23 November 2017
Tiny molecular sensor within cells
Published online 30 November 2016
A group of researchers have come up with a way to assemble a protein sensor inside plant cells to detect previously unclear chemical signalling.
A team of researchers devised a tiny sensor that operates within the plant cell to detect, for the first time, an important class of plant signalling molecules1.
Strigolactones are a group of compounds, closely related in chemical structure, that plant cells use to regulate various aspects of growth and development and are involved in symbiosis with root fungi, but are also used by weeds to recognize host roots incidentally leading to crop yield losses.
When strigolactones are sensed by the cell, a signalling cascade is initiated which culminates in the degradation of a specific target protein called SMLX, as a part of the response process. But the details of how strigolactones signal different responses remain obscure.
Capitalizing on this knowledge, a team of researchers from Germany and Saudi Arabia designed a sensor based on SMLX degradation to better understand strigolactone signalling.
Their sensor is a protein molecule containing SMLX fused to a light-emitting protein called firefly luciferase. This fusion protein is in turn connected via a peptide that cleaves itself in cells to another light-emitting protein called REN luciferase, which emits at a different wavelength. This way, the measured firefly luciferase light signal which drops upon SMLX destruction can be normalized to the unaffected REN luciferase signal for the purpose of monitoring SMLX degradation.
The team encoded this design in the form of DNA, which they could inject into immature plant cells, where the cells’ protein expression machinery would then translate it to assemble the protein sensor.
The team showed that, as expected, cells exposed to strigolactones showed a decrease in the light signal from the firefly luciferase. They went on to demonstrate that by using different mutant backgrounds for candidate members of strigolactone signalling pathways and monitoring SMLX degradation, that new strigolactone-specific receptors in the cell can be identified to better understand this process.
- Samodelov, S. L. et al. StrigoQuant: a genetically encoded biosensor for quantifying strigolactone activity and specificity. Sci. Adv. 2, e1601266 (2016).