Isoforms of NADP-dependent Malic Enzyme in Tissues of the Greening Maize Leaf

Scagliarini, S., Pupillo, P. and Valenti, V. 1988. Isoformsof NADP-dependent malic enzyme in tissues of the greening maizeleaf.—J. exp. Bot. 39: 1109–1119. The compartmentation of the isoforms of NADP-dependent malicenzyme (E.C. 1.1.1.40 [EC] ) has been studied in cell-free extractsand in enzymatically-isolated protoplasts of mesophyll tissue(MT) and bundle sheath (BS) strands of greening maize leaves.The etiolated leaf of 10-d-old seedlings contains a cytosolicisozyme with a pl of 5.4 ?0.1 at low specific activity (s.a,45 ? 3 nmol min^–1 mg^–1 protein), found both in MTand BS. The green leaf on the other hand contains the dominantBS chloroplast isozyme with pl 4.6 ? 0.2 at a s.a, of 370 ?40 nmol min^–1 mg^–1 protein (3.2 ? 0.5 µmolmin^–1 mg^–1 chl) and a minor, previously undescribedisoform with pl 6.5 ? 0.1 also localized in the BS at a s.a.of 38 ? 6 nmol min^–1 mg^–1 protein. Green MT protoplastshave only traces of pl 4.6 isozyme. After illumination of dark-grown seedlings, the total leaf activityshows a rapid increase (1.5-fold within 2 h), attributed mainlyto the pl 5.4 isozyme of MT protoplasts and BS strands. Thisis followed by a large increase of enzyme activity due to thecontinued rise of pl 5.4 isozyme for about 24 h and, after aninitial lag of a few hours, to the accumulation of pl 4.6 isozyme.After 18 h illumination, pl 4.6 and 5.4 isozyme activities tendto decline in the MT whereas they are still increasing in theBS, particularly the former. This pl 4.6 species has becomethe major one by 48 h illumination. The final pattern of greenleaves is established around 96 h light, when the chloroplastisozyme has attained its maximum level, the pl 5.4 isozyme ofBS strands has been superceded by the pl 6.5 species (also supposedto be cytosolic) and MT protoplasts retain little residual activity.Some metabolic implications of the changing pattern of NADP-dependentmalic isozymes during maize leaf greening are discussed. Key words: C₄, isozymes, malic enzyme, photodifferentiation, Zea mays     

Chloroplast development in 4-thiouridine-cultured radish seedlings III. Photochemical activities in isolated plastids

Accumulation of chlorophyll, development of photosystem I andII activities and contents of chloroplastic components wereinvestigated in greening radish seedlings germinated and grownwith 4-thiouridine (4SU). The development of photosystem I activityprior to that of photosystem II was observed also in the 4SU-culturedgreening radish cotyledons in which chlorophyll accumulationwas inhibited up to 60–80% of that of the control. Photochemicalactivities expressed on a plastid protein basis decreased withthe increase of 4SU in the culture medium. In contrast to ferredoxinand ferredoxin-NADP reductase, which were present in significantamounts in the treated cotyledons, chloroplastic cytochromes(f, b₅₅₉ and b₆ decreased in the plastids from 4SU-culturedcotyledons. These results suggest that 4SU interferes in partwith protein synthesis in plastids and thereby with chloroplastdevelopment. (Received December 4, 1979; )     

Characteristics of Chlorophyll Formation in the Green Alga Golenkinia

Cells of the alga Golenkinia are bleached by growth in darknessin media containing sodium acetate. Re-greening of these cellsis light dependent; neither glucose nor intermediates of chlorophyllsynthesis can substitute. The amount of chlorophyll synthesizedis proportional to the light intensity between darkness and1,000 lux and to the duration of the exposure. Initially, onlychlorophyll a is synthesized. After 9–12 hr illumination,formation of chlorophyll b and carotenoids begins. Chlorophyllproduction apparently occurs in two stages: (1) the first 12–16hr of greening. This stage is sensitive to cyanide, azide oranaerobiosis and relatively resistant to DCMU. (2) the second16–24 hr of greening. This stage is sensitive to DCMUand relatively resistant to inhibitors of respiration. Glucosestimulates greening in both stages. The metabolic requirementsof chlorophyll synthesis are discussed. (Received December 17, 1980; Accepted June 25, 1981)     

Appearance of Chlorophyll-Protein Complexes in Greening Barley Seedlings

The sequential appearance of chlorophyll-protein complexes (CP)in greening barley leaves was studied by an improved methodof SDS-polyacrylamide gel electrophoresis (PAGE). Solubilizedthylakoid membranes were purified using a sucrose step gradientand CPs were separated by PAGE with low concentrations of SDSin solubilizing and reservoir buffers. At 10 min after the onsetof illumination, a chlorophyll-protein complex (CPX) was detected.It was a labile CP, its chlorophyll (Chl) being easily releasedfrom the apoprotein during electrophoresis. The P700-chlorophylla/b-protein complex (CPl) appeared after 45–60 min ofillumination together with P700 activity. Light-harvesting chlorophylla/b-protein complex (LHCP) began to accumulate at 2.5 h withthe beginning of Chl b synthesis. In some cases a small amountof CPa could be detected after 6 h of greening. The time-differencespectrum between homogenates of leaves illuminated for 30 and60 min had an absorbance maximum at 677 nm, showing that a redshift indicative of CPl formation began soon after completionof the Shibata shift. The time-difference spectrum between 3.5-hand 4.0-h illuminated leaves resembled the absolute spectrumof fully greened leaves, indicating that at this stage, spectralcomponents were being synthesized at the same ratio at whichthey exist in fully greened tissues. Both absolute and time-differencespectral data supported the SDS-PAGE results. (Received February 27, 1985; Accepted May 8, 1985)     

The Photochemical Activity of Chloroplasts and Subchloroplast Particles Isolated from Etiolated Bean Leaves Exposed to Continuous Light

The photochemical activity of chloroplasts and subchloroplastparticles isolated from primary bean leaves between the 4thand 24th hour of illumination of etiolated seedlings is thesubject of this paper. The photosystem I activity (oxygen uptakein the presence of MV, DCIP, ascorbate and DCMU), expressedon a unit chlorophyll basis, decreased approximately 10-foldbetween 4 and 8 h of greening. At the same time the photosystemII activity (DCIP photoreduction in the presence of DPC) wasreduced to a half. The photosystem I activity also decreasedin all hitherto investigated fractions which were isolated fromthe digitonin-treated chloroplasts. However, at the initialphase of greening this decrease was the most significant inthe fraction containing heavy particles. After 24 h of greening DCMU, at concentrations higher than 10^–10M, limited the rate of ferricyanide photoreduction by isolatedchloroplasts, whereas after 6 h of greening this effect wasobservable even in the presence of 10^–12 M DCMU. The resultsobtained demonstrated that under those conditions both photosystemswere active after 4 h of greening and PS I activity developedmore rapidly than that of PS II. It also follows from the presenteddata that the water splitting reactions were delayed in developmentas compared to the other reactions investigated, and that PSII units may limit the electron flow in chloroplasts at earlierstages of leaf greening.     

Inhibition of growth and photosynthesis of freshwater phytoplankton by ultraviolet A (UVA) radiation and subsequent recovery from stress

The effect of ultraviolet A (UVA) on growth and photosyntheticrate was studied in diatoms (Melosira spp.) of the phytoplanktonof a eutrophic lake and a cultured green alga Chloretla ellipsoidea.The cells were incubated under photosynthetically active radiation(PAR) (–UVA) or PAR + UVA conditions (+UVA). Growth ofC.ellipsoidea was retarded under +UVA, as shown by an increasein the lag period, but the rate of exponential growth was almostthe same in + and –UVA conditions. The photosyntheticrate was depressed markedly by UVA in Chlorella cells grownunder –UVA. In contrast, cells grown in +UVA showed onlyslight inhibition by UVA and after exposure to UVA for 6 daysthere was no inhibition. During the growth experiment, the cellularchlorophyll a content was higher in +UVA than +UVA grown cells.A similar effect was observed in diatoms from the eutrophicLake Suwa. In vivo fluorescence with (F_a) and without 3-(3,4-dichloropheny)-l,l-dimethylurea (DCMU) (F_b) and the photosynthetic rate were measured forC.ellipsoidea and the diatoms for 5 h under + and –UVAconditions. Soon after C.ellipsoidea had been subjected to +UVA,F_b and F_a / F_b decreased quickly and reached minima after 40min and 1 h, respectively. The suppressed in vivo fluorescenceresumed and full recovery was achieved after 4 h. This suggeststhat reactivation of the photosystem is acquired under prolongedexposure to UVA. A similar shift of F_a + F_b, but no change inFb, was found in diatoms by exposure to UVA. Changes in photosyntheticoxygen evolution by C.ellipsoidea under +UVA were similar tochanges in F_a + F_b. Degradation of chlorophyll a extracted inmethanol was enhanced by UVA. The rate of degradation by UVAwas independent of temperature from 15 to 34°C, suggestinga photochemical reaction. The results indicate that C.ellipsoideaand Melosira spp. acclimatize to prolonged UVA exposure by reactivationof the photosystem and enhanced cellular chlorophyll a synthesis.The ecological importance of these results to phytoplanktonproductivity in natural aquatic environments is discussed.     

Studies on chloroplast development in Chlamydomonas reinhardtii I. Effect of brief illumination on chlorophyll synthesis

When dark grown cells of Chlamydomonas reinhardtii y-1 mutantwere exposed to continuous light, an immediate transformationof small amounts of protochlorophyll(ide), which had been presentin the dark grown cells, to chlorophyll was observed. Afterthis, there was a slow accumulation of chlorophyll lasting for2.5-3 hr before the start of exponential synthesis. Initialaccumulation of chlorophyll was distinctly slower at a highlight intensity (13,000 lux) than it was at moderate intensitiesof light (2,000–5,000 lux). However, the exponential synthesisof chlorophyll started after the same 2.5–3 hr of illumination. A brief pre-illumination of cells followed by incubation indarkness was effective in promoting chlorophyll synthesis undersubsequent continuous illumination at high, as well as moderatelight intensities. Pretreatment alleviated retardation of theinitial chlorophyll accumulation by light of high intensity.The promoting effect of preillumination on chlorophyll synthesiswas sufficient, even when a light impulse as short as 10 secwas given. However, the effect was dependent on length of thedark period after the short pre-illumination. The full extentof this effect was observed when the dark period was about 2.5–3hr long. Further dark incubation gradually decreased the effect. On the basis of these findings, it is assumed that a factor(s)responsible for promotion of chlorophyll (or chloroplast) synthesisin the process of greening of dark grown cells is produced duringthe dark period after a brief pre-illumination, and that thefactor is turned over at a relatively fast rate. The possiblenature of the presumed factor is discussed in relation to chloroplastdevelopment. ¹Present address: Department of Biology, Faculty of Science,Kobe University, Nada-ku, Kobe, Japan. (Received August 18, 1970; )     

Development of the photosynthetic apparatus during light-dependent greening of a mutant of Chlorella fusca

The formation of chlorophyll, cytochrome f, P-700, ribulose bisphosphate carboxylase as well as photosynthesis and Hill reaction activities were tested during the light-dependent greening process of the Chlorella fusca mutant G 10. Neither chlorophyll nor protochlorophyllide was detected in the darkgrown cells. When transferred to light the mutant cells developed chlorophyll and established its photosynthetic capacity after a short lag phase. In the in vivo absorption spectra a spectral shift of the red absorption peak position from 674 to 680 nm was indicated during the first 3 h of greening. Cytochrome f was already present in the dark-grown cells, but during the greening phase a threefold increase in the cytochrome f content could be seen. At the early stages of greening a characteristic primary oscillation in the content of cytochrome f was observed. P-700 was lacking in the dark and during the first 30 min of illumination. From the first to the second h of light a forced synthesis of P-700 took place and the time-course curve for the ratios of P-700/chlorophyll rose to a sharp maximum. The synthesis of P-700 started together with photosystem I activity and showed similar kinetics. We found the simultaneous appearance of photosystem II, photosystem I, and photosynthetic activities 30 min after the beginning of the illumination. Based on chlorophyll content they attained maximum activity after 2 h of light, but at this time photosystem I capacity proved to be remarkably higher than photosynthetic and photosystem II activities. Highest carboxylase activity existed in darkgrown cells. During the greening process the activity of the enzyme decreased continuously. After 2 h of illumination chlorophyll synthesis partially served to increase the size of the photosynthetic unit, which consequently led to a decrease in the light energy needed to saturate photosynthesis and also to a decrease of photosynthetic rate based on chlorophyll content.Abbreviations Chl chlorophyll - Cyt f cytochrome f - DPIP 2,6-dichlorophenolindophenol - EDTA ethylenediaminetetraacetic acid - GSH glutathione - LH light-harvesting - PS photosystem - RuBP ribulose bisphosphate     

Promotion of Plant Cell Division by an Epidermal Growth Factor

In some specified treatments, an epidermal growth factor (EGF)promoted adventitious root formation in epicotyl cuttings ofVigna angularis. The number of the roots induced in cuttingstreated with 0.1 mg liter^-1 EGF during the first 24 h and with210^-4 M IAA during the second 24 h was 15% greater than thatof the roots in cuttings treated without EGF and with IAA. Analysisof the optimum timing of EGF application was performed by dividingthe first 24 h period into three sequential 8 h periods (0–8h, 8–16 h and 16–24 h). The most effective timeperiods in terms of the root formation were 8–16 h and16–24 h. The 0–8 h period was ineffective with respectto the formation. When carrot suspension cells were culturedfor 15 days at a very low cell density (1,000 cells/3 ml Murashigeand Skoog's medium) with more than 0.1 mg liter^-1 EGF, cellnumbers were 72% higher than those cultured without EGF. Theseresults suggest that EGF promotes cell division of plants. (Received October 5, 1992; Accepted May 24, 1993)     

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     

Mechanism of Photoregulated Carotenogenesis in Rhodotorula minuta I. Photocontrol of Carotenoid Production

Rhodotorula minuta cells, which have only traces of carotenoidswhen grown in the dark, started carotenoid production with theonset of illumination and the amount increased almost linearlyuntil 70 hr then remained constant thereafter when incubationwas continued under illumination, with the number of cells continuingto increase. The rate of carotenoid production [Vc (µgg^–1 hr^–1)] depended on the intensity of light [I(ergcm^–2 sec^–1)], with the relationship of Vc=0.74 logI–1.46. The final carotenoid content [C(µg g^–1)]of cells incubated under continuous light was also controlledby the light intensity [I], with the relationship of C=52 logI–81. Control of carotenoid production by light occursas a two-phase process consisting of a temperatureindependentphotochemical reaction and light-independent biochemical reactions. (Received September 12, 1981; Accepted February 20, 1982)     

Accumulation of Pigments during the Greening of Etiolated Seedlings of Hordeum vulgare L.

The pigment changes that occur during transformation of etioplaststo fully developed chloroplasts have been studied in seedlingsof barley (Hordeum vulgare L.) by greening with white lightof low (15–25 µmol m^–2 s^–1) and medium(150 µmol m^–2 s^–1) intensity. At least 24h longer was required in the low light regime for the same concentrationof pigment to be accumulated in the seedlings. The increasein pigment content was mainly due to the synthesis of chlorophyllsa and b. Of the carotenoids present, the increases in the levelsof neoxanthin and, especially, ß-carotene were muchgreater than those observed for the other carotenoids. Levelsof lutein also increased but this change was small by comparisonto those observed for neoxanthin and ß-carotene. Inthe long-term the concentration of violaxanthin remained unalteredalthough significant transient changes were recorded. The levelsof antheraxanthin and zeaxanthin were markedly reduced duringgreening. The rate of pigment synthesis decreased with increasingcell age, i.e. from the base to the tip of the primary leaf.Overall, carotenoid levels increased by approximately 100% atthe base of the seedling but hardly at all at the tip. Key words: Hordeum vulgare, carotenoids, violaxanthin-cycle, etiolation     

Appearance of Photochemical Activity in Isolated Chloroplasts from Far-red-illuminated Leaves of Phaseolus vulgaris

Chloroplast development was followed in intact bean leaves illuminatedwith far-red light by extracting chloroplasts at various timesto assay photosynthetic activities. Photochemical activity wasdetected in isolated chloroplasts prior to the times which werepreviously reported for intact leaf discs. Cyclic phosphorylationwas observed in isolated chloroplasts after 8 h of far-red illuminationwhile non-cyclic electron transport and phosphorylation weremeasurable after 12 and 16 h of illumination respectively. TheP/2e ratios were less than 0.5 after 24 h of far-red exposurebut approached a value of 1.0 by 60 h of illumination. Ammoniumchloride (10^–3 M) had little effect on electron transportin isolated chloroplasts until after 24 h of far-red illumination.Chlorophyll a accumulated slowly from the onset of far-red illuminationwhile chlorophyll b was not detected until after 48 h of far-redexposure. Leaf fresh weight increased four-fold over the 60h illumination period. Electron microscopy of isolated chloroplasts from far-red-illuminatedleaves indicated the presence of unfused primary thylakoidsby 12 h of exposure and prolamellar bodies throughout the entire60 h illumination period. Grana were not observed in isolatedchloroplasts nor were they induced by a 2 min exposure of thechloroplasts to 172 000 lx of white light. O₂ evolution in leaf discs of far-red-illuminated plants wasmeasurable after 16 h of illumination, attained a maximum valueby 36 h of far-red exposure, and then declined. Net CO₂ fixationwas observed in leaf discs after 8 h of far-red illuminationand the rates remained constant for an additional 16 h, beforeincreasing at least two-fold.     

Formation of Chlorophyll-Protein Complexes in Greening Cucumber Cotyledons in Light and then in Darkness

The changes in chlorophyll-protein complexes (CPs) in cucumbercotyledons during illumination and subsequent dark incubationwere studied by SDS-polyacrylamide gel electrophoresis. Whenetiolated cucumber seedlings were illuminated, chlorophyll wassynthesized and CPs were formed. In the early phase of greening(6 h of illumination), light-harvesting chlorophyll a/b-proteincomplex (LHCP) was the main GP. As the greening proceeded, P700chlorophyll a-protein complex (CP1) accumulated. When 6-h illuminatedseedlings were transferred to darkness, CP1 accumulated concomitantlywith a decrease in LHCP without new chlorophyll synthesis. Thechanges in the amounts of CPs in the dark became smaller withthe progress of greening and were not observed after 72 h ofillumination. These changes were confirmed by examining thechlorophyll/P700 ratio and the low temperature absorption spectrumof cotyledons. These results suggest that in the early phaseof greening, CPs were unstable and their chlorophyll moleculeseasily exchanged with those of other kinds of CPs. (Received October 14, 1982; Accepted December 1, 1982)     

The Nuclear Endoreduplication Cycle in Metaxylem Cells of Primary Roots of Zea mays L.

The nuclear DNA content of metaxylem cells in roots of Zea mayscv. Golden Bantam reaches 16C or 32C by successive rounds ofDNA endoreduplication. Each phase of endoreduplication (endo-S)is separated by a non-DNA synthetic phase (endo-G). These phasesseem to occur in zones at fixed distances from the root tip.The duration of the phases in two of the endoreduplication cycles(4C–8C, 8C–16C) has been estimated in two ways.The first makes use of the rate of movement of cells throughthe positions along the root where the different phases of thecycle are occurring, the second uses labelling with methyl-[³H]thymidineand autoradiography. Both methods indicate that the endo-S phaseswhich cause the nuclear DNA content to rise from 4C to 8C andfrom 8C to 16C last 8–10 h, and that the intervening endo-Gphase lasts 8–12 h. DNA endoreduplication keeps pace withthe increase of nuclear volume; cell volume increases at a morerapid rate, however. Comparison of the endoreduplication cyclein the metaxylem with the mitotic cycle in the adjoining filesof parenchyma cells shows that the mitotic cells complete theircycle more slowly. DNA synthesis, endoreduplication cycle, mitotic cycle, root apex, Zea mays     

Time of Appearance of Photosystems I and II in Chloroplasts of Greening Jack Bean Leaves

The time of appearance of photochemical activities togetherwith the chlorophyll-protein complexes associated with photosystemsI and II was followed in greening primary leaves of jack bean(Canavalia ensiformis (L.) DC.). When greening of the etiolatedleaves occurred under high relative humidity conditions, nolag phase in chlorophyll-accumulation was observed. These environmentalconditions also promoted rapid and uniform development of thechloroplast lamellar system. Chlorophyll-protein complexes ofthe lamellae were separated by means of sodium dodecylsulphate-polyacrylamidegel electrophoresis and by hydroxylapatite chromatography. Thephotosystem II complex, containing chlorophyll a/b-protein,was detected after 2 h of greening. Its appearance was correlatedwith a sharp decrease in the chlorophyll a/b ratio and withthe onset of oxygen evolution. Subsequently, the photosystemI complex, containing a chlorophyll a-protein, was detected—after6 h of illumination. Its appearance coincided with the detectionof light-induced bleaching of P700 and the beginning of a risingchlorophyll a/b ratio that plateaued some time later.     

Stomatal Functioning of In Vitro and Greenhouse Apple Leaves in Darkness, Mannitol, ABA, and CO2

Leaves from in vitro and greenhouse cultured plants of Malusdomestica (Borkh.) cv. Mark were subjected to 4 h of darkness;4 h of 1 M mannitol induced water stress; 1 h of 10^–4M to 10^–7 M cis-trans abscisic acid (ABA) treatment; 1h of 0.12% atmospheric CO₂. Stomatal closure was determinedby microscopic examination of leaf imprints. In all treatments,less than 5% of the stomata from leaves of in vitro culturedplants were closed. The diameter of open stomata on leaves fromin vitro culture remained at 8 µm. In contrast, an averageof 96% of the stomata on leaves of greenhouse grown plants wereclosed after 4 h in darkness; 56% after 4 h of mannitol inducedwater stress; 90% after 1 h of 10^–4 M ABA treatment; 61%after 1 h in an atmosphere of 0.12% CO₂. Stomata of in vitroapple leaves did not seem to have a closure mechanism, but acquiredone during acclimatization to the greenhouse environment. Thelack of stomatal closure in in vitro plants was the main causeof rapid water loss during transfer to low relative humidity.     

Some Biochemical Changes Related to Starch Breakdown Induced by Blue Light Illumination and by Addition of Ammonia to Chlorella Cells

Illumination with blue light enhanced the production of ammoniaby cells of C. vulgaris 11h, while no such effect was inducedby red light illumination. Addition of ammonia caused increasesin ATP levels and decreases in Pi and ADP levels. When 5 mMNH₄Cl was added to phosphorylase and amylase isolated from thecells of C. vulgaris 11h, their activities increased about 5–15%and 40–100%, respectively. (Received June 21, 1986; Accepted December 23, 1986)     

A Far-Upstream Sequence of the Wheat Histone H3 Promoter Functions Differently in Rice and Tobacco Cultured Cells

The cis-regulatory function of a far-upstream sequence (–1,711to –186) of the promoter of the wheat gene for histoneH3 (TH012) was analyzed in cultured rice and tobacco cells ina transient expression system with the gene for rß-D-glucuronidaseas a reporter gene. The far-upstream sequence was necessaryfor full activity of the H3 promoter in rice cells but did notenhance the activity of the proximal promoter in tobacco cells.Dissection analysis of the far-upstream sequence revealed theexistence of several positive and negative cis-acting sequencesin this region, some of which functioned differently in riceand tobacco cells. In gain-of-function experiments with ricecells, the sequence from –848 to –704, containingthe CCAAT and octamer (CaCGGATC) motifs, functioned in an orientation-independentmanner, whereas the sequence from –703 to –486 functionedin an orientation-dependent manner. By contrast, both sequencesexhibited an orientation-dependent cis-function in tobacco cells.These findings suggest that some cis-regulatory sequences inthe far-upstream region of the H3 promoter function differentlyin rice and tobacco cells. (Received May 10, 1995; Accepted August 8, 1995)     

Food selection and growth of the planktonic ciliate Coleps hirtus isolated from a monomictic subtropical lake

A strain of Coleps hirtus (Ciliophora, Prorodontida) was isolatedfrom the epilimnion of monomictic Lake Kinneret. Growth of thisciliate was tested in response to 12 species of planktonic algaeand seven species of cultured bacteria from lake isolates whichwere offered as food. Eight species of algae (one Cryptophyceaeand seven Chlorophyceae) and four bacteria supported good toexcellent growth of C.hirtus. Growth rates (µ) and doublingtimes (DT) ranged from 0.008 to 0.029 h^–1 and from 23.9to 90.8 h respectively. C.hirtus was able to grow on bacteriaat concentration levels as low as 2–8 x 10⁵ cells ml^–1.No correlation was observed between growth rate of C.hirtusand cell volume of the prey. ^aPresent address: Istituto di Ecologia, Universita di Parma,43100 Parma, Italy