Difference between revisions of "Team:HKUST-Rice/Description"

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  • OVERVIEW
  • POTASSIUM
    • P_kdpF
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    • P_araBAD characterization
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Overview

Nitrogen (N), Phosphorus (P), and potassium (K) are three macronutrients for plants, and deficiencies in any of these can lead to plant diseases. By creating a biological sensor that can quickly provide soil status to plant owners, we can prevent plant diseases due to the lack of nutrients. In view of this, our team is constructing a biological sensor in E. coli, which can detect NPK levels in the surrounding environment and give responses in the form of colors. In addition, we are characterizing the effects of a dual output system, in contrast to a single output system, in order to anticipate the expression of multiple outputs in a single system.

KdpFABC transporter is a high affinity K+ uptake system (Siebers, A. & Altendorf, K., 1988). The promoter upstream of kdpFABC operon, kdpFp, works under low K+ concentration (Polarek, J. W., et al., 1992; Walderhaug, M. O., et al., 1992). The goal is to characterize kdpFp and build a device which is able to sense different concentration of K+ and express different level of GFP accordingly.

For phosphate sensing, we decided to use PphoA promoter (Hsieh, Y. J., & Wanner, B. L.,2010).. PphoA promoter is cross-regulated by phoB, a DNA binding response regulator and phoR, a sensory histidine kinase, and is usually repressed under high phosphate concentration. phoR behaves as an activator as well as an inactivator for phoB. When phosphate is limited, phoR will phosphorylate phoB and the phosphorylated phoB will directly activates the expression of PphoA promoter. In contrast, when in high concentration of phosphate, phoR will dephosphorylate phoB and thus, inactivates the expression of PphoA promoter. As the biobrick of PphoA promoter with a GFP coding device submitted is not released, we have to clone the promoter from E. coli strain DH10B.

For nitrate sensing, we decided to use PyeaR promoter (Lin, et al, 2007). It is normally cross-regulated by the Nar two-component regulatory system (T.Nohno, et,al. , 1989) and nsrR, a regulatory protein that prevents the transcription of a number of operons in E. coli. When there is nitrate and nitrite in the environment, it will enter the cell and then being converted into nitric oxide. The nitric oxide will bind to nsrR and relieve the repression on the PyeaR promoter. As a result, any genes that are downstream of the PyeaR promoter will be expressed. As the biobrick of PyeaR promoter with a GFP coding device has already been submitted by the University of Bristol in 2010, we could characterize it and directly apply to our biosensor.

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