Attachment of Agrobacterium tumefaciens to leaf tissue in response to infiltration conditions

Authors

  • Christopher W. Simmons,

    1. Dept. of Biological and Agricultural Engineering, University of California, Davis, Davis, CA
    2. Dept. of Food Science and Technology, University of California, Davis, Davis, CA
    Current affiliation:
    1. Department of Food Science and Technology, University of California, Davis, Davis, CA, USA
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  • Jean S. VanderGheynst,

    Corresponding author
    1. Dept. of Biological and Agricultural Engineering, University of California, Davis, Davis, CA
    • Correspondence concerning this article should be addressed to Jean S. VanderGheynst at jsvander@ucdavis.edu

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  • N. Nitin

    1. Dept. of Biological and Agricultural Engineering, University of California, Davis, Davis, CA
    2. Dept. of Food Science and Technology, University of California, Davis, Davis, CA
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Abstract

Transient expression of recombinant proteins in plant tissues following Agrobacterium-mediated gene transfer is a promising technique for rapid protein production. However, transformation rates and transient expression levels can be sub-optimal depending on process conditions. Attachment of Agrobacterium tumefaciens to plant cells is an early, critical step in the gene transfer pathway. Bacterial attachment levels and patterns may influence transformation and, by extension, transient expression. In this study, attachment of A. tumefaciens to lettuce leaf tissue was investigated in response to varying infiltration conditions, including bacterial density, surfactant concentration, and applied vacuum level. Bacterial density was found to most influence attachment levels for the levels tested (108, 109, and 1010 CFU/mL), with the relationship between bacterial density and attachment levels following a saturation trend. Surfactant levels tested (Break-Thru S240: 1, 10, 100, and 1,000 µL/L) also had a significant positive effect on bacterial attachment while vacuum level (5, 25, and 45 kPa) did not significantly affect attachment in areas exposed to bacteria. In planta transgene transient expression levels were measured following infiltration with 108, 109, and 1010 CFU/mL bacterial suspension. Notably, the highest attachment level tested led to a decrease in transient expression, suggesting a potential link between bacterial attachment levels and downstream phenomena that may induce gene silencing. These results illustrate that attachment can be controlled by adjusting infiltration conditions and that attachment levels can impact transgene transient expression in leaf tissue. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1137–1144, 2014

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