Effects of sulfur limitation on photosystem II functioning in Chlamydomonas reinhardtii as probed by chlorophyll a fluorescence

Abstract

Chlorophyll fluorescence methods were applied to probe in vivo photosystem II (PSII) function in Chlamydomonas reinhardtii grown in sulfur-depleted media under aerobic conditions. The rates of oxygen evolution and P 700 þ dark reduction decreased during a 24-h incubation in sulfur-deficient medium, while the respiration rate increased. The analysis of chlorophyll fluorescence induction curves suggests that electron transport was perturbed on both the acceptor and donor sides of PSII. Light-induced violaxanthin de-epoxidation and non-photochemical fluorescence quenching were suppressed, owing to dark accumulation of zeaxanthin. Also sulfurdeprived cells showed elevated concentrations of violaxanthin and lutein. Sulfur deprivation stimulated a pronounced (three-to four-fold) increase in chlorophyll a fluorescence intensity (parameters F o and F m ), probably due to greater light absorption by carotenoids and changes in the excitation energy transfer and deactivation in PSII of C. reinhardtii.

Multiple regulatory mechanisms in the chloroplast of green algae: relation to hydrogen production

“…Examination of the functionality of the xanthophyll cycle showed that S-deprived cells contain an elevated amount of zeaxanthin both in the dark and light adapted state, whereas control cells have a low zeaxanthin concentration in the dark-adapted state and high zeaxanthin content in the light adapted state (Antal et al 2006). The result indicates dysfunction of the xanthophyll cycle under S deficiency.…”

“…The back transition from state 2 to state 1 in green algae can be promoted by oxidizing the PQ pool by intensive aeration of suspension or by exposure to strong illumination in the presence of DCMU. We have shown that these treatments enable transition from state 2 to state 1 if C. reinhardtii cells are depleted of sulfur for less than 48 h (Antal et al 2006). During longer incubations, thylakoid membranes become locked in state 2 and only readdition of sulfur enables re-establishment of state 1.…”

“…S-deprived C. reinhardtii cells were characterized by noticeably elevated yield of the maximum Chl fluorescence Fm, whereas their Chl content remained unaltered (Antal et al 2006). The molecular mechanisms underlying this unusual phenomenon are not clear, but reorganization of PSII antenna in stressed cells (Nguyen et al 2008) can be involved.…”

“…These data suggest elevated NPQ in stressed cells. However light-induced development of NPQ was shown to be disturbed in S-deprived cells and to remain unchanged under N deprivation (Antal et al 2006;Juergens et al 2015).…”

Relevance of nutrient media composition for hydrogen production in Chlamydomonas

“…Evidence of this was demonstrated by Mignolet et al (2012) who reported that a NDA2 mutant accounts for a 30 % loss in the H 2 production in S-depleted cultures. Also, increased rate of electrons flow from stromal reductants, such as NAD(P)H, to the PQ pool has been directly observed (Antal et al 2006). The degradation of the previously accumulated starch has been proposed as the main source of ATP and NAD(P)H Chochois et al 2009).…”