Use of Bacterial Quorum-Sensing Components to Regulate Gene Expression in Plants  

Abstract

We describe an efficient inducible system to regulate gene expression in plants based on quorum-sensing components found in Gram-negative bacteria such as Agrobacterium tumefaciens. These bacteria monitor their own population density by utilizing members of the N-acyl homoserine lactone family as inducers and a transcriptional activator as its receptor. In our study, we utilize the components from A. tumefaciens (i.e. 3-oxooctanyl-L-homoserine lactone [OOHL]) synthesized by the TraI protein and its receptor, TraR. When OOHL binds to TraR, it recognizes its specific cis-element, the tra box. We translationally fused the eukaryotic VP16 activation domain to the N terminus of TraR. In the presence of OOHL, the chimeric VP16:TraR transcriptional regulator induces reporter gene expression in moss (Physcomitrella patens), barley (Hordeum vulgare), and carrot (Daucus carota) cells, as well as in transgenic Arabidopsis (Arabidopsis thaliana) seedlings. The inducible system shows a low level of reporter gene expression in the absence of the inducer. Foliar application and a floating-leaf assay in the presence of the inducer shows a 30-and 200-fold induction, respectively. Induction by foliar application of the inducer to whole seedlings is achieved within 8 h. The VP16:TraR activator also shows specificity for binding to its cognate inducer, OOHL. Based on microarray analyses, endogenous gene expression is not significantly affected due to overexpression of the TraR protein or presence of OOHL in either wild-type or lactone-inducible transgenic plants.

Response of Arabidopsis thaliana to N-hexanoyl-dl-homoserine-lactone, a bacterial quorum sensing molecule produced in the rhizosphere

“…These data suggested that AHL play an important role in plant bacterial communication and a possible role in pathogen defense, and we decided to analyze the eVect of AHLs on A. thaliana with the primary focus on the transcriptional level. It should be noted that in a recent report You and colleagues did not Wnd a signiWcant induction of genes after spraying leaves with 3-oxo-octanoyl-L-homoserine lactone (OOHL) (You et al 2006). On the other hand, their experimental system diVered from the one we and others (Mathesius et al 2003;Schuhegger et al 2006) used especially regarding AHL application (uptake through roots vs. spraying on leaf surface).…”

“…On the other hand, their experimental system diVered from the one we and others (Mathesius et al 2003;Schuhegger et al 2006) used especially regarding AHL application (uptake through roots vs. spraying on leaf surface). Furthermore, the cut-oV You et al (2006) applied to their array data was log § 1, while we worked with log § 0.7. Nevertheless, while our treatments of Arabidopsis with C6-HSL induced clear changes in transcript levels, only a small number of the induced genes were related to or associated with defense.…”

A structurally unrelated mimic of a Pseudomonas aeruginosa acyl-homoserine lactone quorum-sensing signal

“…Thus, the mimic is a useful tool for manipulating LasR under environmental conditions where the natural signal is ineffective. Acyl-homoserine lactone signaling has been explored as a means for heterologous expression in eukaryotic cells (23)(24)(25). The stability and potency of TP-1 make it an ideal substitute for activating such a system.…”

Arabidopsis Transcriptome Reveals Control Circuits Regulating Redox Homeostasis and the Role of an AP2 Transcription Factor

“…RNA samples were given to MOgene for microarray analysis (You et al, 2006). Agilent's technology was used for microarray and each treated sample was hybridized with control and a dye swap was performed.…”