Abscisic acid (ABA) is an essential drought stress molecule and simple methods for detecting its levels could benefit agriculture. Here, we present as proof-of-concept biosensor to detect ABA in aqueous solutions using a Cyanine 5.5 (Cy5.5) fluorophore- and BHQ3 quencher conjugated to endogenous abscisic acid receptor pyrabactin resistance 1 like proteins (PYL3), which monomerize upon ABA binding. A mixture of the two protein conjugates was used to detect nM to mM ABA in aqueous solution. As the ABA concentration increased from less than one µM to one mM, fluorescence intensity of the mixture more than doubled. In addition to BHQ3 quenching the fluorescence of Cy5.5 in PYL3-Cy5.5/PYL3-BHQ3 heterodimers, self-quenching was observed between two fluorophores in PYL3-Cy5.5 homodimers. BHQ3 concentration-dependent attenuation of Cy5.5 was observed as well, which was significant at the BHQ3 concentrations used in this work. A kinetic model was developed to simulate the fluorescence response from the mixture and the results generally agree with the experimentally observed trend. This work demonstrates that fluorescence measurements of a single dissociation reaction in one spectral region are adequate to assess the ABA concentration of a solution.

Towards development of fluorescence quenching-based biosensors for drought stress in plants

2019 Fall National Meeting

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