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Pantoea ananatis carotenoid production confers toxoflavin tolerance and is regulated by Hfq-controlled quorum sensing
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  • Okhee Choi,
  • Byeongsam Kang,
  • Yongsang Lee,
  • Yeyeong Lee,
  • Jinwoo Kim
Okhee Choi
Gyeongsang National University
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Byeongsam Kang
Gyeongsang National University
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Yongsang Lee
Gyeongsang National University
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Yeyeong Lee
Gyeongsang National University
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Jinwoo Kim
Gyeongsang National University
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Abstract

Carotenoids are widely used in functional foods, cosmetics, and health supplements, and their importance and scope of use are continuously expanding. Here, we characterised carotenoid biosynthetic genes of the plant-pathogenic bacterium Pantoea ananatis, which carries a carotenoid biosynthetic gene cluster (including crtE, X, Y, I, B, and Z) on a plasmid. Reverse transcription–polymerase chain reaction (RT-PCR) analysis revealed that the crtEXYIB gene cluster is transcribed as a single transcript and crtZ is independently transcribed in the opposite direction. Using splicing by overlap extension with polymerase chain reaction (SOE by PCR) based on asymmetric amplification, we reassembled crtE–B, crtE–B–I, and crtE–B–I–Y. High-performance liquid chromatography confirmed that Escherichia coli expressing the reassembled crtE–B, crtE–B–I, and crtE–B–I–Y operons produced phytoene, lycopene, and β-carotene, respectively. We found that the carotenoids conferred tolerance to UV radiation and toxoflavin. Pantoea ananatis shares rice environments with the toxoflavin producer Burkholderia glumae and is considered to be the first reported example of producing and using carotenoids to withstand toxoflavin. We confirmed that the carotenoid production of P. ananatis is dependent on RpoS, which is positively regulated by Hfq/ArcZ and negatively regulated by ClpP, similar to an important regulatory network of E. coli (HfqArcZ → RpoS Ͱ ClpXP). We also demonstrated that Hfq-controlled quorum signalling de-represses EanR to activate RpoS, thereby initiating carotenoid production. Survival genes such as those responsible for the production of carotenoids of the plant-pathogenic P. ananatis must be expressed in a timely manner to overcome stressful environments and compete with other microorganisms. This mechanism is likely maintained by a brake with excellent performance, such as EanR.

Peer review status:Published

06 Oct 2020Submitted to MicrobiologyOpen
07 Oct 2020Submission Checks Completed
07 Oct 2020Assigned to Editor
19 Oct 2020Reviewer(s) Assigned
30 Oct 2020Review(s) Completed, Editorial Evaluation Pending
30 Oct 2020Editorial Decision: Revise Minor
09 Nov 20201st Revision Received
09 Nov 2020Submission Checks Completed
09 Nov 2020Assigned to Editor
09 Nov 2020Review(s) Completed, Editorial Evaluation Pending
10 Nov 2020Reviewer(s) Assigned
19 Nov 2020Editorial Decision: Accept
Jan 2021Published in MicrobiologyOpen volume 10 issue 1. 10.1002/mbo3.1143