Non-Thermal Radio Frequency Stimulation Inhibits the Tryptophan Synthase Beta Subunit in the Algae <i>Chlamydomonas reinhardtii</i>

Abstract

To demonstrate the ability of the Nativis signal transduction technology (Butters et al. 2014) to modulate the expression of algae mRNA and protein, we tested if we can alter specific enzyme levels in Chlamydomonas reinhardtii. We inhibited the synthesis of the enzyme tryptophan synthase beta subunit (MAA7) by applying the signal derived from a published siRNA (Zhao et al. 2009). With lower levels of MAA7, Chlamydomonas reinhardtii can grow in the presence of the prodrug 5-Fluoroindole (5-FI), because less 5-Fluoroin-dole can be converted to the toxic 5-Fluoro-L-tryptophan (5-FT). We find a 24% (±5%) increase of growth with the signal versus no signal. To see if that effect was due to the reduction of the amount of mRNA encoding MAA7, we used Real-Time Quantitative PCR (RT-QPCR) to measure the levels of MAA7 mRNA. To normalize the MAA7 mRNA level, we compared them to the levels of a mRNA that is not affected by the signal (G protein beta subunit-like polypeptide, Cblp). Two conditions increase the effectiveness of the signal. One can either treat the cell cultures during the logarithmic growth phase (starting the cultures at density of 0.104 OD at 750 nm). Or one can treat the cultures at a later stage of the logarithmic growth, but treating them for a longer time (8.7% versus 3.5% of the culture time). Under these conditions we found around a 50% decrease in the mRNA levels for MAA7. Treating the cultures at the earlier growth phase or at a later growth phase is less effective, with only a 20% effect.