Mechanistic Study Of The Broad-spectrum Growth-promoting Effect Of Herbaspirillum Huttiense 5-28 On Plants

Herbaspirillum huttitense 5-28 is a plant growth promoting bacteria(PGPB)isolated from Aconitum carmichaeli Debx.by our research group.The remarkable adaptability of plants enables them to respond to a wide range of environmental conditions.Appropriate plant growth-promoting bacteria will occupy a plant-compatible niche without causing damage to the plant.Herbaspirillum promotes plant growth by fixing nitrogen,dissolving phosphorus,secreting siderophores and plant hormones,and using nutrients exuded from plant roots to achieve mutual benefit and symbiosis.For exploring H.5-28 on plants' growth-promoting effect,this work verified the growth-promoting effect of H.5-28 on the model plant Arabidopsis thaliana based on the results of the previous research of the research group.This study combined whole-genome and comparative genome information to analyze the effect of H.5-28 on plant growth.With Twenty species of plants from different families as materials,this study further explored the scope of application of H.5-28 to promote plant growth and studied the broad spectrum of H.5-28 to promote plant growth.These discussions aim to provide a theoretical basis for further developing and utilizing H.5-28.This study analyzed the complete genome data of H.5-28 and performed comparative genome analysis.H.5-28 was inoculated to 20 different plants,including Arabidopsis thaliana,to verify its growth-promoting effect and the effects of different plants;and analyzed the growth promotion effect in detail.This study uses qRT-PCR technology and LC-MS technology to explore the mechanism of H.5-28 promoting plant growth from the perspective of plant transcriptional differential gene expression and plant endogenous hormone metabolism.The main findings are as follows:1.The whole genome of H.5-28 is 5890788 bp,its GC content is 62.45%,and it has 1 chromosome and 0 plasmids.H.5-28 encodes 5136 genes,and it has nine rRNAs,59 tRNAs,24 other ncRNAs,6 CRISPRs,one pseudogene,14 gene islands,and five prephages.Combined with GO analysis,COG analysis,and KEGG analysis,H.5-28 contains ampicillin resistance genes and can fix nitrogen,dissolve phosphorus and synthesize plant hormones.According to ANI analysis,the ANI value of H.5-28 and H.huttiense is 97.41%,so H.5-28 belongs to H.huttiense.Our research team named it Herbaspirillum huttiense 5-28.2.Compared with the control group,the fresh weight,dry weight,root length,and the number of lateral roots of Arabidopsis thaliana in the H.5-28 treatment group were 2.63 times,1.98 times,1.24 times,and 1.81 times,respectively.This result shows that H.5-28 can promote the growth of Arabidopsis thaliana and promote the growth of the Arabidopsis thaliana root system,which is consistent with the previous results of this research group.After H.5-28 inoculation of plants,H.5-28 can increase the biomass and yield of 20 plants from 9 different families.3.Compared with the control group,the qRT-PCR results of the experimental group treated with H.5-28 show that the relative expression of growth-related genes from 20 plants from 8 different families changed,and they generally had significant up-regulation.Therefore,H.5-28 on plants may realize the growth-promoting effect by influencing growth hormone-related pathways.4.Using LC-MS technology to detect growth-related hormones in 20 plants from 8 families,it finds that the experimental group's hormone content treated with H.5-28 was generally different compared with the control group.Among them,the overall difference in growth hormones is more prominent.Compared with the control group,the experimental group treated with H.5-28 had more species with significantly up-regulated zeatin,gibberellin,kinetin,and the species distributed in many different families.It indicates that H.5-28 can promote plant growth by influencing endogenous plant hormones' metabolism and regulating plant hormone levels.In summary,H.5-28 can affect the transcription and metabolism of endogenous plant hormones,regulate the level of plant hormone metabolism,promote the growth of various plants of different families and genera,and promote plant biomass accumulation and yield improvement.H.5-28 is a plant growth-promoting bacterium with great potential,and it has a broad spectrum of growth-promoting effects on plants.H.5-28 has the potential to be developed into a broad-spectrum biological fertilizer.In the future,the growth-promoting properties of H.5-28 can develop abundant biological bacterial fertilizers to realize sustainable green agriculture.