Composition, architecture and dynamics of the photosynthetic apparatus in higher plants

Abstract

Summary The process of oxygenic photosynthesis enabled and still sustains aerobic life on Earth. The most elaborate form of the apparatus that carries out the primary steps of this vital process is the one present in higher plants. Here, we review the overall composition and supramolecular organization of this apparatus, as well as the complex architecture of the lamellar system within which it is harbored. Along the way, we refer to the genetic, biochemical, spectroscopic and, in particular, microscopic studies that have been employed to elucidate the structure and working of this remarkable molecular energy conversion device. As an example of the highly dynamic nature of the apparatus, we discuss the molecular and structural events that enable it to maintain high photosynthetic yields under fluctuating light conditions. We conclude the review with a summary of the hypotheses made over the years about the driving forces that underlie the partition of the lamellar system of higher plants and certain green algae into appressed and non‐appressed membrane domains and the segregation of the photosynthetic protein complexes within these domains.

Nanodomains of Cytochromeb 6 fand Photosystem II Complexes in Spinach Grana Thylakoid Membranes

“…The electron transfer reactions performed by cytb 6 f are coupled to the generation of an electrochemical proton gradient across the chloroplast thylakoid membrane, which is harnessed by ATP synthase to form ATP. The membrane location and organization of cytb 6 f complexes is crucial to their function; it is known that the thylakoid membrane in vascular plants is divided into two domains, the grana stacks, which are enriched in PSII, and the interconnecting stromal lamellae, which are enriched in PSI and ATP synthase complexes (reviewed in Albertsson, 2001;Dekker and Boekema, 2005;Daum and Kühlbrandt, 2011;Nevo et al, 2012). The distribution of the cytb 6 f complexes between the grana and stromal lamellae is much less clear.…”

Low-pH induced reversible reorganizations of chloroplast thylakoid membranes — As revealed by small-angle neutron scattering

“…It is generally agreed that NPQ requires the structural flexibility of thylakoid membranes. In fact, there are several reports demonstrating the involvement of structural changes at different levels of structural complexity [4][5][6][7][8][9][10][11][12][13][14]. Some of these changes might be directly linked to the generation of ∆pH, e.g., via the redistribution of ions in the 'electrolyte' following the generation of ∆µ H + [15,16] and, in particular, upon the acidification of lumen and the binding of protons to different polypeptide residues [2,17,18].…”

Acclimation of leaves to low light produces large grana: the origin of the predominant attractive force at work

“…Although not essential for photosynthesis, granal stacking helps to fine-tune (i) photosynthesis, (ii) photoprotection and (iii) acclimation to ever-changing environments [1,[7][8][9][10][11][12][13]. Some advantages associated with thylakoid stacking include: (i) an extremely large membrane surface-to-volume ratio to accommodate an optimally high density of light-harvesting pigments [14]; (ii) an extreme spatial separation of the two photosystems [15] that limits excessive spillover of excitation energy from photosystem II (PSII) to PSI [7,8], specifically to keep the rapidly functioning PSI and the relatively slow PSII apart [11]; (iii) enhancement of non-cyclic photophosphorylation [16]; (iv) regulation of non-photochemical dissipation of energy [10]; (v) delay of premature degradation of D1 protein in PSII [17]; (vi) regulation of non-cyclic versus cyclic electron transport and the associated photophosphorylation [18]; and (vii) a potential increase in photosynthetic capacity for a given chloroplast composition in full sunlight [12].…”