A synthetic de‐greening gene circuit provides a reporting system that is remotely detectable and has a re‐set capacity

Abstract

SummaryPlants have evolved elegant mechanisms to continuously sense and respond to their environment, suggesting that these properties can be adapted to make inexpensive and widely used biological monitors, or sentinels, for human threats. For a plant to be a sentinel, a reporting system is needed for large areas and widespread monitoring. The reporter or readout mechanism must be easily detectable, allow remote monitoring and provide a re-set capacity; all current gene reporting technologies fall short of these requirements.Chlorophyll is one of the best-recognized plant pigments with an already well-developed remote imaging technology. However, chlorophyll is very abundant, with levels regulated by both genetic and environmental factors. We designed a synthetic de-greening circuit that produced rapid chlorophyll loss on perception of a specific input. With induction of the de-greening circuit, changes were remotely detected within 2 h. Analyses of multiple de-greening circuits suggested that the de-greening circuit functioned, in part, via light-dependent damage to photosystem cores and the production of reactive oxygen species. Within 24 -48 h of induction, an easily recognized white phenotype resulted.Microarray analysis showed that the synthetic de-greening initiated a process largely distinct from normal chlorophyll loss in senescence. Remarkably, synthetically de-greened white plants re-greened after removal of the inducer, providing the first easily re-settable reporter system for plants and the capacity to make re-settable biosensors. Our results showed that the de-greening circuit allowed chlorophyll to be employed as a simple but powerful reporter system useful for widespread areas.

Chloroplast iron-sulfur cluster protein maturation requires the essential cysteine desulfurase CpNifS

“…Leaves were sampled from soil-grown plants 10 days after the start of ethanol treatment. Fixation and sectioning before analysis by transmission electron microscopy were performed as described (40).…”

Synthetic biology of cell signaling

“…TCS naturally occur in plants, as opposed to vertebrate cells (Hwang and Sheen 2001). Works by Antunes et al (2006Antunes et al ( , 2009Antunes et al ( , 2011 have set out to rewire the signaling pathways of the host plant cells in order to impart new sensing capacities using TCSs integrated with a de-greening reporter circuit (rapid reduction of chlorophyll levels and turning leaves colorless as a result) and the ability to reset itself (turn leaves back to green color) for repeated use. They modified the histidine kinase function of the PhoRB TCS by exchanging the sensing portion with that of Trg, creating a Trg:PhoR hybrid capable of sensing trinitrotoluene and propagating a signal (Antunes et al 2011).…”

A demonstration of hyperspectral image exploitation for military applications

“…The BIOS program's objective was to produce basic biochemical modules for future use in plant or microbialbased detectors of chemical and biological compounds of strategic interest. Collaboration between the two projects advanced efforts in developing a human-readable biological signalling event (Deyholos et al, 2007;Antunes et al, 2006) The DARPA-funded team at Colorado State University went on to develop the first generation plant-based sensor capable of detecting 2,4,6-TNT in the low ppt (parts per trillion) range. The Canadian effort made significant progress in the development of a rootto-shoot transducer system and an effective visual reporter system (Deyholos, 2009).…”