Comparative Study On The Interaction Mechanism Between Tsukamurella Tyrosinosolvens P9,Burkholderia Pyrrocinia P10 And Peanut

Peanut is the main oil crop in China.Fertilization can increase its yield,but large-scale fertilization will lead to agricultural pollution.The new type of fertilizer,based on plant growth-promoting rhizobacteria(PGPR),can partially replace chemical fertilizers.In this study,the interaction mechanism between peanut and Tsukamurella tyrosinosolvens P9 and Burkholderia pyrrocinia P10 with multiple growth-promoting characteristics was studied,respectively.By constructing the interaction co-culture system between two PGPR strains and peanut,the effects of two different PGPR strains on gene expression,metabolic pathways and metabolomics of peanuts were analyzed by transcriptome and metabolomics methods.And the effects of peanut root exudates on the growth,growth-promoting and colonization of the two strains were studied,too.The main research results are as follows:The co-culture system of the interaction between Tsukamurella tyrosinosolvens P9,Burkholderia pyrrocinia and peanut was constructed,respectively.It was found that the root branches of peanut seedlings increased after 1 days’ inoculation,and the growth of the inoculated seedlings was significantly better than that of the control after 3 days’ inoculation.Therefore,the peanut roots inoculated for 24 h and 72 h were selected for transcriptome sequencing,respectively,and the culture medium at the same time was collected for metabolomics analysis.The results of transcriptome analysis showed that compared with the peanut seedlings without inoculation,the P9 strain induced the expression of metabolic pathways and differential genes involved in plant growth,cell wall modification enzymes,plant defense,signal transduction and transcription factors in peanut roots after co-culture for 24 h,such as flavonoids biosynthesis pathway,phenylpropanoid biosynthesis pathway and WRKY transcription factor.After co-culture for 72 h,it not only enhanced the induction of plant growth and cell wall modification enzymes,but also stimulated the uptake and accumulation of nutrients,stress resistance and other metabolic pathways and gene expression,such as the transformation of pentose and glucuronic acid,ascorbic acid pathway and zeatin biosynthesis pathway.Transcriptome analysis of peanut seedlings inoculated with P10 showed that the dominant metabolic pathways enriched in the co-culture of 24 h and 72 h were mostly the same.P10 also mainly induced the expression of metabolic pathways involved in plant growth,cell wall modification enzymes,plant defense and stress resistance,and nutrient uptake and accumulation.With the extension of co-culture time,the induction of plant growth and cell wall modification related pathways by the two strains was gradually strengthened,but the regulated genes were partially different,and the regulation modes involved in plant defense and nutrient uptake were also different.The results of metabolomics analysis showed that the inoculation of the two strains caused the reprogramming of multiple metabolites in peanut.Three categories were included according to the metabolic pathways and physiological functions,that is,plant phenylpropanoids and their derivatives(including coumarin,flavonoids,etc.),plant growth and development related hormones(including trans zeatin,indole acetic acid,abscisic acid,gibberellin,etc.),and plant system-induced resistance related metabolites(including azelaic acid,jasmonic acid,cinnamic acid,etc.).These metabolites were consistent with the metabolic pathways of root transcriptome analysis.The amino acid ingredients of peanut root exudates,including glycine,proline and alanine,can significantly promote the growth of the two strains and the production of IAA.And organic acids ingredients including citric acid,oxalic acid,and malic acid can promote the formation of the biofilm of the two strains.The results show that the root exudates of peanut could promote the growth of the two strains,but also improve the growth-promoting and colonization of P9 and P10 strains.The above study analyzed the fundamental molecular mechanism of two strains inoculation on peanut growth,and laid a solid theoretical foundation for the application of the next strain.