The Structure-herbicidal Activity Relationship Of Mycotoxin Produced By Fungi Which Are Photosynthesis Inhibitor

Since the discovery of 2,4-D butylate,the herbicide industry has experienced 70 years of development.It has become an important part of modern agricultural production systems and is indispensable means in the farmland weeding technology.So far,there are 400-500 kinds of herbicides into commercial operation on a global level and every year new products continue to spring up.In terms of the chemical herbicide,a large number of selective herbicides have emerged.In the era of agriculture modernization,application of the chemical herbicides provides a strong technical support for food production However,use of chemical herbicides has caused serious residues pollution to the environment,leading to damage to the environment,and even gradually threatens the physical and mental health of human beings as well.Meantime,long-term use of chemical herbicides gradually increases resistance of weeds,eventually resulting in occurrence of a large number of new and malignant weeds in succession of farmland weed communities.Therefore,it is of greater social significance and economic value to develop the new herbicides that is efficient,environmentally friendly harmless,which has become the future trend of herbicide research and development.New bioherbicides are mainly explored based on allelochemicals and natural products as precursory compound.Usually,these herbicides exhibit higher secure and efficient due to their unique mechanism of action.Compared with chemical herbicides,such bioherbicides are featured by the novel chemical structure,low toxicity,quick degradation,high specificity,moreover,have many advantages such as abundant resources,no residues,safety to the ecological environment.With the progress of social civilization and the improvement of public health awareness,there is an increasing attention on how to develop new herbicide using natural products.Obviously,these natural products can provide some important theoretical basis and reference to develop new herbicides.It's possible to discover new herbicides with novel action target and mechanismby directly utilizing the natural products or modifying their structure.In this study,some compounds with excellent inhibition of the physiological activity of plants,especially herbicidal activity,are selected from 61 natural mycotoxins products.Their action targets are studied by biochemistry,physiology and biophysics methods.At the same time,molecular model of the photosynthetic inhibitor candidates interacting with target D1 protein is analyzed using Discovery Studio software in order to establish the relationship between toxin structure,targets and biological activity.To build a quik screening platform,model plant Chlamydomonas reinhardtii was selected as metarials to study the effect of all toxins on photosynthesis activity by chlorophyll fluorometer Imaging-PAM.Preliminary 23 photosynthetic inhibitor toxins were screened out,which have significant inhibition in PS? potential maximum quantum yield?F_V/F_M?)and electronic transfer rate?ETR?.These 23 toxins are classified into three group based on the standard of 50%inhibitory concentration?pl50?of ETR.Among them,the high-activity(0<pI₅₀<100?M),the moderate-inhibitory-activity(100 ?M<pI₅₀<500 ?M),and the weak-activity(pI₅₀>500?M)toxins are 9,11 and 3 species,respectively.Taking Arabidopsis as material,16 kinds of toxins which can significantly inhibite the growth of Arabidopsis root were discovered.To probe the precise action site in photosynthesis apparatus of the selected photosynthetic inhibitor toxins,the fastchlorophyll fluorescence rise kinetics OJIP and JIP-test,oxygen evolution activity were carried out.Additionally,4 representative toxins----usnic acid,benzoic acid,cinnamic acid,andsalicylic acid,are selected to do further study,which including chlorophyll content,electron transport activity of PS? and PSI,content of the total soluble proteins,thylakoid proteins and the analysis of fast chlorophyll fluorescence rise kinetics.It is concluded that these four toxins significantly affect on the acceptor side of PS?.The structure-activity relationship of 23 selected photosyntheic inhibitor toxinswas studied through Discovery Studio software.Interaction analysis based on molecular model between toxin molecules and target D1 proteinwas made by homollogy modeling.The pathogenic ability of these compounds to Eupatorium adenophoruum leaves also was checked by monitoring the form of disease spot.Finally,the relationship between the chemical structure of the toxins,targets and herbicidal activity was build.This is useful to providea theoretical basis and tehcnical support for the new compounds synthesis as the toxin as precusor in the future.