AUTHOR=Augimeri Richard V. , Strap Janice L. 

TITLE=The Phytohormone Ethylene Enhances Cellulose Production, Regulates CRP/FNRKx Transcription and Causes Differential Gene Expression within the Bacterial Cellulose Synthesis Operon of Komagataeibacter (Gluconacetobacter) xylinus ATCC 53582

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.01459

DOI=10.3389/fmicb.2015.01459

ISSN=1664-302X

ABSTRACT=<p><italic>Komagataeibacter</italic> (formerly <italic>Gluconacetobacter</italic>) <italic>xylinus</italic> ATCC 53582 is a plant-associated model organism for bacterial cellulose (BC) biosynthesis. This bacterium inhabits the carposphere where it interacts with fruit through the bi-directional transfer of phytohormones. The majority of research regarding <italic>K. xylinus</italic> has been focused on identifying and characterizing structural and regulatory factors that control BC biosynthesis, but its ecophysiology has been generally overlooked. Ethylene is a phytohormone that regulates plant development in a variety of ways, but is most commonly known for its positive role on fruit ripening. In this study, we utilized ethephon (2-chloroethylphosphonic acid) to produce <italic>in situ</italic> ethylene to investigate the effects of this phytohormone on BC production and the expression of genes known to be involved in <italic>K. xylinus</italic> BC biosynthesis (<italic>bcsA, bcsB, bcsC, bcsD, cmcAx, ccpAx and bglAx</italic>). Using pellicle assays and reverse transcription quantitative polymerase chain reaction (RT-qPCR), we demonstrate that ethephon-derived ethylene enhances BC directly in <italic>K. xylinus</italic> by up-regulating the expression of <italic>bcsA</italic> and <italic>bcsB</italic>, and indirectly though the up-regulation of <italic>cmcAx, ccpAx</italic>, and <italic>bglAx</italic>. We confirm that IAA directly decreases BC biosynthesis by showing that IAA down-regulates <italic>bcsA</italic> expression. Similarly, we confirm that ABA indirectly influences BC biosynthesis by showing it does not affect the expression of <italic>bcs</italic> operon genes. In addition, we are the first to report the ethylene and indole-3-acetic acid (IAA) induced differential expression of genes within the bacterial cellulose synthesis (<italic>bcs</italic>) operon. Using bioinformatics we have identified a novel phytohormone-regulated CRP/FNR<sub>Kx</sub> transcription factor and provide evidence that it influences BC biosynthesis in <italic>K. xylinus</italic>. Lastly, utilizing current and previous data, we propose a model for the phytohormone-mediated fruit-bacteria interactions that <italic>K. xylinus</italic> experiences in nature.</p>