Physiological And Molecular Mechanism Of Resistance To Rice Blast Induced By Streptomyces JD211 In Rice

Microbes have a wide variety of species in nature,they are widely distributed,and fast propagated.The beneficial microorganism is one of the important resources of plant protection because of its advantages of environmentally friendly,pollution-free,green,and economical and so on.The use of beneficial microorganism to control plant diseases is in line with the need of green development in current society.Streptomyces JD211?JD211?,which can inhibit the growth of mycelium of many pathogenic fungi,is a potential biocontrol strain.In this paper,powders of JD211 were prepared and mixed with the soil to cultivate the susceptible rice in the pot.The mechanism of JD211 regulating rice growth and disease resistance was investigated from two aspects:physiology and biochemistry,and the molecular mechanism,respectively.The results are as follows:?1?The effect of JD211 on rice blast were studied by measuring the control efficacy of rice inoculated with Magnaporthe oryzae?M.oryzae?.The results showed that the disease incidence of rice blast could be reduced by adding 0.1%,0.5%,1%concentrations of JD211.The 1%JD211 treatment achieved the highest biocontrol efficacy.15 days after inoculation of M.oryzae,the control efficacy of 1%JD211 treatment was 18.76%.?2?Rice was cultivated with 5 g/kg JD211 and inoculated with M.oryzae spore suspension.To explore the effect of JD211 on the hypersensitive response in rice,hydrogen peroxide?H₂O₂?,catalase?CAT?,lipoxygenase?LOX?,malondialdehyde?MDA?and cell membrane permeability in rice leaves were determined.Results showed that the activities of CAT,LOX,and the content of H₂O₂ in the JD211treatment were increased by 33.50%,4.07%,47.76%than the group without JD211 in the age of 30d,the content pf malondialdehyde decreased by 38.68%.Cell membrane permeability in the treatment group added JD211 were increased by 38.94%,39.03%,8.08%compared to the group without JD211 when the seedling age was 32 days,34 days,and 36 days,respectively.These results suggested that JD211 could effectively regulate the hypersensitivity reaction,induce the anaphylactic necrosis and prevent the further infection of pathogen.?3?To further clarify the effect of JD211 on rice resistance,effects of JD211 on the phenolic metabolism and activities of pathogenesis-related proteins in rice was investigated by pot experiment.The results showed that JD211 increased the content of lignin,flavonoid,and total phenol,the activities of peroxidase?POD?,polyphenol oxidase?PPO?,phenylalanine ammonia-lyase?PAL?,chitinase,and?-1,3-glucanase were also increased.After inoculating with M.oryzae,the content of lignin and the activity of POD in the treatment group with JD211 increased by 17.74%?9.10%at the seedling age of 27d.PPO activity,total phenols and flavonoids content of the treatments adding JD211 were increased by 13.40%,11.22%,130.34%in the seedling age of 31d.When the seedling age was 31d,the activity of PAL increased by 27.24%in the rice treated with JD211.After infection with pathogen,the activity of chitinase increased rapidly in the JD211 treatment,while?-1,3-glucanase activity increased by 74.98%at the seedling age of 35d.Suggesting that JD211could increase the activity of phenolics-related enzymes,promote the accumulation of phenolic substances,and increase the activity of chitinase and?-1,3-glucanase,finally,improved the disease resistance of rice.?4?Using the real-time fluorescence quantitative PCR technology,the resistance genes?CatA,PAL,Rcht2,Prla?expression level were detected in rice leaves,CatA,PAL,Rcht2,Prla encoding CAT,PAL,chitinase,and PR-1,respectively.The results showed that JD211could promote the accumlation of gene expression of CatA and PAL.The expression level of Prla in the rice treated with 10 g/kg was higher than that of in the control group at the seedling age of 22 days,24 days and 26 days.After inoculating with pathogen,the expression level of Prla in 10 g/kg JD211treatment was 2.22 times that of in the control group at the seedling age of 24 days.The expression level of Rcht2 in the 10 g/kg JD211 treatment was1.57,2.19 times that of in the control group at 24 days and 26 days.JD211 increased the expression level of Rcht2,the higher concentration of JD211 could stimulate the expression of Rcht2 more quickly.?5?The proteome analysis of rice leaves treated with JD211 alone,and co-inoculation of JD211 and M.oryzae,was carried out by using iTRAQ proteomics technique.A total of3062 reliable proteins were identified.213 differentially expressed proteins?DEPs?was induce by JD211,mainly involved in glyoxylate metabolism,carbon synthesis,porphyrin and chlorophyll metabolism.278 DEPs were induced by M.oryzae,mainly involved in photosynthesis,photosynthesis antenna protein metabolism.After inoculating with M.oryzae,there were 158 DEPs,mainly involved in glyoxylate metabolism,carbon metabolism,photosynthesis,and photosynthesis-antenna protein metabolism,were induced by JD211.It was found that the induced resistance by JD211 was mainly related to chlorophyll synthesis,glyoxylate metabolism,signal transduction and phenolic synthesis,which suggested that JD211 could activate the recognition of pathogens quickly,stimulate the resistance of rice,promote the production of phenolic substances,meanwhile,promote the energy synthesis.Finally,all of these work together to protect rice from the damage of pathogen.In summary,the induction mechanism of JD211 against M.oryzae was very complex,it related to several pathways.By promoting signal transmission,JD211 could timely and effective trigger defense responses,such as accumulation of phenolics,regulation of hypersensitive response.Meanwhile,JD211 promoted the synthesis of energy for defense responses in rice.Ultimately,JD211 improve the disease resistance of rice.