Wheat leaf rust, caused by the basidiomycete Puccinia triticina, can cause yield losses of up to 20% in wheat producing regions. During infection, the fungus forms haustoria that secrete proteins into the plant cell and effect changes in plant transcription, metabolism, and defense. It is hypothesized that new races emerge as a result of overcoming plant resistance via changes in the secreted effector proteins. To understand gene expression during infection and find genetic differences associated with races, RNA from wheat leaves infected with six different rust races, at 6 days post inoculation, was sequenced using Illumina. As P. triticina is an obligate biotroph, RNA from both the host and fungi were present and separated by alignment to the P. triticina genome and a wheat EST reference. A total of 222,571 rust contigs were assembled from 165 million reads. An examination of the resulting contigs revealed 532 predicted secreted proteins among the transcripts. Of these, 456 were found in all races. Fifteen genes were found with amino acid changes, corresponding to putative avirulence effectors potentially recognized by 11 different leaf rust resistance (Lr) genes. Twelve of the potential avirulence effectors have no homology to known genes. One gene had significant similarity to cerato-platanin, a known fungal elicitor, and another showed similarity to fungal tyrosinase, an enzyme involved in melanin synthesis. Temporal expression profiles were developed for these genes by qRT-PCR and show that the genes expression patterns were consistent between races from infection initiation to just prior to spore eruption.
Keywords: Puccinia triticina, secreted peptides, effectors, leaf rust, RNA sequencing
Citation: Bruce M, Neugebauer KA, Joly DL, Migeon P, Cuomo CA, Wang S, Akhunov E, Bakkeren G, Kolmer JA and Fellers JP (2014) Using transcription of six Puccinia triticina races to identify the effective secretome during infection of wheat. Front. Plant Sci. 4:520. doi: 10.3389/fpls.2013.00520
Received: 01 October 2013; Accepted: 02 December 2013;
Published online: 13 January 2014.
Edited by:Sébastien Duplessis, INRA, France
Copyright © 2014 Bruce, Neugebauer, Joly, Migeon, Cuomo, Wang, Akhunov, Bakkeren, Kolmer and Fellers. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: John P. Fellers, USDA-ARS, Department of Plant Pathology, 4008 Throckmorton Hall, Manhattan, KS 66506, USA e-mail: email@example.com