Adenine and Guanine Salvage in Suspension Cultured Cells of Catharanthus roseus

Changes in the activity of adenine and guanine salvage in nucleotideand nucleic acid synthesis during the growth of Catharanthusroseus were investigated. Incorporation of [8-¹⁴C]adenine intoATP and ADP and that of [8-¹⁴C]guanine into GTP and GDP increasedmarkedly in the lag phase of cell growth and then sharply decreased.The incorporation into RNA from both precursors showed a similarpattern. The role of rapid purine salvage observed in the lagphase of cell growth is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture cells, purine salvage, adenine, guanine     

Anatomical and physiological aspects of developmental processes of adventitious root formation in Azukia cuttings

In Azukia stem cuttings, root primordia always appeared in theinterfascicular regions between the endodermis and the interfascicularcambium. Transverse cell divisions were observed as the first eventsin the process of root formation. They began to occur 10 hrafter cuttings had been made and were restricted to the interfascicularregions about 1 mm above the basal cut end of the cutting. Ineach of interfascicular region, 10 to 20 cells divided. Transversedivisions were followed by longitudinal divisions, which beganto occur 18 hr after cuttings had been made. The early process of root primordium formation is distinguishedby the following three phases: the first phase during whichno cell division occurs (0–8 hr), the second phase duringwhich transverse cell divisions occur (8–16 hr) and thethird phase during which longitudinal divisions occur (16–24hr). Cuttings in each phase responded differently to test substances. ¹Supported in part by Grant No. 139011 from the Ministry ofEducation, Japan. ² Present address: Junior College of Toyo University, Hakusan,Bunkyo-ku, Tokyo 112, Japan. (Received October 24, 1977; )     

Altered Synthesis and Composition of Cell Wall of Grape (Vitis vinifera L.) Leaves during Expansion and Growth-Inhibiting Water Deficits

The rate and composition of cell wall polysaccharide synthesisduring development and growth-inhibiting water deficits wereinvestigated in leaves of grape (Vitis vinifera L.). The rateof leaf expansion was monitored as plant water status was manipulatedby modulating the supply of irrigation water to potted plantsover several days. The corresponding wall synthesis was determinedby incubating leaf tissue with [¹⁴C]glucose and quantifyingincorporation into wall components. Samples were obtained fromrapidly expanding and mature leaves before, during, and following(recovery from) moderate water deficits. Uptake was approximately2-fold greater for mature leaf tissue than for rapidly expandingtissue at both high and low water status. In contrast, incorporationinto cell wall polysaccharides was 18 to 41% (under low andhigh water status) of uptake in expanding leaves but less than4% in mature tissue. Incorporation of precursor into wall polysaccharideswas insensitive to plant water status in mature leaves, butwas inhibited to less than 50% of well-watered controls in expandingleaves at low water potential. Incorporation of label into cellulose,uronic acid, and neutral sugar fractions was differentiallyaffected by water deficits, with cellulose synthesis apparentlyexhibiting the greatest sensitivity to low water status. Afterrewatering, growth, as well as uptake and incorporation of labelrecovered, although the latter did not attain prestress rates.The results indicate a high sensitivity of wall polysaccharide(particularly cellulose) synthesis to growth-inhibiting waterdeficits. ¹ Supported by United States Department of Agriculture, CompetitiveResearch grant GAM 8502539. (Received November 15, 1989; Accepted January 17, 1990)     

Chimeras and the Origin of Lateral Root Primordia in Zea mays

The difficulty of determining the contribution made by the pericycleand endodermis of mother roots to lateral primordia in the Gramineaehas been solved by inducing polyploid chimeras at initiation. The endodermis forms a layer covering the primordium, but thislayer does not form the epidermis of the lateral. It does formthe root cap of the young primordium, but this is replaced ata variable stage of development by the quiescent centre donatinga new set of cap initials of pericyclic origin. Reasons forthe previous diversity of interpretations are presented. chimera, lateral root primordia, Zea mays     

Origin of Epidermis and Development of Root Primordia in Pistia, Hydrocharis and Eichhornia

All three floating plants have roots bearing laterals derivedfrom both pericycle and endodermis. In Pistia and Eichhornialaterals arise within the meristem of the mother root; in Hydrocharisthey arise from mature tissue. In Pistia and Hydrocharis theepidermis becomes anatomically discrete between cortex and cap:in Pistia it is derived from the endodermis of the mother root,in Hydrocharis from the pericycle. The epidermis is not discretein Eichhornia and is derived from the pericycle of the motherroot with the cortex. Stathmokinetic data were used to construct timetables of developmentwhich show how the differences arise. In Pistia the first periclinaldivision of the endodermis-derived tissue individualizes theepidermis and occurs early, before a quiescent centre forms.In Hydrocharis the epidermis also becomes discrete before thepole of the meristem becomes quiescent, but it does so by apericlinal division of the pericycle-derived tissue. In Eichhorniapericlinal divisions occur in the outermost layer of the pericycle-derivedtissue long after quiescence has set in at the pole and afterthe fourth periclinal division in the endodermis derived cap.Its epidermis therefore never becomes anatomically discretethough it becomes functionally discrete because its polar cellsstop dividing as in the other plants. The involvement of the endodermis of mother roots in the formationof laterals is discussed in relation to the state of differentiationat sites of primordium formation, discreteness of the epidermisand subsequent fate of primordia. Pistia stratiotes L., Hydrocharis morsus-ranae L., Eichhornia crassipes Solms., primordia, lateral root, discrete epidermis, development, chimera, stathmokinetics     

Regulation of Sterol Biosynthesis in Solanum Species

Regulation of sterol synthesis was studied in Solanum species.A significant negative correlation was found between sterolcontent and rate of sterol synthesis from (1-¹⁴C) acetate inplant organs of Solanum nigrum and cell cultures of S. dulcamara.Exogenous cholesterol significantly inhibited the rate of sterolsynthesis from (¹⁴C) acetate in cell cultures of S. dulcamarawithout affecting synthesis from (³H) mevalonate. Exogenouscholesterol stimulated the rate of total lipid synthesis fromboth (¹⁴C) acetate and (³H) mevalonate. Thus, cholesterol inhibitedconversion of acetate to mevalonate; this is taken as evidenceof a negative feedback control on sterol synthesis. Key words: Feedback control, Phytosterol biosynthesis, Plant cell culture, Solanum species     

Translocation Profiles of [11C] and [13N]-Labelled Metabolites after Assimilation of 11CO2 and [13N]-Labelled Ammonia Gas by Leaves of Helianthus annuus L. and Lupinus albus L.

Tracer amounts of atmospheric [¹³N]-Iabelled ammonia gas, wereabsorbed by leaves of Lupinus albus and Helianthus annuus inboth the light and the dark. Exogenous [¹³N]-ammonia was onlyabsorbed in the dark when the feeding occurred shortly aftera period of illumination and the tissue was not depleted ofits carbohydrate reserves (e.g. starch). Incorporation of the[¹³N]-ammonia appeared to occur via the leaf glutamine synthetase/glutamatesynthase (GS/GOGAT) cycle since 2.0 mol m^–3 MSX, an inhibitorof the GS reduced uptake in both the light and dark. Photosyntheticincorporation of ¹¹CO₂ was not affected by this treatment Therate of movement of [¹³N]-assimilates in the petiole of attachedleaves of Helianthus and Lupinus was similar to that of the¹¹Cl-photo assimilates. Export of both [¹³N] and [¹¹C]-Iabelledassimilates from the leaf and movement in the petiole in boththe light and the dark was inhibited by source leaf anoxia (i.e.nitrogen gas). Translocation was re-established at the samerate when the feed leaf was exposed to gas containing more than2% O₂ which permitted dark respiration to proceed. After aninitial feeding of either ¹¹CO₂ or [¹³N]-ammonia at ambient(21%) O₂ exposure of the source leaf to 2% O2, or 50% O² didnot alter the rates of translocation, indicating that changesin photosynthetic activity in the source leaf due to photorespiratoryactivity need not markedly alter, at least during the shortperiod, the loading and translocation of either [¹¹C ] or [¹³N]-labelledleaf products. Key words: Translocation, CO₂, NH₃, Leaves, Helianthus annuus, Lupinus albus     

Relationship between Tracheary Element Differentiation and DNA Synthesis in Single Cells Isolated from the Mesophyll of Zinnia elegans--Analysis by Inhibitors of DNA Synthesis

Effects of inhibitors of DNA synthesis on tracheary element(TE) differentiation were investigated in a culture of singlecells isolated from the mesophyll of Zinnia elegans L. cv. Canarybird. In this system, neither mitosis nor replication of thewhole genome during the S phase in the cell cycle is a prerequisitefor TE differentiation [Fukuda and Komamine (1980) Plant Physiol.65: 61, unpublished data]. Fluorouracil (FU), fluorodeoxyuridine(FUdR), mitomycin G (MC), arabinosyl cytosine (ara-C) and aphidicolin,inhibitors of DNA synthesis, prevented the incorporation of[³H]-thymidine into nucleic acid, cell division and cytodifferentiationto TE. However, neither FUdR nor aphidicolin prevented the incorporationof [14C]-leucine into protein. Thymidine reversed the inhibitoryeffect of FUdR when given simultaneously with FUdR. These resultsshow that the inhibitors of DNA synthesis prevent TE differentiationvia blockage of the synthesis of some DNA, although replicationof the whole genome during the S phase is not a prerequisitefor cytodifferentiation. The role of DNA synthesis in TE differentiationis discussed. (Received October 13, 1980; Accepted November 17, 1980)     

The Effect of Cycloheximide (Actidione) on Protein and Nucleic Acid Synthesis by Chlorella

Incorporation of ¹⁴C-phenylalanine, ¹⁴C-carbon dioxide, ¹⁴C-glucose,and ¹⁴C-glycine into the protein of Chlorella is inhibited bycycloheximide. A concentration of 2.5 µg per ml inhibitsincorporation by about 80 per cent; increasing the concentrationup to 10 µg per ml does not increase the degree of inhibition.The incorporation of ¹⁴C-adenine into ribonucleic acid (RNA)and deoxyribonucleic acid (DNA), and of ¹⁴C-glucose into polysaccharideis also inhibited. Unlike inhibition of protein synthesis, thatof nucleic acid and polysaccharide synthesis is observed onlyafter some delay. The delay is shortest for DNA synthesis andlongest for polysaccharide synthesis. Inhibition of ¹⁴C-glycineincorporation into DNA and RNA follows a similar pattern tothat obtained with ¹⁴C-adenine but the delay is much shorter.Cycloheximide also inhibits the formation of isocitrate lyasc(isocitrate-glyoxylate lyase, EC 4.1.3.1 [EC] ) when autotrophicallygrown cells are supplied with acetate.     

The Interaction Between Silicon and Aluminium in Sorghum bicolor (L.) Moench: Growth Analysis and X-ray Microanalysis

Seeds of Sorghum bicolor (L.) Moench. were germinated on moistfilter paper for 6 d, before the seedlings were transferredto pots containing 500 µmol l^-1 Ca(NO₃)₂ for 2 d. Theseedlings were then treated with 0 or 100 µmol l^-1 Alin factorial combination with 0, 1400 or 2800 µmol l^-1Si for 8 d. The background solution used throughout was 500µmol l^-1 Ca(NO₃)₂. Aluminium treatment reduced root growthand caused a significant increase in shoot/root ratio. The presenceof silica in the solution significantly ameliorated the effectsof aluminium on root growth. Three treatment were selected for a microanalytical investigationof the basal region of the root: 2800 µmol l^-1 Si only;100 µmol l^-1 Al only; and a combination of the two. Inthe 2800 µmol l^-1 treatment silica was deposited in theendodermis, with the greatest accumulation being in the innertangential wall (ITW). When plants were treated with 100 µmoll^-1 Al only, aluminium concentration was highest in the outertangential wall (OTW) of the epidermis. The element was presentin the hypodermal walls and OTW of the endodermis and was notdetectable in the stele. With both 2800 µmol l^-1 Si and100 µmol l^-1 Al in the nutrient solution the two biomineralizationsites were the ITW of the endodermis, where silicon was themajor element deposited, and atypically in the OTW of the epidermiswhere both aluminium and silicon were present. The sequestrationof aluminium in the Al-Si deposit in the OTW of the epidermismay represent the mechanism that allows greater root growthin this treatment.Copyright 1993, 1999 Academic Press Sorghum bicolor (L.) Moench., aluminium, silicon, calcium, root, toxicity, biomineralization, X-ray microanalysis, freeze substitution     

Inhibitory effect of lycorine on cell division and cell elongation

Lycorine, an alkaloid isolated from bulbs of Amarillidaceae,was found to be a powerful inhibitor of cell division and elongation.Adding different concentrations of lycorine from 10^–6M to 10^–4 M in an appropriate growth-medium strongly inhibitedcell division in explants of lettuce pith parenchyma. The sameresult was obtained with liquid yeast cultures growing exponentially. Lycorine-treated meristematic cells of the primary roots ofVicia faba also showed rapid inhibition of the mitotic indexwhile interphase cells increased proportionately. Lycorine alsoinhibited endogenous and auxin-induced cell elongation in Avenacoleoptiles and pea segments. Since both cell division and cell elongation require proteinsynthesis and RNA synthesis, the assumption is that lycorineprobably inhibits one of the two syntheses. ¹This study was supported by a contract between the NationalResearch Council of Italy and University of Bari, Instituteof Botany. (Received November 27, 1972; )     

Cluster root development in Grevillea robusta (Proteaceae). II. The development of the endodermis in a determinate root and in an indeterminate, lateral root

Light, fluorescence and electron microscopy were employed to follow the development of the endodermis in cluster roots and lateral roots of Grevillea robusta A. Cunn. ex R. Br. Endodermal cells had three different origins: rootlet endodermis arose from the rootlet meristem; endodermis covering the primordium shortly after initiation came from division of parental endodermis; cells at the junction between parent and rootlet endodermis developed from re-differentiated rootlet cortical cells. In the cluster root, the Casparian band formed in three ways, and was not initially present opposite the two sets of single xylem elements in the rootlet stele. A new clearing technique was developed that allowed visualization of xylem, suberized endodermis, Casparian band formation and phenolic compounds. In lateral roots, endodermal differentiation was asynchronous, but was related to position relative to protoxylem poles. However, the observed delay began before these poles had differentiated. At the tip of mature rootlets, which are determinate, the endodermis terminates in a 'dome' of cells, with the initial cell differentiating as an endodermal cell. Results are discussed in terms of determinate development in roots and the spatial and temporal contexts within which this development takes place.     

Caco-2 intestinal cell differentiation is associated with G1 arrest and suppression of CDK2 and CDK4

The cellular mechanisms regulating intestinal proliferation anddifferentiation remain largely undefined. Previously, we showed anearly induction of the cyclin-dependent kinase (CDK) inhibitor p21^Waf1/Cip1 in Caco-2 cells, ahuman colon cancer line that spontaneously differentiates into a smallbowel phenotype. The purpose of our present study was to assess thetiming of cell cycle arrest in relation to differentiation in Caco-2cells and to examine the mechanisms responsible for CDK inactivation.Caco-2 cells undergo a relativeG₁/S block and cease toproliferate at day3 postconfluency; an increase in theactivity of terminally differentiated brush-border enzymes (sucrase andalkaline phosphatase) was noted at day6 postconfluency. Cell cycle block wasassociated with suppression of both CDK2 and CDK4 activities, which areimportant for G₁/S progression.Treatment of the CDK immune complexes with the detergent deoxycholate(DOC) resulted in restoration of CDK2, but not CDK4, activity atday 3 postconfluency, suggesting the presence of inhibitory protein(s)binding to the cyclin/CDK2 complex at this time point. An increasedbinding of p21^Waf1/Cip1 to CDK2complexes at day3 postconfluency was noted, suggesting a potential role for p21^Waf1/Cip1in CDK2 inactivation; however, immunodepletion ofp21^Waf1/Cip1 from Caco-2 proteinextracts demonstrated thatp21^Waf1/Cip1 is only partiallyresponsible for CDK2 suppression atday 3 postconfluency. A decrease in the cyclin E/CDK2 complex appears tocontribute to the CDK2 inactivation noted atdays6 and12 postconfluency. Taken together, ourresults suggest that multiple mechanisms contribute to CDK suppressionduring Caco-2 cell differentiation. Inhibition of CDK2 and CDK4 leadsto G₁ arrest and inhibition ofproliferation that precede Caco-2 cell differentiation.

     

Mating type specific induction of cell wall lytic factor by agglutination of gametes in Chlamydomonas reinhardtii

When mt⁺ and mt^– gametes of Chlamydomonas reinhardtiiwere mixed, shedding of cell walls took place in both matingtypes during massive agglutination and/or pairing. This wascaused by a cell wall lytic factor that had been induced byflagellar agglutination and excreted into the medium by cellsconcurrently with their cell wall release. When glutaraldehyde-fixed gametes and isolated flagella of onemating type caused isoagglutination of live gametes of the othermating type, the live mt⁺ gametes induced the lytic factor andshed their walls, whereas none of the live mt^– did this.The cell walls of mt^– gametes were lost only when thelytic factor, which had been excreted by mt⁺ gametes into themedium, acted from the outside. These data imply that mt⁺ gametesare responsible for the induction of the lytic factor by agglutination,which acts on cell walls of both mating types either endogenouslyor exogenously. (Received February 28, 1978; )     

Metabolism of Caffeine and Related Purine Alkaloids in Leaves of Tea (Camellia sinensis L.)

Purine alkaloid catabolism pathways in young, mature and agedleaves of tea (Camellia sinensis L.) were investigated by incubatingleaf sections with ¹⁴C-labelled theobromine, caffeine, theophyllineand xanthine. Incorporation of label into CO₂ was determinedand methanol-soluble metabolites were analysed by high-performanceliquid chromatography-radiocounting and thin layer chro-matography.The data obtained demonstrate that theobromine is the immediateprecursor of caffeine, which accumulates in tea leaves becauseits conversion to theophylline is the rate limiting step inthe purine alkaloid catabolism pathway. The main fate of [8-¹⁴C]theophyllineincubated with mature and aged leaves, and to a lesser extentyoung leaves, is conversion to 3-methylxanthine and onto xanthinewhich is degraded to ¹⁴CO₂ via the purine catabolism pathway.However, with young leaves, sizable amounts of [8-¹⁴C]-theophyllinewere salvaged for the synthesis of caffeine via a 3-methylxanthine     

Distribution of Growth in the Apical Region of the Shoot of Lupinus albus

The purpose of the investigation is the determination of thevolumes and numbers of cells of the meristematic dome and ofeach of the first 7 primordia and internodes at the apex ofthe shoot of Lupinui albus. This system occupies a zone whichis about 0·4 mm. in length. Techniques are describedfor dissecting the region in which the observations are made,for determining the numbers of cells and the volumes of theseveral fragments. From the number of cells and the volume ofeach fragment an average cell volume it calculated. It is shown that in the midphase of the plastochron the domecontains 3,500 cells and has a volume of 1·6 x10^–3mm.³,the first primordium contains 1,630 cells and has a volume of0·38 x10^–3 mm.³, and the first intemode containsabout 700 cells and has a volume of about 1·4 x10^–3mm³The number of cells and the volume of the primordium increaseexponentially with increasing plastochron age, and the seventhprimordium contains 26,000 cells and has a volume of 20·9x 10^–3mm³ The seventh intemode contains about 5,000 cellsand has a volume of 8·6x10^–3mm³ The average cell volume in the dome is 4·7 x 10^–7mm.³in the first primorndium it is 2·3 x 10^–7mm.³ andin the first internode it is 20·9x 10^–7mm.³ Inthe seventh primordium the average cell volume increases to7·9 x 10^–7mm.³ In the internodes there is little,if. any, change in cell volume from the first to the seventhof the series. The significance of these changes is discussed.     

Determination and Differentiation of Leaf and Petal Primordia in Impatiens balsamina

The development of primordia as leaves, petals, or as organsintermediate between leaves and petals can be regulated by photoperiodin Impatiens. In intermediate organs only some parts of theorgan differentiated as petal, and then only in some cell layers.Allometric measurements of primordium shape suggested that intermediateorgans may begin development as petals, and that their intermediatecharacter at maturity resulted from a switch of some parts ofthe organs from petal to leaf development when the primordiawere between 0.5 and 1 mm long. In reverted apices made to re-flower,primordia were not completely determined as leaves until theywere about 750 µm long. Determination typically occurredfirst at the tips and last at the bases of these primordia.The determination of primordia as leaves or petals in Impatiensis discussed in relation to primordium determination in otherspecies. It is suggested that the lack of commitment to flowermay result in relatively late primordium determination in Impatiens. Impatiens balsamina, determination, differentiation, leaf and petal development, flowering, reversion     

Effects of Colchicine, Vinblastine, Cytochalasin B and Phalloidin on the Seismonastic Movement of Mimosa pudica Leaf and on Motor Cell Ultrastructure

Fleurat-Lessard, P., Roblin, G., Bonmort, J. and Besse, C. 1988.Effects of colchicine, vinblastine, cytochalasin B and phalloidinon the seismonastic movement of Mimosa pudica leaf and on motorcell ultrastructure.—J. exp. Bot. 39: 209–221. Colchicine at 1 x 10^–3 mol dm^–3 does not affectthe seismonastic movement of Mimosa pudica leaves but disruptsmicrotubules in motor cells. Vinblastine at 5 x 10^–3 moldm^–3 does not affect this movement and partly disruptsmicrotubules. Vinblastine at 1 x 10^–4 mol dm^–3 alwaysdisrupts microtubules, even after a 12 h reversibility whenthe movement is restored. These drugs, applied at the same respectiveconcentrations, do not alter cytoplasmic and vacuolar fibrils.Cytochalasin B and phalloidin alter the seismonastic movementof Mimosa leaves when applied at concentrations of 1.25 x 10^–3and 2.4 x 10^–4 mol dm^–3 respectively. These drugs,used at the same respective concentrations, also affect themotor cell structure and, in particular, modify the arrangementand the structure of the fibrils but they do not destroy themicrotubules. These data suggest that microtubules are not directly involvedin the seismonastic reaction whereas fibrils, formed by thin(3.0 nm wide) filaments, may be implicated in this reaction. Key words: Colchicine, cytochalasin B, phalloidin, Mimosa pudica, motor cells, vinblastine