Light-mediated control of translational initiation of ribulose-1, 5-bisphosphate carboxylase in amaranth cotyledons.

In cotyledons of 6-day-old amaranth seedlings, the large subunit (LSU) and the small subunit (SSU) polypeptides of ribulose-1,5-bisphosphate carboxylase are not synthesized in the absence of light. When dark-grown seedlings were transferred into light, synthesis of both polypeptides was induced within the first 3 to 5 hr of illumination without any significant changes in levels of their mRNAs. In cotyledons of light-grown seedlings and of dark-grown seedlings transferred into light for 5 hr (where ribulose-1,5-bisphosphate carboxylase synthesis was readily detected in vivo), the LSU and SSU mRNAs were associated with polysomes. In cotyledons of dark-grown seedlings, these two mRNAs were not found on polysomes. In contrast to the SSU message, mRNAs encoding the nonlight-regulated, nuclear-encoded proteins actin and ubiquitin were associated with polysomes regardless of the light conditions. Similarly, mRNA from at least one chloroplast-encoded gene (rpl2) was found on polysomes in the dark as well as in the light. These results indicate an absence of translational initiation in cotyledons of dark-grown seedlings which is specific to a subset of nuclear- and chloroplast-encoded genes including the SSU and LSU, respectively. Upon illumination, synthesis of both polypeptides, and possibly other proteins involved in light-mediated chloroplast development, was induced at the level of translational initiation.     

The Presence of Two Types of Gene That Encode the Chlorophyll a/b-Binding Protein (LHCPII) and Their Light-Independent Expression in Pine (Pinus thunbergii)

A cDNA clone (pPDLHC3117) for LHCPII of pine (Pinus thunbergii)was isolated and sequenced. From a comparison of the deducedamino acid sequence with those of proteins from other seed plants,pPDLHC3117 was identified as encoding a type I LHCPII. Specificprobes for genes for type I and type II LHCPII were made frompPDLHC3117 and a type II cDNA (pPDLHC2176), respectively. Northernblotting with the specific probes showed that both types ofLHCPII were expressed in dark-grown seedlings of pine. ¹This work was supported by a Grant-in-Aid from the Ministryof Agriculture, Forestry and Fisheries of Japan (IntegratedResearch Program for the Use of Biotechnological Proceduresfor Plant Breeding).     

Construction of a gene bank and identification of the ribulose bisphosphate carboxylase/oxygenase genes from the nutritionally versatile cyanobacterium Chlorogloeopsis fritschii

A gene bank of the nutritionally versatile, nitrogen-fixing cyanobacterium Chlorogloeopsis fritschii was constructed in Charon 4A. 2,800 recombinants containing 10–20 kbp C. fritschii DNA fragments were screened by Southern hybridization using probes containing the genes for the large (LSU) and small (SSU) subunits of ribulose bisphosphate carboxylase/oxygenase (RuBisCO) from Anacystis nidulans. A single recombinant plaque (CDG1) containing a 10.9 kbp EcoR1 fragment from C. fritschii hybridized to both the LSU and SSU probes, indicating a possible linkage of these RuBisCO genes in C. fritschii. RuBisCO activity and protein were detected in CDG1 lysates of Escherichia coli. Hybridization was also obtained between C. fritschii DNA and the LSU probe from Chlamydomonas reinhardtii, although no homology was detected using the LSU probe from maize or the SSU probe from pea.Abbreviations RuBisCO d-ribulose 1,5-bisphosphate carboxylase/oxygenase - RuBP d-ribulose 1,5-bisphosphate - LSU large subunit of RuBisCO - SSU small subunit of RuBisCO - SDS sodium dodecyl sulphate - DOC deoxycholate     

Chlorophyll-Protein Complexes and other Thylakoid Components at the Low Intensity Threshold in Euglena Chloroplast Development

The plastids of dark-grown resting cells of Euglena gracilisKlebs var. bacillaris Cori undergo only limited developmentwhen illuminated at the developmental threshold for light intensity7 foot-candles (ft-c) (27 µW/cm²). In the present work,we have found that these low intensity cells have substantialamounts of electron transport components such as ferredoxin-NADPreductase and Cyt c-552 but only trace amounts of the majorantenna components such as the light-harvesting Chl-proteincomplex (LHCP), the LHCP oligomer, CP la, Chi b and the 26.5kDa apo-LHCP; CP I and CPa are at levels comparable to the electrontransport components. Exposure of the low intensity cells tonormal light intensity causes large increases in major antennacomponents and small increases in electron transport components.The kinetics of accumulation of the antenna components Chi band apo-LHCP during greening of dark-grown resting cells atnormal intensities are the same as for Chi a. The low intensitywild-type cells strongly resemble mutants of Euglena low inChi b grown at normal intensities in lacking major antenna components. (Received April 7, 1987; Accepted June 19, 1987)     

Differential regulation of the accumulation of the light-harvesting chlorophyll a/b complex and ribulose bisphosphate carboxylase/oxygenase in greening pea leaves

The photoregulation of chloroplast development in pea leaves has been studied by reference to three polypeptides and their mRNAs. The polypeptides were the large subunit (LSU) and the small subunit (SSU) of ribulose 1,5-bisphosphate carboxylase/oxygenase (RUBISCO), and the light-harvesting chlorophyll a/b protein (LHCP). The polypeptides were assayed by a sensitive radioimmune assay, and the mRNAs were assayed by hybridization to cloned DNA probes. LSU, LSU mRNA, and LHCP mRNA were detectable in etiolated seedlings but LHCP, SSU, and SSU mRNA were at or below the limit of detection. During the first 48 hr of de-etiolation under continuous white light, the mRNAs for LSU, SSU, and LHCP increased in concentration per apical bud by about 40-fold, at least 200-fold, and about 25-fold, respectively, while the total RNA content per apical bud increased only 3.5-fold. In the same period, the LSU, SSU, and LHCP contents per bud increased at least 60-, 100-, and 200-fold, respectively. The LHCP increased steadily in concentration during de-etiolation, whereas the accumulation LSU, SSU, and SSU mRNA showed a 24-hr lag. The accumulation of SSU, SSU mRNA, and LHCP mRNA showed classical red/far-red reversibility, indicating the involvement of phytochrome in the regulatory mechanism. LSU and LSU mRNA were induced equally well by red and far-red light. The LHCP failed to accumulate except under continuous illumination. These results indicate that the accumulation of SSU is controlled largely through the steady-state level of its mRNA, which is in turn almost totally dependent on light as an inducer and on phytochrome as one of the photoreceptors. The accumulation of LSU is largely but not totally determined by the level of its mRNA, which appears to be under strong photoregulation, which has yet to be shown to involve phytochrome. Phytochrome is involved in the regulation of LHCP mRNA levels but substantial levels of the mRNA also occur in the dark. LHCP accumulation is not primarily governed by the levels of LHCP mRNA but by posttranslational stabilization in which chlorophyll synthesis plays a necessary but not sufficient role.     

Dimethipin (2,3-Dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetraoxide) Effects on Soybean Seedling Growth and Metabolism

Three-day-old dark-grown soybean [Glycine max (L.) Merr.] seedlingswere transferred to 2 mM CaSO₄ or 10^–5 M dimethipin in2 nM CaSO₄ and root-fed via liquid culture. Plants were placedin continuous darkness or in continuous white light (200 µE.m^–2?s^–11,PAR) at 25?C. Dimethipin inhibited root and shoot elongationin dark-grown plants after 24 h and 48 h, respectively. In thelight, root elongation was inhibited also after 24 h, but hypocotylelongation was not significantly affected. Extractable phenylalanineammonia-lyase (PAL) activity per axis in dimethipin-treateddark-grown axes was not generally affected but, in the lightdimethipin caused a significant decrease in PAL activity (24to 96 h). Total soluble hydroxyphenolics in axes were not affectedby dimethipin in light- or dark-grown plants. Anthocyanin andchlorophyll levels were lowered in hypocotyls of dimethipin-treatedplants after 48 to 96 h. Soluble protein in hypocotyls of light-or dark-grown seedlings was not substantially affected by dimethipin.Nitrate reductase (NR) activity (per organ) was generally notaffected by dimethipin in light-grown cotyledons, but in theroots of these seedlings, NR activity was significantly decreased.Proteolytic enzyme activity using three substrates (leucine-p-nitroanilide,LPNA; proline-p-nitroanilide, PPNA; and benzoylarginine-p-nitroanilide,BAPA) indicated little effect on enzyme activities per organin roots and hypocotyls. These data suggest that dimethipinat low concentrations can cause significant growth inhibitionin soybean seedlings grown in either light or darkness and thatfurthermore, extractable activities of some enzymes associatedwith nitrogen metabolism and secondary metabolism are alteredby this chemical. Light also plays a role in the activity ofthis chemical. (Received November 29, 1983; Accepted January 25, 1984)     

Intravacuolar Spherical Bodies in Polygonum cuspidatum

The vacuoles in the epidermal cells of light-grown seedlingsof Polygonum cuspidatum were found to contain intensely pigmentedspherical bodies (anthocyanoplasts). Dark-grown seedlings containedsimilar spherical bodies that were unpigmented. The unpigmentedspherical bodies accumulated anthocyanin and turned into anthocyanoplastswhen dark-grown seedlings were irradiated. The unpigmented sphericalbodies of dark-grown seedlings were heavily stained upon treatmentof seedlings with neutral red. The absorption spectra of sphericalbodies and vacuoles showed that the contents of the sphericalbody were different from those of the vacuole. The sphericalbody was stable in darkness or at low temperature but was unstableat 25°C in the light. There was no correlation between theamount of anthocyanin and the percentage of cells that containedspherical bodies, suggesting that, in P. cuspidatum, the sphericalbody is not the main site of anthocyanin synthesis. ²Present address: Department of Applied Biology, Faculty ofTextile Science and Technology, Shinshu University, Ueda, 386Japan     

Photooxidative destruction of chloroplasts and its consequences for expression of nuclear genes

Expression of nuclear genes involved in plastidogenesis is known to be controlled by light via phytochrome. Examples are the small subunit (SSU) of ribulose-1,5-bisphosphate carboxylase and the light harvesting chlorophyll a/b binding protein of photosystem II (LHCP). In the present study we show that, beside phytochrome, the integrity of the plastid is essential for the expression of the pertinent nuclear genes as measured at the level of translatable mRNA. When the plastids are severely damaged by photooxidation in virtually carotenoid-free mustard (Sinapis alba L.) seedling cotyledons (made carotenoid-free by the application of Norflurazon, NF), almost no SSU, no SSU precursor, LHCP and LHCP precursor can be detected by immunological assays, and almost no translatable mRNA of SSU and LHCP can be found, although the levels and rates of phytochrome-mediated syntheses of representative cytoplasmic, mitochondrial and glyoxisomal enzymes are not adversely affected and morphogenesis of the mustard seedling proceeds normally (Reiß et al. 1983; Planta 159, 518–528). Norflurazon per se has no effect on the amount of translatable mRNA of SSU and LHCP as shown by irradiation of NF-treated seedlings with far-red light (FR) which strongly activates phytochrome but does not cause photooxidation in the plastids. It is concluded that a signal from the plastid is required to allow the phytochrome-mediated appearance of translatable mRNA for SSU and LHCP. Seedlings not treated with NF show a higher level of translatable mRNA_LHCP in red light (RL) compared to FR, whereas the mRNA_SSU levels are the same in RL and FR. These facts indicate that the level of translatable mRNA_LHCP is adversely affected if the apoprotein is not incorporated into the thylakoid membrane.Abbreviations FR far-red light (3.5 W m^-2) - LHCP light harvesting chlorophyll a/b binding protein of photosystem II - LSU large subunit of RuBPCase - NF Norflurazon - RL red light (6.8 W m^-2) - RuBPCase ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) - SSU small subunit of RuBPCase - WL white light (28 W m^-2)     

Natural Inhibitors in Normal and Dwarf Peas

Extracts of light- and dark-grown, normal and dwarf pea seedlings(Pisum sativum L. cv. Alaska and Radio respectively) were purifiedby solvent partitioning, column, paper and thin layer chromatography.Conventional acid-base partitioning was modified because thelarge volumes of material processed caused considerable crosscontamination between neutral and acidic phases. At each stepof the purification, fractions were tested for inhibitory activitywith the wheat coleoptile and pea section tests. Recovery ofabscisic acid was monitored using ¹⁴C-abscisic acid. Estimatesof abscisic acid content were marie using gas-liquid chromatographyand the wheat coleoptile bioassay. Two main inhibitors were found; one of these was identifiedas (+)-abscisic acid, the other (inhibitor Y) has not been identifiedbut displays chromatographic properties which suggest that itis neutral in nature. Abscisic acid was found in both rootsand shoots of light- and dark-grown pea seedlings. InhibitorY was found in trace amounts in the roots of dark-grown plantsbut could not be detected in the shoots. Growth in light induceda manifold increase in inhibitor Y concentration compared withdark-grown plants. The level of Y was threefold greater in light-growndwarf shoots than in comparable light-grown tall shoots. Therewas, thus, a correlation between the concentration of inhibitorY and the light-induced inhibition of stem elongation.     

O-Benzylhydroxylamine: An Inhibitor of Phenylpropanoid Metabolism in Plants

O-Benzylhydroxylamine (OBHA) is a potent inhibitor of phenylalanineammonialyase (PAL, EC 4.3.1.5 [EC] ) and phenylpropanoid metabolismas evidenced by its effects on three plant species [soybean(Glycine max (L.) Merr.), buckwheat (Fagopyrum esculentum Moench.),and mung bean (Vigna radiata L.)]. When supplied to roots, OBHA(10^–5 M) did not significantly inhibit light- or dark-growthof soybean seedlings, but reduced (25%) soluble hydroxyphenoliccompound accumulation in light-grown axes. Higher concentrations(510^–5 M) of OBHA caused reductions (25%) in axis freshweight of light-grown seedlings (72 h), but did not lower axisweight of dark-grown seedlings. Anthocyanin accumulation inhypocotyls of intact mung bean seedlings was reduced by 25%after 3 days light growth after treatment with OBHA (10^–5M) via root feeding. Anthocyanin content of excised, etiolatedbuckwheat hypocotyls floated on solutions of OBHA (10^–5M) and incubated in the light for 24 h was reduced by 40%. L-Phenylalanineand t-cinnamic acid, intermediates of phenylpropanoid metabolism,were able to partially reverse this inhibition in buckwheat.Extractable PAL activity (specific activity basis) in soybeanaxes was substantially reduced (20% in dark, 40% in light) asearly as 24 h after root feeding with OBHA (10^–5 M). Reductionof PAL activity (specific activity or per axis basis) by OBHAcompared to control levels, continued throughout a time courseof 96 h. Kinetic studies on soybean PAL revealed a K_m of 1.1mM for L-phenylalanine and an apparent K_i of 3.5 µM forOBHA. (Received May 31, 1985; Accepted August 6, 1985)     

DNA Levels in Dividing and Developing Plastids in Expanding Primary Leaves of Avena sativa

The amounts of plastid DNA in the primary leaves of 4-d-oldlight- and dark-grown seedlings of Avena sativa were measuredby microspectrofluorometry using the DNA-fluorochrome DAPI (4',6-diamidino-2-phenylindole). In the light-grown primary leaves (40–45 mm long) therewas a marked increase in DNA level per plastid from 10.2 to18.5 ? 10^–15 g between 2.0 mm and 10 mm from the leafbase, resulting from the rate of plastid DNA synthesis beinghigher than the rate of plastid division. Beyond 30 mm the plastidDNA level was reduced to 14 ? 10^–15g due to chloroplastdivision rates being higher than the rate of plastid DNA synthesis,while from 20 mm plastid DNA levels were constant at 2.2 ? 10^–12g per cell, which corresponds to 16000 plastome copies per cell. Observations of dark-grown leaves establish that, in Avena,light is not necessary for plastid division and the dark-grownleaf cells accumulate higher amounts of plastid DNA than light-grownleaf cells. Plastid nucleoids showed a change of distribution after completionof plastid DNA synthesis in light-grown leaves. A change inthe distribution of plastid nucleoids was also observed duringthe greening of etioplasts of dark-grown leaves while plastidDNA level remained constant. Such changes in plastid nucleoiddistribution appear to be independent of plastid DNA synthesisand correlate with the formation of grana stacks. Key words: Avena sativa, microspectrofluorometry, plastid DNA     

Distribution of Fallover in the Carboxylase Reaction and Fallover-Inducible Sites among Ribulose 1,5-Bisphosphate Carboxylase/Oxygenases of Photosynthetic Organisms

The biphasic reaction course, fallover, of carboxyla-tion catalysedby ribulose 1,5-bisphosphate carboxylase/ox-ygenase (RuBisCO)has been known as a characteristic of the enzyme from higherland plants. Fallover consists of hysteresis in the reactionseen during the initial several minutes and a very slow suicideinhibition by inhibitors formed from the substrate ribulose-l,5-bisphosphate(RuBP). This study examined the relationship between occurrenceof fallover and non-catalytic RuBP-binding sites, and the putativehysteresis-inducible sites (Lys-21 and Lys-30S of the largesubunit in spinach RuBisCO) amongst RuBisCOs of a wide varietyof photosynthetic organisms. Fallover could be detected by followingthe course of the carboxylase reaction at 1 mM RuBP and thenon-catalytic binding sites by alleviation of fallover at 5mM RuBP. RuBisCO from Euglena gracilis showed the same linearreaction course at both RuBP concentrations, indicating an associationbetween an absence of fallover and an absence of the non-catalyticbinding sites. This was supported by the results of an equilibriumbinding assay for this enzyme with a transition state analogue.Green macroalgae and non-green algae contained the plant-type,fallover enzyme. RuBisCOs from Conjugatae, Closterium ehrenbergii,Gona-tozygon monotaenium and Netrium digitus, showed a muchsmaller decrease in activity at 1 mM RuBP than the spinach enzymeand the reaction courses of these enzymes at 5 mM RuBP werealmost linear. RuBisCO of a primitive type Conjugatae, Mesotaeniumcaldariorum, showed the same linear course at both RuBP concentrations.Sequencing of rbcL of these organisms indicated that Lys-305was changed into arginine with Lys-21 conserved. ⁷ On leave from Research and Development Center, Unitika Ltd.,23 Kozakura, Uji, Kyoto, 611 Japan. ⁸ Present address: Department of Applied Biological Chemistry,Faculty of Agriculture, Tohoku University, Tsutsumidori-Ama-miyamachi, Sendai, 981 Japan. ⁹ Present address: National Institute for Basic Biology, Myodaiji,Okazaki, 444 Japan. ¹⁰ Present address: Department of Environmental Biology, TokyoPharmaceutical University, Hachioji, Tokyo, 192-03 Japan.     

Inhibitory Effect of Gabaculine on the Biosynthesis of 5-Aminolevulinate in the Tigrina d12 Mutant of Barley

Six-day-old, dark-grown, seedlings of barley homozygous forthe recessive mutation tigrina d¹² accumulated 5-aminolevulinicacid (ALA) and protochlorophyll (ide) in amounts exceeding thewild type level. Transferring the etiolated mutant to lightresulted in the destruction of pigments and the deteriorationof the ALA forming system. Such deleterious effects did notoccurusing light-grown mutant or etiolated and greened wildtype seedlings. Gabaculine (GAB) at 50 µM inhibited ALAsynthesis by about 85% when etiolated wild type seedlings wereexposed to light. In light-grown leaves of either wild typeor mutant strain, ALA production was also sharply (ca. 75%)inhibited by GAB. During dark incubation, however, the inhibitionof ALA accumulation did not exceed 50% in all types of tissues.The results give further evidence for the operation of the C₅pathway in such seedlings since GAB decreased the biosynthesisof ALA to the same extent in both tigrina d¹² mutant and wildtype of barley. (Received July 2, 1990; Accepted May 7, 1991)     

The distribution of protochlorophyllide and chlorophyll within seedlings of the lip1 mutant of Pea

The distribution of protochlorophyllide (Pchlide) and NADPH-Pchlideoxidoreductase (POR) was characterized in the epicotyls androots of wild-type pea (Pisum sativum L. cv. Alaska) and lip1,a mutant with light-independent photomorphogenesis caused bya mutation in the COP1 locus. The upper part of the dark-grownlip1 mutant epicotyls had a high Pchlide content that decreaseddownward the organ. The elevated Pchlide level in lip1 seedlingswas a result of the differentiation of more proplastids intoPchlide-containing plastids. The cortex cells in the lip1 epicotylwere filled with such plastids in contrast to the cortex cellsof wild-type seedlings. The mutant also developed Pchlide-containingplastids in the roots, indicating the suppressing effect ofthe COP1 locus on development of plastids in the correspondingtissues in dark-grown wild-type plants. The distribution ofPchlide-containing plastids in dark-grown lip1 mutant stem androot was similar to the distribution of chloroplasts in irradiatedwild-type plants. Both wild-type and lip1 epicotyls containedmostly short wavelength Pchlide fluorescing at 631 nm withonly a small shoulder at 654 nm, which was transformedto a minute amount of chlorophyllide (Chlide) by flash irradiation.In contrast, with continuous irradiation a considerable amountof Chlide was formed especially in the lip1 epicotyls. Immunoblotsindicated the presence of POR, as a 36 kDa band, in epicotylsof both dark-grown wild-type and lip1 mutant seedlings. However,lip1 stem tissue had a higher content of POR than the wild-typepea. The high content of POR was unexpected as lip1 lacked boththe 654 nm fluorescing Pchlide form and the regular PLBs.In light, a significant amount of chlorophyll was formed alsoin the roots of the lip1 seedlings. ³ Corresponding author: E-mail, mahdi.seyedi@molbio.gu.se; Fax,+46-31-773-2626.     

Development of photosynthetic activities in dark-grown spruce seedlings

The chloroplasts in dark-grown, 5-day-old seedlings of Piceaabies contained doubly stacked primary thylakoid membranes connectedwith prolamellar bodies. The photo-system II reaction centerand photosystem II-associated electron transfer were assembledin the primary thylakoid membranes, but the oxygen-evolvingsystem remained latent unless the seedlings were exposed tolight. The photoactivation of this system was strongly dependenton temperature during pre-illumination. This implies that somethermal process, in addition to the photoprocess, is involvedin the photoactivation of the oxygen-evolving system. ¹Laboratory of Plant Physiology, The Institute of Physical andChemical Research, Wako-shi, Saitama 351, Japan. ²Department of Biology, Fukuoka Dental College, Fukuoka 814,Japan. (Received June 22, 1977; )     

Biological Activities of the Methyl Ester of Gibberellin A73, a Novel and Principal Antheridiogen in Lygodium japonicum

The synthetic methyl ester of GA₇₃ (GA₇₃-Me) and the naturalantheridiogen of Lygodium japonicum showed almost the same activityto induce the formation of antheridia in dark-grown protonemataof L. japonicum at concentrations of 10^-14 M and higher. Thus,it appears that the principal antheridiogen in L. japonicumis GA₇₃-Me. GA₇₃-Me inhibited formation of ar-chegonia in light-grownprothallia of L. japonicum at concentrations of 10^-11 M andhigher and induced germination of spores in the dark in thisspecies at the same range of concentrations. GA₇₃(free acidform) promoted growth of seedlings of dwarf rice and hypocotylsof cucumber seedlings at dosages of and above 1 and 100 ng/plant,respectively. Eight compounds related to GA₇₃-Me, includingantheridiogens of Anemia phyllitidis and Anemia mexicana, wereactive in inducing an-theridial formation in L. japonicum, althoughtheir activities were considerably lower than that of GA₇₃-Me. (Received August 24, 1988; Accepted November 28, 1988)     

Presence of the Photoactive Reaction-Center Chlorophyll of PSI (P700) in Dark-Grown Cells of a Chlorophyll-Deficient Mutant of Chlorella kessleri

Compositions of pigments and polypeptides of pale green membranesthat had been isolated from dark-grown cells of a chlorophyll-deficientmutant of Chlorella kessleri were investigated. They containedChl a in a level corresponding to about 1% of that present inthe thylakoid membranes isolated from autotrophically grownwild-type cells and a trace amount of chlorophyllide a, butneither Chl b nor carotenoids. The polypeptide profile of themutant membranes was similar to that of membranes isolated fromwild-type cells that were grown in the dark. Neither the chlorophyll-bindingsubunits of PSI nor the apoproteins of LHCP were detected bySDS-PAGE and immunoblot analysis. However, the light-minus-darkdifference spectrum of the mutant membranes revealed the presenceof the reaction-center chlorophyll of PSI (P700) at a molarratio of 190 chlorophyll (Chl a plus Chlide a) per P700. P700was more stable than Chl a and Chlide a in the light so thatprolonged illumination led to a decline in the Chl/P700 ratioto 24. The initial rate of P700 photooxidation in the mutantmembranes was comparable to that in CP1 isolated from the dark-grownwild-type cells. Under illumination with strong light, the initialrate was decreased in parallel to the decrease in Chl/P700 ratio.The results suggest that most of Chi present in the mutant membranescan transfer excitation energy to P700. (Received March 13, 1998; Accepted August 7, 1998)