Pyrenoid localization of Rubisco in relation to the cell cycle and growth phase of Dunaliella tertiolecta (Chlorophyceae) (original) (raw)
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RuBisCo activase is present in the pyrenoid of green algae
Protoplasma, 1991
RuBisCo activase catalyzes the activation and maintains the activated state of the photosynthetic enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCo, EC 4.1.1.39). We employed antisera prepared against the RuBisCo holoenzyme purified from tobacco and RuBisCo activase isolated from spinach to determine the localization of these proteins in leaves of C3-type higher plants and green algae. In leaves of Viciafaba, both RuBisCo activase and RuBisCo are distributed throughout the chloroplast stroma. In contrast, RuBisCo activase and RuBisCo are predominantly localized to the pyrenoid in the green algae Chlamydomonas reinhardtii and Coleochaete scutata. The eo-immunolocalization of RuBisCo activase and RuBisCo to the pyrenoid in these two green algal species suggests that pyrenoid-localized RuBisCo is catalytically competent. We conclude that the pyrenoid functions as a unique metabolic compartment of the chloroplast in which the reactions of the photosynthetic carbon reduction pathway are initiated.
Responses of Rubisco activation and deactivation rates to variations in growth-light conditions
Photosynthesis research, 1997
Basil (Ocimum basilicum) and impatiens (Impatiens wallerana) were grown in sun, shade, or fluctuating light (15 min sun, 15 min shade) to examine the effects of growth-light conditions on the rates of light-induced Rubisco activation and deactivation. Rubisco activation and deactivation rates were determined from gas-exchange measurements of photosynthesis following a step increase in PFD. Rubisco deactivation rates were also determined from biochemical analyses of leaf extracts. There were no significant differences in Rubisco activation rate among the growth conditions or between the two species. However, there were significant differences in Rubisco deactivation rate among the growth conditions in basil and between the two species. In basil, Rubisco deactivated more slowly following a decrease in PFD in sun-and fluctuating-light grown plants than in shade grown plants. Slower rates of Rubisco deactivation during periods at low PFD resulted in higher activation states at the onset of increased PFD. Thus, the contribution of Rubisco activation to the induction process was less for basil plants grown under sun and fluctuating light than for those grown under shade. Impatiens deactivated Rubisco more rapidly than in basil, but there was no substantial effect of the three growth-light conditions on Rubisco deactivation rates in impatiens.
Journal of Applied Phycology, 2016
Growth and biochemical parameters of two strains of Rhodomonas salina (Cryptophyceae), cultivated under different combinations of irradiance, temperature, and nutrients, were compared. The microalgae were grown in batch mode for 10 days, in f/2 medium at 33‰ salinity. The experimental design was a 2 5 factorial design with the following variables: nitrate [0.441 mM (N1) and 3.529 mM (N2)], phosphate [0.018 mM (P1) and 0.144 mM (P2)], temperature [19 and 29°C], continued irradiance [100 μmol photons m −2 s −1 (low light, LL), and 200 μmol photons m −2 s −1 (high light, HL)] and microalgae strains (CS-174 and CS-24). Growth parameters, protein and lipid content, and fatty acids profiles were analyzed. Principal component analysis showed that combined high nitrate, high phosphate availability, and high light, regardless of temperature, achieved the best growth in both strains; while combined high nitrate and high phosphate, regardless of irradiance or temperature, resulted in the highest protein accumulation in both strains. On the other hand, the content of total lipid, arachidonic (ARA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, as well as EPA/ DHA ratio, were strongly influenced by temperature in both strains. Strain CS-174 grew better and achieved significantly higher (p < 0.05) total lipid content (maximum 25.4 ± 1.5 %), ARA, EPA and DHA content (maximum 3.5, 13.2 and 6.5 %, respectively), and EPA / DHA ratio (maximum 2.03), than strain CS-24, being thus more suitable for use in aquaculture nutrition.
1997
The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was examined in three marine microalgae: the chlorophyte Dunaliella tertiolecta and the chromophytes Pavlova lutheri and Thalassiosira pseudonana. The three species differed in the sensitivity of Rubisco activity in crude extracts to magnesium ion concentration, the presence of protease inhibitors, the duration of the incubation on activity, and the potential for full activation of Rubisco with 20 mM magnesium chloride and 20 mM bicarbonate in vitro. D. tertiolecta had responses that were similar to those described in vascular plants: regulation of initial activity on a gradient of irradiances; maximum initial activities that were 80-90% of light-saturated photosynthesis; total activities that exceeded light-saturated photosynthesis by 30-100%; and deactivation of Rubisco in darkness. Both initial and total activity declined in darkness and increased on a return to growth irradiance. First-order time constants were about 9 min for deactivation and 3 min for reactivation of initial activity. The decline in total activity after a transition into darkness could not be reversed in vitro but could be reversed by exposing D. tertiolecta to light, a characteristic of regulation by CA1P. The responses of T. pseudonana were qualitatively similar, except that recovery of initial activity was low and could only account for 30-40% of light-saturated photosynthesis. Rubisco from T. pseudonana exposed to low irradiance could be activated in vitro but at growth irradiance and higher, total activity was lower than initial activity. The time constants for deactivation and reactivation of initial activity after reciprocal switches between growth irradiance and darkness were 12-18 min and 3 min in T. pseudonana. P. lutheri showed no regulation of Rubisco activity in response to changes in irradiance or light-dark transitions. This may have been an artifact of the conditions chosen to measure activity. Abbreviations: A i-initial Rubisco activity; A t-total Rubisco activity; CA1P-2-carboxyarabinitol 1phosphate; Chl-chlorophyll a; DCMU-3-(3,4-dichlorophenyl)-1,1-dimethylurea; DTT-dithiothreitol; EDTAethylenediaminetetraacetic acid; PEA-phenylethylamine; P chl m-chlorophyll-specific maximum (i.e. lightsaturated) rate of photosynthesis; PMSF-phenylmethylsulfonyl fluoride; PSU-practical salinity units; PVPPpolyvinylpolypyrrolidone; R-5-P-ribose 5-phosphate; RuBP-ribulose 1,5-bisphosphate; Rubisco-ribulose-1,5bisphosphate carboxylase/oxygenase; a-time constant for activation of Rubisco; d-time constant for deactivation of Rubisco
Biogenesis and Metabolic Maintenance of Rubisco
Annual Review of Plant Biology, 2017
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) mediates the fixation of atmospheric CO2 in photosynthesis by catalyzing the carboxylation of the 5-carbon sugar ribulose-1,5-bisphosphate (RuBP). Rubisco is a remarkably inefficient enzyme, fixing only 2–10 CO2 molecules per second. Efforts to increase crop yields by bioengineering Rubisco remain unsuccessful, owing in part to the complex cellular machinery required for Rubisco biogenesis and metabolic maintenance. The large subunit of Rubisco requires the chaperonin system for folding, and recent studies have shown that assembly of hexadecameric Rubisco is mediated by specific assembly chaperones. Moreover, Rubisco function can be inhibited by a range of sugar-phosphate ligands, including RuBP. Metabolic repair depends on remodeling of Rubisco by the ATP-dependent Rubisco activase and hydrolysis of inhibitory sugar phosphates by specific phosphatases. Here, we review our present understanding of the structure and function o...
Rubiscolytics: fate of Rubisco after its enzymatic function in a cell is terminated
Journal of Experimental Botany, 2007
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the predominant protein in photosynthesizing plant parts and the most abundant protein on earth. Amino acids deriving from its net degradation during senescence are transported to sinks (e.g. developing leaves, fruits). Rubisco catabolism is not controlled only by the overall sink demand. An accumulation of carbohydrates may also accelerate senescence and Rubisco degradation under certain conditions. Amino acids produced by proteolysis are rapidly redistributed in plants with proper source-sink relationships. In leaves of wheat plants with reduced sink capacity (e.g. sink removal, phloem interruption by steam girdling at the leaf base), Rubisco is degraded and free amino acids accumulate. They may be washed out in the rain during late senescence. In leaves of depodded soybeans, Rubisco is degraded and amino acids can be reutilized in these leaves for the synthesis of special vacuolar proteins in the paraveinal mesophyll (vegetative storage proteins). Nitrogen deriving from Rubisco degradation in older (senescing) leaves of annual crops is integrated to some extent again in newly synthesized Rubisco in younger leaves or photosynthesizing tissues of fruits. Finally, a high percentage of this nitrogen is accumulated in protein bodies (storage proteins). At the subcellular level, Rubisco can be degraded in intact chloroplasts. Reactive oxygen species may directly cleave the large subunit or modify it to become more susceptible to proteolysis. A metalloendopeptidase may play an important role in Rubisco degradation within intact chloroplasts. Additionally, the involvement of vacuolar endopeptidase(s) in Rubisco catabo-lism (at least under certain conditions) was postulated by various laboratories.
2013
The lipoxygenase pathway is responsible for the production of oxylipins, which are important compounds for plant defence responses. Jasmonic acid, the final product of the allene oxide synthase/allene oxide cyclase branch of the pathway, regulates wound-induced gene expression. In contrast, C6 aliphatic aldehydes produced via an alternative branch catalysed by hydroperoxide lyase, are themselves toxic to pests and pathogens. Current evidence on the subcellular localization of the lipoxygenase pathway is conflicting, and the regulation of metabolic channelling between the two branches of the pathway is largely unknown. It is shown here that while a 13-lipoxygenase (LOX H3), allene oxide synthase and allene oxide cyclase proteins accumulate upon wounding in potato, a second 13lipoxygenase (LOX H1) and hydroperoxide lyase are present at constant levels in both non-wounded and wounded tissues. Wound-induced accumulation of the jasmonic acid biosynthetic enzymes may thus commit the lipoxygenase pathway to jasmonic acid production in damaged plants. It is shown that all enzymes of the lipoxygenase pathway differentially localize within chloroplasts, and are largely found associated to thylakoid membranes. This differential localization is consistently observed using confocal microscopy of GFP-tagged proteins, chloroplast fractionation, and western blotting, and immunodetection by electron microscopy. While LOX H1 and LOX H3 are localized both in stroma and thylakoids, both allene oxide synthase and hydroperoxide lyase protein localize almost exclusively to thylakoids and are strongly bound to membranes. Allene oxide cyclase is weakly associated with the thylakoid membrane and is also detected in the stroma. Moreover, allene oxide synthase and hydroperoxide lyase are differentially distributed in thylakoids, with hydroperoxide lyase localized almost exclusively to the stromal part, thus closely resembling the localization pattern of LOX H1. It is suggested that, in addition to their differential expression pattern, this segregation underlies the regulation of metabolic fluxes through the alternative branches of the lipoxygenase pathway.
The pyrenoid ultrastructure in Oocystis lacustris Chodat (Chlorophyta, Trebouxiophyceae)
The fine structure of vegetative cells of Oocystis lacustris has been studied with special attention to the ultrastructure of the pyrenoid and its starch sheath. The TEM-investigation showed that the pyrenoid matrix is homogenous, not traversed by thylakoids and the surrounding starch sheath is continuous, horseshoe-shaped or fragmented in 2 starch plates. This starch sheath structure is regarded as a common feature within Oocystis and closely related genera Eremosphaera and Neglectella.