Organization and activity of photosystems in the mesophyll and bundle sheath chloroplasts of maize (original) (raw)
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Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2006
The regulation by light of the photosynthetic apparatus, and composition of light-harvesting complexes in mesophyll and bundle sheath chloroplasts was investigated in maize. Leaf chlorophyll content, level of plastoquinone, PSI and PSII activities and Lhc polypeptide compositions were determined in plants grown under high, moderate and low irradiances. Photochemical efficiency of PSII, photochemical fluorescence quenching and non-photochemical fluorescence quenching over a range of actinic irradiances were also determined, using chlorophyll a fluorescence analysis. Acclimation of plants to different light conditions caused marked changes in light-harvesting complexes, LHCI and LHCII, and antenna complexes were also reorganized in these types of chloroplasts. The level of LHCII increased in plants grown in low light, even in agranal bundle sheath chloroplasts where the amount of PSII was strongly reduced. Irradiance also affected LHCI complex and the number of structural polypeptides, in this complex, generally decreased in chloroplasts from plants grown under lower light. Surprisingly moderate and low irradiances during growth do not affect the light reaction and fluorescence parameters of plants but generated differences in composition of lightharvesting complexes in chloroplasts. On the other hand, the changes in photosynthetic apparatus in plants acclimated to high light, resulted in a higher efficiency of photosynthesis. Based on these observations we propose that light acclimation to high light in maize is tightly coordinated adjustment of light reaction components/activity in both mesophyll and bundle sheath chloroplasts. Acclimation is concerned with balancing light utilization and level of the content of LHC complexes differently in both types of chloroplasts.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2009
Photoinhibition is caused by an imbalance between the rates of the damage and repair cycle of photosystem II D1 protein in thylakoid membranes. The PSII repair processes include (i) disassembly of damaged PSII-LHCII supercomplexes and PSII core dimers into monomers, (ii) migration of the PSII monomers to the stroma regions of thylakoid membranes, (iii) dephosphorylation of the CP43, D1 and D2 subunits, (iv) degradation of damaged D1 protein, and (v) co-translational insertion of the newly synthesized D1 polypeptide and reassembly of functional PSII complex. Here, we studied the D1 turnover cycle in maize mesophyll and bundle sheath chloroplasts using a protein synthesis inhibitor, lincomycin. In both types of maize chloroplasts, PSII was found as the PSII-LHCII supercomplex, dimer and monomer. The PSII core and the LHCII proteins were phosphorylated in both types of chloroplasts in a light-dependent manner. The rate constants for photoinhibition measured for lincomycin-treated leaves were comparable to those reported for C3 plants, suggesting that the kinetics of the PSII photodamage is similar in C3 and C4 species. During the photoinhibitory treatment the D1 protein was dephosphorylated in both types of chloroplasts but it was rapidly degraded only in the bundle sheath chloroplasts. In mesophyll chloroplasts, PSII monomers accumulated and little degradation of D1 protein was observed. We postulate that the low content of the Deg1 enzyme observed in mesophyll chloroplasts isolated from moderate light grown maize may retard the D1 repair processes in this type of plastids.
Planta, 2015
Main conclusion Light quality has various effects on photochemistry and protein phosphorylation in Zea mays and Arabidopsis thaliana thylakoids due to different degrees of light penetration across leaves and redox status in chloroplasts. The effect of the spectral quality of light (red, R and far red, FR) on the function of thylakoid proteins in Zea mays and Arabidopsis thaliana was investigated. It was concluded that red light stimulates PSII activity in A. thaliana thylakoids and in maize bundle sheath (BS) thylakoids, but not in mesophyll (M) thylakoids. The light quality did not change PSI activity in M thylakoids of maize. FR used after a white light period increased PSI activity significantly in maize BS and only slightly in A. thaliana thylakoids. As shown by blue native (BN)-PAGE followed by SDS-PAGE, proteins were differently phosphorylated in the thylakoids, indicating their different functions. FR light increased dephosphorylation of LHCII proteins in A. thaliana thylakoids, whereas in maize, dephosphorylation did not occur at all. The rate of phosphorylation was higher in maize BS than in M thylakoids. D1 protein phosphorylation increased in maize and decreased in A. thaliana upon irradiation with both R and growth light (white light, W). Light variations did not change the level of proteins in thylakoids. Our data strongly suggest that response to light quality is a species-dependent phenomenon. We concluded that the maize chloroplasts were differently stimulated, probably due to different degrees of light penetration across the leaf and thereby the redox status in the chloroplasts. These acclimation changes induced by light quality are important in the regulation of chloroplast membrane flexibility and thus its function. Keywords Acclimation to light quality Á Bundle sheath chloroplasts Á Mesophyll chloroplasts Á PSI Á PSII Á Protein phosphorylation Á Red and far red light Á Thylakoids Abbreviations BS Bundle sheath BN-PAGE Blue native electrophoresis CET Cyclic electron transport FR Far red light LHCII Chlorophyll a/b-binding protein of photosystem II M Mesophyll R Red light W White light & El_ zbieta Romanowska
Chlorophyll-proteins of two photosystem I preparations from maize
Carlsberg Research Communications, 1985
Two photosystem I (PSI) preparations were purified by non-denaturing SDS-PAGE or sucrose gradient ultracentrifugation and examined as to their chlorophyll-protein composition. In both preparations a minimum of two chlorophyll-proteins can be distinguished in addition to the 110 kD P-700 Chlo-P 1 complex. One (LHCI-730) is a chlorophyll-protein (Mr 40 kD) having a high chlorophyll a/b ratio, and a major 77 K fluorescence peak at 730 nm. It consists of three polypeptides with apparent molecular weights of 21, 22.5 and 24 kD. Another chlorophyll-protein (LHCI-680) with a lower molecular weight (Mr 25 kD) fluoresces at 77 K with a maximum at 680 nm. This chlorophyll-protein has a high chlorophyll b content and two constituent polypeptides of 20 and 25 kD. Absorption, 77 K fluorescence and circular dichroism spectra of the PSI related chlorophyll-proteins are presented and compared with those of photosystem II chlorophyll-proteins from maize thylakoids. We propose a model for energy transfer in the photosystem I reaction centre with the following sequence: LHCI-730 ~ LHCI-680
Chloroplast acclimation in leaves of Guzmania monostachia in response to high light
Plant physiology, 1999
Acclimation of leaves to high light (HL; 650 micromol m(-2) s(-1)) was investigated in the long-lived epiphytic bromeliad Guzmania monostachia and compared with plants maintained under low light (LL; 50 micromol m(-2) s(-1)). Despite a 60% decrease in total chlorophyll in HL-grown plants, the chlorophyll a/b ratio remained stable. Additionally, chloroplasts from HL-grown plants had a much lower thylakoid content and reduced granal stacking. Immunofluorescent labeling techniques were used to quantify the level of photosynthetic polypeptides. HL-grown plants had 30% to 40% of the content observed in LL-grown plants for the light-harvesting complex associated with photosystems I and II, the 33-kD photosystem II polypeptide, and Rubisco. These results were verified using conventional biochemical techniques, which revealed a comparable 60% decrease in Rubisco and total soluble protein. When expressed on a chlorophyll basis, the amount of protein and Rubisco was constant for HL- and LL-gr...
Chlorophyll-proteins from maize seedlings grown under intermittent light conditions
Planta, 1993
We studied the organization of the antenna system of maize (Zea mays L.) seedlings grown under intermittent light conditions for 11 d. These plants had a higher chlorophyll-a/b ratio, a higher ratio of carotenoids to chlorophyll and a lower ratio of chlorophyll to protein than plants grown in continuous light. We found all chlorophyll-protein complexes of maize to be present. However, the minor chlorophyll a/b-proteins CP29 and CP26, and to a greater extent CP24 and the major light-harvesting complex II were reduced relative to the photosystem (PS) II core-complex. Also the chlorophyll a/b-antennae of PSI were reduced relative to the reaction-centre polypeptides. When isolated by flatbed isoelectrofocussing, the chlorophyll-a/b complexes of PSII showed a higher chlorophyll-a/b ratio and a lower ratio of chlorophyll to protein than the same complexes from continuous light; additionally, they bound more carotenoids per protein than the latter. Thus the altered organization of the photosynthetic apparatus of plants from intermittent light is caused by two different factors: (i) the altered stoichiometry of chlorophyll-binding proteins and (ii) a different ratio of pigment to protein within individual chlorophyll-proteins.
Maize bundle sheath chloroplasts - a unique model of permanent State 2
Environmental and Experimental Botany, 2018
The effect of high intensity of far red (FR) light on the energy distribution between PSII and PSI, measured as a change in the fluorescence emission in mesophyll (M) and bundle sheath (BS) chloroplasts of Zea mays was investigated in this paper. In bundle sheath thylakoids, FR light (730 nm) significantly stimulates 77K fluorescence of PSII but does not change the PSI fluorescence. In mesophyll thylakoids, the FR light used after the white light increased and decreased the PSII and PSI fluorescence, respectively. This indicates that in M chloroplasts light quality controls photosynthetic state transitions. The blue native (BN) PAGE, followed by SDS PAGE demonstrated that LHCII proteins associated with PSI were phosphorylated in the BS thylakoids in FR light. In M chloroplasts FR-light induced dephosphorylation of LHCII and the detachment of antenna from PSI occurred. In the BS thylakoids, the FR light initiated dephosphorylation of free and aggregated LHCII antenna, the dephosphorylated antenna can bound to PSII, thereby strongly increase its fluorescence, while part of LHCII pool stays associated with PSI. Thus aggregates of LHCII tended to be resolubilized in FR light and this allowed LHCII to connect to PSII, without changes in the pool of PSI-LHCI-LHCII. Our data indicate that PSI is locked in State 2 in agranal bundle sheath chloroplasts of maize. These results allow us to better understand the complexity of regulatory mechanisms of state transitions activated in response to light changes in M and BS chloroplasts of maize.
Structural organization of photosynthetic apparatus in agranal chloroplasts of maize
2008
We investigated the organization of photosystem II (PSII) in agranal bundle sheath thylakoids from a C 4 plant maize. Using blue native/SDS-PAGE and single particle analysis, we show for the first time that PSII in the bundle sheath (BS) chloroplasts exists in a dimeric form and forms light-harvesting complex II (LHCII)⅐PSII supercomplexes. We also demonstrate that a similar set of photosynthetic membrane complexes exists in mesophyll and agranal BS chloroplasts, including intact LHCI⅐PSI supercomplexes, PSI monomers, PSII core dimers, PSII monomers devoid of CP43, LHCII trimers, LHCII monomers, ATP synthase, and cytochrome b 6 f complex. Fluorescence functional measurements clearly indicate that BS chloroplasts contain PSII complexes that are capable of performing charge separation and are efficiently sensitized by the associated LHCII. We identified a fraction of LHCII present within BS thylakoids that is weakly energetically coupled to the PSII reaction center; however, the majority of BS LHCII is shown to be tightly connected to PSII. Overall, we demonstrate that organization of the photosynthetic apparatus in BS agranal chloroplasts of a model C 4 plant is clearly distinct from that of the stroma lamellae of the C 3 plants. In particular, supramolecular organization of the dimeric LHCII⅐PSII in the BS thylakoids strongly suggests that PSII in the BS agranal membranes may donate electrons to PSI. We propose that the residual PSII activity may supply electrons to poise cyclic electron flow around PSI and prevent PSI overoxidation, which is essential for the CO 2 fixation in BS cells, and hence, may optimize ATP production within this compartment. Oxygenic photosynthesis sustains life on Earth. It couples the formation of molecular oxygen with the biosynthesis of carbohydrates, thus providing the ultimate source of biomass, food, and fossil fuels. In the first step of photosynthesis, the solar energy is captured and converted into the energy-rich molecule ATP and the reducing equivalents (in the form of water-derived protons and electrons) used for the conversion of CO 2 into 3 The abbreviations used are: PSI and PSII, photosystem I and II, respectively; BS, bundle sheath; BN, blue native; Chl, chlorophyll; cyt, cytochrome; DDM, -Ddodecyl maltoside; LHCI and LHCII, light harvesting complex I and II, respectively; MS, mesophyll; DCMU, 3-(3,4-dichloro-phenyl)-1,1-dimethylurea.
Plant Physiology, 1985
It is shown that the monovinyl and divinyl protochlorophyllide biosynthetic patterns of etiolated maize (Zea mays L.), and cucumber (Cucumis sativus L.) seedlings and of their isolated etiochloroplasts can be modulated by light and darkness as was shown for green photoperiodically grown plants (E. E. Carey, C. A. Rebeiz 1985 Plant Physiol. 79: 1-6). In etiolated corn and cucumber seedlings and isolated etiochloroplasts poised in the divinyl protochlorophyllide biosynthetic mode by a 2 hour light pretreatment, darkness induced predominantly the biosynthesis of monovinyl protochlorophyllide in maize and of divinyl protochlorophyllide in cucumber. When etiolated seedlings and their isolated etiochloroplasts were poised in the monovinyl protochlorophyllide biosynthetic mode by a prolonged dark-pretreatment, light induced mainly the biosynthesis of divinyl protochlorophyllide in both maize and cucumber. 'Abbreviations: DV, divinyl; MV, monovinyl; ALA, 3-aminolevulinic acid. Unless preceded by MV or DV, the terms Pchlide, Chlide and Chl are used generically to designate metabolic pools that may consist of MV and DV components.
The light-dependent control of chloroplast development in barley (Hordeum vulgare L)
Journal of Cellular Biochemistry, 1983
The light-induced greening of etiolated barley plants is used as a model to study the light-dependent control of plastid development. Upon illumination a rapid transformation of etioplasts to chloroplasts is induced. The effect of illumination does not only include the light-dependent chlorophyll synthesis but also the appearance or dedine of specific proteins within the plastid membrane fractions. So far two of these proteins have been studied in detail. The light-harvesting chlorophyll a/b protein (LHCP) is one of the major protein constituents of the thylakoid membrane of chloroplasts. However, this protein is not detectable among the membrane polypeptides of etioplasts. Illumination of dark-grown barley plants induces a massive insertion of the LHCP. The appearance of the protein is controlled by the cooperation of at least two distinct photoreceptors: protochlorophyllide and phytochrome. In dark-grown barley plants not only the LHCP but also its mRNA is not detectable. The light-dependent appearance of mRNA activity for the LHCP is under the control of phytochrome (Pf,). Even though the appearance of mRNA activity is induced via Pf, by a single red light pulse, the assembly of the complete LHCP takes place only under continuous illumination, which allows chlorophyll synthesis. The second protein analyzed so far is the NADPH-protochlorophyllide-oxidoreductase. This enzyme catalyzes the lightdependent reduction of protochlorophyllide to chlorophyllide and thus controls one of the first detectable light-dependent reactions during the greening period. It is generally assumed that this enzyme is responsible for the overall chlorophyll synthesis and accumulation during the greening period. In contrast to this hypothesis, we found a rapid decline of the enzyme during illumination. In addition to the decrease of the enzyme protein, the translatable mRNA coding for the enzyme also declines rapidly under the influence of light. Also this effect is mediated by phytochrome. Using cloned cDNA as hybridization probes we have demonstrated that the light-induced changes of the two translatable mRNAs for the NADPHprotochlorophyllide oxidoreductase and the LHCP are both paralleled by corresponding changes in the steady-state concentration of the mRNA sequences. Thus, it seems likely that one major point of control at which phytochrome regulates the development of chloroplasts is the expression of genes at the level of transcription.