To Explore The Role Of Salicylic Acid During Induced Defense Response Of Wheat To Puccinia Triticina

Puccinia triticcina is a living parasitical fungi with high specificity. In the incompatible combinations, the host resisted Puccinia triticcina by producing HR. It has been proved that salicylic acid(SA) participated in some processes of hypersensitive response(HR) and systemic acquired resistance(SAR) in many plants(such as tobacco, cucumber, arabidopsis). Studies found that SA-dependent oxidation signal enhancement was transmitted to the nucleus and promoted HR at the infection portion, so that the plants can prevent the diffusion of pathogens. Previous research has shown that enhanced disease susceptibility 1(EDS1) is not only the important factor in SAR, but also the key component of HR in the resistance system of TIR-NB-LRR type of R proteins. EDS1 can promote SA accumulated and SA can up-regulate EDS1 and phytoalexin deficient 4(PAD4). So SA and EDS1 are considered to function in a positive feedback regulatory loop. Based on the previous research of our laboratory, we got gene silencing lines of Ta EDS1 by RNA interference(RNAi) technology and researched the changes of HR in silencing lines. In the interaction of Triticum aestivum and Puccinia triticcina, we measured SA content by high performance liquid chromatography(HPLC) and analyzed gene expression profiles of two different SA synthase genes(Ta ICS and Ta PAL). And on this basis we got gene silencing lines of Ta ICS by RNAi technology. In addition, we preliminary discussed the role of SA in plant disease resistance. Our findings are of great importance to the further research.This study was to obtain the following results:1. In the early interaction(8h after inoculation), in incompatible combinations the content of free and conjugated SA is significantly higher than 0h after inoculation, while in mock and compatible combinations the content of SA at different time points did not change significantly. These results indicated that SA is involved in the process of wheat resistance.2. The results of real-time quantitative PCR showed that in the early interaction, in incompatible combination the gene expression of Ta ICS and Ta PAL was significantly higher than 0h. While in the compatible combination, the gene expression of Ta ICS after inoculation at different time points did not change evidently, 8h after inoculation the expression level of Ta PAL is also increased, but lower than that in the incompatible combination. We speculated that the Ta ICS gene played an essential role in the control of SA biosynthesis.3. And then we got PCR-positive gene silencing lines of Ta ICS and Ta EDS1 by RNAi technology and Agrobacterium-mediated transformation. The T1 generation of Ta EDS1-R2 Line4 was tested positive by southern blotting. The results of semi-quantitative PCR showed that Ta EDS1 was silenced in Line4.4. Ta EDS1-R2 Line4 T1 plants were inoculated Puccinia triticina race 260. The results showed that silencing EDS1 can significantly reduce the HR area of single infection court, the number of HMC had significant increased. These results indicated that Ta EDS1 maybe regulate the progress of HR.