title: Enterococcus faecium LKE12 Cell-Free Extract Accelerates Host Plant Growth via Gibberellin and Indole-3-Acetic Acid Secretion.
abstract: The use of microbial extracts containing plant hormones is a promising technique to improve crop growth. Little is known about the effect of bacterial cell-free extracts on plant growth promotion. This study, based on phytohormonal analyses, aimed at exploring the potential mechanisms by which Enterococcus faecium LKE12 enhances plant growth in oriental melon. A bacterial strain, LKE12, was isolated from soil, and further identified as E. faecium by 16S rDNA sequencing and phylogenetic analysis. The plant growth-promoting ability of an LKE12 bacterial culture was tested in a gibberellin (GA)-deficient rice dwarf mutant (waito-C) and a normal GA biosynthesis rice cultivar (Hwayongbyeo). E. faecium LKE12 significantly improved the length and biomass of rice shoots in both normal and dwarf cultivars through the secretion of an array of gibberellins (GA1, GA3, GA7, GA8, GA9, GA12, GA19, GA20, GA24, and GA53), as well as indole-3-acetic acid (IAA). To the best of our knowledge, this is the first study indicating that E. faecium can produce GAs. Increases in shoot and root lengths, plant fresh weight, and chlorophyll content promoted by E. faecium LKE12 and its cell-free extract inoculated in oriental melon plants revealed a favorable interaction of E. faecium LKE12 with plants. Higher plant growth rates and nutrient contents of magnesium, calcium, sodium, iron, manganese, silicon, zinc, and nitrogen were found in cell-free extract-treated plants than in control plants. The results of the current study suggest that E. faecium LKE12 promotes plant growth by producing GAs and IAA; interestingly, the exogenous application of its cell-free culture extract can be a potential strategy to accelerate plant growth.
authors.affiliation: School of Ecology and Environmental Science, Kyungpook National University, Sangju 741-711, Republic of Korea.
authors.forename: Ko-Eun
authors.initials: KE
authors.lastname: Lee
authors.affiliation: School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Ramalingam
authors.initials: R
authors.lastname: Radhakrishnan
authors.affiliation: School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Sang-Mo
authors.initials: SM
authors.lastname: Kang
authors.affiliation: Horticultural & Herbal Crop Environment Division, National Institute of Horticultural & Herbal Science, Rural Development Administration, Wanju 565-852, Republic of Korea.
authors.forename: Young-Hyun
authors.initials: YH
authors.lastname: You
authors.affiliation: Institute of Agricultural Science and Technology, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Gil-Jae
authors.initials: GJ
authors.lastname: Joo
authors.affiliation: School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: In-Jung
authors.initials: IJ
authors.lastname: Lee
authors.affiliation: School of Ecology and Environmental Science, Kyungpook National University, Sangju 741-711, Republic of Korea.
authors.forename: Jae-Hwan
authors.initials: JH
authors.lastname: Ko
authors.affiliation: School of Ecology and Environmental Science, Kyungpook National University, Sangju 741-711, Republic of Korea.
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Kim
mesh_terms: D016000:Cluster Analysis; D045424:Complex Mixtures / Q000302:isolation & purification / Q000378:metabolism*; D019662:Cucurbitaceae / Q000187:drug effects / Q000254:growth & development; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D016984:Enterococcus faecium / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D005875:Gibberellins / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000187:drug effects / Q000254:growth & development; D010802:Phylogeny; D063245:Plant Development / Q000187:drug effects*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
chemical_list: D045424:Complex Mixtures; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D005875:Gibberellins; D007210:Indoleacetic Acids; D012336:RNA, Ribosomal, 16S; C030737:indoleacetic acid
keywords: Enterococcus faecium; gibberellins; waito-C rice; yellow-melon