Evidence for the role of the light-harvesting chlorophyll ab protein complex in photosystem II heterogeneity

Heterogeneity in chloroplast photosystem II

“…In recent work using monochromatic light it has been shown that a monophasic induction curve can be observed using 550 nm;this data was interpreted as indicating direct excitation of PSII chlorophylls causing PSIIa to display PSII/3 kinetics (Percival et al, 1984). These observations are consistent with the notion that it is the association between LHCP and PSII that gives rise to a kinetics and that PSII/3 characteristics are generated either by a PSII population lacking LHCP or by preferentially exciting PSII relative to LHCP.…”

Photoregulation of the Composition, Function, and Structure of Thylakoid Membranes

“…Melis et al propose that PSII occurs as two structural-functional entities , termed PSIIu and PSIII3, which differ in both their effective light harvesting chi antenna sizes (166,168) and location in the membranes . Recently Percival et al (191) showed that the contribution of PSIIu and PSIII3 to the fluorescence induction curves depends on the ratio of PSII to LHCII, with PSIII3 characteristics being generated either by disconnect ing LHCII from PSII or by preferentially exciting PSII relative to LHCII . Alternatively, it has been suggested that apparent PSII heterogeneity is the result of incomplete blockage by DCMU of some PSII units (108), or arises as a consequence of connectivity between PSII units (55, 128).…”

“…PSIIu has the larger antenna unit size because of a fu ll complement of chI alb-proteins of LHCII, and it is located in appressed thylakoids (18,164), whereas PSIII3, which has a smaller complement of LHCII, is located in the nonappressed stroma thylakoids (18,163,164,223). In any event, the ratios of PSIIu/PSIII3 vary under different growth conditions (162,165,167,191). Recently Percival et al (191) showed that the contribution of PSIIu and PSIII3 to the fluorescence induction curves depends on the ratio of PSII to LHCII, with PSIII3 characteristics being generated either by disconnect ing LHCII from PSII or by preferentially exciting PSII relative to LHCII .…”

Changes in Photosystem II fluorescence in Chlamydomonas reinhardtii exposed to increasing levels of irradiance in relationship to the photosynthetic response to light

“…Two major aspects of the heterogeneity have been identified. There are heterogeneities in antenna size (PS li e and PS 118 centers;Melis and Homann 1975, 1976, Melis and Duysens 1979, Percival et al 1984 and in the rate of QB-reduction (PS II QB-reducing and QB-nonreducing centers; Thielen and Van Gorkom 1981, Lavergne 1982, Guenther et al 1988. Apart from having a larger antenna size than PS II~ (Melis and Duysens 1979, Melis and Anderson 1983, Morrisey et al 1989) and to be located in the grana region of the thylakoid membranes Melis 1983, Melis andAnderson 1983), PSII~ centers are also believed to exhibit a well developed exciton sharing system (Joliot and Joliot 1964, Herron and Mauzerall 1972, Butler 1980, Baker and Webber 1987.…”