Study On Acetyl Lactate Synthetase (ALS) And Its Inhibitors For Plant Pathogenic Fungi

Rhizoctonia solani and Fusarium graminearum, are important pathogens of gramineous crops. They can cause rice sheath blight and wheat scab, which damaged hardly and caused huge losses every year. Acetolactate synthase(ALS), a key enzyme for the synthesis of the three branched-chain amino acids(valine, leucine and isoleucine) in plants and micro-organisms, but not existing in animals, is widely proved and used as a significant herbicide target. This article aims to explore the possibility of using ALS as targets for the development of R.solani and F. graminearum fungicides. The results of the study are as follows:1. The two plant pathogenic fungi, R. solani and F. graminearum, and the two plants, rice and rape, were chosed as the materials for the preparation of ALS and the testing of compounds inhibitory effect in vitro. The influencing factors of ALS activity, including the methods of pathogenic fungi inoculation, incubation, extract of crude enzyme and activity testing, were summed up. These provide a good fundation for the research of specifity of ALS activity and the sreening of ALS-inhibitors.2. The inhibitory effects of31pyrimidinyloxybenzylamine derivatives, designed and synthesized according to the structural features of ALS-inhibitors, on the ALS of rice, rape, R. solani and F. graminearum were analyzed, bispyribac-sodium was used as the control. The effect of compounds differs on different ALSs. Six compounds were found to inhibit the activity of ALS isolated from R. solani, ten inhibit the activity of ALS isolated from F. graminearum, twelve inhibit the activity of ALS isolated from rice and eight inhibit the activity of ALS isolated from rape. Eleven compounds were found to inhibit only one type of ALS, four inhibit two types of ALS, three inhibit three types of ALS, and two inhibit all four types of ALS. Inhibitory effect of compounds that can inhibit more than one type of ALS differs on different ALSs.3. The inhibitory detection of31compounds on the growth of R. solani and F. graminearum showed that27compounds have fungistatic activity on R. solani and11have fungistatic activity on F. graminearum. Inhibitory effect of compounds on ALS differs from that on the hypha growth. Among the27compounds, five could inhibit both ALS and growth of R. solani. Twenty-two compounds were found to inhibit the growth of R. solani, but not inhibit the activitiy of ALS from R. solani. While, one compound inhibits the R. solani ALS only. Among the11compounds, six could inhibit both ALS and growth of F. graminearum. Four compounds were found to inhibit the growth of F. graminearum, but not inhibit the activitiy of ALS from F. graminearum. Five compounds were found to inhibit F. graminearum growth only.4. The detection of different concentrations showed that the inhibitory effect of compound12#on the growth of F. graminearunm was positively correlated with its concentration.Inhibitory test of ALS, combined with fungiatatic test in vivo could be used in the preliminary screening of fungiatatic compounds, providing beneficial basis for the development of ALS-targeted R. solani and F. graminearum fungicides. By designing new compounds according to the structural features and inhibitory effect of31compounds in this study, combining with biological analysis, it might be possible to find new better effectly compounds fungistatic to R. solani and F. graminearum, which offered a new thought for the development of new safe and efficient fungicide.