Modulation of the light-harvesting chlorophyll antenna size in
            Chlamydomonas reinhardtii
            by
            TLA1
            gene over-expression and RNA interference

Truncated light-harvesting antenna 1 ( TLA1 ) is a nuclear gene proposed to regulate the chlorophyll (Chl) antenna size in Chlamydomonas reinhardtii . The Chl antenna size of the photosystems and the chloroplast ultrastructure were manipulated upon TLA1 gene over-expression and RNAi downregulation. The TLA1 over-expressing lines possessed a larger chlorophyll antenna size for both photosystems and contained greater levels of Chl b per cell relative to the wild type. Conversely, TLA1 RNAi transformants had a smaller Chl antenna size for both photosystems and lower levels of Chl b per cell. Western blot analyses of the TLA1 over-expressing and RNAi transformants showed that modulation of TLA1 gene expression was paralleled by modulation in the expression of light-harvesting protein, reaction centre D1 and D2, and VIPP1 genes. Transmission electron microscopy showed that modulation of TLA1 gene expression impacts the organization of thylakoid membranes in the chloroplast. Over-expressing lines showed well-defined grana, whereas RNAi transformants possessed loosely held together and more stroma-exposed thylakoids. Cell fractionation suggested localization of the TLA1 protein in the inner chloroplast envelope and potentially in association with nascent thylakoid membranes, indicating a role in Chl antenna assembly and thylakoid membrane biogenesis. The results provide a mechanistic understanding of the Chl antenna size regulation by the TLA1 gene.

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Spectroscopic methods in photosynthesis: photosystem stoichiometry and chlorophyll antenna size

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1989.0019 ◽

1989 ◽

Vol 323 (1216) ◽

pp. 397-409 ◽

Cited By ~ 61

Keyword(s):

Plant Species ◽

Light Harvesting ◽

Electron Flow ◽

Vascular Plant ◽

Thylakoid Membranes ◽

Reaction Centre ◽

Antenna Size ◽

Fluorescence Measurements ◽

Photosystem Stoichiometry ◽

Absorption Of Light

Light-induced absorbance change and fluorescence measurements were employed in the quantitation of photosystem stoichiometry and in the measurement of the chlorophyll (Chl) antenna size in thylakoid membranes. Results with thylakoid membranes from diverse photosynthetic tissues indicated a PSII/PSI reaction-centre stoichiometry that deviates from unity. Cyanobacteria and red algae have a PSII/PSI ratio in the range of 0.3 to 0.7. Chloroplasts from spinach and other vascular-plant species grown under direct sunlight have PSII/PSI = 1.8±0.3. Chlorophyll b -deficient and Chi b -lacking mutants have PSII/PSI > 2. The observation that PSII/PSI ratios are not unity and show a large variation among different photosynthetic membranes appears to be contrary to the conventional assumption derived from the Z-scheme. However, the photosystem stoichiometry is not the only factor that needs to be taken into account to explain the coordination of the two photosystems in the process of linear electron transport. The light-harvesting capacity of each photosystem must also be considered. In cyanobacterial thylakoids (from Synechococcus 6301, PSII/PSI = 0.5±0.2), the phycobilisome-PSII complexes collectively harvest as much light as the PSI complexes. In vascular plant chloroplasts, the light-harvesting capacity of a PSI I complex (250 molecules, Chi a/Chi b = 1.7) is lower than that of a PSI complex (230 Chl, Chl a /Chl b = 8.0) because Chi b has a lower extinction coefficient than Chi a . A differential attenuation of light intensity through the grana further reduces the light absorbed by PSII. Hence, a PSII/PSI ratio greater than one in vascular-plant chloroplasts compensates for the lower absorption of light by individual PSII complexes and ensures that, on average, PSII will harvest about as much light as PSI. In conclusion, distinct light-harvesting strategies among diverse plant species complement widely different photosystem stoichiometries to ensure a balanced absorption of light and a balanced electron flow between the two photoreactions, thereby satisfying the requirement set forth upon the formulation of the Z-scheme by Hill & Bendall ( Nature, Lond. 186, 136-137 (1960)) and by Duysens, Amesz & Kamp ( Nature, Lond . 190, 510-511 (1961)).

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tla1, a DNA insertional transformant of the green alga Chlamydomonas reinhardtii with a truncated light-harvesting chlorophyll antenna size

Planta ◽

10.1007/s00425-002-0968-1 ◽

2003 ◽

Vol 217 (1) ◽

pp. 49-59 ◽

Cited By ~ 144

Author(s):

Juergen E. W. Polle ◽

Sarada-Devi Kanakagiri ◽

Anastasios Melis

Keyword(s):

Chlamydomonas Reinhardtii ◽

Green Alga ◽

Light Harvesting ◽

Antenna Size ◽

Chlorophyll Antenna Size

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Light-harvesting complex gene expression is controlled by both transcriptional and post-transcriptional mechanisms during photoacclimation in Chlamydomonas reinhardtii

Physiologia Plantarum ◽

10.1034/j.1399-3054.2003.00078.x ◽

2003 ◽

Vol 118 (2) ◽

pp. 193-205 ◽

Cited By ~ 61

Author(s):

Dion G. Durnford ◽

Julie A. Price ◽

Sarah M. McKim ◽

Michelle L. Sarchfield

Keyword(s):

Gene Expression ◽

Chlamydomonas Reinhardtii ◽

Light Harvesting ◽

Light Harvesting Complex

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Loss of CpSRP54 function leads to a truncated light-harvesting antenna size in Chlamydomonas reinhardtii

Biochimica et Biophysica Acta (BBA) - Bioenergetics ◽

10.1016/j.bbabio.2016.10.007 ◽

2017 ◽

Vol 1858 (1) ◽

pp. 45-55 ◽

Cited By ~ 18

Author(s):

Jooyeon Jeong ◽

Kwangryul Baek ◽

Henning Kirst ◽

Anastasios Melis ◽

EonSeon Jin

Keyword(s):

Chlamydomonas Reinhardtii ◽

Light Harvesting ◽

Antenna Size ◽

Light Harvesting Antenna

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Regulation of light harvesting complex gene expression in Chlamydomonas reinhardtii

10.14264/uql.2014.163 ◽

2014 ◽

Author(s):

Anne Sawyer

Keyword(s):

Gene Expression ◽

Chlamydomonas Reinhardtii ◽

Light Harvesting ◽

Light Harvesting Complex

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Biosynthetic pathways of two polypeptide subunits of the light-harvesting chlorophyll a/b protein complex.

The Journal of Cell Biology ◽

10.1083/jcb.91.2.468 ◽

1981 ◽

Vol 91 (2) ◽

pp. 468-478 ◽

Cited By ~ 135

Author(s):

G W Schmidt ◽

S G Bartlett ◽

A R Grossman ◽

A R Cashmore ◽

N H Chua

Keyword(s):

Protein Complex ◽

Light Harvesting ◽

Thylakoid Membranes ◽

Chloroplast Envelope ◽

Antigenic Determinants ◽

Intact Chloroplasts ◽

Free Translation ◽

Chlorophyll Protein ◽

Envelope Membranes

We have used an in vitro reconstitution system, consisting of cell-free translation products and intact chloroplasts, to investigate the pathway from synthesis to assembly of two polypeptide subunits of the light-harvesting chlorophyll-protein complex. These polypeptides, designated 15 and 16, are integral components of the thylakoid membranes, but they are products of cytoplasmic protein synthesis. Double immunodiffusion experiments reveal that the two polypeptides share common antigenic determinants and therefore are structurally related. Nevertheless, they are synthesized in vitro from distinct mRNAs to yield separate precursors, p15 and p16, each of which is 4,000 to 5,000 daltons larger than its mature form. In contrast to the hydrophobic mature polypeptides, the precursors are soluble in aqueous solutions. Along with other cytoplasmically synthesized precursors, p15 and p16 are imported into purified intact chloroplasts by a post-translational mechanism. The imported precursors are processed to the mature membrane polypeptides which are recovered exclusively in the thylakoids. The newly imported polypeptides are assembled correctly in the thylakoid lipid bilayer and they bind chlorophylls. Thus, these soluble membrane polypeptide precursors must move from the cytoplasm through the two chloroplast envelope membranes, the stroma, and finally insert into the thylakoid membranes, where they assemble with chlorophyll to form the light-harvesting chlorophyll protein complex.

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

Plant and Cell Physiology ◽

10.1093/pcp/pcab146 ◽

2021 ◽

Author(s):

Mithun Kumar Rathod ◽

Nellaipalli Sreedhar ◽

Shin-ichiro Ozawa ◽

Hiroshi Kuroda ◽

Natsumi Kodama ◽

...

Keyword(s):

Chlamydomonas Reinhardtii ◽

Green Alga ◽

Light Harvesting ◽

Affinity Purification ◽

Signal Recognition Particle ◽

Thylakoid Membranes ◽

Signal Recognition ◽

Light Harvesting Complexes ◽

C Terminus ◽

Unicellular Green Alga

Abstract The unicellular green alga, Chlamydomonas reinhardtii, contains many light-harvesting complexes (LHCs) associating chlorophylls a/b and carotenoids; the major light-harvesting complexes, LHCIIs (types I, II, III, and IV), and minor light-harvesting complexes, CP26 and CP29, for photosystem II, as well as nine light-harvesting complexes, LHCIs (LHCA1-9), for photosystem I. A pale green mutant BF4 exhibited impaired accumulation of LHCs due to deficiency in Alb3.1 gene which encodes the insertase involved in insertion, folding and assembly of LHC proteins in the thylakoid membranes. To elucidate the molecular mechanism by which ALB3.1 assists LHC assembly, we complemented BF4 to express ALB3.1 fused with no, single, or triple HA tag at its C-terminus (cAlb3.1, cAlb3.1-HA, or cAlb3.1-3HA). The resulting complemented strains accumulated most LHC proteins comparable to wild-type levels. The affinity purification of Alb3.1-HA and Alb3.1-3HA preparations showed that ALB3.1 interacts with cpSRP43 and cpSRP54 proteins of chloroplast signal recognition particle cpSRP and several LHC proteins; two major LHCII proteins (types I and III), two minor LHCII proteins (CP26 and CP29), and eight LHCI proteins (LHCA1, 2, 3, 4, 5, 6, 8, and 9). Pulse-chase labeling experiments revealed that the newly synthesized major LHCII proteins were transiently bound to the Alb3.1 complex. We propose that Alb3.1 interacts with cpSRP43 and cpSRP54 to form an assembly apparatus for most LHCs in the thylakoid membranes. Interestingly, PSI proteins were also detected in the Alb3.1 preparations, suggesting that the integration of LHCIs to a PSI core complex to form a PSI-LHCI subcomplex occurs before assembled LHCIs dissociate from the Alb3.1-cpSRP complex.

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