title: Endophytic microbes Bacillus sp. LZR216-regulated root development is dependent on polar auxin transport in Arabidopsis seedlings.
abstract: Endophytic microbes Bacillus sp. LZR216 isolated from Arabidopsis root promoted Arabidopsis seedlings growth. It may be achieved by promoting the lateral root growth and inhibiting the primary root elongation. Plant roots are colonized by an immense number of microbes, including epiphytic and endophytic microbes. It was found that they have the ability to promote plant growth and protect roots from biotic and abiotic stresses. But little is known about the mechanism of the endophytic microbes-regulated root development. We isolated and identified a Bacillus sp., named as LZR216, of endophytic bacteria from Arabidopsis root. By employing a sterile experimental system, we found that LZR216 promoted the Arabidopsis seedlings growth, which may be achieved by promoting the lateral root growth and inhibiting the primary root elongation. By testing the cell type-specific developmental markers, we demonstrated that Bacillus sp. LZR216 increases the DR5::GUS and DR5::GFP expression but decreases the CYCB1;1::GUS expression in Arabidopsis root tips. Further studies indicated that LZR216 is able to inhibit the meristematic length and decrease the cell division capability but has little effect on the quiescent center function of the root meristem. Subsequently, it was also shown that LZR216 has no significant effects on the primary root length of the pin2 and aux1-7 mutants. Furthermore, LZR216 down-regulates the levels of PIN1-GFP, PIN2-GFP, PIN3-GFP, and AUX1-YFP. In addition, the wild-type Arabidopsis seedlings in the present of 1 or 5 µM NPA (an auxin transport inhibitor) were insensitive to LZR216-inhibited primary root elongation. Collectively, LZR216 regulates the development of root system architecture depending on polar auxin transport. This study shows a new insight on the ability of beneficial endophytic bacteria in regulating postembryonic root development.
authors.affiliation: Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, People's Republic of China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Wang
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Wang
authors.forename: Wenbin
authors.initials: W
authors.lastname: Nan
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Hu
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Chengzhou
authors.initials: C
authors.lastname: Zhao
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Hongyong
authors.initials: H
authors.lastname: Shi
authors.forename: Yurong
authors.initials: Y
authors.lastname: Bi
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics; D001407:Bacillus / Q000302:isolation & purification / Q000502:physiology*; D001692:Biological Transport; D060026:Endophytes / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics; D010802:Phylogeny; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development* / Q000382:microbiology; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000382:microbiology
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C449300:PIN3 protein, Arabidopsis