Analysis of PSII antenna size heterogeneity of Chlamydomonas reinhardtii during state transitions

Abstract

PSII antenna size heterogeneity has been intensively studied in the past. Based on DCMU fluorescence rise kinetics, multiple types of photosystems with different properties were described. However, due to the complexity of fluorescence signal analysis, multiple questions remain unanswered. The number of different types of PSII is still debated as well as their degree of connectivity. In Chlamydomonas reinhardtii we found that PSIIα possesses a high degree of connectivity and an antenna 2-3 times larger than PSIIβ, as described previously. We also found some connectivity for PSIIβ in contrast with the majority of previous studies. This is in agreement with biochemical studies which describe PSII mega-, super- and core-complexes in Chlamydomonas. In these studies, the smallest unit of PSII in vivo would be a dimer of two core complexes hence allowing connectivity. We discuss the possible relationships between PSIIα and PSIIβ and the PSII mega-, super- and core-complexes. We also showed that strain and medium dependent variations in the half-time of the fluorescence rise can be explained by variations in the proportions of PSIIα and PSIIβ. When analyzing the state transition process in vivo, we found that this process induces an inter-conversion of PSIIα and PSIIβ. During a transition from state 2 to state 1, DCMU fluorescence rise kinetics are satisfactorily fitted by considering two PSII populations with constant kinetic parameters. We discuss our findings about PSII heterogeneity during state transitions in relation with recent results on the remodeling of the pigment-protein PSII architecture during this process.

Photosynthesis of Scenedesmus obliquus in outdoor open thin-layer cascade system in high and low CO2 in Belgium

“…In presence of this inhibitor, the fluo- rescence rise represents the photochemical reduction of Q A without influence of its reoxidation by plastoquinones. This measurement has been shown to be a good indicator of the PSII antenna size in Chlamydomonas reinhardtii (de Marchin et al, 2014). We couldn't notice significant difference in the halftime between the control and the CO 2 supplemented culture during linear growth phase (Fig.…”

Impacts of nitrogen and phosphorus starvation on the physiology of Chlamydomonas reinhardtii

“…Moreover, cells exposed to N stress can mobilize molecules of Chl a and other pigments as an internal source of N, resulting in a decrease of photosynthetic unit size (Perry et al 1981). Thus, as suggested by the higher values of ABS/RC, the O-J steps could reflect only an apparent increase of PSII antenna size, attributed to either inactivated PSII reaction centers which transfer their antenna to the remaining active PSII or changes in the PSIIα/β-centers heterogeneity (Falkowski and Kolber 1995;Strasser et al 2000;Zhang et al 2010;Stirbet 2011;de Marchin et al 2014). In our case, the shape of the O-J step is not indicative of a defined change of PSIIα/PSIIβ heterogeneity.…”

Photo-acclimation to low light—Changes from growth to antenna size in the cyanobacterium Cylindrospermopsis raciborskii

“…The effective absorption crosssectional area of PSII (sPSII), defines the size of the antennapigments transferring excitation to the functional PSII reaction centre and thus, the rate at which photons are delivered to PSII reaction centres for a given photon flux to the antenna (Falkowski and LaRoche, 1991;Falkowski and Kolber, 1995;Suggett et al, 2007). In C. raciborskii, as well as other species, the s is larger for PSIIa centres (Zhang et al, 2010;de Marchin et al, 2014;Pierangelini et al, 2014c). The enlarged sPSIIa for C. raciborskii NPD grown under low light suggests that under this condition higher amounts of pigments (Chl a and PC) are associated with each PSIIa centre (Moore et al, 2006).…”