Structure and dynamics of thylakoids in land plants

Abstract

Thylakoids of land plants have a bipartite structure, consisting of cylindrical grana stacks, made of membranous discs piled one on top of the other, and stroma lamellae which are helically wound around the cylinders. Protein complexes predominantly located in the stroma lamellae and grana end membranes are either bulky [photosystem I (PSI) and the chloroplast ATP synthase (cpATPase)] or are involved in cyclic electron flow [the NAD(P)H dehydrogenase (NDH) and PGRL1-PGR5 heterodimers], whereas photosystem II (PSII) and its light-harvesting complex (LHCII) are found in the appressed membranes of the granum. Stacking of grana is thought to be due to adhesion between Lhcb proteins (LHCII or CP26) located in opposed thylakoid membranes. The grana margins contain oligomers of CURT1 proteins, which appear to control the size and number of grana discs in a dosage- and phosphorylation-dependent manner. Depending on light conditions, thylakoid membranes undergo dynamic structural changes that involve alterations in granum diameter and height, vertical unstacking of grana, and swelling of the thylakoid lumen. This plasticity is realized predominantly by reorganization of the supramolecular structure of protein complexes within grana stacks and by changes in multiprotein complex composition between appressed and non-appressed membrane domains. Reversible phosphorylation of LHC proteins (LHCPs) and PSII components appears to initiate most of the underlying regulatory mechanisms. An update on the roles of lipids, proteins, and protein complexes, as well as possible trafficking mechanisms, during thylakoid biogenesis and the de-etiolation process complements this review.

IM30 triggers membrane fusion in cyanobacteria and chloroplasts

“…As in chloroplasts, also in cyanobacteria, the TM network can be highly interconnected 41 , and it is thus likely that the TM system of cyanobacteria is as ARTICLE dynamic as in chloroplasts and undergoes remodelling under changing growth conditions or in the course of development 6 . However, proteins involved in this dynamic rearrangement of membranes in chloroplasts have not yet been identified 42 . The recent observation that in maize mesophyll cell chloroplasts, which harbour a rather extended TM network, the amount of IM30 is B10-fold higher than in maize bundle sheet chloroplasts indicates a crucial involvement of IM30 in TM biogenesis and maintenance 43 .…”

Carbon Supply and Photoacclimation Cross Talk in the Green Alga Chlamydomonas reinhardtii

“…In land plants, the changes in membrane organization upon long-term acclimation to different light conditions are well documented (Anderson et al, 2012;Kirchhoff, 2013;Pribil et al, 2014), while little is known about how algae adapt to light conditions with respect to membrane organization. We used transmission electron microscopy to visualize the structural changes that C. reinhardtii cells undergo in various carbon supply and light conditions (Fig.…”

Knocking Down of Isoprene Emission Modifies the Lipid Matrix of Thylakoid Membranes and Influences the Chloroplast Ultrastructure in Poplar

“…Error bars display the SE (n = 4). Asterisks indicate significant differences from the wild type: **, P , 0.01; and ***, P , 0.001. thylakoid membrane ultrastructure (Pribil et al, 2014), in particular, the assembly of PSII and LHCII into supercomplexes and megacomplexes (Kouril et al, 2012). It was demonstrated (Labate et al, 2004) that the constitutive expression of the pea (Pisum sativum) Lhcb1 gene in transgenic tobacco (Nicotiana tabacum) plants leads to increased grana stacking, indicating that increased concentrations of LHCII result in more stacking.…”