摘要:

The present study was designed (1) to observe the characterization of 5‐bromo‐2′‐dexoyuridine (BrdU) incorporation into culturedBrassicacotyledon protoplasts and (2) to investigate the genetic differences in the levels of nuclear DNA synthesis (expressed by the percentage of nuclei labelled with BrdU) in cotyledon protoplast cultures from 12 cultivars of threeBrassicaspecies (Brassica napus, B. campestrisandB. oleracea) at an early stage using immunocytochemistry. Nuclei labelled with BrdU were different from those showing only staining with 4′‐6′‐diamidino‐2‐phenylindole (DAPI) under fluorescence and light microscopy. Two to 5% of nuclei were labelled with BrdU after 1 h of culture, indicating that nuclear DNA synthesis occurred at a very early stage of culture. The percentage of nuclei labelled with BrdU increased with time over the length of the culture period. The mean percentage of nuclei labelled with BrdU in the 12 cultivars was about 25% at 24 h after culture initiation. The curve of the increase in percentage of nuclei labelled with BrdU exhibited an S‐shape from 1 to 24 h. However, cultivar differences in percentages of nuclei labelled with BrdU were very significant over the time course of 1‐24 h from initial culture, with cultivars Eureka (B. napus), Global (B. napus), Narc 82 (B. napus), Bunyip (B. campestris) and Sugar Loaf (B. oleracea) having a consistently higher percentage of nuclei labelled with BrdU than the other cultivars. Species differences were also significant, with cultivars ofB. napusshowing much higher percentages than the tested cultivars ofB. campestrisandB. oleracea. The results indicate that the differences in nuclear DNA synthesis inBrassicacotyledon protoplast cultures were most likely at both intra

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930111.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

Theshxmutant of barley (Hordeum vulgareL. cv. Bomi) produces grains greatly decreased in starch content and containing smaller A‐starch granules together with normal B‐granules. Soluble starch synthase (SSS) and ADP‐glucose pyrophosphorylase (AGP) are reduced to about 20% normal activity. To help determine the position of the block to starch synthesis inshx, we measured enzyme activities and metabolite levels in developing grains of normal and mutant genotypes in a cv. Bomi background. We demonstrate that sucrose, free hexose, hexose phosphates and, critically, ADP‐Glc accumulate as a result of the mutation. In addition to AGP and SSS, several other enzyme activities are affected in theshxmutant, most of them showing activities 50‐80% of normal. Northern blots showed that transcripts for the AGP small subunit are much less abundant, but of normal size, inshx. These and earlier results together indicate that the metabolic block is at the end of the starch synthetic pathway, with a primary effect on a type I, primer‐independent soluble star

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930112.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

Auxin‐induced changes of wall‐rheological properties during different growth rates of rye coleoptile segments (Secale cerealeL.) were investigated. In addition, changes of osmotic concentration and turgor pressure were measured. Decrease of turgor and of osmotic concentration followed a synchronous time course. Auxin‐incubated segments exhibited a faster decrease and eventually lower values of both parameters. Creep test extensibility measurements demonstrate that apparent plastic as well as elastic extensibility of distilled‐water‐incubated segments strongly decreased during 24 h. In auxin‐incubated segments apparent plastic as well as elastic extensibilities were strongly increased, even in the absence of growth due to insufficient turgor pressure. The increasing effect of auxin on elastic wall properties is also reflected by an increase in relative reversible length (part of segment length by which segments shrink after freezing/thawing as referred to total length) and a complementary decrease of relative irreversible length (remaining length after turgor elimination as referred to turgid length); again the effects were independent of growth rate and turgor pressure. Cellulose synthesis inhibition of approx. 80% by dichlorobenzonitrile (DCB) had no significant effect either on growth or on wall‐rheological properties. Independent of whether the changed rheological wall behaviour of auxin‐incubated segments is causally related to the mechanism of auxin‐induced wall loosening, it indicates changes of wall polymer properties and/or interactions which are conserved when no actual length increase occurs due to insufficient turgor pressure. The results suggest that IAA‐induced wall loosening may be primarily mediated by cell wall changes other than cleavage of covalent, load‐bearing bonds as hypothesized in various

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930113.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

Three thiamine‐binding proteins of 17‐19 kDa (STBP‐I, II, and III) were purified from sesame seed (Sesamum indicumL.). Each of the proteins was composed of two subunits of equal molecular mass and each subunit consisted of a large polypeptide and a small polypeptide linked by a disulfide bond(s). They were rich in glutamic acid (or glutamine) and arginine. Their binding activities were optimal at neutral pH. They bound specifically free thiamine but not thiamine phosphates. STBP‐I had higher affinity for thiamine than STBP‐II or STBP‐III. STBP‐II and STBP‐III bound one molecule of thiamine per molecule, and STBP‐I bound 0.5 molecule. The amino acid composition and structure of the STPBs were similar to those of 2S

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930114.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

We have used a tomato (Lycopersicon esculentumMill.) pericarp disc system to study the inhibition of ripening caused by diazocyclopentadiene (DACP), gibberellic acid (GA3) and calcium (CaCl2), and to compare their modes of action. Treatment of discs with 1‐aminocyclopropane carboxylic acid (ACC) accelerated their ripening while DACP treatment eliminated ripening in the absence or presence of a treatment with the ethylene precursor. Both GA3and calcium retarded color development and tissue softening. Calcium delayed the onset of the climacteric rise in respiration and ethylene evolution, but GA3had no consistent effect in this respect. The different modes of action of the two inhibitors were emphasized by the synergistic effect on inhibition of ripening obtained when both were simultaneously applied. Inhibition of color development and softening was also achieved by applying other divalent cations such as strontium and barium. However, no such effect was observed with manganese or with the monovalent cations potassium and sodium. We concluded that calcium inhibition of ripening is not specific and is not necessarily mediated by the calcium calmodulin comple

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930115.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

The ripening of discs cut from the pericarp of green tomato (Lycopersicon esculentumMill.) fruits is inhibited by treatments with GA3and several divalent cations, including calcium. Normal ripening is marked by an increase in the solubility of wall pectins. Calcium and GA3alter the pattern of pectin solubility changes. In part this may be because polygalacturonase synthesis and/or secretion to the apoplast is reduced. The impact of divalent cations on ripening‐related tissue softening appears to have a nonmetabolic component. Ripening‐inhibiting ions rapidly reduce tissue softening, pectin solubilization and the normal ripening‐related decrease in cellular t

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930116.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

Adventitious rooting inRumexplants, in which the root systems were in hypoxic conditions, differed considerably between two species.R. palustris, a species from frequently flooded river forelands, developed a large number of adventitious roots during hypoxia, whereas adventitious root formation was poor inR. thyrsiflorus, a species from seldom flooded dykes and river dunes. Adventitious rooting could also be evoked in aerated plants of both species by application of auxin (1‐naphthaleneacetic acid or indoleacetic acid) to the leaves. The response to auxin was dose‐dependent, but even high auxin doses could not stimulateR. thyrsiflorusto produce as many adventitious roots asR. palustris. Consequently, the difference between the species in the amount of adventitious root formation was probably genetically determined, and not a result of a different response to auxin.A prerequisite for hypoxia‐induced adventitious root formation is the basipetal transport of auxin within the shoot, as specific inhibition of this transport by N‐1‐naphthylphthalamic acid severely decreased the number of roots in hypoxia‐treated plants. It is suggested that hypoxia of the root system causes stagnation of auxin transport in the root system. This can lead to an accumulation of auxin at the base of the shoot rosette, resulting in adventitious roo

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930117.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

This work reports changes in sucrose synthase and invertase activities throughout endosperm development in wheat, together with the associated substrates and metabolites, sucrose, UDP, glucose, fructose and UDP‐glucose. Throughout endosperm development, sucrose synthase had consistently higher activity than invertase and indeed invertase activity did not change appreciably. The observed variation in pattern and amounts of glucose and fructose present during the mid‐ and late stages of endosperm development confirmed the suggestion that invertase was not the preferred pathway of sucrose catabolism. Kinetic parameters for sucrose synthase were determined in crude extracts. Estimates of UDP and sucrose concentrations suggest that sucrose synthase is unlikely to achieve its potential maximum velocity. This limitation may however be overcome in part by the apparent excess catalytic activity measured during endosperm developm

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930118.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

Uptake, accumulation and xylem transport of K+and Na+in excised roots of soybean were investigated by use of a perfusion technique. This technique permitted independent quantification of, on the one hand, entry of ions into the roots and their transport through the cortex to the xylem vessels, and on the other hand reabsorption from the xylem vessels to the neighbouring cells and the external medium. Data are consistent with a low degree of selective uptake of K+over Na+. However, Na+depletion of the xylem stream by reabsorption limits, although weakly, its translocation to the shoots. Na+reabsorbed is for a great part reexcreted into the external medium. The low efficiency of these processes is discussed in relation to the Na+sensitivity of soybean.

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930119.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY

摘要:

Activity of nitrate reductase (NR; EC 1.6.6.1) in leaves of Komatsuna (Brassica campestrisL. ssp.rapiferacv. Osome) was decreased by sudden darkness, and rapidly recovered upon reillumination. However, the amount of NR protein, estimated by western blots, did not fluctuate during short‐term light/dark/light transitions. This suggests that rapid changes of NR activity in response to light/dark regimes are due to reversible modulation of the protein and not to de novo synthesis/degradation. In mannose‐fed leaves, such light/dark changes in NR activity were not observed. When extracts from illuminated leaves were incubated with MgATP, NR activity decreased in a time‐dependent manner. K‐252a, a specific inhibitor of protein kinases, prevented the in vitro inactivation of NR. The radiolabel of [γ‐32P] ATP was incorporated into NR protein in vitro and the labelling of NR was blocked by K‐252a. On the other hand, extractable NR from darkened leaves was activated by incubation at 30°C without further additions. The in vitro activation of NR was prevented by calyculin A, a potent and specific inhibitor of protein phosphatase. Moreover calyculin A abolished the in vivo activation of NR by illumination. Our results confirm a regulatory system by phosphorylation/dephosphorylation of NR. The data also suggest that the activity of NR depends on the relative phosphorylation/dephosphorylation activities subtly controlled in response to photon

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1995.930120.x

出版商:Munksgaard International Publishers    

年代:1995

数据来源: WILEY