Expanding the bioluminescence reporter toolkit for plant chronobiology with NanoLUC

Abstract

Bioluminescence has been an important tool for gathering circadian data with the main reporter gene exploited firefly luciferase (LUC). In some circumstances the rapid inactivation of LUC could be disadvantageous, e.g. reporting total protein levels through reporter translational fusions. In the latter scenario the commercially available Nano luciferase (NanoLUC) might offer and advantage, however no data in plant has been provided so far. We tested NanoLUC under different research scenarios were LUC has been used, for example enzyme purification, expression in transient plant systems and in stable transgenic lines. We show that NanoLUC is active in these experimental scenarios. We also created a set of NanoLUC variants for example MBP-NanoLUC-3xFlag-10xHis version of NanoLUC can be easily purified and stable for several days (half-life 37.2 at 4{degrees}C) and can be used for generating calibration curves for quantifying protein as the signal is linear over a large dynamic range. In addition, we show that NanoLUC can report in-planta protein levels on circadian time scale thanks to the stability of furimazine. Therefore, opening the possibility of using NanoLUC for reporting protein dynamics in seedlings. With this new technology, we explored the dynamics of protein BROTHER OF LUX ARRHYTHMO (BOA), which has been suggested in mathematical models to be a rhythmic protein from RNA data. Using an automatic plate-reader, we were able to track BOAp:BOA-NL for an extended period of time by just adding a mix of furimazine with Triton X-100, as it is done with LUC-reporter lines. In our experimental context BOA protein does not present strong oscillatory dynamics similar to what has been reported for Phytocrhome B for which rhythmic accumulation of transcript can be observed while total protein levels remain constant under diurnal conditions. Our results support the use NanoLUC for studying the dynamics of plant proteins for extended period of time under different circumstances.