Acclimation of Ribulose Bisphosphate Carboxylase and mRNAs to Changing Irradiance in Adult Tobacco Leaves: Differential Expression in LSU And SSU mRNA (original) (raw)
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Acclimation of Ribulose Bisphosphate Carboxylase and mRNAs
1987
The transfer of Nicotiana tabacum plants grown in low light (60 micromoles quanta per square meter per second) to higher light (360 micromoles quanta per square meter per second) was previously shown to induce adaptive stimulation of photosynthetic capacities. The variations of ribulose bisphosphate carboxylase/oxygenase (RubisCo) expression in mature leaves was examined as a result of this acclimation. Maximum or initial activities increased markedly after lowto highlight transfer with a maximum effect after 2 to 3 days. The higher activity is mainly explained by RubisCo protein synthesis as shown by immunorocket technique. Small subunits of RubisCo (SSU) mRNA relative
Planta, 1988
Mature green leaves from tobacco (Nicotiana tabacum L.) plants were submitted to contrasting light conditions; half of each leaf was shaded (changed from 60 to 25 gmol photons, m-2 9 s-I = L L) and the other half was exposed to higher light (changed from 60 to 360 pmol-m-2s-1 = HL) for 24 h. The activity and quantity of ribulose-l,5-bisphosphate carboxylase (RuBP-Case) were measured during the first 24 h in each leaf region and the variation was compared with that of small subunit (SSU)-and large subunit (LSU)-mRNA contents determined by a hybridot technique. Each leaf half responded separately to the actual light received. The activity of RuBPCase increased progressively in the HL zones and decreased in the LL zones. The RuBPCase-protein content was not significantly modified during the first 24 h but SSU-mRNA content responded very rapidly to the treatment. Within 2 h a significant difference in SSU mRNA appeared between LL and HL zones: at the end of the photoperiod the content in LL zones was approx. 25% of the initial value. The increase in the exposed zone, however, was not significant, indicating that there was a dissymmetry of the response to variation in incident white light. The LSU-mRNA contents from the same leaf extracts were totally unaffected by the light treatment. No day-night variations were noted in either SSU or LSU mRNAs in control plants.
Plant, Cell and Environment, 1994
The effect of nitrogen supply during growth on the contribution of ribulose-l,5-bisphosphate carboxylase-oxygenase (Rubisco; EC 4.1.1.39) to the control of photosynthesis was examined in tobacco (Nicotiana tabacure L.). Transgenic plants transformed with antisense rbcS to produce a series of plants with a progressive decrease in the amount of Rubisco were used to allow the calculation of the flux-control coefficient of Rubisco for photosynthesis (CR). Several points emerged from the data: (i) The strength of Rubisco control of photosynthesis, as measured by CR, was altered by changes in the short-term environmental conditions. Generally, CR was increased in conditions of increased irradiance or decreased CO2. (ii) The amount of Rubisco in wild-type plants was reduced as the nitrogen supply during growth was reduced and this was associated with an increase in CR. This implied that there was a specific reduction in the amount of Rubisco compared with other components of the photosynthetic machinery. (iii) Plants grown with low nitrogen and which had genetically reduced levels of Rubisco had a higher chlorophyll content and a lower chlorophyll a/b ratio than wild-type plants. This indicated that the nitrogen made available by genetically reducing the amount of Rubisco had been re-allocated to other cellular components including light-harvesting and electron-transport proteins. It is argued that there is a "luxury" additional investment of nitrogen into Rubisco in tobacco plants grown in high nitrogen, and that Rubisco can also be considered a nitrogen-store, all be it one Abbreviations: C R=flux control coefficient of Rubisco for photosynthesis; rbcS = gene for the Rubisco small subunit; Rubisco = ribulose-1,5-bisphosphate carboxylase-oxygenase where the opportunity cost of the nitrogen storage is higher than in a non-functional storage protein (i.e. it allows for a slightly higher water-use efficiency and for photosynthesis to respond to temporarily high irradiance).
Plant Physiology, 1990
Phytochrome and the blue ultraviolet-A photoreceptor control light-induced expression of genes encoding the chlorophyll a/b binding protein of photosystem 11 and photosystem I and the genes for the small subunit of the ribulose-1,5-bisphosphate carboxylase in etiolated seedlings of Lycopersicon esculentum (tomato) and Nicotiana tabacum (tobacco). A 'high irradiance response' also controls the induction of these genes. Gernes encoding photosystem 11-and I-associated chlorophyll a/b binding proteins both exhibit a transient rapid increase in expression in response to light pulse or to continuous irradiation. In contrast, genes encoding the small subunit exhibit a continuous increase in expression in response to light. These distinct expression characteristics are shown to reflect differences at the level of transcription. Higher plants have several photoreceptors which detect light quality and intensity. The major photoreceptors are phytochrome (26), which control induction and 'high irradiance responses' (HIR2) (10), a blue/UV-A photoreceptor (27), and a UV-B photoreceptor (34). Studies of expression of nuclear genes encoding CAB, SSU, and CHS proteins revealed that photoregulation of gene expression in higher plants occurs at transcriptional and posttranscriptional levels (33). The dependence ofgene expression on light quality and intensity varies for different genes and different species. For instance, in parsley cell suspension cultures excitation of the UV-B photoreceptor is essential for maximal expression of CHS, while the excitation of the blue/
Plant …, 1992
A complementary DNA for the small subunit of ribulose-1,5bisphosphate carboxylase/oxygenase (Rubisco) was cloned from tobacco (Nicotiana tabacum) and fused in the antisense onentation to the cauliflower mosaic virus 35S promoter. This antisense gene was introduced into the tobacco genome, and the resulting transgenic plants were analyzed to assess the effect of the antisense RNA on Rubisco activity and photosynthesis. The mean content of extractable Rubisco activity from the leaves of 10 antisense plants was 18% of the mean level of activity of control plants. The soluble protein content of the leaves of anti-small subunit plants was reduced by the amount equivalent to the reduction in Rubisco. There was little change in phosphoribulokinase activity, electron transport, and chlorophyll content, indicating that the loss of Rubisco did not affect these other components of photosynthesis. However, there was a significant reduction in carbonic anhydrase activity. The rate of CO2 assimilation measured at 1000 micromoles quanta per square meter per second, 350 microbars C02, and 25°C was reduced by 63% (mean value) in the antisense plants and was limited by Rubisco activity over a wide range of intercellular CO2 partial pressures (pi). In control leaves, Rubisco activity only limited the rate of CO2 assimilation below a pi of 400 microbars. Despite the decrease in photosynthesis, there was no reduction in stomatal conductance in the antisense plants, and the stomata still responded to changes in pi. The unchanged conductance and lower CO2 assimilation resulted in a higher p,, which was reflected in greater carbon isotope discrimination in the leaves of the antisense plants. These results suggest that stomatal function is independent of total leaf Rubisco activity. Studies of CO2 assimilation in leaves of C3 species have focused on the in vivo operation of the bifunctional enzyme Rubisco (EC 4.1.1.39). This enzyme is located in the chloroplast stroma and catalyzes the first steps of the competing photosynthetic carbon reduction (Calvin) and photorespiratory cycles (2). The oxygenase reaction of Rubisco encumbers C3 photosynthesis with the phenomenon of photorespiration, which wastes both reduced carbon and energy. Rubisco is a slow catalyst, and C3 plants must devote up to one-half of 'G.S.H. was supported by a National Research Fellowship, and J.R.E. was supported by a Queen Elizabeth II Fellowship.
Planta, 1993
The effect of nitrogen supply during growth on the contribution of ribulose-l,5-bisphosphate carboxylase-oxygenase (Rubisco; EC 4.1.1.39) to the control of photosynthesis was examined in tobacco (Nicotiana tabacure L.). Transgenic plants transformed with antisense rbcS to produce a series of plants with a progressive decrease in the amount of Rubisco were used to allow the calculation of the flux-control coefficient of Rubisco for photosynthesis (CR). Several points emerged from the data: (i) The strength of Rubisco control of photosynthesis, as measured by CR, was altered by changes in the short-term environmental conditions. Generally, CR was increased in conditions of increased irradiance or decreased CO2. (ii) The amount of Rubisco in wild-type plants was reduced as the nitrogen supply during growth was reduced and this was associated with an increase in CR. This implied that there was a specific reduction in the amount of Rubisco compared with other components of the photosynthetic machinery. (iii) Plants grown with low nitrogen and which had genetically reduced levels of Rubisco had a higher chlorophyll content and a lower chlorophyll a/b ratio than wild-type plants. This indicated that the nitrogen made available by genetically reducing the amount of Rubisco had been re-allocated to other cellular components including light-harvesting and electron-transport proteins. It is argued that there is a "luxury" additional investment of nitrogen into Rubisco in tobacco plants grown in high nitrogen, and that Rubisco can also be considered a nitrogen-store, all be it one Abbreviations: C R=flux control coefficient of Rubisco for photosynthesis; rbcS = gene for the Rubisco small subunit; Rubisco = ribulose-1,5-bisphosphate carboxylase-oxygenase where the opportunity cost of the nitrogen storage is higher than in a non-functional storage protein (i.e. it allows for a slightly higher water-use efficiency and for photosynthesis to respond to temporarily high irradiance).
Journal of Biological Chemistry, 1991
Two genes encode Rbu-Pz-carboxylase activase in barley (RcaA and RcaB): RcaA encodes polypeptides of 46 and 42 kDa, which are generated by the alternatively spliced RcaAl and RcaA2 mRNAs, respectively; RcaB encodes a 42-kDa polypeptide (Rundle, S. J., and Zielinski, R. E. (1991) J. Biol. Chem. 266,[4677][4678][4679][4680][4681][4682][4683][4684][4685]. In the cellular differentiation gradient of the first leaf of barley, the three Rca mRNAs accumulate differentially. RcaAl and A2 mRNAs accumulate predominantly in the mature, most photosynthetically active regions of the leaf in a pattern that parallels accumulation of total Rbu-Pz-carboxylase activase protein. However, the kinetics of accumulation of RcaA1 and RcaA2 mRNA differ slightly, indicating that either changes in RcaA pre-mRNA splicing or mRNA turnover occur during development. RcaB mRNA, in contrast, accumulates in the youngest and oldest cell populations at the base and tip of the leaf, respectively. In the mid-region of the leaf, the difference in accumulation between RcaA and RcaB mRNAs is largely attributable to differences in the rates of transcription of the two Rca genes. In this region of the leaf, the three Rca mRNAs accumulate differentially throughout the course of the diurnal cycle. Steady state levels of the three Rca mRNA species increase in parallel in response to increasing irradiance; these changes were accompanied by increased Rbu-Pz-carboxylase activase protein accumulation.
Increased heat sensitivity of photosynthesis in tobacco plants with reduced Rubisco activase
Photosynthesis research, 2001
High temperature inhibits photosynthesis by several mechanisms including deactivation of Rubisco. The inhibition of photosynthesis by high temperature and its relationship to Rubisco deactivation was studied using tobacco (Nicotiana tabaccum L. cv W38) transformed with a Rubisco activase gene inserted in the antisense orientation and untransformed controls. High temperature (42 degrees C) reduced photosynthesis in both lines of plants. However, photosynthesis recovered nearly completely in wild-type plants and very little in plants lacking Rubisco activase. The F(0)' level of chlorophyll fluorescence decreased and q(N) increased in the control plants during heating. In the antisense plants, q(N) was always high and F(0)' increased slightly during heat stress. NADP-malate dehydrogenase activation was unaffected by heat stress in control plants but was increased in the transgenic plants, consistent with a high redox status in the chloroplast. In wild-type plants, the inhibitio...
Plant Physiology, 1980
Transgenic tobacco (Nicofiana fabacum L. cv W38) plants with an antisense gene directed against the mRNA of ribulose-1,sbiphosphate carboxylase/oxygenase (Rubisco) activase grew more slowly than wild-type plants in a C0,-enriched atmosphere, but eventually attained the same height and number of leaves. Compared with the wild type, the anti-activase plants had reduced CO, assimilation rates, normal contents of chlorophyll and soluble leaf protein, and much higher Rubisco contents, particularly in older leaves. Activase deficiency greatly delayed the usual developmental decline in Rubisco content seen in wild-type leaves. This effect was much less obvious in another transgenic tobacco with an antisense gene directed against chloroplast-located glyceraldehyde-3phosphate dehydrogenase, which also had reduced photosynthetic rates and delayed development. Although Rubisco carbamylation was reduced in the anti-activase plants, the reduction was not sufficient to explain the reduced photosynthetic rate of older antiactivase leaves. Instead, up to a 10-fold reduction in the catalytic turnover rate of carbamylated Rubisco in vivo appeared to be the main cause. Slower catalytic turnover by carbamylated Rubisco was particularly obvious in high-C0,-grown leaves but was also detectable in air-grown leaves. Rubisco activity measured immediately after rapid extraction of anti-activase leaves was not much less than that predicted from its degree of carbamylation, ruling out slow release of an inhibitor from carbamylated sites as a major cause of the phenomenon. Nor could substrate scarcity or product inhibition account for the impairment. We conclude that activase must have a role in vivo, direct or indirect, in promoting the activity of carbamylated Rubisco in addition to its role in promoting carbamylation. Rubisco (EC 4.1.1.39) is a key regulatory enzyme of photosynthetic CO, assimilation. To become catalytically competent, Rubisco must be activated through carbamylation of an active-site Lys residue to allow binding of the catalytically essential divalent metal ion (for review, see Andrews and Lorimer, 1987; Hartman and Harpel, 1994). The carbamylation process can be modulated by a variety of
Chlorophyll b is synthesized by the oxidation of a methyl group on the B ring of a tetrapyrrole molecule to a formyl group by chlorophyllide a oxygenase (CAO). The full-length CAO from Arabidopsis (Arabidopsis thaliana) was overexpressed in tobacco (Nicotiana tabacum) that grows well at light intensities much higher than those tolerated by Arabidopsis. This resulted in an increased synthesis of glutamate semialdehyde, 5-aminolevulinic acid, magnesium-porphyrins, and chlorophylls. Overexpression of CAO resulted in increased chlorophyll b synthesis and a decreased chlorophyll a/b ratio in low light grown as well as high light-grown tobacco plants; this effect, however, was more pronounced in high light. The increased potential of the protochlorophyllide oxidoreductase activity and chlorophyll biosynthesis compensated for the usual loss of chlorophylls in high light. Increased chlorophyll b synthesis in CAO-overexpressed plants was accompanied not only by an increased abundance of light-harvesting chlorophyll proteins but also of other proteins of the electron transport chain, which led to an increase in the capture of light as well as enhanced (40%–80%) electron transport rates of photosystems I and II at both limiting and saturating light intensities. Although the quantum yield of carbon dioxide fixation remained unchanged, the lightsaturated photosynthetic carbon assimilation, starch content, and dry matter accumulation increased in CAO-overexpressed plants grown in both low- and high-light regimes. These results demonstrate that controlled up-regulation of chlorophyll b biosynthesis comodulates the expression of several thylakoid membrane proteins that increase both the antenna size and the electron transport rates and enhance carbon dioxide assimilation, starch content, and dry matter accumulation.