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First published online May 25, 2007; 10.1104/pp.107.099762 Plant Physiology 144:1305-1315 (2007) © 2007 American Society of Plant Biologists OPEN ACCESS ARTICLE
Ethylene Insensitivity Results in Down-Regulation of Rubisco Expression and Photosynthetic Capacity in Tobacco1,[OA]Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, 3508–TB Utrecht, The Netherlands
Little is known about the effect of hormones on the photosynthetic process. Therefore, we studied Rubisco content and expression along with gas exchange parameters in transgenic tobacco (Nicotiana tabacum) plants that are not able to sense ethylene. We also tested for a possible interaction between ethylene insensitivity, abscisic acid (ABA), and sugar feedback on photosynthesis. We measured Rubisco content in seedlings grown in agar with or without added sugar and fluridone, and Rubisco expression in hydroponically grown vegetative plants grown at low and high CO2. Furthermore, we analyzed gas exchange and the photosynthetic machinery of transformants and wild-type plants grown under standard conditions. In the presence of exogenous glucose (Glc), agar-grown seedlings of the ethylene-insensitive genotype had lower amounts of Rubisco per unit leaf area than the wild type. No differences in Rubisco content were found between ethylene-insensitive and wild-type seedlings treated with fluridone, suggesting that inhibition of ABA production nullified the effect of Glc application. When larger, vegetative plants were grown at different atmospheric CO2 concentrations, a negative correlation was found between Glc concentration in the leaves and Rubisco gene expression, with stronger repression by high Glc concentrations in ethylene-insensitive plants. Ethylene insensitivity resulted in plants with comparable fractions of nitrogen invested in light harvesting, but lower amounts in electron transport and Rubisco. Consequently, photosynthetic capacity of the insensitive genotype was clearly lower compared with the wild type. We conclude that the inability to perceive ethylene results in increased sensitivity to Glc, which may be mediated by a higher ABA concentration. This increased sensitivity to endogenous Glc has negative consequences for Rubisco content and photosynthetic capacity of these plants.
There is an impressive body of knowledge on the process of photosynthesis, ranging from the first femtoseconds in the excitation of electrons up to ontogenetic trends over the lifespan of trees. We can very accurately predict how light and CO2 availability affect photosynthesis in the short term (Von Caemmerer, 2000  ) and have good insight into the longer term effects of a plant's environment on the composition of the photosynthetic machinery. Plants grown at low irradiance, for example, maximize light interception by increasing allocation of nitrogen to chlorophyll protein complexes relative to Rubisco and other Calvin cycle enzymes (Hikosaka and Terashima, 1995; Evans and Poorter, 2001; Oguchi et al., 2003, Pons and Anten, 2004). Although there is less insight into the exact mechanisms that determine the composition of the photosynthetic apparatus, we start to become aware that the redox state of the plastoquinone pool may be a regulating factor determining transcription of a range of chloroplastic and nuclear genes (Foyer and Noctor, 2003; Pfannschmidt, 2003). Photosynthetic activity may also be regulated in a feedback manner by carbohydrates (Paul and Pellny, 2003; see also Fig. 1
for a schematic representation of the interactions discussed here). Long-term growth at elevated CO2, for example, generally increases soluble sugar concentration in leaves (Van Oosten and Besford, 1994; Cheng et al., 1998). Such leaves often have lower Rubisco transcript levels and decreased photosynthetic capacity (Krapp et al., 1993; Van Oosten and Besford, 1994, 1995; Cheng et al., 1998). Additional proof of down-regulation of the photosynthetic machinery by sugars came from cold-girdling petioles to prevent sugar export out of the leaf or by exogenously feeding sugar to algae or cell cultures. Also, in these cases, genes related to photosynthesis were repressed, including those for chlorophyll-binding protein and Rubisco (Sheen, 1990; Krapp and Stitt, 1995; Smeekens, 2000). The regulation of photosynthetic gene expression by sugars is thought to be mediated by the enzyme hexokinase, a sensor of endogenous Glc levels (Jang et al., 1997; Dai et al., 1999; Moore et al., 2003). However, a complete understanding of photosynthetic acclimation in response to high CO2 or sugars is still lacking. For example, Stitt and Krapp (1999) outline several problems with the simple feedback response presented above and suggest strong interaction of sugar sensing with the plant's nitrogen status.
Other compounds that have a strong influence on plant development are the phytohormones. However, apart from the effect of abscisic acid (ABA) on stomatal conductance, hardly any attention is paid to the interaction between hormones and photosynthesis in fully developed, nonsenescing leaves. From studies on seedling development, we know that plant hormones modulate sugar sensing (Pego et al., 2000 ; Gazzarrini and McCourt, 2001; Loreti et al., 2001; Gibson, 2004). Research on Arabidopsis (Arabidopsis thaliana) shows that high ABA levels enhance the sensitivity of seedling growth to Glc (León and Sheen, 2003). More related to the process of photosynthesis is the recent finding that a light-responsive element of a Rubisco promoter responds negatively to both ABA and sugars (Acevedo-Hernàndez et al., 2005). Ethylene also plays a role in sugar feedback. Seedlings grown at high sugar concentrations show impaired development and can even remain chlorotic due to hampered chloroplast development (To et al., 2003). This developmental arrest by high sugar levels can be overcome by applying the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (Zhou et al., 1998). In line with these results, ethylene-insensitive seedlings are found to be more strongly inhibited by Glc in their development than wild-type plants (Zhou et al., 1998; León and Sheen, 2003). Although these findings clearly indicate cross talk between ABA, ethylene, and sugar signaling for small seedlings grown on agar in the presence of high Glc concentrations, it has not been shown that an ethylene-induced difference in sugar sensitivity affects Rubisco expression in seedlings. It is also not clear whether such cross talk is physiologically relevant in well-developed vegetative plants that are not exposed to large amounts of externally applied Glc (Gazzarrini and McCourt, 2001).
Based on the observed cross talk between ethylene and sugar signaling in seedling development, we hypothesize that ethylene reduces the negative feedback of carbohydrates on photosynthetic gene expression. This would imply that plants that are unable to sense ethylene would exhibit a lower rate of photosynthesis as a result of increased sensitivity to sugars. Previously, we examined the growth of ethylene-insensitive plants containing a dominant-negative mutant allele of the Arabidopsis ethylene receptor gene ETHYLENE RESPONSE1 (ETR1; Tholen et al., 2004
Seedling Experiment
First, we tested whether Rubisco expression of ethylene-insensitive tobacco is more sensitive to high Glc levels than wild-type plants. To this end, we grew seedlings on agar in the presence and absence of Glc and analyzed the Rubisco content per unit leaf area. Without the application of Glc, the amount of Rubisco protein per unit leaf area was not significantly different between wild-type and ethylene-insensitive seedlings (Fig. 2
). When seedlings were grown in the presence of Glc, a 16% reduction in Rubisco content per unit area was observed in wild-type plants. The reduction in the ethylene-insensitive plants was twice as large (30%; P < 0.05). To check whether ABA plays a role in sensitivity to Glc, we also examined the effect of the ABA production inhibitor fluridone. Pretreatment with this inhibitor resulted in an equal level of Rubisco for Glc and non-Glc-treated seedlings. As a control for possible osmotic effects, we tested the effect of the Glc analog 3-O-methyl-Glc (3-OMG), which is not perceived as Glc by hexokinase, making it a suitable osmotic control for this experiment (Cortès et al., 2003
CO2 Experiment We subsequently tested whether much larger, but still vegetative ethylene-insensitive tobacco plants grown in hydroponics, showed a similar type of hypersensitivity to sugars as agar-grown seedlings. This was more complicated because we were not able to grow large plants for longer times at high exogenous sugar concentrations without considerable microbial infections. To show a possible involvement of ethylene insensitivity in the down-regulation of Rubisco expression at high endogenous Glc levels, we manipulated the internal sugar content by growing 21-d-old plants for 9 d at two different CO2 concentrations (400 and 800 µmol mol–1). Endogenous Glc levels ranged from 1 to 5 mg g–1 dry matter (Fig. 3 ). Because the water content differed very little between the two genotypes (Table I ), the variation in Glc concentration was similar when expressed on a fresh weight basis (data not shown). The outcome of this experiment was a negative correlation between leaf Glc concentration and mRNA level of the gene encoding for the small subunit of Rubisco (RBCS). At very low Glc levels, differences between the two genotypes were small, but at higher Glc concentrations, the ethylene-insensitive plants were progressively inhibited more strongly in RBCS mRNA levels than wild-type plants (Fig. 3). We therefore conclude that well-developed, vegetative plants of the ethylene-insensitive genotype are more sensitive to Glc than wild-type plants with respect to down-regulation of RBCS transcript levels.
Photosynthesis of Vegetative Plants Having found a difference in Glc sensitivity for the expression of Rubisco between the two tobacco genotypes, we subsequently determined what consequences ethylene insensitivity has for the chemical composition of the leaves and functioning of the photosynthetic apparatus. We focused on leaf 6 of 30-d-old plants grown in hydroponics at a light intensity of 200 µmol m–2 s–1. Water content and the leaf area per unit dry mass (SLA) were not different between the two genotypes (Table I). There was a 42% lower Rubisco and a 21% lower cytochrome f content per unit area in the ethylene-insensitive genotype (Table I), and also a much lower level of RBCS transcripts (Fig. 4 ). We could exclude the possibility that ethylene-insensitive plants showed stronger down-regulation of Rubisco as a result of higher endogenous Glc levels because there were no significant differences in leaf Glc concentrations between the two genotypes (Table I).
We already showed that blocking ABA synthesis by adding fluridone could alleviate the negative effect of Glc on Rubisco expression in ethylene-insensitive tobacco seedlings (Fig. 2). However, application of fluridone to plants inhibits carotenoid synthesis and irreversible damage may occur to the photosynthetic machinery if plants are grown at higher light conditions for longer periods (Gamble and Mullet, 1986 , and refs. therein). Therefore, instead of lowering the ABA concentration of the leaves, we determined the actual ABA concentrations present in the sixth leaf of the two tobacco genotypes. The ethylene-insensitive plants had a 54% higher ABA concentration than the wild-type controls (Table I). This observation confirms the negative relationship between ethylene sensing, on the one hand, and ABA on the other. Total organic nitrogen content per unit leaf area was slightly lower in the insensitive plants. Expression of a transcript encoding a chlorophyll a/b-binding protein (CAB21; Fig. 3) was similar and so was the chlorophyll content per unit area. The chlorophyll a/b ratio was lower in ethylene-insensitive plants. The investment of nitrogen in light harvesting was very similar between the genotypes, but ethylene-insensitive plants had a somewhat lower investment of nitrogen in electron transport and, as mentioned above, a clearly lower investment in Rubisco. The chlorophyll to Rubisco ratio, therefore, is considerably higher (Table I).
Gas exchange parameters of the sixth leaf were measured at growth irradiance (200 µmol m–2 s–1), as well as at saturating light levels (1,600 µmol m–2 s–1). At growth light conditions, there was a marginal and nonsignificantly lower rate of photosynthesis per unit area (Agrowth) in the transformed plants (Table II
). Stomatal conductance (gs) and the intercellular CO2 concentration, as represented by the Ci/Ca ratio, were clearly higher in ethylene-insensitive plants. This compensated, in part, for the effect of a lower Rubisco content. When photosynthesis of ethylene-insensitive plants was calculated at the same Ci/Ca ratio as the wild-type plants, using the method of Evans (1994)
At saturating light levels, the rate of photosynthesis (Amax) in ethylene-insensitive plants was 22% lower compared with wild-type plants (Table III ), even though the Ci/Ca ratio was higher. We found similar results in an independent ethylene-insensitive transgenic line of tobacco (28% lower Amax in line Tetr-20 [Knoester et al., 1998 ]; data not shown). Because Rubisco protein content was lower in the ethylene-insensitive genotype (Table I), their lower Amax is likely to be the result of a decrease in carboxylation capacity; that is, the maximal in vivo activity of Rubisco. Therefore, we examined the CO2 response curve of photosynthesis at saturating light levels (Fig. 5
). The rate of photosynthesis per unit leaf area was found to be less in ethylene-insensitive tobacco plants, especially at a higher CO2 partial pressure (Ci). Using the Farquhar and von Caemmerer (1982) model, these data allowed us to calculate carboxylation capacity (Vcmax) and electron transport capacity (Jmax). Both Vcmax and Jmax were lower in ethylene-insensitive plants compared with wild-type controls, with Vcmax slightly more reduced than Jmax, as illustrated by the higher Jmax/Vcmax ratio (Table III). Based on expression as well as gas exchange data, we conclude that Rubisco and cytochrome f content, and as a consequence photosynthetic capacity, are down-regulated in ethylene-insensitive plants.
Rubisco Content of Tobacco Plants Is Down-Regulated by Glc
In the first experiment with agar-grown seedlings, we added different Glc levels to the medium; in the second, we induced different sugar levels in hydroponically grown plants by exposing them to different concentrations of atmospheric CO2. In both cases, the sugar concentration correlated negatively with the Rubisco content or the RBCS transcript levels (Figs. 2 and 3). In addition, leaf growth was impaired in the seedlings if more than 0.3 M Glc was added to the growth medium (data not shown). This is consistent with the finding for Arabidopsis and other species that intermediate levels of sugars inhibit Rubisco expression (Van Oosten and Besford, 1994
In both the experiment with Glc addition and the one with elevated CO2, ethylene-insensitive plants showed stronger down-regulation of Rubisco than wild-type plants (Figs. 2 and 3). In addition, when high concentrations (>0.3 M) of Glc were added to the medium, seedling growth of the ethylene-insensitive seedlings was more strongly impaired than that of the wild type, in accordance with observations of Zhou et al. (1998) Also, in well-developed vegetative plants, Rubisco gene expression (Figs. 3 and 4) and Rubisco protein content (Table I) was lower in the ethylene-insensitive genotype. There was no significant difference between the two genotypes in the Glc concentration of the leaves (Table I), indicating that lower Rubisco expression is not a result of a difference in Glc concentration. However, manipulating endogenous Glc levels by growing plants at two different CO2 concentrations showed that Rubisco gene expression decreases with increasing endogenous Glc levels, and this occurred to a greater degree in ethylene-insensitive plants (Fig. 3). These findings indicate that the inability to perceive ethylene results in a lower level of Rubisco expression, not only in seedlings (Fig. 2), but also in later stages of development.
Previously we showed that, at the whole-plant level and under growth light irradiance, the rate of photosynthesis per unit leaf area is lower in ethylene-insensitive genotypes of Arabidopsis and tobacco (Tholen et al., 2004
The decrease in photosynthetic capacity was associated with a strong reduction of Rubisco protein content (Table I) and with a 76% lower level of RBCS gene expression (Fig. 4). All these parameters were measured at the same time for a leaf approaching full expansion. Total Rubisco content of a leaf is the net result of synthesis and turnover throughout a leaf's life. We are not aware of any studies examining this in dicots, but in the grasses investigated synthesis takes place until the leaf reaches its final length (Mae et al., 1983
It should be noted that we found a larger decrease in Rubisco content (42%; Table I) than in the light-saturated rate of photosynthesis (22%; Table III) or the rate of photosynthesis under growth light conditions (5%; Table II). These data are in line with data on flux control coefficients (FCC) for Rubisco compiled by Stitt (1996)
The reduction in Rubisco protein content may well explain the lower total in vivo carboxylation activity (Vcmax) of Rubisco in ethylene-insensitive plants. The lower Vcmax is consistent with earlier work by Grbi
In Arabidopsis, external application of Suc or Glc results in a decreased level of chlorophyll a/b-binding protein mRNA (Martin et al., 2002
The ethylene-insensitive genotype showed higher stomatal conductance at both growth and saturating light conditions (Tables II and III). We found similar differences when measurements were made at the whole-plant level (Tholen et al., 2004
When responses of plants to stress such as low light or low nitrogen nutrition are considered, photosynthetic activity and capacity generally scale positively with stomatal conductance (Wong et al., 1979
Temporary treatment of leaves of adult plants with high ethylene concentrations generally causes chlorophyll loss and senescence (Bleecker et al., 1988
Rubisco expression is reduced in ethylene-insensitive tobacco seedlings grown in the presence of exogenous Glc and this is likely to be mediated by ABA. High endogenous Glc concentration results in stronger repression of Rubisco mRNA levels in ethylene-insensitive plants. Rubisco protein content and consequently carboxylation capacity were down-regulated in those plants, but chlorophyll content was not affected. These findings indicate that, in vegetative tobacco plants, ethylene plays a regulating role by suppressing Glc-mediated inhibition of photosynthesis.
Seedling Experiment
Seeds of tobacco (Nicotiana tabacum ‘Samsun NN’) and transgenic lines (Tetr-18, Tetr-20) expressing the mutant allele etr1-1 from Arabidopsis (Arabidopsis thaliana; Knoester et al., 1998
Seeds were surface sterilized and subsequently incubated on petri dishes containing 0.6% plant agar and modified Hoagland solution with 2 mM nitrate (Poorter and Remkes, 1990
Seeds were germinated on sand in trays covered with a glass plate and watered with a modified Hoagland solution containing 2 mM nitrate (Poorter and Remkes, 1990
Individual soluble sugars were measured according to Sweeley et al. (1963)
ABA extractions were done as described in Benschop et al. (2005)
Seeds were germinated on sand as described above and transferred at day 14 to hydroponics. At day 30 after emergence, when plants had a total leaf area of approximately 140 cm2, the sixth leaf was used to determine photosynthetic characteristics. Water and CO2 exchange were measured using an infrared gas analyzer (LI-6262; LI-COR) in an open system at different CO2 and light intensities. Leaf temperature was maintained at 20°C and relative humidity at 70%. Details of this system are described in Pons and Welschen (2002)
Leaf area was measured with a LI-COR LI-3100 leaf area meter. Small discs (Ø = 25 mm) were cut from the leaves and frozen in liquid nitrogen for ABA and transcript analysis. The rest of the material was freeze dried for 48 h. Nitrogen concentrations of the freeze-dried material were determined with a CN analyzer (model 1106; Carlo Erba). Nitrate content was determined using a colorimetric assay (Cataldo et al., 1975
For protein extraction, frozen leaf material was ground in Eppendorf tubes with a bead beater and 0.7 mL extraction buffer was added containing 100 mM bicine, pH 7.8, 20 mM MgCl2, 150 µM NaHCO3, 1 mM EDTA, 4 mM amino-n-caproic acid, 0.8 mM benzamidine, 20% (v/v) glycerol, 5 µM dithiothreitol, 0.5% (v/v) Triton X-100, and 3% (w/v) polyvinylpolypyrrolidone. The samples were centrifuged and the pellet discarded. Salt solutions were added to the supernatant to create a final concentration of 10 mM NaHCO3 and 20 mM MgCl2; 17% SDS-PAGE was used to separate the proteins. The amount of Rubisco large and small subunit was determined as previously described (Westbeek et al., 1999
For determination of cytochrome f content, frozen leaf discs (10.5 cm2 per leaf) were homogenized with 1.8 mL extraction buffer containing 50 mM sodium-phosphate buffer (pH 6.5), 0.33 M mannitol, 1 mM MgCl2, 2 mM EDTA, 1 mM dithiothreitol, 0.5 mM phenylmethylsulfonyl fluoride, and 0.5% polyvinylpyrrolidone (w/v). Samples were centrifuged at 10,000g and the supernatant was discarded. The pellet was resuspended in the same extraction buffer and centrifuged again. The supernatant was discarded again and the pellet was resuspended in 1.5 mL extraction buffer with 1% Triton X-100. After centrifugation for 1 min at 1,000g, the supernatant was transferred to a new tube. This last step was repeated once. Cytochrome f content was estimated on the resulting supernatant from the difference between the hydroquinone-reduced and ferricyanide-oxidized absorption spectrum of the thylakoid membranes according to Bendall et al. (1971) For RNA extraction, frozen samples were ground in Eppendorf tubes and RNA was extracted using the mini RNeasy kit (Qiagen). The extracted RNA was treated with DNase using DNA-free DNase treatment and removal reagents (Ambion). cDNA was synthesized in triplicate from approximately 2 µg RNA using 1 unit of SuperScript III reverse transcriptase (Invitrogen) and oligo(dT) primers (Roche Diagnostics). Samples were checked on agarose gels for genomic DNA contaminations after PCR with RBCS primers flanking an intron sequence (5'-CATGGTTGCACCTTTCACTG-3' and 5'-TCCAAGCAAGGAACCCATC-3'). Real-time quantitative reverse transcription-PCR was performed on each cDNA sample with a Bio-Rad iCycler with SYBR-Green Supermix (Bio-Rad) using standard cycle temperatures. Primers used were 5'-TGGCCACCAATTAACAAGAA-3', 5'-AAGCAAGGAACCCATCCA-3' for RBCS, 5'-GGCTGGATCCCAAATCTTTA-3', 5'-ACGGCTCCCATCAAGATAAC-3' for CAB21. As control genes, both ribosomal L25 (5'-ATTGTGGACATCAAGGCTGA-3' and 5'-GCAACGTCCAAAGCATCATA-3') and a tobacco actin (Act66, 5'-CACTAGTGCTGAACGGGAAA-3' and 5'-ACCTGCCCATCTGGTAACTC-3') were used. Melt curves obtained after PCR confirmed the amplification of single products.
All primers were designed using the primer3 program (http://primer3.sourceforge.net/). Rubisco primers were designed based on homologous areas of the known RBCS genes in tobacco (Jamet et al., 1991
The model of Farquhar and von Caemmerer (1982)
Results were analyzed using the R statistical software package (R Development Core Team, 2003
We thank Rob Welschen and Petra Burger for technical assistance, Robert Vreeburg for his advice on protein extraction, Maarten Terlou for the optical analysis of SDS-PAGE gels, Joris Benschop for help with ABA measurements, Wataru Yamori for explaining the cytochrome f measurement technique, and Henri Groeneveld and Yvonne de Jong-van Berkel for the carbohydrate measurements. Ichiro Terashima, John Evans, Mike Jackson, Sjef Smeekens, Kees van Loon, and Ronald Pierik made helpful comments on earlier versions of this manuscript. Received March 19, 2007; accepted April 29, 2007; published May 25, 2007.
1 This work was supported by the Earth and Life Sciences Foundation, which is subsidized by the Netherlands Organization for Scientific Research (NWO; grant no. 805.33.463), and by NWO PIONIER grant number 800.84.470 to L.A.C.J.V. 
2 Present address: Department of Biological Science, Graduate School of Science, University of Tokyo, 7–3–1 Hongo, Bunkyo-ku, Tokyo, Japan. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Hendrik Poorter (h.poorter{at}uu.nl).
[OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.107.099762 * Corresponding author; e-mail h.poorter{at}uu.nl; fax 31–30–251–8366.
Abeles FB, Morgan PW, Saltveit ME (1992) Ethylene in Plant Biology. Academic Press, New York Acevedo-Hernàndez G, León P, Herrera-Estrella L (2005) Sugar and ABA responsiveness of a minimal RBCS light-responsive unit is mediated by direct binding of ABI4. Plant J 43: 506–519[CrossRef][ISI][Medline] Bendall DS, Davenport HE, Hill R (1971) Cytochrome components in chloroplasts of the higher plants. Methods Enzymol 23: 327–344 Benschop JJ, Jackson MB, Guhl K, Vreeburg RAM, Croker SJ, Peeters AJM, Voesenek LACJ (2005) Contrasting interactions between ethylene and abscisic acid in Rumex species differing in submergence tolerance. Plant J 44: 756–768[ISI][Medline] Bleecker AB, Estelle MA, Somerville C, Kende H (1988) Insensitivity to ethylene conferred by a dominant mutation in Arabidopsis thaliana. Science 141: 1086–1087 Bradford MM (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 72: 248–254[CrossRef][ISI][Medline] Cataldo DA, Haroon M, Schrader LF, Youngs VL (1975) Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid. Commun Soil Sci Plant Anal 6: 71–80[ISI] Cheng SH, Moore BD, Seemann JR (1998) Effects of short and long term elevated CO2 on the expression of ribulose-1,5-bisphosphate carboxylase/oxygenase genes and carbohydrate accumulation in leaves of Arabidopsis thaliana (L.) Heynh. Plant Physiol 116: 715–723 Cheng WH, Endo A, Zhou L, Penney J, Chen HC, Arroyo A, León P, Nambara E, Asami T, Seo M, et al (2002) A unique short-chain dehydrogenase/reductase in Arabidopsis glucose signaling and abscisic acid biosynthesis and functions. Plant Cell 14: 2723–2743 Cortès S, Gromova M, Evrard A, Roby C, Heyraud A, Rolin DB, Raymond P, Brouquisselant RM (2003) In plants, 3-O-methylglucose is phosphorylated by hexokinase but not perceived as a sugar. Plant Physiol 131: 824–837 Dai N, Schaffer A, Petreikov M, Shahak Y, Giller Y, Ratner K, Levine A, Granot D (1999) Overexpression of Arabidopsis hexokinase in tomato plants inhibits growth, reduces photosynthesis, and induces rapid senescence. Plant Cell 11: 1253–1266 Evans JR (1989) Photosynthesis and nitrogen relationships in leaves of C-3 plants. Oecologia 78: 9–19[CrossRef][ISI] Evans JR (1994) The relationship between CO2 transfer conductance and leaf anatomy in transgenic tobacco with a reduced content of Rubisco. Aust J Plant Physiol 21: 475–495[ISI] Evans JR, Poorter H (2001) Photosynthetic acclimation of plants to growth irradiance: the relative importance of SLA and nitrogen partitioning in maximizing carbon gain. Plant Cell Environ 24: 755–767[CrossRef] Evans JR, Seemann JR (1989) The allocation of protein nitrogen in the photosynthetic apparatus: costs, consequences, and control. In WR Briggs, ed, Photosynthesis. Liss, New York, pp 183–205 Evans JR, Terashima I (1987). Effects of nitrogen nutrition on electron transport components and photosynthesis in spinach. Aust J Plant Pysiol 14: 59–68 Farquhar GD, von Caemmerer S (1982) Modeling of photosynthetic response to environmental conditions. In OL Lange, PS Nobel, CB Osmond, H Ziegler, eds, Encyclopedia of Plant Physiology, NS, Vol. 12B: Physiological Plant Ecology II. Springer-Verlag, New York, pp 549–587 Foyer CH, Noctor G (2003) Redox sensing and signalling associated with reactive oxygen in chloroplasts, peroxisomes and mitochondria. Physiol Plant 119: 355–364[CrossRef] Gamble PE, Mullet JF (1986) Inhibition of carotenoid accumulation and abscisic acid biosynthesis in fluridone-treated dark-grown barley. Eur J Biochem. 160: 117–120[ISI][Medline] Gazzarrini S, McCourt P (2001) Genetic interactions between ABA, ethylene and sugar signaling pathways. Curr Opin Plant Biol 4: 387–391[CrossRef][ISI][Medline] Ghassemian M, Nambara E, Cutler S, Kawaide H, Kamiya Y, McCourt P (2000) Regulation of abscisic acid signaling by the ethylene response pathway in Arabidopsis. Plant Cell 12: 1117–1126 Gibson SI (2004) Sugar and phytohormone response pathways: navigating a signaling network. J Exp Bot 55: 253–264 Grbi Hikosaka K, Terashima I (1995) A model of the acclimation of photosynthesis in the leaves of C3 plants to sun and shade with respect to nitrogen use. Plant Cell Environ 18: 605–618[CrossRef] Hoffmann-Benning S, Kende H (1992) On the role of abscisic-acid and gibberellin in the regulation of growth in rice. Plant Physiol 99: 1156–1161 Holloway PJ, Maclean DJ, Scott KJ (1983) Rate-limiting steps of electron transport in chloroplasts during ontogeny and senescence of barley. Plant Physiol 72: 795–801 Inada N, Sakai A, Kuroiwa H, Kuroiwa T (1998) Three-dimensional analysis of the senescence program in rice (Oryza sativa L.) coleoptiles. Planta 205: 153–164[CrossRef][ISI][Medline] Irving LJ, Robinson D (2006) A dynamic model of Rubisco turnover in cereal leaves. New Phytol 169: 493–504[CrossRef][ISI][Medline] Jamet E, Parmentier Y, Durr A, Fleck J (1991) Genes encoding the small subunit of RUBISCO belong to two highly conserved subfamilies in Nicotianeae. J Mol Evol 33: 226–236[CrossRef][ISI][Medline] Jang JC, León P, Zhou L, Sheen J (1997) Hexokinase as sugar sensor in higher plants. Plant Cell 9: 5–19[Medline] Knoester M, van Loon L, van den Heuvel J, Hennig J, Bol J, Linthorst H (1998) Ethylene-insensitive tobacco lacks nonhost resistance against soil-borne fungi. Proc Natl Acad Sci USA 95: 1933–1937 Kobayashi H, Saka H (2000) Relationship between ethylene evolution and sucrose content in excised leaf blades of rice. Plant Prod Sci 3: 398–403 Krapp A, Hofmann B, Schafer C, Stitt M (1993) Regulation of the expression of rbcS and other photosynthetic genes by carbohydrates: a mechanism for the sink regulation of photosynthesis? Plant J 3: 817–828[CrossRef][ISI] Krapp A, Stitt M (1995) An evaluation of direct and indirect mechanisms for the "sink-regulation" of photosynthesis in spinach: changes in gas exchange, carbohydrates, metabolites, enzyme activities and steady-state transcript levels after cold-girdling source leaves. Planta 195: 313–323[ISI] Lake JA (2004). Gas exchange: new challenges with Arabidopsis. New Phytol 162: 1–3[CrossRef][ISI] LeNoble ME, Spollen W., Sharp RE (2004) Maintenance of shoot growth by endogenous ABA: genetic assessment of the involvement of ethylene suppression. J Exp Bot 55: 237–245 León P, Sheen J (2003). Sugar and hormone connections. Trends Plant Sci 8: 110–116[CrossRef][ISI][Medline] Loreti E, De Bellis L, Alpi A, Perata P (2001) Why and how do plants cells sense sugars? Ann Bot (Lond) 88: 803–812 Mae T, Makino A, Ohira K (1983) Changes in the amounts of ribulose bisphosphate carboxylase synthesized and degraded during the life span of rice leaf (Oryza sativa L.). Plant Cell Physiol 24: 1079–1086 Martin T, Oswald O, Graham IA (2002) Arabidopsis seedling growth, storage lipid mobilization and photosynthetic gene expression are regulated by carbon:nitrogen availability. Plant Physiol 128: 472–481 Moore B, Zhou L, Rolland F, Hall Q, Cheng WH, Lui YX, Hwang I, Jones T, Sheen J (2003). Role of the Arabidopsis glucose sensor HXK1 in nutrient, light, and hormonal signaling. Science 300: 332–336 Oguchi R, Hikosaka K, Hirose T (2003) Does the photosynthetic light-acclimation need change in leaf anatomy? Plant Cell Environ 26: 505–512[CrossRef] Onoda Y, Hikosaka K, Hirose T (2005) Seasonal change in the balance between capacities of RuBP carboxylation and RuBP regeneration affects CO2 response of photosynthesis in Polygonum cuspidatum. J Exp Bot 56: 755–763 Paul MJ, Pellny TK (2003) Carbon metabolite feedback regulation of leaf photosynthesis and development. J Exp Bot 54: 539–547 Pego JV, Kortstee A, Huijser C, Smeekens S (2000) Photosynthesis, sugars and the regulation of gene expression. J Exp Bot 51: 407–416 Pfannschmidt T (2003) Chloroplast redox signals: how photosynthesis controls its own genes. Trends Plant Sci 8: 33–41[CrossRef][ISI][Medline] Pierik R, Tholen D, Poorter H, Visser EJW, Voesenek LACJ (2006) The Janus face of ethylene: growth stimulation and inhibition. Trends Plant Sci 11: 176–183[CrossRef][ISI][Medline] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
TOP
ABSTRACT
RESULTS
and Bleecker (1995)
*) was calculated to be 33.06 µmol mol–1, Michaelis-Menten constants of Rubisco for carboxylase (Kc) and oxygenase (Ko) were 27.0 Pa and 19.4 kPa, respectively. Estimation of fractions of total organic nitrogen invested in pigment protein, electron transport, and Rubisco followed Evans (1989)