High light grown Chromera velia displays similar physiological response to lincomycin-treated plants

Erica Belgio, Eliška Trsková, Eva Kotabová, Ondřej Prášil, Radek Kaňa
Institute of Microbiology, Academy of Sciences of the Czech Republic, Opatovický mlýn, 379 81 Třeboň, Czech Republic

It has been previously shown [1] that the long-term treatment of Arabidopsis thaliana with the chloroplast inhibitor lincomycin leads to photosynthetic membranes enriched in antennas, strongly reduced in reaction centre (RCII) content, with low Fv/Fm and a fast-forming/slowly-relaxing non-photochemical quenching (NPQ) significatively greater than control. Here for the first time we found similar physiological features in a totally natural “antibiotic free” system. High light (>100 µE) adaptation induced in Chromera velia algae a re-organisation of the photosynthetic membrane consisting in a four-times drop of RCII content, a decrease of Fv/Fm (< 0.3) and NPQ levels 5 times higher than control. Despite reduction in RCII, the antenna content was even stimulated, similar to lincomycin-treated plants, thus suggesting that, in line with [1], a large proportion of the absorbed energy does not reach the reaction centres due to energetic uncoupling of the antennas. These results could explain how  Chromera velia maximises photosynthetic rates under both light-limited and light-saturating conditions [2]. We propose that keeping high antenna content under high light could represent a physiological advantage under natural light fluctuations.

Figure 1: Fluorescence induction traces of: left, higer plant control (top) and lincomycin-treated (bottom); right C. velia grown under low-light (top) and high light (bottom).