Functional architecture of higher plant photosystem II supercomplexes

Abstract

Photosystem II (PSII) is a large multiprotein complex, which catalyses water splitting and plastoquinone reduction necessary to transform sunlight into chemical energy. Detailed functional and structural studies of the complex from higher plants have been hampered by the impossibility to purify it to homogeneity. In this work, homogeneous preparations ranging from a newly identified particle composed by a monomeric core and antenna proteins to the largest C 2 S 2 M 2 supercomplex were isolated. Characterization by biochemical methods and single particle electron microscopy allowed to relate for the first time the supramolecular organization to the protein content. A projection map of C 2 S 2 M 2 at 12 Å resolution was obtained, which allowed determining the location and the orientation of the antenna proteins. Comparison of the supercomplexes obtained from WT and Lhcb-deficient plants reveals the importance of the individual subunits for the supramolecular organization. The functional implications of these findings are discussed and allow redefining previous suggestions on PSII energy transfer, assembly, photoinhibition, state transition and non-photochemical quenching.

A single locus confers tolerance to continuous light and allows substantial yield increase in tomato

“…Tomato CAB-13 gene is homologous to Arabidopsis LHCB3. In Arabidopsis, LHCB1-3 form the 'major' trimeric LHCII antenna complexes, and LHCB4-6 form the monomeric 'minor' antenna complexes 42 . The antenna complexes harvest light and transfer the energy to the PSII core; together they constitute the PSII-LHCII supercomplex (see ref.…”

“…43 for a recent review). In Arabidopsis, absence of LHCB3 results in alterations of the composition, structure, stability and efficiency of PSII-LHCII supercomplexes 42,[44][45][46] . For instance, LHCB3 can be replaced by LHCB1 and/or LHCB2, but the resulting LHCII trimer binds to the PSII-LHCII supercomplex in a slightly altered position 44 .…”

“…For instance, LHCB3 can be replaced by LHCB1 and/or LHCB2, but the resulting LHCII trimer binds to the PSII-LHCII supercomplex in a slightly altered position 44 . In knockout plants lacking LHCB3 (koLhcb3), the PSII-LHCII supercomplex stability is compromised in such a way that it lacks some LHCII subunits 42 . Similarly, high-lightacclimated plants show a reduction in LHCB3, which leads to higher PSII quantum yield of charge separation and supercomplexes lacking the same subunits as in koLhcb3 plants 45,46 .…”

Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light

“…Since the mode of action of PsbS is still not well understood, and since PSII particles are densely packed within the grana, it might be possible that one PsbS per ten PSII is enough to efficiently protect the photosynthetic apparatus. However, PsbS in Arabidopsis accumulates at higher and likely stoichiometric amounts with PSII (see, for instance, 2D gels in Li et al [2004] and Caffarri et al [2009]) where PsbS is present in amounts comparable to those of monomeric Lhc proteins). Due to the fact that PsbS in algae and plants likely works in a similar manner and that there is a correlation between the amount of PsbS and NPQ level, we suggest that the low amount of PsbS in vivo might contribute to only a small part of the NPQ capacity of Chlamydomonas.…”

Generality of relationships between leaf pigment contents and spectral vegetation indices in Mallorca (Spain)

“…The spectral properties of individual pigments are well studied in solution where interactions with other pigments and pigment-protein complexes are absent (Lichtenthaler 1987;Porra 2002), but less is known of spectral properties of pigment-binding complexes as they occur and function in intact leaves (Marin et al 2011). Despite of the difficulties in purification of pigment-protein complexes, significant advancements have been also made in biochemical and spectroscopic characterization of components of PSI and PSII (Caffarri et al 2009;Wientjes and Croce 2011) and their acclimation to growth-light spectrum (Hogewoning et al 2012).…”