Research On The Growth-Promoting Mechanism Of VOCs Produced By Two VOCs Plant Growth-Promoting Bacteria And Verification Of Their Multi-Function

Microbial volatile organic compound(MVOCs),as an important component of microbial resources and utilization research,has gradually become a global hot spot in microbial function research.On the basis of isolation and identification of microorganisms in Beihai mangrove rhizosphere soil,we screened five strains that could promote the growth of VOCs with Ⅰ-plate.Two strains,GXUN15128 and GXUN15103,were screened by entropy calculation.They were identified as Paenibacillus Peoriae and a new strain of Niabella sp.and their VOCs functions were studied,the main results are as follows:(1)Both GXUN15128 and GXUN15103 had stable growthpromoting effects.Growth medium and inoculation quantity could affect the growth-promoting effects of VOCs.The growth-promoting effect mainly focused on the growth of stem and leaf and the development of lateral roots,but not the increase of root length.The growth-promoting effect of TSA group was slightly better than that of LBA group,and GXUN15103 group had significant dose effect.(2)The combined analysis of SPME-GC/MS and Headspace Sampler-GC/MS can be used to analyze the composition and relative content of MVOCs stably and reliably.GXUN15128 and GXUN15103 identified 12 and 18 components,respectively.It was found that the change of growth medium could cause the change of VOCs composition.(3)Transcriptome analysis of Arabidopsis thaliana receptor revealed that volatile organic compounds of GXUN15128 could reduce the expression of light capture complex and avoid light damage,thus promoting the growth of A.thaliana.It is possible that up-regulation of CHS gene results in down-regulation of CCA1 expression,which leads to down-regulation of PRR5/7/9 gene expression,and finally downregulation of LHCA1/3/4 and LHCB1/2/3/4/7.The verification experiment of functional components and related studies indicated that the bioactive substances of GXUN15128 may be pyrazine derivatives.GXUN15128 has extensive in vitro growth inhibitory activity against plant pathogenic fungi,and whole genome analysis showed that it was obtained by producing biological polypeptides.And it has a stable PGPR characteristics,has a strong application potential.(4)GXUN15103 has the multi-function of promoting plant growth and inhibiting the growth of plant pathogenic fungi.It produces abnormal,atrophic and disordered spatial structure to the hyphae of Cryphonectria parasitica and Neofusicoccum parvum.The functional components of VOCs are Indoles,Benzyl alcohols and Dimethyl disulfide.The antibacterial components of VOCs are Indole and 2,4-Di-tert-butylphenol.And genome-wide analysis showed that Indole,the major functional component of VOCs in GXUN15103,was produced by pentose phosphate pathway and glycolysis via “Phenylanine,tyrosine and tryptophan biosynthesis” pathway.The two strains screened in this study have excellent growthpromoting effect and PGPR characteristics,which provides a functional strain with important application potential for agricultural production.The research on the growth-promoting mechanism,the effect of growth medium and inoculation amount on the function of strains and the multifunction provided new ideas and experiences for the mechanism of VOCs functional strains.