殺菌劑毒理學(xué)上

1、殺菌劑毒理學(xué)-Introduction,Fungicide：A substance possessing the power of killing or preventing the growth of fungi. 殺菌劑（fungicide）：殺菌、抑菌、提高抗病力，所有這種能達(dá)到防治植物病害的農(nóng)藥都是殺菌劑。,1,Introduction,Fungicides are used to eradicate or prevent t

2、he undesirable growth of fungal microorganism in many agricultural, horticultural, and industrial situations.,Introduction,殺菌劑（fungicide）：殺真菌劑（fungicide）抑真菌劑 (fungistat)殺細(xì)菌劑（bactericide）殺病毒劑 （viricides）,3,殺菌劑的發(fā)展,1、第一

3、代殺菌劑（inorganic chemicals）; 2、第二代殺菌劑（organic chemicals）傳統(tǒng)保護(hù)劑(conventional protectants) 植物藥害(phytotoxicity) ；3、第三代殺菌劑：內(nèi)吸性殺菌劑（systemic fungicide ）4、第四代殺菌劑：三環(huán)唑等較早使用的無殺菌毒性化合物。,4,殺菌劑的發(fā)展,1、無機(jī) ----有機(jī)2、多作用位點-----少作用位點----單一

4、位點3、非內(nèi)吸----內(nèi)吸4、保護(hù)劑----治療劑,5,low mammalian toxicitylow ecotoxicitylow phytotoxicityhigh penetration rates for spores and mycelialimited biodegradation on the plant surface.,6,Classification of Fungicide,In addition

5、to classification by chemical structural grouping, fungicides can be categorized agriculturally and horticulturally according to the mode of application (use) as:,7,Classification according to use,(a) soil application fu

6、ngicides,(b) foliar fungicides which are applied to plants above the ground;(c) dressing fungicides applied after harvesting with the aim of preventing fungus development on stored crops.,8,Classification according to

7、action,Fungicides may also be described according to their general mode of action:(a) protective fungicides inhibiting the development of fungi by either sporicidal effects or foliar effects creating an environment on t

8、he plant surface not conducive to fungal growth;,9,Classification according to action,(b) post-infection curative fungicides which kill (inhibit) the developing mycelium in the plant epidermis.(c) Post-symptomatic eradi

9、cation fungicides which penetrate and kill the mycelium and new spores.,10,Classification according to action,保護(hù)型殺菌劑 protective fungicide鏟除性殺菌劑 eradication fungicide治療性殺菌劑 curative fungicide內(nèi)吸性殺菌劑 systemic fungicide,

10、11,Toxicity of fungicide,In general, fungicides are of low to moderate mammalian toxicology, although they are believed to have a higher overall incidence than other pesticides to cause developmental toxicology and oncog

11、enesis.,12,Toxicity of fungicide,It has, for example, been estimated that more than 80 per cent of all oncogenic risk from the use of pesticides comes from a few fungicides.,13,Toxicity of fungicide,Fungicides usually ar

12、e responsible for only a small proportion of pesticide-related deaths, and account for only about 5 per cent or less of human pesticide exposures reported to Poison Control Centers.,14,Toxicity of fungicide,It has been n

13、oted that since fungi differ significantly in morphology and physiology from other forms of life, they may be successfully combated by compounds of low toxicity to other organisms, notably mammals.,15,,Part IIMode of A

14、ction,16,殺菌劑毒理學(xué),殺菌作用(fungitoxicity) 抑菌作用(fungistasis) 內(nèi)吸性殺菌劑(systemic fungicides, systemics) 抗產(chǎn)孢劑(antisporulants),17,內(nèi)吸性殺菌劑（systemic fungicide ）,選擇性(selectivity) (1) 靶標(biāo)位點(target site)和作用位點(site of action) (2)靶標(biāo)受體(re

15、ceptor)對藥劑的親合力(affinity)的差異 (3)藥劑對原生質(zhì)膜滲透性(permeability)的差異(4)對殺菌劑的積累(或排出)、解毒(detoxify)作用的差異等,18,殺菌劑毒理學(xué),離體（in vitro） 活體（in vivo）無殺菌毒性化合物(non-fungitoxic compounds) (1)干擾病原菌的致病機(jī)理，削弱病原菌的致病力或使病原菌不能侵入；三環(huán)唑(tricyclazole)為抗穿

16、透劑(antipenetrant) (2)提高寄主植物的抗病能力。系統(tǒng)性獲得抗病性(systemic acquired resistance, SAR) ;植物防衛(wèi)激活劑(plant defense activators) .,19,殺菌劑毒理學(xué),病害防治化合物(disease control compounds): 無殺菌毒性但是又能夠防治植物病害的化合物。在離體下無殺菌毒性，在活體內(nèi)通過削弱病原菌的致病能力或者提高寄主抗病能力來

17、達(dá)到防治病害的作用機(jī)理也被稱為間接作用機(jī)理(indirect mode of action) 。,20,Mechanisms of Fungicide Action,Biosynthesis: Sterol, Nucleic acid, protein, mitosis and cell division, lipid, glucan(葡聚糖), cell wallRespiration: Electron transport, ox

18、idative phosphorylationGrowth regulator: cell wall biosynthesis-inhibiting oomyceticidesStructure,21,1: Nucleic acids synthesis,(1) RNA polymerase I PhenylAmides苯酰胺類: Metalaxyl甲霜靈(2) Adenosin-deaminasehydroxy-pyri

19、midines(嘧啶): Resistance in powdery mildews(3) DNA/RNA synthesis(4) DNA topoisomerase,22,2: Mitosis and cell division,(1)β-tubulin assembly in mitosis Benzimidazole: Carbendazim多菌靈Diethofencarb乙霉威 Negative cross resi

20、stance to Diethofencarb乙霉威,23,３Respiration,(1) Complex I NADH Oxidoreductase: Pyrimidinamine (2) Complex II: succinate-dehydrogenase琥珀酸脫氫酶SDHI(Succianate dehydrogenase inhibitor)Boscalid:啶酰菌胺,24,３Respiration,(3) Compl

21、ex III: cytochrome bc1 (ubiquinol 輔酶oxidase at Qo site (cyt b)) Qol (Quinone outside Inhibitors)Azoxystrobin,嘧菌酯kresoxim-methyl,醚菌酯,25,３Respiration,(4) complex III: cytochrome bc1 (ubiquinone-reductase) at Qi site Qi

22、l-fungicides (Quinone inside inhibitors)(5) uncouplers of oxidative phosphorylation(6) inhibitors of oxidative phosphorylation, ATP synthase: organo tin compounds,26,4 amino acids and protein synthesis,(1)methionine bi

23、osynthesis Pyrimethanil 嘧霉胺(2) protein synthesisAntibiotic: kasugamycin春雷霉素，streptomycin鏈霉素，oxytetracycline土霉素,27,5 signal transduction,(1) G-proteins in early cell signalling: quinolines(喹啉類)(2) MAP (Mitogen-activat

24、ed protein ) /Histidine-Kinase on osmotic signal transduction: dicarboximides二甲酰亞胺類 ：iprodione異菌脲，procymidone 速克靈，vinclozolin乙烯菌核利，,28,6 lipids and membrane synthesis,(1) phospholipid biosynthesis, methyltransferase: py

25、razophos 定菌磷(2) lipid peroxidation: (3) cell membrane permeability, fatty acids: (4) phospholipid biosynthesis and cell wall deposition: Carboxylic acid amides (5) microbial disrupter of pathogen cell membranes: Mi

26、crobial (Bacillus sp)枯草桿菌,29,7 Sterol biosynthesis in membrances,(1) C14-demethylase in sterol biosynthesis : DMI-fungicides (DeMethylation inhibitors)imidazole,咪唑類，imazalil抑霉唑Triazoles: propiconazole,丙環(huán)唑 triadimefon三唑

27、酮，diniconazole烯唑醇，difenoconazole苯醚甲環(huán)唑 (世高),30,7 Sterol biosynthesis in membrances,(2) 3-keto reductase, C4-demethylation Fenhexamid 環(huán)酰菌胺(3) squalene(角)鯊烯epoxidase in sterol biosynthesis,31,8. Glucan葡聚糖synthesis,(1) tre

28、halase海藻糖酶and inositol (纖維醇, 纖維糖)-biosynthesis: antibiotic, validamycin有效霉素(2)chitin synthase: polyoxins多氧菌素,32,9 melanin synthesis in cell wall,(1) reductase in melanin biosynthesis MBI-R (Melanin Biosynthesis inhib

29、itors- reductase)Tricyclazole:三環(huán)唑(2) dehydratase in melanin biosynthesisMBI-D (Melanin Biosynthesis inhibitors -dehydratase),33,10 host plant defence induction,(1)salicylic acid(水楊酸) pathwayAcibenzolar-S-methyl阿拉酸式

30、苯S-甲基Probenazole噻菌靈,34,11 Multi-site contact activity,(1) inorganic: copper, sulphur(2) dithiocarbamate and relatives: mancozeb代森錳鋅，thiram福美雙(3) chloronitriles氯化氰類: chlorothalonil百菌清(4) sulfamides 硫酰胺類Dichloflu

31、anid抑菌靈,35,11 Multi-site contact activity,(4) guanidines胍(5) triazines三嗪類Anilazine敵菌靈(6) quinones醌類Dithianon二噻農(nóng),36,Biological mode of actionFungicidal action can be expressed in one of two physically visible ways.

32、,Inhibition of spore germination.Inhibition of fungus growth.,37,Physiological mode of action What happens at the cellular level to cause the visible effects on spore germination and fungal growth?,38,Why is it impor

33、tant to be familiar with the physiological mode of action of a fungicide ?,For resistance management and preservation of fungicide effectiveness.,39,The physiological mode of action,Fungicides are metabolic inhibitors an

34、d their modes of action can be classified into four broad groups.Inhibitors of electron transport chain.Inhibitors of enzymes.Inhibitors of nucleic acid metabolism and protein synthesis.Inhibitors of sterol synthesis

35、.,40,Inhibition of electron transport chain(Respiration in mitochondria),Sulfur Disrupts electron transport along the cytochromesStrobilurins (azoxystrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin)Inhibit mi

36、tochondrial respiration, blocking the cytochrome bc1 complex.,41,Inhibition of enzymes,CopperNonspecific denaturation of proteins and enzymes.Dithiocarbamates (maneb(代森錳), manzate, dithane, etc)Inactivate –SH groups i

37、n amino acids, proteins and enzymes.,42,Inhibition of enzymes,Substituted aromatics (chlorothalonil, 百菌清)Inactivate amino acids, proteins and enzymes by combining with amino and thiol groups.Organophosphonate (fosetyl-

38、Al，三乙磷鋁)Disrupts amino acid metabolism.,43,Inhibition of nucleic acid metabolism and protein synthesis,Benzimidazoles (thiophanate-methyl)Inhibit DNA synthesis (nuclear division).Phenylamides (mefenoxam精甲霜靈)Inhibits

39、RNA synthesis.Dicarboximides (iprodione, vinclozolin)Inhibits DNA and RNA synthesis, cell division and cellular metabolism.,44,Inhibition of sterol synthesis(Inhibit demethylation of ergosterol),Ergosterol (麥角固醇) is t

40、he major sterol in most fungi.It is essential for membrane structure and function.,45,Sterol inhibiting fungicides,Imidazoles (imazalil抑霉唑)Triazoles (propiconazole, myclobutanil腈菌唑, tebuconazole戊唑醇, triflumazole) Morp

41、holines (dimethomorph烯酰嗎啉)Inhibits sterol production at different site than imidazoles and triazoles. Affects cell wall production.,46,Why is it important to know the physiological mode of action of fungicides ?,For re

42、sistance management and preservation of fungicide effectiveness. Incorporate fungicides with different modes of action into a disease management program.In alternation or as a mixture.,47,Plant activators,In contrast

43、to conventional fungicides, plant activators have no direct effect on pathogens.Plant activators induce plants to produce natural disease-fighting compounds.,48,Plant activators,Acibenzolar (Actigard苯并噻二唑)Harpin (Mess

44、enger)Biological control organisms,49,Natural Plant Defense Mechanisms,Salicylic acid (水楊酸) pathway – Induces SAR (systemic acquired resistance), a natural biological defense response to pathogen attack. Jasmonic Acid

45、(茉莉酸) Pathway- Induces the production of disease and insect defense compounds.,50,Salicylic Acid Pathway,Production of active oxygen (hydrogen peroxide, peroxidase)Peroxidases have been associated with fungal cell wall

46、degradation and pathogen defense signalingThickening plant cell wallIncreasing lignification(木質(zhì)化)Production of phenolic esters that strengthen cross linking,51,Salicylic Acid Pathway,Systemic and local accumulation of

47、 Pathogenesis Related Proteins (PR-Proteins) chitinasesß-1,3 Glucanase（葡聚糖酶）Systemic accumulation of anti-microbial compounds called phytoalexins（植物抗毒素）.,52,Chitinases,Chitin is the major component of all fungal

48、 cell walls except for the Oomycetes Chitinases break down fungal cell wallsChitinases can break down insect exo-skeletonsActivity is greatly enhanced by Glucanase,53,ß-1,3 Glucanases （葡聚糖酶）,Glucans and cellu

49、lose are the major components of Oomycete cell wallsAntifungal activity is most often in combination with ChitinaseDirect defense: Degrade fungal cell wallsIndirect defense: Promoting the release of oligosaccharide

50、s that act as elicitors of defense reactions,54,Jasmonic Acid (茉莉酸) Pathway,Farmer and Ryan (1990) discovered that jasmonic acid volatilized from sagebrush could trigger defense gene expression in adjacent tomatoesJasm

51、onic acid volatiles act as attractants for beneficial insectsJasmonic acid induces the production of disease and insect defense compounds.Defense ProteinsPhytochemicals,55,Phytochemicals,Different from phytoalexins (

52、植物抗毒素) in that phytochemicals are induced by wounding. PhenolicsFuranocoumarins, Coumarins(香豆素類) , Tannins(單寧), Lignin(木質(zhì)素), other phenolicsTerpenoids(萜類化合物)Alkaloids (生物堿),56,Examples of plant activators,Acibenzola

53、r (Actigard)Harpin (Messenger)Harpin is a natural protein found in many common pathogenic microorganisms;Erwinia amylovora, E. chrysanthemi, Pseudomonas syringae, Pseudomonas solanecarum, Xanthomonas campestris.Biolo

54、gical control organisms,57,Mode of action - Actigard,Induction of Systemic Acquired Resistance,58,,,SAR gene expression,Classical SAR,PDF1.2 and othergene expression,Pest resistance,Gene expressioninvolvedin plant gro