Study On The Function And Mechanism Of Autophagy In The Process Of Interaction Between Wheat And Puccinia Triticina

Wheat is one of the food crops most widely planted around the world, and it is also one of the favorite principal food for the people in our country. Wheat is easily affected by a variety of diseases, in the growth period, leading to the lower of its output. Puccinia triticina is one of the worst wheat diseases which is the most widely popular and the most destructive in the world, and it has not been cut off in all major wheat producing areas in our country, which can cause huge economic losses. Therefore, the study for resistance to Puccinia triticina has been highly viewed and widely studied by researchers both at home and abroad.During deep research in recent years, we found that autophagy played an important role in the process of plant resistance to pathogen infection. Autophagy is a pathway of protein degradation, it happens in the condition that the cells are under stress or in the special period during growth and development. When it is induced, autophagy can form autophagosome which has a double membrane structure packaging cytoplasm,and then transports these to vacuole or lysosomes for degradation. Autophagy is a highly conserved mechanism which is formed during the long-term evolution, playing a part in the organism’s growth, development, reproduction, apoptosis, and a series of process.Early results of the experiment showed that in the wheat Puccinia triticina –interaction system, using wheat and Puccinia triticina physiological imcompatibility combination of 260, the expression of key genes Ta ATG8 autophagy formed was higher significantly. Using virus induced gene silence(VIGS) to silence the key genes Ta ATG8 which contributes to autophagy formation, Puccinia triticina induced HR extension, the results suggest that autophagy may be associated with resistance to Puccinia triticina infection. In order to further study of autophagy in the interaction system and the regulatory mechanism of HR, via series of tests, this paper obtain the following main results:1.Autophagosomes in incompatible combination was more than compatible combination by the observation of fluorescence microscope and transmission electron microscope.2.After RNAi- Ta ATG8 wheat plant inoculated by Puccinia triticina physiological races 260, for 48 hours, the area of the HR expansion enlarged compared with the control group of common wheat plant and the number of haustorium mother cells increased. Late stage, the HR extension area and the number of haustorial mother cells of them were roughly same.3.In the HR of incompatible combination, inclusions of autophagosomes included protein from organelles such as endoplasmic reticulum, mitochondria, chloroplasts and so on were found through immune gold tag test.4.Through real-time quantitative PCR monitoring of several genes including Ta ATG1、Ta ATG4、Ta ATG5、Ta ATG7 and Ta ATG9, related to autophagosomes, there was something founded. The expression level was low in the compatible combination system and it did not change significantly since 0h after vaccination but the expression of the first four gene incresaed in the incompatible combination system since 72 h after inoculation and reached maximum until 96 h, then tended to decline until 120 h which was some with 0 h, while the expression of Ta ATG9 appeared two peaks 24 h and 72 h after inoculation. Expression pattern of autophagy genes reflected protein components involved in the formation of autophagy and function of autophagy might be different in the different stages of the incompatible combination system.5.In the incompatible combination system, the accumulation of intracellular ROS may be one of the factors inducing autophagy.All of these manifested that the accumulation of intracellular ROS might be one of the factors inducing autophagy in the two systems. Autophagy might have negative regulation of HR which was the defense response when autophagy was induced.Autophagy might take a part in degradation process of protein and organelles such as endoplasmic reticulum, mitochondria, chloroplasts and so on in the cells where HR was occurring and that was to say that autophagy was good to the speed of death of the host cells. The patterns of expression of autophagy related to genes different may participated in the formation of autophagosomes in different period, which implied that formation and function of autophagy formed in different period was different. These conclusions was good for us to understand of the positive function of autophagy which happened in the process of plants and fungi interaction system, and will also promote people understanding of the processes involved in plant when autophagy participated in immune responses.