|
|
||||||||
|
Plant Physiol. (1998) 118: 929-934 Carbonic Anhydrase Activity and CO2-Transfer Resistance in Zn-Deficient Rice Leaves1
Graduate School of Agriculture and Life Science, University of Tokyo, Yayoi, Bunkyo, Tokyo 113, Japan (H.S.); National Institute of Agrobiological Resources, Tsukuba, Ibaraki 305, Japan (T.H., R.O.); and National Institute of Radiological Sciences, Inage, Chiba 263, Japan (Y.W.)
It has been reported that carbonic anhydrase (CA) activity in plant leaves is decreased by Zn deficiency. We examined the effects of Zn deficiency on the activity of CA and on photosynthesis by leaves in rice plants (Oryza sativa L.). Zn deficiency increased the transfer resistance from the stomatal cavity to the site of CO2 fixation 2.3-fold and, consequently, the value of the transfer resistance relative to the total resistance in the CO2-assimilation process increased from 10% to 21%. This change led to a reduced CO2 concentration at the site of CO2 fixation, resulting in an increased gradient of CO2 between the stomatal cavity and this site. The present findings support the hypothesis that CA functions to facilitate the supply of CO2 from the stomatal cavity to the site of CO2 fixation. We also showed that the level of mRNA for CA decreased to 13% of the control level during Zn deficiency. This decrease resembled the decrease in CA activity, suggesting the possible involvement of the CA mRNA level in the regulation of CA activity.
CA (EC 4.2.1.1) catalyzes the reversible conversion of
CO2 to HCO3, which can be
dissolved more easily, and has been recognized as an important enzyme
that is closely associated with photosynthesis. However, the
application of inhibitors of CA to intact chloroplasts did not lower
the rate of photosynthesis (Swader and Jacobson, 1972 In a previous study we tried to separate the
rm into the rr
and the rc by measuring the
CA is a Zn-containing enzyme, so Zn is essential for its catalytic
activity (Bar-Akiva and Lavon, 1969 Cultivation of Plants
Determination of Zn Content The leaf area of the uppermost fully expanded leaf on the main stem was measured for 6 plants from each container (18 plants for each treatment) 13 weeks after germination, and these leaves were dried in an electric dryer. The dry weight was determined and the specific leaf weight was calculated. Samples of 0.1 g dry weight were digested overnight in 5.0 mL of concentrated HNO3 and 0.3 mL of 40% (w/v) HF in a 50-mL Teflon beaker, and wet ashed on the heater the following day. The Zn content was determined with an inductively coupled plasma atomic spectrometer (SPS-7000A, Seiko Instruments, Tokyo, Japan).Measurement of the Gas-Exchange Rate Leaf photosynthesis and transpiration were measured simultaneously for the uppermost fully expanded leaf on the main stem for 6 plants from each container (18 plants for each treatment) 13 weeks after germination using a handmade gas-exchange system with an IR gas analyzer (ZAP-AZ012, Fuji Electric Co. Ltd., Tokyo, Japan) and a humidity sensor (HMP111Y, Visala, Helsinki, Finland). A leaf (approximately 8-12 cm2) was clamped in the leaf chamber with a water jacket providing background cooling, and maintained under controlled conditions of temperature, light, humidity, and CO2 concentration. The measurements were made at a CO2 concentration of 340 µL L 1, an irradiance greater than 1400 µmol
m 2 s 1 photon flux
density under artificial light, and a leaf temperature of 30°C ± 3°C, after preillumination for 60 min to obtain steady-state readings of photosynthesis and transpiration.
Measurement of 13C Values of Soluble Sugars Ten plants in each container were placed in darkness at 12 PM to starve the leaves of photosynthetic products. The next morning the leaves were exposed to artificial light at an irradiance greater than 1400 µmol m 2
s 1 photon flux density from 9 AM to
12 PM in a 72-m3 laboratory
ventilated at 2160 m3 h 1,
and were then cut off from the plant. No one entered the laboratory during the exposure and there was no difference between the values of
the isotopic composition of CO2 in the air in
this room and outside. The accumulation of soluble sugars was conducted
for three treatments at the same time. The soluble sugars were
extracted and 13C was determined with a mass
spectrometer (MAT-252, Finnigan MAT, San Jose, CA) as reported
previously (Sasaki et al., 199613C Determination 13C of soluble sugars was determined with a mass spectrometer according to the method of Sasaki et al. (1996) can be expressed by the following equation (Hubick et al., 1986
a and p
are the relative concentrations of 13C in the
atmospheric air and in the photosynthetic products, respectively. The
a was determined as 8.0 ± 0.1 from
the actual measurement of the air in our laboratory, and
p was determined by the mass-spectrometric method with soluble sugars extracted from the leaves. The obtained was inserted into Equation 2 (Sasaki et al., 1996
1 in this experiment and
[CO2]stc was obtained
from the measurement of photosynthesis and transpiration. Therefore,
[CO2]cht can be obtained
from Equation 2 after inserting the value of determined from
Equation 1.
Calculation of Stomatal Transfer and Fixation Resistances The rs and the rm were calculated using the following equations:
Determination of CA Activity CA activity was measured in the uppermost fully expanded leaf on the main stem for 6 plants from each container (18 plants for each treatment). The detached leaves, which had been illuminated for 1 h at 1400 µmol m 2 s 1
photon flux density, were ground with a buffered solution (pH 8.3) that
contained 50 mM
barbital-H2SO4, 5 mM DTT, and 0.2% (w/v) PVP. The homogenate was centrifuged
at 12,000g for 2 min, and the supernatant was used for the
determination of CA activity, according to the method of Sasaki et al.
(1996)Determination of Rubisco Content and Activity The content of Rubisco was determined in the uppermost fully expanded leaf on the main stem for six plants from each container (18 plants for each treatment). The leaves were excised immediately after the measurement of leaf photosynthesis and stored at 80°C in a
freezer before the determinations. The content of Rubisco was
determined by the method of Sasaki et al. (1996) 2 s 1 photon
flux density.
Quantitation of Soluble Protein The amount of soluble protein in the supernatant prepared for the measurement of the content of Rubisco was determined as described by Lowry et al. (1951)Quantitation of Chlorophyll The amount of chlorophyll in the homogenate prepared for the measurement of Rubisco was determined for 6 plants from each container (18 plants for each treatment) as described by Schmid (1971)Isolation of RNA and Northern-Blot Hybridization Total RNA was isolated from 0.2 g of frozen sample as described by Fromm et al. (1985)
Levels of Zn and Enzymes and Rates of Photosynthesis The Zn contents per unit leaf area of the Zn and ±Zn plants
were as low as 0.19 and 0.23 mg m 2,
respectively, compared with 0.51 mg m 2 in the
+Zn plants (Table I). In spite of the
great reduction in the Zn content of leaves, we observed no change in
specific leaf weight or in chlorophyll content, which is considered to be a critical indicator of Zn deficiency. Therefore, Zn and ±Zn plants were only moderately stressed. In contrast, although the CA
activity in Zn plants decreased dramatically to as little as 14% of
that in +Zn plants, the Rubisco activity decreased only to 89% of that
in +Zn plants. The levels of soluble protein and Rubisco increased
slightly. Moreover, little change in the rate of photosynthesis was
observed in the leaves with a reduced Zn content. These results
indicated that Zn deficiency resulted in the specific inhibition of CA
activity.
Stomatal Transfer and Fixation Resistance To clarify the contribution of CA activity to the assimilation process, we calculated the rc and the rr by measuring leaf photosynthesis and 13C in the soluble sugars extracted from the leaves (Table II). Although no significant difference was found in rc and rs in leaves of +Zn, Zn, and ±Zn plants,
we observed a 2.3-fold increase in rr,
which increased from 1.2 mol 1
CO2 m2 s in +Zn plants
to 2.7 mol 1 CO2 m2 s in Zn plants. This
corresponded to an increase from 10% to 21% when
rr was calculated as a percentage of total
resistance. This indicates that the Zn deficiency affected only the
CO2-transfer step in the
CO2-assimilation process.
The Concentration of CO2 in Leaves In all leaves examined [CO2]stc was maintained at about 220 µL L 1. In contrast,
[CO2]cht in +Zn leaves
was 195 ± 4 µL L 1, and
[CO2]cht decreased with a
reduction in the Zn content of leaves to 171 ± 6 and 166 ± 5 µL L 1 in ±Zn and Zn leaves,
respectively. The gradient of the CO2 concentration between the stomatal cavity and the site of
CO2 fixation increased from 29 to 59 µL
L 1 (Fig. 1). The
resistance in CO2 flux with Zn deficiency and our findings support the hypothesis that CA plays a role in facilitating the supply of CO2 to the sites of carboxylation.
Northern-Blot Analysis The results of northern-blot analysis of mRNAs for CA and Rubisco are shown in Figure 2. The level of the mRNA for CA decreased with the reduction in Zn content of the leaf, decreasing to 26% (±Zn) and 13% ( Zn) of that in control plants
(+Zn). In contrast, the level of the mRNA for the small subunit of
Rubisco showed no consistent trend. It seems likely that the
reduction in CA activity was caused not by deactivation of the enzyme
but, rather, by a decrease in the expression of the CA mRNA caused
by Zn deficiency.
CA has been recognized as an important enzyme that is closely
associated with photosynthesis. In C3 plants CA
activity is located mainly in the mesophyll chloroplast, with much
smaller activity in the cytosol. Chloroplastic CA activity was reported as 87% of total cellular activity in potato leaves (Rumeau et al.,
1996
* Corresponding author; e-mail asa3ki{at}ecc-mail.hongo.ecc.u-tokyo.ac.jp; fax 81-3-5689-8097. Received May 1, 1998;
accepted August 10, 1998.
Abbreviations:
CA, carbonic anhydrase.
[CO2]atm, CO2 concentration in
the atmospheric air.
[CO2]cht, CO2 concentration at the site of CO2 fixation
in the chloroplast.
[CO2]stc, CO2
concentration in the stomatal cavity.
Bar-Akiva A, Lavon R (1969) Carbonic anhydrase activity as an indicator of zinc deficiency in citrus leaves. J Hortic Sci 44: 359-362
Edwards GE,
Mohamed AK
(1973)
Reduction in carbonic anhydrase activity in zinc-deficient leaves of Phaseolus vulgaris L.
Crop Sci
13:
351-354
Evans JR, Sharkey TD, Berry JA, Farquhar GD (1986) Carbon isotope discrimination measured concurrently with gas exchange to investigate CO2 diffusion in leaves of higher plants. Aust J Plant Physiol 13: 281-292 Farquhar GD, Ball MC, von Caemmerer S, Roksandic Z (1982) Effect of salinity and humidity on 13C values of halophytes: evidence for diffusional isotope fractionation determined by the ratio of intercellular/atmospheric partial pressure of CO2 under different environmental conditions. Oecologia 52: 121-124 [CrossRef][ISI] Fett JP, Coleman JR (1994) Characterization and expression of two cDNAs encoding carbon anhydrase in Arabidopsis thaliana. Plant Physiol 105: 707-713 [Abstract] Fromm H, Devic M, Fluhr R, Edelman M (1985) Control of psbA gene expression: in mature Spirodela oligorrhiza chloroplasts light regulation of 32 kD protein synthesis is independent of transcript level. EMBO J 4: 291-295 [ISI][Medline] Guliev NM, Briramov SM, Aliev DA (1992) Functional organization of carbonic anhydrase in higher plants. Sov Plant Physiol 39: 537-544 Hubick KT, Farquhar GD, Shorter R (1986) Correlation between water-use efficiency and carbon isotope discrimination in diverse peanut (Arachis) germplasm. Aust J Plant Physiol 13: 803-816
Hudson GS,
Evans JR,
von Caemmerer S,
Arvidsson YBC,
Andrews TJ
(1992)
Reduction of ribulose-1,5-bisphosphate carboxylase/oxygenase content by antisense RNA reduces photosynthesis in transgenic tobacco plants.
Plant Physiol
98:
294-302
Jacobson BS,
Fong F,
Heath RL
(1975)
Carbonic anhydrase of spinach. Studies on its location, inhibition and physiological function.
Plant Physiol
55:
468-474
Johansson IM, Forsman C (1992) Processing of chloroplast transit peptide of pea carbonic anhydrase in chloroplasts and in Escherichia coli: identification of two cleavage sites. FEBS Lett 314: 232-236 [Medline]
Lowry OH,
Rosebrough NJ,
Farr AL,
Randall RJ
(1951)
Protein measurement with the Folin phenol reagent.
J Biol Chem
193:
265-275
Majeau N, Arnold MA, Coleman JR (1994) Modification of carbonic anhydrase activity by antisense and over-expression constructs in transgenic tobacco. Plant Mol Biol 25: 377-385 [CrossRef][ISI][Medline] Majeau N, Coleman JR (1994) Correlation of carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase expression in pea. Plant Physiol 104: 1393-1399 [Abstract]
Makino A,
Sakashita H,
Hidema J,
Mae T,
Ojima K,
Osmond B
(1992)
Distinctive responses of ribulose-1,5-bisphosphate carboxylase and carbonic anhydrase in wheat leaves to nitrogen nutrition and their possible relationships to CO2-transfer resistance.
Plant Physiol
100:
1737-1743
Matsuoka M,
Kano-Murakami Y,
Tanaka Y,
Ozeki Y,
Yamamoto N
(1988)
Classification and nucleotide sequence of cDNA encoding the small subunit of ribulose-1,5-bisphosphate carboxylase from rice.
Plant Cell Physiol
29:
1015-1022
Ohki K (1976) Effect of zinc nutrition on photosynthesis and carbonic anhydrase activity in cotton. Plant Physiol 38: 300-304
Ohki K
(1978)
Zinc concentration in soybean as related to growth, photosynthesis, and carbonic anhydrase activity.
Crop Sci
18:
79-82
Peet MM,
Huber SC,
Patterson DT
(1986)
Acclimation to high CO2 in monoecious cucumber. Carbon exchange rates, enzyme activities, and starch and nutrient conditions.
Plant Physiol
80:
63-67
Porter MA,
Grodzinski B
(1984)
Assimilation to high CO2 in bean: carbonic anhydrase and ribulose bisphosphate carboxylase.
Plant Physiol
74:
413-416
Price GD, von Caemmerer S, Evans JR, Yu J-W, Lloyd J, Oja V, Kell P, Harrison K, Gallagher A, Badger MR (1994) Specific reduction of chloroplast carbonic anhydrase activity by antisense RNA in transgenic tobacco plants has a minor effect on photosynthetic CO2 assimilation. Planta 193: 331-340 [ISI]
Randall PJ,
Bouma D
(1973)
Zinc deficiency, carbonic anhydrase, and photosynthesis in leaves of spinach.
Plant Physiol
52:
229-232
Rumeau D, Cuiné S, Fina L, Gault N, Nicole M, Peltier G (1996) Subcellular distribution of carbonic anhydrase in Solanum tuberosum L. leaves. Planta 199: 79-88 [Medline]
Sasaki H,
Samejima M,
Ishii R
(1996)
13C measurement on mechanism of cultivar difference in leaf photosynthesis of rice (Oryza sativa L.).
Plant Cell Physiol
37:
1161-1166
Schmid GH (1971) Origin and properties of mutant plants: yellow tobacco. Methods Enzymol 23: 171-194 Silverman DN (1991) The catalytic mechanism of carbonic anhydrase. Can J Bot 69: 1070-1078 Swader JA, Jacobson BS (1972) Acetazolamide inhibition of photosystem in isolated spinach chloroplasts. Phytochemistry 11: 65-70
Tsuzuki M,
Miyachi S,
Edwards GE
(1985)
Localization of carbonic anhydrase in mesophyll cells of terrestrial C3 plants in relation to CO2 assimilation.
Plant Cell Physiol
26:
881-891
Usuda H
(1985)
The activation state of ribulose-1,5-bisphosphate carboxylase in maize (Zea mays) leaves in dark and light.
Plant Cell Physiol
26:
1455-1464
Williams TG, Flanagan LB, Coleman JR (1996) Photosynthetic gas exchange and discrimination against 13CO2 and C18O16O in tobacco plants modified by an antisense construct to have low chloroplastic carbonic anhydrase. Plant Physiol 112: 319-326 [Abstract] Yoshida S, Forno DA, Cock JH, Gomes KA (1976) Routine procedure for growing rice plants in culture solution. In Laboratory Manual for Physiological Studies of Rice. The International Rice Research Institute, Los Vanõs, Philippines, pp 61-66
Copyright Clearance Center: 0032-0889/98/118//06
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() |
C. R. Warren Stand aside stomata, another actor deserves centre stage: the forgotten role of the internal conductance to CO2 transfer J. Exp. Bot., May 1, 2008; 59(7): 1475 - 1487. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Hacisalihoglu, J. J. Hart, Y.-H. Wang, I. Cakmak, and L. V. Kochian Zinc Efficiency Is Correlated with Enhanced Expression and Activity of Zinc-Requiring Enzymes in Wheat Plant Physiology, February 1, 2003; 131(2): 595 - 602. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. S. Gillon and D. Yakir Internal Conductance to CO2 Diffusion and C18OO Discrimination in C3 Leaves Plant Physiology, May 1, 2000; 123(1): 201 - 214. [Abstract] [Full Text] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ASPB Publications | PLANT PHYSIOLOGY | THE PLANT CELL | |
|---|---|---|---|