 Mbp. At an E-value 10(-5), 3670 unigenes (38%) matched sequences in various databases and collections but only 694 unigenes (7%) were similar to genes with known functions. In total, 296 unigenes were identified as most probably wheat and ten as rRNA sequences. Annotation rates were low for germinated urediniospores (4%) and appressoria (2%). Gene sets obtained from the various life-cycle stages appear to be remarkably different, suggesting drastic reprogramming of the transcriptome during these major differentiation processes. Redundancy within contigs yielded information about possible expression levels of certain genes among stages. Many sequences were similar to genes from other rusts such as Uromyces and Melampsora species; some of these genes have been implicated in pathogenicity and virulence.
authors.affiliation: Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Highway 97, Summerland, BC V0H 1Z0, Canada.
authors.forename: Guanggan
authors.initials: G
authors.lastname: Hu
authors.forename: Rob
authors.initials: R
authors.lastname: Linning
authors.forename: Brent
authors.initials: B
authors.lastname: McCallum
authors.forename: Travis
authors.initials: T
authors.lastname: Banks
authors.forename: Sylvie
authors.initials: S
authors.lastname: Cloutier
authors.forename: Yaron
authors.initials: Y
authors.lastname: Butterfield
authors.forename: Jerry
authors.initials: J
authors.lastname: Liu
authors.forename: Robert
authors.initials: R
authors.lastname: Kirkpatrick
authors.forename: Jeff
authors.initials: J
authors.lastname: Stott
authors.forename: George
authors.initials: G
authors.lastname: Yang
authors.forename: Duane
authors.initials: D
authors.lastname: Smailus
authors.forename: Steven
authors.initials: S
authors.lastname: Jones
authors.forename: Marco
authors.initials: M
authors.lastname: Marra
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Schein
authors.forename: Guus
authors.initials: G
authors.lastname: Bakkeren