www.sciencejournal.in Volume- 4 Issue- 1 (2015) ISSN: 2319–4731 (p); 2319–5037 (e) © 2015 DAMA International. All rights reserved. 17 THE PROTEOMIC ANALYSIS OF RESISTANCE TO SCLEROTINIA SCLEROTIORUM FUNGUS IN SUNFLOWER SEEDLING STAGE Akram Emamgholi, Mohamad Zaefizadeh*, Aliakbar Imani 1-Department of agriculture, Ardabil Branch ,Islamic Azad University, Ardabil, Iran. 2-Department of agriculture, science and research branch, Islamic Azad university, Ardabil, Iran. *Corresponding E-mail: mzaefi@gmail.com ABSTRACT Sclerotinia sclerotiorum is one of the most important soil-borne fungi which infect wide variety of plants such as sunflower. Study on resistance sources at the molecular level can have a significant role in the identification of resistant plants in the early stages. Considering the importance of Sclerotinia in sunflower, the current study was carried out to identify resistance sources at protein levels of two sensitive (CMS Farokh) and resistant (Tub-3234) sunflower lines. For this purpose, proteins were extracted from cotyledon leaves 12 h after infection and analyzed by two-dimensional electrophoresis. Due to the relative expression of proteins, six protein spot (SOD, CAT, AOS, LSP, LOX and ICL) were identified through Maldi-TOF-TOF or mass spectrophotometry. The results indicated that, relative expression of LOX and ICL proteins increased in sensitive line, while relative expression of enzymes such as SOD, CAT, AOS and LSP increased in resistant line. Consider the obtained results; resistance sources in sunflower are highly related to antioxidant system and programmed cell death is justifiable. On the other hand, susceptibility to Sclerotinia sclerotiorum might be due to a switch from the TCA to glyoxylate pathway which describes more carbohydrates production for fungi. KEYWORDS: Glyoxylate, Maldi-TOF-TOF, Protein spot, Sclerotinia sclerotiorum, TCA pathway. INTRODUCTION The production of oilseeds is increasing worldwide due to the growing demand of oil as the main source of edible and industrial oil. The sunflower (Helianthus annus L.) is one of the most important oil crops globally and its oil is among the highest quality vegetable oils on the market. In addition to provide edible and industrial oil, sunflower meal can be also used to provide minerals, vitamins and antioxidants (Nasim and Bano, 2012). The fungal pathogen Sclerotinia sclerotiorum (Lib.) is a common and widespread soil borne fungal pathogen to more than 400 plant species. It was first described in 1837, and recognized as a sunflower pathogen in 1861 (Lu, 2003). It is encountered in all sunflower- growing regions of the world and attack several plant parts including stem, root, leaf and head. Under favorable climatic conditions the fungus causes important yield reductions, especially in the case of stem (stalk rot) or capitulum (head rot) infection. As chemical control is not practical, genetic control through the development of resistant lines appears to be the best crop protection strategy (Parts et al., 2003). In the recent years, proteomic analyses are widely used in understanding the plant responses to biotic and abiotic stress (Cánovas et al., 2004; Rossignol et al., 2006). Proteomics, which is known as the large-scale study of proteins, particularly their structures and functions is a complement to genomics techniques such as micro-arrays, providing information about gene expression and function. Proteomic analyses, combined with transcriptomics, have been used as a tool for identifying proteins involved in plant defense responses to different pathogens. Identifying these proteins is crucial, not only for understanding the plants defense system, but also for testing interaction between plants and pathogens (Mehta et al., 2008). Plants have complex defense mechanisms, including stimulation of antioxidant enzymes which respond to pathogen attack quickly. A protein spot as peroxidase (POX) antioxidant enzyme in relation with S. sclerotiorum was observed in canola (Brassica napus L.) proteome (Yang et al., 2010). This enzyme plays many important roles in plants cells for instance scavenging reactive oxygen species by removing H 2 O 2 , lignin biosynthesis and degradation in cell wall, hormone signaling, chemical oxidation and defense against pathogens. There are many reports suggesting that POX synthesis is stimulated due to pathogen attack (Fossdal et al., 2001). In other words, increase in antioxidant enzymes, especially peroxidases in plant cells is known as a common sign of pathogens attack. Other antioxidant enzymes such as superoxide dismutases (SOD) are also synthesized under unfavorable conditions of pathogens attack (Subramanian et al., 2005). The role of SOD in relation to S. sclerotiorum has been well documented by SOD enzymatic assays in canola. According to Yang et al. (2010), SOD activity in canola significantly decreased 24 h after inoculating with S. sclerotiorum followed by considerable increase was observed after 36-48 h. In