Geranylgeranylated-chlorophyll-protein complexes in lhl3 mutant of the green alga Chlamydomonas reinhardtii.

Chlorophylls a and b (Chl a and b) are involved in light harvesting, photochemical reactions, and electron transfer reactions in plants and green algae. The core complexes of the photosystems (PSI and PSII) associate with Chl a, while the peripheral antenna complexes (LHCI and LHCII) bind Chls a and b. One of the final steps of Chl biosynthesis is the conversion of geranylgeranylated Chls (Chls) to phytylated Chls by geranylgeranyl reductase (GGR).

Chloroplast protein translocation pathways and ubiquitin-dependent regulation at a glance.

Chloroplasts conduct photosynthesis and numerous metabolic and signalling processes that enable plant growth and development. Most of the ∼3000 proteins in chloroplasts are nucleus encoded and must be imported from the cytosol. Thus, the protein import machinery of the organelle (the TOC-TIC apparatus) is of fundamental importance for chloroplast biogenesis and operation.

Assembly Apparatus of Light-Harvesting Complexes: Identification of Alb3.1-cpSRP-LHCP Complexes in the Green Alga Chlamydomonas reinhardtii.

The unicellular green alga, Chlamydomonas reinhardtii, contains many light-harvesting complexes (LHCs) associating chlorophylls a/b and carotenoids; the major LHCIIs (types I, II, III and IV) and minor light-harvesting complexes, CP26 and CP29, for photosystem II, as well as nine LHCIs (LHCA1-9), for photosystem I. A pale green mutant BF4 exhibited impaired accumulation of LHCs due to deficiency in the Alb3.1 gene, which encodes the insertase involved in insertion, folding and assembly of LHC proteins in the thylakoid membranes.

The photosystem I assembly apparatus consisting of Ycf3-Y3IP1 and Ycf4 modules.

In oxygenic photosynthesis, light energy is converted into redox energy by two photosystems (PSI and PSII). PSI forms one of the largest multiprotein complexes in thylakoid membranes consisting of a core complex, peripheral light-harvesting complexes (LHCIs) and cofactors. Although the high-resolution structure of the PSI-LHCI complex has been determined, the assembly process remains unclear due to the rapid nature of the assembly process.

Antimycin A sensitive pathway independent from PGR5 cyclic electron transfer triggers non-photochemical reduction of PQ pool and state transitions in Arabidopsis thaliana.

We investigated the mechanism involved in triggering state transitions at 40°C in Arabidopsis thaliana. Leaves (1-6 week old) exposed to 40°C exhibited state II transition indicating its role as one of the earliest stress responsive mechanism apart from regulation of light energy distribution between photosystem (PS)II and PSI. Post illumination transients (rise in Fo') revealed that non-photochemical reduction of PQ pool at 40°C in dark is responsible for activation of STN7 kinase, consequently light harvesting complex (LHC)II phosphorylation leading to state II condition.

The slow S to M rise of chlorophyll a fluorescence reflects transition from state 2 to state 1 in the green alga Chlamydomonas reinhardtii.

The green alga Chlamydomonas (C.) reinhardtii is a model organism for photosynthesis research. State transitions regulate redistribution of excitation energy between photosystem I (PS I) and photosystem II (PS II) to provide balanced photosynthesis.

Heat- and light-induced detachment of the light harvesting complex from isolated photosystem I supercomplexes.

In a previous study, using photosystem I enriched stroma thylakoid membrane vesicles, we have shown that the light harvesting complexes of this photosystem are prone to heat- and light-induced, thermo-optically driven detachment from the supercomplex [43]. We have also shown that the splitting of the supercomplex occurs in a gradual and specific manner, selectively affecting the different constituents of the antenna complexes. Here we further analyse these heat- and light-induced processes in isolated Photosystem I supercomplex using circular dichroism and 77K fluorescence emission spectroscopy and immuno blotting, and obtain further details on the sequence of events of the dissociation process as well as on the thermal stability of the different components.

Change in fast Chl a fluorescence transients, 2 dimensional protein profile and pigment protein interactions during state transitions in Arabidopsis thaliana.

Photosynthetic organisms during acclimation to light, differences in the amount of energy absorbed by photosystems leads to an imbalance in the energy distribution between photosystem (PS) II and PSI. Here, we describe the changes in fast chlorophyll (Chl) a fluorescence transients (OJIP) in wild type and stn7 under state I and state II light conditions. Fluorescence quenching in the OJIP transients recorded from state II exposed wt leaves is due to mobilization of LHCII to PSI.

Anaerobiosis induced state transition: a non photochemical reduction of PQ pool mediated by NDH in Arabidopsis thaliana.

Background: Non photochemical reduction of PQ pool and mobilization of LHCII between PSII and PSI are found to be linked under abiotic stress conditions. The interaction of non photochemical reduction of PQ pool and state transitions associated physiological changes are critically important under anaerobic condition in higher plants.

Methodology/findings: The present study focused on the effect of anaerobiosis on non-photochemical reduction of PQ pool which trigger state II transition in Arabidopsis thaliana.

RNA helicase, CrhR is indispensable for the energy redistribution and the regulation of photosystem stoichiometry at low temperature in Synechocystis sp. PCC6803.

We investigated the role of a cold-inducible and redox-regulated RNA helicase, CrhR, in the energy redistribution and adjustment of stoichiometry between photosystem I (PSI) and photosystem II (PSII), at low temperature in Synechocystis sp. PCC 6803. The results suggest that during low temperature incubation, i.

Effect of cold temperature on regulation of state transitions in Arabidopsis thaliana.

Low temperature is one of the most important abiotic factors limiting growth, development and distribution of plants. The effect of cold temperature on phosphorylation and migration of LHCII has been studied by 77K fluorescence emission spectroscopy and immuno-blotting in Arabidopsis thaliana. It has been reported that the mechanism of state transitions has been well operated at optimum growth temperatures.

Moderate heat stress induces state transitions in Arabidopsis thaliana.

The effect of temperature on the photosynthetic machinery is crucial for the fundamental understanding of plant physiology and the bioengineering of heat-tolerant varieties. In our study, Arabidopsis thaliana was exposed to mild (40°C), short-term heat stress in the dark to evaluate the heat-triggered phosphorylation and migration of light harvesting complex (LHC) II in both wild-type (wt) and mutant lacking STN7 kinase. The 77K emission spectra revealed an increase in PSI relative to PSII emission similar to increases observed in light-induced state I to state II transitions in wt but not in stn7 mutant.

Proteomic analysis of thylakoid membranes.

Chlamydomonas is a model organism to study photosynthesis. Thylakoid membranes comprise several proteins belonging to photosystems I and II. In this chapter, we show the accurate proteomic measurements in thylakoid membranes.

Structural and functional changes of PSI-LHCI supercomplexes of Chlamydomonas reinhardtii cells grown under high salt conditions.

The eVect of high salt concentration (100 mM NaCl) on the organization of photosystem I-light harvesting complex I supercomplexes (PSI-LHCI) of Chlamydomonas reinhardtii was studied. The electron transfer activity was reduced by 39% in isolated PSI-LHCI supercomplexes. The visible circular dichroism (CD) spectra associated with strongly coupled chlorophyll (Chl) dimers were reduced in intensity, indicating that pigment-pigment interactions were disrupted.

Novel binding studies of human serum albumin with trans-feruloyl maslinic acid.

Human serum albumin (HSA) is a predominant protein in the blood. Most drugs can bind to HSA and be transported to target locations of the body. For this study, we have extracted 3-trans-feruloyl maslinic acid (FMA) from the medicinal plant Tetracera asiatica, its a non-fluorescent derivative have potent anti-cancer, anti-HIV, anti-diabetic, and anti-inflammatory activities.