Single-cell microfluidics in combination with chlorophyll a fluorescence measurements to assess the lifetime of the Chlamydomonas PSBO protein

Abstract

PSBO is an essential subunit of the oxygen-evolving complex and we recently demonstrated that its lifetime depends on environmental conditions in <i>Chlamydomonas reinhardtii</i>. To assess PSBO lifetime with a high time resolution, we employed (<i>1</i>) a microfluidic platform enabling the trapping of single cells and the parallel measurement of photosynthetic activity, and (<i>2</i>) a nitrate-inducible <i>PSBO</i> amiRNA line. Our microfluidic platform allowed the rapid replacement of the nutrient solution necessary for induction. It also enabled the precise monitoring of the decline in the F_v/F_m value, reflecting PSBO loss. We found that in the dark, at medium and high light intensity, the F_v/F_m value decreased with halftimes of about 25, 12.5, and 5 h, respectively. We also observed that photosynthetic activity was better sustained upon carbon limitation. In the absence of acetate, the halftimes of F_v/F_m diminishment doubled to quadrupled compared with the control, acetate-supplied cultures.