Open Access Research article

Proteomic characterization of the Rph15 barley resistance gene-mediated defence responses to leaf rust

Letizia Bernardo1, Bhakti Prinsi2, Alfredo Simone Negri2, Luigi Cattivelli1, Luca Espen2 and Giampiero Valè13*

Author affiliations

1 CRA-Consiglio per la ricerca e la sperimentazione in agricoltura, Genomics Research Centre, Via S. Protaso 302, Fiorenzuola d’Arda, PC, I-29017, Italy

2 Dipartimento di Scienze agrarie ambientali – Produzione – Territorio – Agroenergia (Di.S.A.A), University of Milan, via Celoria 2, Milano, I-20133, Italy

3 CRA-Consiglio per la ricerca e la sperimentazione in agricoltura, Rice Research Unit, S.S. 11 to Torino, Km 2,5, Vercelli, 13100, Italy

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Citation and License

BMC Genomics 2012, 13:642  doi:10.1186/1471-2164-13-642

Published: 20 November 2012

Abstract

Background

Leaf rust, caused by the biotrophic fungal pathogen Puccinia hordei, is one of the most important foliar disease of barley (Hordeum vulgare) and represents a serious threat in many production regions of the world. The leaf rust resistance gene Rph15 is of outstanding interest for resistance breeding because it confers resistance to over 350 Puccinia hordei isolates collected from around the world. Molecular and biochemical mechanisms responsible for the Rph15 effectiveness are currently not investigated. The aim of the present work was to study the Rph15-based defence responses using a proteomic approach.

Results

Protein pattern changes in response to the leaf rust pathogen infection were investigated in two barley near isogenic lines (NILs), Bowman (leaf rust susceptible) and Bowman-Rph15 (leaf rust resistant), differing for the introgression of the leaf rust resistance gene Rph15. Two infection time points, 24 hours and four days post inoculation (dpi), were analysed. No statistically significant differences were identified at the early time point, while at 4 dpi eighteen protein spots were significantly up or down regulated with a fold-change equal or higher than two in response to pathogen infection. Almost all the pathogen-responsive proteins were identified in the Bowman-Rph15 resistant NIL. Protein spots were characterized by LC-MS/MS analysis and found to be involved in photosynthesis and energy metabolism, carbohydrate metabolism, protein degradation and defence. Proteomic data were complemented by transcriptional analysis of the respective genes. The identified proteins can be related to modulation of the photosynthetic apparatus components, re-direction of the metabolism to sustain defence responses and deployment of defence proteins.

Conclusions

The identification of leaf rust infection-modulated defence responses restricted to the resistant NIL support the hypothesis that basal defence responses of Bowman, but not the Rph15 resistance gene-based ones, are suppressed or delayed by pathogen effectors to levels below the detection power of the adopted proteomic approach. Additionally, Rph15-mediated resistance processes identified mainly resides on a modulation of primary metabolism, affecting photosyntesis and carbohydrate pool.

Keywords:
Barley; Leaf rust; Resistance gene; Rph15; Proteomics; Near isogenic lines