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    Unearthing Bacillus endophytes from desert plants that enhance growth of Arabidopsis thaliana under abiotic stress conditions

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    Ameerah_Bokhari_DissertationForExaminers_Final.pdf
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    Ameerah_Bokhari_DissertationForExaminers_Final
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    Type
    Dissertation
    Authors
    Bokhari, Ameerah cc
    Advisors
    Hirt, Heribert cc
    Committee members
    Bajic, Vladimir B. cc
    Pain, Arnab cc
    Schikora, Adam
    Program
    Bioscience
    KAUST Department
    Biological and Environmental Sciences and Engineering (BESE) Division
    Date
    2018-04
    Embargo End Date
    2019-05-02
    Permanent link to this record
    http://hdl.handle.net/10754/627740
    
    Metadata
    Show full item record
    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2019-05-02.
    Abstract
    Here, we embarked a bioprospecting project that focuses on the isolation and characterization of plant root endophytes, collected from the Thar Desert. A total of 381 endophytes were isolated and based on their 16S rRNA gene sequences, genus Bacillus (58 strains) was identified as the major taxon and only endophytes from this genus were isolated from all plant types. Of the 58 Bacillus strains, only 16 strains were selected for screening of plant growth promotion traits such as P and Zn solubilization, indole-3-acetic acid and siderophore production, and antimicrobial activity. Based on the presence of specific plant growth promotion traits 10 strains were shortlisted for further in vitro screening with A. thaliana; to confirm that these bacteria can confer resilience to plants under salt stress conditions. B. circulans (PK3-15 and PK3-109), B. cereus (PK6-15) B. subtilis (PK3-9) and B. licheniformis (PK5-26) displayed the ability to increased the fresh weight of A. thaliana under salt stress conditions by more than 50 % compared to the uninoculated control. An interesting observation was that B. circulans (PK3-109) (shown to produce IAA exopolysaccharide) and B. circulans (PK3-138) (shown to produce IAA) in vitro results were substantially different as B. circulans (PK3-138) decreased the total fresh weight of A. thaliana by 47 %, whilst B. circulans (PK3-109) was one of the best performing strains. Thus, the genomes of these two strains were sequences to unravel the molecular versatility of B. circulans strains, specifically with respect to their interaction with plants. Most of the genome of these strains is identical but the most interesting feature was the presence of 1/ the DegS–DegU two-component system that is known to mediate the salt stress response and DegU also represses toxin wapA similar to antitoxin wapI, and 2/ YxiG, a gene in the unique orthogroup of PK3-109 was found to be linked to WapI. Thus, PK3-138 substantially decreasing the total fresh weight of A. thaliana under salt stress conditions suggests that the toxic activity of a toxin such as WapA is not effectively ameliorated by the antitoxin such as WapI in the absence of a functional YxiG gene.
    Citation
    Bokhari, A. (2018). Unearthing Bacillus endophytes from desert plants that enhance growth of Arabidopsis thaliana under abiotic stress conditions. KAUST Research Repository. https://doi.org/10.25781/KAUST-339QA
    DOI
    10.25781/KAUST-339QA
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-339QA
    Scopus Count
    Collections
    Biological and Environmental Sciences and Engineering (BESE) Division; Bioscience Program; Dissertations; Dissertations

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