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Title: Identification of promising host-induced silencing targets among genes preferentially transcribed in haustoria of Puccinia

Author
item YIN, C. - Washington State University
item DOWNEY, S. - Washington State University
item KLASGES-MUNDT, N. - Washington State University
item RAMACHANDRAN, S. - Washington State University
item Chen, Xianming
item Szabo, Les
item PUMPHREY, M. - Washington State University
item HULBERT, S. - Washington State University

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2015
Publication Date: 8/5/2015
Citation: Yin, C.T., Downey, S.I., Klasges-Mundt, N.L., Ramachandran, S., Chen, X., Szabo, L.J., Pumphrey, M., Hulbert, S.H. 2015. Identification of promising host-induced silencing targets among genes preferentially transcribed in haustoria of Puccinia. Biomed Central (BMC) Genomics. 16:579.

Interpretive Summary: Expression of dsRNA fragments of rust pathogen genes in wheat seedlings through the barley stripe mosaic virus (BSMV) based host-induced gene silencing (HIGS) system can reduce the expression of the corresponding genes in the rust fungus. The highest levels of suppression have generally been observed in genes that are expressed mainly in haustorial cells. Comparative RNA sequencing was used to identify genes from the wheat stem rust pathogen with haustorium-specific expression. Virus induced gene silencing (VIGS) constructs with fragments of 86 stem rust fungal genes, or stripe rust fungal homologs, were tested for their ability to interfere with pathogenicity of these rust fungi. Most of the tested genes did not interfere with pathogenicity, but 10 genes reduced rust development and pathogenicity after co-inoculation with the gene VIGS constructs and the wheat stem rust pathogen. These genes were predicted to have various biochemical and biophysical functions. Transient silencing of four of these genes reduced development of the stripe rust pathogen and three of them suppressed disease of leaf rust, indicating that it may be possible to engineer resistance to multiple rusts with a single gene in transgenic wheat plants.

Technical Abstract: Expression of dsRNA fragments of rust pathogen genes in wheat seedlings through the barley stripe mosaic virus (BSMV) based host-induced gene silencing (HIGS) system can reduce the expression of the corresponding genes in the rust fungus. The highest levels of suppression have generally been observed in genes that are expressed mainly in haustorial cells. Comparative RNA sequencing was used to identify genes from Puccinia graminis f. sp. tritici (Pgt) with haustoriuma-specific expression. VIGS constructs with fragments of 86 Pgt genes, or P. striiformis f. sp. tritici (Pst) homologs, were tested for their ability to interfere with pathogenicity of these rust fungi. Most of the tested genes did not interfere with pathogenicity, but 10 genes reduced rust development and pathogenicity after co-inoculation with the gene VIGS constructs and Pgt. These included a predicted glycolytic enzyme, two other proteins that are probably secreted and involved in carbohydrate or sugar metabolism, a protein involved in thiazol biosynthesis, a protein involved in auxin biosynthesis, an amino acid permease, two hypothetical proteins with no conserved domains, a small secreted protein and another secreted protein with similarity to bacterial proteins involved in membrane transport. Transient silencing of four of these genes reduced development of Pst and three of them suppressed disease of P. triticina (Pt), indicating that it may be possible to engineer resistance to multiple rusts with a single gene in transgenic wheat plants.