H_2O_2参与AM真菌与烟草共生过程

Hydrogen peroxide participates symbiosis between AM fungi and tobacco plants

以烟草((Nicotiana tabacum,品种CF90NF)为寄主,苗期接种丛枝菌根(AM)真菌摩西球囊霉(Glomus mosseae,G.m),测定G.m与烟草共生过程中烟草根部H2O2含量以及多胺氧化酶(PAO)和过氧化物酶(POD)活性;研究外源H2O2对G.m侵染烟草的影响以及H2O2清除剂和合成抑制剂对烟草侧根H2O2含量及烟草侧根和菌丝中H2O2荧光强度的影响,以探究H2O2在AM真菌侵染烟草过程中的作用。结果表明,接种G.m 20d后烟草侧根中出现H2O2含量的猝发,一定浓度的外源H2O2促进G.m对烟草的侵染,而H2O2清除剂抗坏血酸(AsA)显著削弱烟草侧根和菌丝中的H2O2荧光强度,降低G.m对烟草的侵染率,表明H2O2参与G.m与烟草共生过程;在G.m与烟草共生过程中,PAO和POD活性显著升高,PAO抑制剂二氨基十二烷(DADD)和POD抑制剂水杨羟肟酸(SHAM)显著降低烟草侧根中H2O2荧光强度,对菌丝中H2O2荧光强度无显著影响,表明烟草根部和G.m均可产生H2O2,PAO和POD参与烟草侧根中H2O2的合成,菌丝中可能存在其他来源的H2O2。

Arbuscular mycorrhiza（AM） formed between AM fungi and the vast majority of higher plants is a widely spreading mutualistic symbiosis in the world.It has been proved that AM establishment starts with a chemical signal exchange between host plant roots and the fungi.Hydrogen peroxide（H2O2） is an important signal substance,which takes part in interaction among plants and many microorganisms.Does H2O2 also participate in the interaction between host plants and AM fungi？ And we hypothesized that H2O2 may involve in the formation and colonization of AM.The purpose of the present research was to investigate the role of H2O2 in colonizing tobacco roots by arbuscular mycorrhizal（AM） fungi.Seedlings of tobacco cultivar CF90NF were inoculated with Glomus mosseae（G.m）.H2O2 contents,the effects of exogenous H2O2 on colonization percentage of tobacco by G.m,H2O2 scavenger and production inhibiter effects on H2O2 contents and fluorescence intensity in tobacco root and fungal hyphae were studied.The results showed that H2O2 burst in lateral roots of tobacco 20 days after inoculation,the earlier stage of colonization,at this time,fungal hyphae just began to contact with tobacco root and penetrate root cortical cell,exogenous H2O2 increased the colonization percentage of tobacco by G.m,H2O2 scavenger ascorbic acid（AsA） had adverse effect,decreased the colonization percentage;Fluorescence assay showed that G.m colonization induced intense H2O2 fluorescence in tobacco root,but AsA decreased H2O2 fluorescence intensity in tobacco lateral roots,and fungal hyphae.These results indicate that H2O2 have positive effect in symbiosis development between AM fungi and tobacco plants;PAO and POD is the main enzymes catalyzing the production of H2O2,we estimated the PAO and POD activities in tobacco roots,and the results showed that,when colonized with G.m,PAO and POD activities in lateral root of tobacco increased significantly,importantly,treatments with salicylhydroxamic acid（SHAM,POD inhibiter） and 1,12-diaminododecane（DADD,PAO inhibiter） decreased H2O2 fluorescence intensity in tobacco lateral roots,but had no significant effects on that in the fungal hyphae.The present study suggests that H2O2 may participate in tobacco-AM symbiosis,H2O2 be produced both in tobacco root and in fungal hyphae,PAO and POD take part in H2O2 production in tobacco root,and there should be other resource of H2O2 in AM fungal hyphae.While the interrelationship between H2O2 and the other signal substances,and their effects on the development of AM need to be further investigated with molecular techniques.