Proteomic analysis of proteins in susceptible wheat cultivar (Triticum aestivum L.) seri82 upon development of yellow rust (Puccinia striiformis f. sp. tritici) infection

Wheat (Triticum aestivum L.) yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat worldwide. Pst has high potential to develop new pathotypes in very short time intervals and spreading easily and rapidly by the effect of wind. There has been attempts to control yellow rust disease by the usage of resistant wheat cultivars and the application of fungicides. However devastating outbreaks of epidemies occur in different parts of world by the effect of environmental conditions and new pathotypes. Therefore development of more effective and rapid disease control strategies are required. It is important to elucidate the molecular mechanisms of wheat-Pst interaction and genes and gene products which are functional in this processes. In the thesis, plant defence responses against virulent yellow rust attack were invastigated by using proteomic approach. This study is one of the first proteomic studies about disease responses in wheat-Pst interaction. Obtained data will be supplementary for the similar genomic and funtional genomic studies. In the scope of this study, yellow rust-susceptible wheat cultivar Seri82 was used. Total protein extracts from pathogen-inoculated (infected) and mock-inoculated (control) plant leaves at 24, 48, 72 and 96th following infection were fractionated with PF2D (Protein Fractionation 2 Dimensional) system. Protein profiles of infected and control samples were compared for each time point. Differentially expressed proteins were selected and identified in Pst-inoculated samples as compared with mock-inoculated controls by nanoLC-ESI-MS/MS system. Totally 193 differentially expressed proteins were identified for all the time point samples. Thirty percent of identified proteins were found to have fungal origin, meanwhile, 70% of proteins were found to have host origin. Both fungal and plant proteins were categorized into different groups based on their basic biological functions. These groups include pathogen attack, plant defence, stress responses, signal transduction, transport, transcription, metabolism, energy metabolism (photosynthesis and electron transport), protein metabolism and structure. In addition, 70% of fungal proteins do not show homology with any known proteins and they were classified as hypotetical group. Relative representation of each group and percentages of proteins showed variations between different time points. One of the fungal proteins identified at 24th hour post inoculation that showed homology to ?Methyl-accepting chemotaxis protein? (MCP) that were found to be functional in adsorption of pathogen to the host cell surfaces. Another fungal protein showed homology to ?FliO/FliZ? that is found to be expressed for biosynthesis of flagella which germinate from Pst spores for penetration to the plant cell. Two wheat proteins showed homology to ?Superoxide dismutases? (SODs) and ?Flavanone 3 hydroxylase? (F3H) proteins which have significant roles in early stages of plant defence responses. There was increased expression of ?Endoxylanase Precursor? fungal protein at 48th hour and this may indicate that pathogenicity is going on for the penetration to the plant cell. Important plant defensive proteins such as ?Metacaspase 4? (MCA4), ?Rust resistance kinase Lr10? (LRK10), ?Agmatine Coumaroyl Transferase? (ACT) and ?Lipid Transfer Protein? (LTP) proteins were also identified at the same time point. Up-regulation of fungal ?Isochorismatase hydrolase? protein were observed at 72 and 96th hours. Isochorismatase hydrolase is inhibitor of salicylic acid production and one of the most important plant defence suppressor. In the same time points, plant ?Citinase? and ?Endocitinase? enzymes were found to be up-regulated. These are important for plant defence due to their effect on pathogen cell wall degradation and other antifungal features. As a result; presented thesis is the most extensive proteomic study that can be find in the screened literatures about wheat-Pst interaction and results contain unique findings. We expect that our findings will contribute to development of more rapid and effective disease control methods.