| Plant rhizosphere growth promoting bacteria(PGPR)are microorganisms that can colonize plant roots and promote plant growth,which plays an important role in regulating soil health and crop growth and development.Streptomyces is an important type of PGPR,which can produce a variety of secondary metabolites and plays the key role in adjusting crop growth and development and keeping soil ecology.Previous studies of our team have shown that Streptomyces TOR3209 can significantly promote plant growth,induce plant disease resistance and tolerance,etc.At the same time,volatile compounds(VOCs)of Streptomyces TOR3209 have a conspicuous effect on the growth and development of tobacco,but the regulatory mechanism of Streptomyces TOR3209 on plants is still unclear.In this study,Streptomyces TOR3209 was used as a test strain and tobacco was used as a test plant to explore the biological mechanism of the interaction between Streptomyces and plants.The main studies were as follows:(1)PGPR characteristics of Streptomyces TOR3209 and its effect on tobacco growth and development.(2)Effects of VOCs from Streptomyces TOR3209 on tobacco growth and development;The VOCs components of Streptomyces TOR3209 were identified by GC-MS and verified.(3)Transcriptome analysis of tobacco seedlings exposed to VOCs of Streptomyces TOR3209.The main experimental results are as follows:(1)Streptomyces TOR3209 has the ability of IAA production,siderophore production and phosphorus solubilization.The IAA production capacity is8.85-14.89mg/L,the solubility index of siderophore production is 1.25,and the solubility index of organophosphorus solubilization is 2.35.Streptomyces TOR3209inhibited the growth of tobacco at high concentration(1.0×10~9CFU/m L),but promoted the growth of tobacco at low concentration(1.0×10~3CFU/m L).However,the effect of Streptomyces TOR3209 suspension on the growth of tobacco was not markedly.(2)The effects of VOCs produced by Streptomyces TOR3209 on the growth and development of tobacco were studied by in-plate co-culture method.The results showed that the fresh weight of the treatment group was significantly increased by 100%compared with the control group,which proved that the VOCs of Streptomyces TOR3209 had a significant ability to promote the growth of tobacco.(3)The VOCs components of Streptomyces TOR3209 were identified by solid phase microextraction method,and a total of 38 substances were found.Compared with CK,the contents of 2,4-Di-tert-butylphenol and 1-ethyl-1-isopentyloxy-1-silacyclo hexane were the highest,31.32%and 17.93%,respectively.The contents of heptadecanoic acid,lauric acid,isoamyl alcohol and 4-tert-butyl anisole in the treatment group were significantly different from those of CK.(4)The functions of heptadecanoic acid,lauric acid,isoamyl alcohol and4-tert-butyl anisole were verified.The results showed that isoamyl alcohol could promote the growth of tobacco at different concentrations of 1mol/m L,1mmol/m L and1μmol/m L,while the effects of the other three compounds were not significant compared with CK.(5)Transcriptome sequencing was performed on tobacco treated with VOCs of Streptomyces TOR3209.The results showed that Streptomyces TOR3209 significantly affected the expression of tobacco genes,among which peroxygenase 4,ACCSL protein,UDP-glycosyltransferase and glutamate receptor were most significantly up-regulated.These genes play an important role in the regulation of plant growth and development.In the enrichment analysis of KEGG pathways,the main pathways were glutathione metabolism,taurine and hypotaurine metabolism,plant-pathogen interaction,glutamate metabolism,which are closely related to plant growth,development and metabolism.The expression of transcription factors are mainly concentrated in bHLH family,WRKY family,ERF family and C2H2 family,which all play an important role in plant development.This study initially revealed the mechanism of Streptomyces TOR3209 regulating the growth and development of tobacco,which will expand the biological mechanism of the interaction between microorganisms and plants,and laid a foundation for the development of novel and efficient microbial products. |
