Particles Associated with the Outer Epidermal Wall in Internodes of Deepwater Rice

Partial submergence induces rapid internodal growth in deepwaterrice (Oryza saliva L., cv. Habiganj Aman II). The infrastructureof the cell wall/plasmalemma interface of air-grown and submergedinternodes was investigated in the region where cell elongationtakes place. In submerged internodes, electron-dense particlesof about 100 nm diameter were found. These particles were detectableonly at the thick outer wall of the outer epidermis but notat the inner walls. In air-grown control plants, no such granuleswere visible. We suggest that these particles are related tothe process of cell wall growth. The wall weight per unit lengthwas 75% lower in the submerged internode as compared to thatof the air-grown control. This indicates that secondary wallformation is suppressed during submergence of the plant Oryza saliva, deepwater rice, intemodal growth, electron-dense particles     

The biophysical basis of elongation growth in internodes of deepwater rice

Partial submergence induces rapid internodal elongation in deepwater rice (Oryza sativa L., cv Habiganj Aman II). We measured in vivo extensibility, tissue tension, hydraulic conductance and osmotic potential in the region of cell elongation in the uppermost internode. The in vivo extensibility of the internode, measured by stretching of living tissue with a custom-made constant stress extensiometer, rose rapidly following submergence of the plant. Both the elastic (E_el) and plastic (E_pl) extensibility increased when growth of the internode was induced. The submerged internode displayed tissue tension (elastic outward bending of longitudinally split internode sections); in air-grown control internodes, no such bending occurred. The hydraulic conductance, estimated from the kinetics of tissue shrinkage in 0.5 molar mannitol and subsequent swelling in distilled water, was not changed by submergence. The osmotic potential, measured with a dew-point hygrometer using frozen-thawed tissue, was only 18% less negative in the submerged internode than in the air-grown control. This indicates that osmoregulation takes place in rapidly elongating rice internodes. We suggest that the rapid expansion of the newly formed internodal cells of submerged plants is controlled by the yielding properties (E_pl) of the cell walls. Experiments with excised stem sections indicate that gibberellin is involved in increasing the E_pl of the elongating cell walls.     

Changes in cell wall polysaccharides in the internodes of submerged floating rice

In excised stem segments of floating rice (Oryza sativa L.), as well as in intact plants, submergence greatly stimulates the elongation of internodes. The differences in the composition of cell wall polysaccharides along the highest internodes of submerged and air-grown stem segments were examined. The newly elongated parts of internodes that had been submerged for two days contained considerably less cellulosic and noncellulosic polysaccharides than air-grown internodes, an indication that the cell walls of the newly elongated parts of submerged internodes are extremely thin. In the young parts of both air-grown and submerged internodes, the relative amounts of noncellulosic polysaccharides were equal to those of -cellulose, whereas the relative amounts of -cellulose were higher than those of noncellulosic polysaccharides in the upper, old parts. In the cell-elongation zones of both air-grown and submerged internodes, glucose was predominant among the noncellulosic neutral sugars of cell wall. The relative amount of glucose in noncellulosic neutral sugars decreased toward the upper, old parts of internodes, whereas that of xylose increased.     

Effect of submergence on the cell wall composition of deep-water rice internodes

The cell wall composition of internodes of deep-water rice plants (Oryza sativa L. cv Habiganj Aman II) which were induced to grow rapidly by submergence in water was compared to that of nonsubmerged plants which grew slowly. No differences could be detected in cellulose, uronic acid, and lignin content expressed on a dry weight basis. Cell wall preparations of rapidly growing, submerged internodes contained more hydroxyproline and had a higher hydration capacity than those of control internodes. The silicon content of submerged rice internodes was considerably lower than that of air-grown plants. The role of silicon as a structural component of the cell wall of grasses is discussed in relation to lodging of deep-water rice plants after the flood waters have receded.     

Internode Length in Pisum. A New Allele at the le Locus

In Pisum sativum L. a third, more severe, allele at the internodelength locus le is identified and named le^d. Plants homozygousfor le^d possess shorter internodes and appear relatively lessresponsive to GA₂₀ than comparable le (dwarf) plants. Gene le^dmay act by reducing the 3ß-hydroxylation of GA₂₀ tothe highly active GA₁ more effectively than does gene le. Theresults indicate that le is a leaky mutant and therefore thatendogenous GA₁ influences internode elongation in dwarf (le)plants. Pisum sativum, peas, internode length, genetics, gibberellin, dwarf elongation     

Pumpkin (Cucurbita sp.) seed globulin V. Proteolytic activities involved in globulin degradation in ungerminated seeds

Two proteolytic activities I and II involved in the globulindegradation were detected in pumpkin seeds. Activity I, hydrolyzing and ß subunits of the globulin to form F_ß,was found in both dry seeds and cycloheximide-treated cotyledons,and decreased during germination. Activity II, hydrolyzing F_ßto produce small peptides and amino acids, was not observedin dry seeds but found in cycloheximide-treated cotyledons,increased up to 4 days, and gradually decreased during germination. Activity I gave limited hydrolytic products from the globulinand the chain, but not from F_ß, the chain and some animal proteins. It was inhibitedby EDTA. On the other hand, activity II hydrolyzed F_ßand the chain faster than the globulin, the chain and some animal proteins. It was inhibitedby EDTA and p-chloromer-curibenzoate, and activated by ß-mercaptoethanol,dithiothreitol and CoCl₂. Optimum pH's were at about 6.8 andat 6.0 to 6.8 for activities I and II, respectively. The degradation process of the globulin can be divided intotwo steps: the first step is the conversion of globulin to F_ßand the second step, F_ß to small peptides and aminoacids. (Received November 9, 1979; )     

Invertase Activity, Carbohydrate Metabolism and Cell Expansion in the Stem of Phaseolus vulgaris L.

In the stem of Phaseolus vulgaris L. the specific activity ofacid invertase was highest in the most rapidly elongating internode.Activity of the enzyme was very low in internodes which hadcompleted their elongation, in young internodes before the onsetof rapid elongation, and in the apical bud. From shortly afterits emergence from the apical bud the elongation of internode3 was attributable mainly to cell expansion. Total and specificactivities of acid invertase in this internode rose to a maximumat the time of most rapid elongation and then declined. Transferof plants to complete darkness, or treatment of plants withgibberellic acid (GA₃), increased the rate of internode elongationand final internode length by stimulating cell expansion. Bothtreatments rapidly increased the total and specific activitiesof acid invertase in the responding internodes; peak activitiesof the enzyme occurred at the time of most rapid cell expansion. In light-grown plants, including those treated with GA₃, rapidcell and internode elongation and high specific activities ofacid invertase were associated with high concentrations of hexosesugar and low concentrations of sucrose. As cell growth ratesand invertase activities declined, the concentration of hexosefell and that of sucrose rose. In plants transferred to darkness,stimulated cell elongation was accompanied by a rapid decreasein hexose concentration and the disappearance of sucrose, indicatingrapid utilization of hexose. No sucrose was detected in theapical tissues of light-grown plants. The results are discussed in relation to the role of acid invertasein the provision of carbon substrates for cell growth. Key words: Cell expansion, Acid invertase, Hexose, Sucrose, Phaseolus     

Pumpkin (Cucurbita sp.) seed globulin VI. Proteolytic activities appearing in germinating cotyledons

N--benzoyl D,L-arginine p-nitroanilide (BAPA), leucine p-nitroanilide(LPA) and casein hydrolytic activities were assayed in germinatingcotyledons. BAPA hydrolytic activity was not detected in dryseeds, but increased rapidly from 1 to 4 days of germinationand then decreased. LPA and casein hydrolytic activities weredetected in dry seeds and increased from 2 to 4 days. Caseinhydrolytic activity decreased faster than the other two activities. BAPA hydrolytic enzyme was partially purified. It was inhibitedby p-chloromercuribenzoate and activated by ß-mercaptoethanoland dithiothreitol, but was not affected by EDTA, phenylmethylsulfonylfluoride, pumpkin trypsin inhibitor and several divalent cations.It had no ability to hydrolyze globulin or the chain to produce F_ß or smaller polypeptides,respectively, which was referred to as proteolytic activityI in the preceding paper (14), but released small peptides andamino acids from the chain and F_ß. However, it wasdifferent from proteolytic enzyme II which was present in dryseeds and inhibited by EDTA (14). Pumpkin trypsin inhibitor was purified. Its molecular weightwas estimated to be 10,500 by gel filtration. It did not inhibitthe BAPA hydrolytic enzyme. Both proteolytic activities I andII were also not reduced by the inhibitor (14). The inhibitoryactivity decreased gradually during germination. (Received November 9, 1979; )     

Isolation of Subunits of Coupling Factor 1 from Maize and Spinach Chloroplasts and Properties of Combinations of Subunits with ATPase Activity

Subunits (, ß, ) and mixtures of subunits ( ß, , ß , ß ) were isolated without denaturationfrom a chloroform extract of chloroplast coupling factor 1 (CF₁)from maize (Zea mays var. Ushiku 5-4) and from spinach by fastprotein liquid chromatography (FPLC), on an anion-exchange columnof Mono-Q in the presence of n-octylglucoside (OG) and on achromatofocusing column of Mono-P. The ß -subunitcomplex (CF¹ ß ) was the minimum unit required forATPase activity, as was confirmed by the reconstituted complexof ß and subunits. An subunit isolated from maizeinhibited the ATPase activity of CF₁ ß from bothmaize and spinach. CF₁ ß was found to contain anOG-dependent Mg²⁺-ATPase. The ATPase activity of CF₁ ß required divalent cations, such as Mg²⁺ or Mn²⁺, for its expressionin the presence of OG; its optimum pH was 8.0 and it was markedlyinhibited by NaN₃. The enzyme hydrolyzed ATP in prefernece toGTP but not CTP, UTP, ADP, AMP or pNPP. Lineweaver-Burk plotsof its activity were curvilinear in the range of 0.6–0.7mM ATP.Mg²⁺. ¹Present address: Department of Biology, School of Education,Waseda University, Shinjuku-ku, Tokyo, 160 Japan. (Received February 15, 1989; Accepted April 20, 1989)     

Effects of Gibberellins and Prohexadione on the Activities of Oryzain and {alpha}-Amylase in Rice Seeds

Oryzains, cysteine proteinases of rice seeds, are induced byGA₃ in germinating rice seeds [Abe et al. (1987) Agric. Biol.Chem. 51: 1509]. The effects of GA₁, GA₃, GA₄, GA₉, and GA₂₀on the production of oryzain and -amylase were investigatedin embryoless half- and whole-seeds of rice (cv. Nipponbare).When gibberellins (GAs) were incubated with embryoless half-seeds,GA₁, GA₃ and GA₄ induced oryzain and -amylase, but GA₉, andGA₂₀ did not. GA₉ and GAM induced oryzain and -amylase productionin whole seeds, but this production was inhibited by the simultaneousapplication of prohexadione, an inhibitor of 2ß- and3ß-hydroxylation of GAs. Prohexadione did not inhibitthe activities of oryzain and -amylase induced by GA₁. Theseresults suggest that GAs possessing the 3ß-hydroxylgroup induce activities of oryzain and -amylase in rice seedsand that GA₉ and GA₂₀ have activity only after they are convertedmetabolically to active GAs, probably GA₄ and GA₁, respectively.GA₁, was more active than GA₄ in both half seeds and wholeseeds incubation. Oryzain and -amylase activities induced byGA₄ were significantly inhibited in the presence of 10^–4M prohexadione. This suggests that the conversion of GA₁, toGA₄ (13-hydroxylation) might be inhibited at a high dose ofprohexadione in whole seeds. ⁴Present address: Institute of Food Development, Kyung Hee University,Suwon 449-701, Korea     

Maternal Effects of mto1 Mutation, That Causes Overaccumulation of Soluble Methionine, on the Expression of a Soybean {beta}Conglycinin Gene Promoter-GUS Fusion in Transgenic Arabidopsis thaliana

ß-Conglycinin, the 7S seed storage protein of soybean(Glycine max [L.] Merr.), is comprised mainly of three subunits,designated , ' and ß. Expression of the gene encodingthe ß subunit is unique because its expression hasbeen shown to be down-regulated by exogenously applied L-methioninein immature soybean cotyledon cultures in vitro. Arabidopsisthaliana strain carrying a mto1-1 mutation overaccumulates solublemethionine. By using this mutant, we analyzed the effects ofmethionine on expression of the ß subunit gene invivo. Reciprocal crosses were made between the mto1-1 mutantand a transgenic A. thaliana strain, designated SNTß3,which carries a ß-glucuronidase (GUS) reporter geneunder the control of the promoter region of the ßsubunit gene. Analysis of GUS activity in F₁ seeds indicatedthat the GUS activity was dramatically repressed when the mto1-1mutant plants were used as female parents. We constructed astrain which carries both the transgene and mto1-1 mutationin the homozygous state. Analyses of the GUS activity in seedsof this double homozygous strain indicated that the GUS activitywas repressed to 2.5% of control by introduction of the mto1-1mutation. These results indicate that the ß subunitgene promoter activity in seeds is down-regulated by maternalgenotype and suggest that soluble methionine, or its mobilemetabolite, is translocated from mother plants to repress ßsubunit gene expression in seeds. ⁵Present address: Division of Biological Sciences, GraduateSchool of Science, Hokkaido University, Kita-ku, Sapporo, 060Japan ⁶Present address: Department of Biotechnology, Faculty of Agriculture,The University of Tokyo, Bunkyo-ku, Tokyo, 113 Japan     

Electrotonic Coupling between Adjacent Internodal Cells of Chara braunii: Transmission of Action Potentials beyond the Node

Many nodal cells are interposed between two internodal cellsof Chara braunii. When an action potential conducted in an internodereached the node, no electrical activation in the nodal cellscould be found, although an area of the membrane bordering thenodal cells in this internode was partially activated (end-membraneaction potential). When the action potential approached thenode along the stimulated internode, an electrotonic potentialchange (depolarization) was produced in the other internode.This depolarization was greatly depressed by the end-membraneaction potential of the stimulated internode, so that hardlyany transmission took place. The ratio of the potential changein the surface membrane of the adjoining ("postsynaptic") internode(cell b) to that of the stimulated one (cell a), the couplingratio, e_b/e_a, can be estimated from a simple equivalent circuitof the nodal region composed of two surface-membrane resistances(R_a, R_b) and intercellular resistance (R_n). If R_n remains thesame, a higher ratio should be produced with a larger R_b, butthe ratio does not depend on any change in R_a, which could beproved experimentally. Transmission of the action potentialbeyond the node was frequent when the coupling ratio was increasedand when the threshold that elicits the action potential waslowered by immersing the node in a K or Na salt solution. ¹ Present address: Department of Physiology, Tohoku UniversitySchool of Dentistry, Sendai 980, Japan. (Received December 1, 1980; Accepted January 23, 1981)     

Abscisic Acid and Apical Dominance in Phaseolus coccineus L. The Role of Tissue Age

Abscisic acid (ABA) applied to the decapitated second internodeof runner bean plants enhanced outgrowth of lateral buds onlywhen internode stumps were no longer elongating. Applied toelongating internodes of slightly younger plants, ABA causesinhibition of bud outgrowth. Together with 10^–4 M indol-3-ylacetic acid (IAA), ABA stimulated internode elongation and interactedadditively in the inhibition of bud outgrowth. A mixture of10^–5 M ABA and 10^–6 M gibberellic acid (GA₃ ) causedsimilar effects on internode growth as IAA + ABA, but was mutuallyantagonistic in effect on growth of the lateral buds. Abscisic acid, apical dominance, gibberellic acid, indol-3yl acetic acid, Phaseolus coccineus, bean     

Gas Composition in the Internal Air Spaces of Deepwater Rice in Relation to Growth Induced by Submergence

Deepwater rice (Oryza sativa L.) responds to partial submergenceby rapid elongation of the internodes. The elongation of intactplants was measured during 7 days of submergence using angulartransducers. Growth rates began to increase within 3 to 4 hupon submergence and peaked after 3 days; they were higher inthe light than in the dark. The composition of the gas phasein the internodal air spaces was analyzed at different timesafter partial submergence. In the light, the O₂ concentrationsin internal gas compartments of intact plants dropped initially,but recovered largely within 90 min. During longer periods ofsubmergence, the internal O₂ concentration followed a diurnalpattern with O₂ levels being lower during the night than duringthe day. An O₂ gradient was found from the apical parts of theplant near the water surface to the basal parts of the shoot. Concentrations of CO₂ changed with a pattern inverse to thatof the O₂concentrations. The level of ethylene in the internodallacunae increased upon submergence and reached 1µl-liter^–1after 72 h. It was higher at the end of the dark period thanduring the day. The gas exchange of the submerged parts of the plant seems todepend mainly on mass flow of air from the atmosphere to theroot system. Mass flow through this pathway was determined atdifferent pressure gradients and was compared to the intakeof air into plants as established in earlier investigations.A significant decrease in gas flow resistance found during 7days of submergence may constitute a long-term adaptation toflooding. (Received August 30, 1988; Accepted October 25, 1988)     

An {alpha}-Glucan from Suspension-Cultured Rice Cells

An -glucan was isolated from 11-day-old suspension-culturedrice cells by extraction with hot Na-phosphate buffer (pH 6.8).The -glucan had []_D=+234? (C = 0.14, in water) and its averagemolecular weight was estimated to be about 1.4 ? 10⁴, basedon elution characteristics on acalibrated Sepharose CL-6B column.Upon partial acid hydrolysis, the -glucan gave mainly malto-oligosaccharides.The maximum absorption of the iodine complex of the -glucanin the presence of Na₂SO₄ was at 470 nm. The results of hydrolysisby , ß- and iso-amylases and methylation analysisindicated that the isolated -glucan is a highly branched polysaccharidewith an average chain length of 9. The exterior and interiorchain lengths of the -glucan were calculated to be 5 and 3,respectively. (Received July 23, 1986; Accepted February 7, 1987)     

Ethylene and Gibberellin: Regulation of Internodal Elongation and Nodal Root Development in Floating Rice

Ethylene and GA₃ stimulated internodal elongation in the excisedstem sections of floating rice. The combined application ofethylene and GA₃ exerted a cooperative effect on internodalelongation, although the effect was variety dependent. Stimulativeeffect of ethylene on internodal growth in intact floating riceplants was virtually absent when the plants were pre-treatedwith Ancymidol, -cyclopropyl--(4-methoxyphenyl)-5-pyrimidinemethanol, an inhibitor of gibberellin biosynthesis. Submergenceof intact plants, which also induced internodal elongation,had no stimulative effect when the plants were pre-treated withAncymidol. Submergence of intact plants increased the endogenousgibberellin level. The internode of young, intact 9 day oldseedlings responded neither to submergence nor ethylene, butwhen seedlings were pre-treated with GA₃ they responded to eitherone. Nodal root development was also enhanced by either ethyleneor GA₃. Combined application of ethylene and GA₃ exerted a co-operativeeffect on nodal root development. Ancymidol-treated plants didnot produce nodal roots even though they were subjected to submergence,whereas nontreated control plants produced nodal roots normally. (Received September 12, 1984; Accepted February 15, 1985)     

Brassinosteroid-Induced Bending of the Leaf Lamina of Dwarf Rice Seedlings: An Auxin-Mediated Phenomenon

A synthetic brassinosteroid (BR), 2,3,22ß,23ß-tetrahydroxy-24ß-methyl-B-homo7-oxa-5-cholestan-6-one, an isomer of the growth promoter brassinolide,when applied to seedlings of dwarf rice Oryza sativa var. Tan-ginbozuand Waito-C, induced a significant bending of the second leaflamina at 100 ng/plant and higher dosages. Promotion of thesecond leaf sheath elongation, the characteristic response ofdwarf rice varieties to gibberellins, was significantly butmodestly enhanced by BR at a dosage of 10,000 ng/plant, fiveorders of magnitude higher than the minimal dosage responseto GA₃. Gibberellin A₃ had no significant effect on the bendingof the second leaf lamina, nor did any synergism exist betweenBR and GA₃ in leaf lamina bending or leaf sheath elongation.Neither ethylene nor (2-chloroethyl)phosphonic acid (ethephon)caused the bending of the second leaf lamina, and neither synergizedthe BR effect. However, IAA and -naphthaleneacetic acid causedsignificant bending at 5,000 ng/plant, and both auxins significantlysynergized the effect of BR on the bending, IAA being effectiveat 500 ng/ plant in this regard. The antiauxins, 2,3,5-triiodobenzoicacid (TIBA) and -(p-chlorophenoxy)isobutyric acid (PCIB) completelynullified both the BR-induced bending and the BR$IAA-synergizedbending. The BR-induced bending response may thus be mediatedthrough endogenous auxin. (Received May 11, 1982; Accepted August 25, 1982)     

Biochemical Characterization of Casein Kinases II (CK-II) from Cultured Cells of the Liverwort, Marchantia polymorpha

Monomeric and oligomeric forms of CK-II have been purified froma 1.0 M KC1 extract of the liverwort, Marchantia polymorpha,by means of heparin-agarose column chromatography and gel filtrationon Superose 6HR (HPLC). It was found that (i) a monomeric kinase(approximately 38 kDa) is the main form of CK-II in the cells;and (ii) the enzymatic properties of oligomeric kinase (approximately140 kDa), which cross-reacts with anti-serum against DrosophilaCK-IIß, are similar to those of CK-II (₂ß₂)in various animal cells. (Received November 10, 1992; Accepted February 18, 1993)     

Expansins and Internodal Growth of Deepwater Rice

The distribution and activity of the cell wall-loosening protein expansin is correlated with internodal growth in deepwater rice (Oryza sativa L.). Acid-induced extension of native cell walls and reconstituted extension of boiled cell walls were confined to the growing region of the internode, i.e. to the intercalary meristem (IM) and the elongation zone. Immunolocalization by tissue printing and immunoblot analysis, using antibody against cucumber expansin 29 as a probe, confirmed that rice expansin occurred primarily in the IM and elongation zone. Rice expansin was localized mainly around the vascular bundles at the base of the IM and along the inner epidermal cell layer surrounding the internodal cavity. Submergence greatly promoted the growth of rice internodes, and cell walls of submerged internodes extended much more in response to acidification than did the cell walls of air-grown internodes. Susceptibility of cell walls to added expansin was also increased in submerged internodes, and analysis by immunoblotting showed that cell walls of submerged internodes contained more expansin than did cell walls of air-grown internodes. Based on these data, we propose that expansin is involved in mediating rapid internodal elongation in submerged deepwater rice internodes.     

Pumpkin (Cucurbita sp.) seed globulin III. Comparison of subunit structures among seed globulins of various Cucurbita species and characterization of peptide components

Various Cucurbita seed globulins showed patterns similar toone another on SDS-gel electrophoresis, and ß bandsfor unreduced globulins and , ', and ' bands for reduced ones.On gel electrophoresis in 6 M urea, reduced globulin gave twoacidic and two basic bands. These corresponded to and ' chainsand ₁ and ₂ chains, respectively, identified by two-dimensionalurea-SDS gel electrophoresis. The compositions of the and ßsubunits were proposed. (Received September 8, 1977; )