Another thing to consider: combining high-activity CREs with binding sites for heterologous transcriptional activators to create chimeric promoters that are strong, minimally disruptive, and chemically inducible.

Lee et al. (2018) demonstrated ethanol-inducible expression in C. reinhardtii using the two-component AlcR-PalcA system from Aspergillus nidulans, but induction was modest (~1.74-fold) due largely to the weak transcriptional output of native PalcA in algae. Augmenting PalcA with the high-activity CREs from this study — particularly given the authors' finding that tandem CRE copies amplify output — could yield a robust, titratable system where gene expression is switched on simply by adding ethanol to the culture medium.

Reference: Lee et al. (2018) Journal of Applied Phycology. https://doi.org/10.1007/s10811-018-1480-8

We can't be sure that the albedo of the different pigments is what is driving the melt rate, since excreted or surface-presenting compounds are not quantified here. One could simply perform a titration of the pigments themselves in ice crystals as a control.