Molecular responses to prolonged darkness and subsequent acclimation to re-illumination in the diatom Phaeodactylum tricornutum

We have investigated both the response to prolonged darkness and the re-acclimation to “moderate intensity” white irradiance (E = 100 µmol m-2 s-1) in the diatom Phaeodactylum tricornutum, using an integrated approach involving global transcriptional profiling, pigment analyses, imaging and photo-physiological measurements. The responses were studied during continuous white light, after 48 h of dark treatment and after 0.5 h, 6 h, and 24 h of re-exposure to the initial irradiance. The cultures were incubated at 15C under cool white fluorescent light at a scalar irradiance (EPAR) of ~100 µmol m-2 s-1 under continuous white light (CWL) conditions. The cultures were dark-treated for 48 h (DT) before re-exposure to the previous light conditions for 0.5 h, 6 h or 24 h (WL 0.5, 6 and 24 h). Sampling of CWL cultures and DT cultures were performed in addition to the sampling at the WL incubation times of 0.5 h, 6 h, and 24 h. Three biological replicas for each of the five treatments were harvested.