摘要:

Extracts from pollen grains of maize (Zea maysL.) show a low activity of aminoacyltRNA synthetases (EC 6. 1. 1). They also contain a specific factor inhibiting the activity of these enzymes. The molecular mass of this factor, which may be a short peptide, is about 3000 Da as determined by column chromatography on Sephadex G‐25 Fine. The Michaelis constant (Km), determined for the amino acid in the presence of this factor, suggests its allosteric influence on the affinity of the enzyme. Short‐term incubation of the factor with pronase R resulted in conversion of the inhibiting action into a stimulating one. Kinetics of aminoacylation reactions confirm inhibitory and stimulative influences of the effector on the enzyme activity. High performance liquid chromatography shows that inhibition of the activity of aminoacyl‐tRNA synthetases is affected by a group of compounds of similar molecular m

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01350.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Plasma membrane vesicles were extracted from the shoots of 10‐day‐old oat, rye and rice plants and incubated with either cholesterol, stigmasterol or a mixture of sitosterol+campesterol (60:40). After ascertaining that the sterol composition of the vesicles had been altered by this treatment, the specific hydrolytic activity of the membrane‐bound H+‐ATPase (EC 3. 6. 1. 35) was measured. The results indicated that, although all sterols were taken up, cholesterol was best integrated into the plasma membrane of the species tested. After treatment, ATPase activity was altered in oat and rice, but not in rye. The results are discussed in the context of sterol/lipid and sterol/protein interactions in the plasma m

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01351.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Apical dominance, internode elongation, radial growth and xylem cell size in coppice and apical shoots ofBetula pubescens B. Pendulawere determined and related to endogenous indole‐3‐acetic acid (IAA) levels, measured by gas chromatography‐selected ion monitoring in the apical bud and at three positions along the stem. The effects of defoliation and debudding on morphological and anatomical characters and endogenous IAA levels were also investigated. The coppice shoots displayed superior stem elongation and increased branching during the initial phase of growth, after which their growth pattern was similar to that of the seedlings; however, their radial growth was greater throughout the experiment. Both plant types produced smaller‐sized xylem cells at the top of the shoot than at the bottom with coppice shoots tending to form larger tracheids and smaller vessels than the seedlings. There was no consistent difference in IAA concentration between the coppice shoots and the seedlings. Defoliation and debudding reduced the IAA level in the stem within 36 h and it was still low after 25 days. Although the extent of the IAA decrease was similar in both coppice shoots and seedlings, the treatments affected the morphological and anatomical characters differently in the two plant types. The results suggest that the observed differences between seedlings and coppice shoots were not mediated through a drastic change in IA

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01352.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Plasma membranes were isolated from green leaves of maize (Zea mays), spinach (Spinacia oleracea),Setaria viridisand wheat (Triticum aestivumcv. Omase) by aqueous two‐phase partitioning. Carbonic anhydrase activity was detected in these membranes. The activity was inhibited by specific inhibitors for carbonic anhydrase, acetazolamide and ethoxyzolamide. The carbonic anhydrase activity was markedly enhanced by the addition of Triton X‐100 to the plasma membranes. The highest activity was obtained in the presence of 0.015% detergent. The activity was scarcelyaffected when the plasma membrane vesicleswere treated with proteinase K, but largely inactivated by the protease after treating the membranes with Triton X‐100. These results indicate that carbonic anhydrase faces the cytoplasmic side of the membrane since plasma membranes purified by aqueous two‐phase partitioning are tightly sealed vesicles of right side‐out orientation (apoplastic side‐out). With leaves of C4plants, 20 to 60% of the total carbonic anhydrase activity was found in the microsomal fraction. By contrast, only 1 to 3% of the activity was found in the microsomal fraction from leaves of C3plants. Western blot analysis showed that a polypeptide in the spinach plasma membrane cross‐reacted with an antiserum raised against spinach chloroplast carbonic anhydrase, and that the molecular mass of the plasma membrane enzyme was higher than that of the chloroplast carbonic anhydrase (28 and 26 kDa, respectively). This indicates the presence of different molecular species of carbonic anhydrase in the chloroplast and the pl

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01353.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The time course of ethylene production by senescing carnation (Dianthus caryophyllusL. cv. Sandrosa) flowers was studied. These flowers are unusual in that they do not exhibit an autocatalytic increase in ethylene production nor do they develop petal in‐rolling. Exposure of the flowers to exogenous ethylene resulted in a rise in their ethylene‐forming enzyme (EFE) activity and ethylene production, and at the same time a marked decline in their fresh weight. Natural senescence was also accompanied by a rise in EFE activity, but with no concomitant rise in 1‐amino cyclopropane carboxylic acid synthase activity nor in ethylene production. A shift in responsiveness to ethylene was observed, with young flowers more responsive to exogenous ethylene than older flowers. The results are discussed in terms of a proposed mechanism allowing for the decline in competence of this cultivar to respond to ethylene during senes

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01354.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

One of the main seed storage proteins of Norway spruce (Picea abies), is a salt‐soluble protein with an average molecular mass of 42 kDa. This protein was localized by immunocytochemical methods in ultrathin sections of megagametophytes active in storage protein synthesis, as analyzed by SDS‐PAGE. The megagametophyte in spruce starts accumulating storage materials, proteins and lipids, as the young embryo grows into the gametophytic tissue. It then continues to accumulate these storage products throughout seed development (Hakman 1993). Megagametophytes at an early stage of storage protein accumulation were chosen in this study for analysing the likely transport pathway of the proteins, since only a small amount of lipid had yet accumulated in the cells, and cell organelles were still easy to distinguish. An antibody against the 42 kDa storage protein showed very good reactivity with the 42 kDa protein in immunoblot experiments with total protein extracts from megagametophytes and embryos. In ultrathin sections of the megagametophyte, the antibodies were preferentially localized in the lumen of Golgi cisterna, in Golgi‐associated vesicles, protein deposits close to the vacuolar membrane and in protein storage vacuoles (protein bodies). These observations indicate that the transport is mediated by the Golgi apparatus.Also, proteins present in storage vacuoles in mature zygotic and somatic embryos showed intense labelling with these antibodies in ultrathin sec

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01355.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The intracellular localization of sucrose‐phosphate phosphatase (SPP) in photosynthetic cells of lettuce (Lactuca sativa) was investigated by using protoplasts isolated directly from leaf tissue. No SPP activity was detected in either vacuolar, chloroplast or mitochondrial preparations. The recovered activity of SPP was found in the cytosolic fractions at proportions parallel with those of the cytoplasmic marker alcohol dehydrogenase. Maximal activity was measured between pH 6. 0 and 7. 0. The data demonstrate a cytosolic location for SPP. Neither sucrose nor any other saccharide tested at 100 mMwas a strong inhibitor of the enzyme, which was inactive in the presence of 35 mMethylenediammetetraacetic aci

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01356.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Willow cells transformed with aniptgene fromAgrobacterium tumefaciensgrow in tissue culture as undifferentiated callus without shoot induction. We show that the transformed calluses contained high levels of the cytokinins 9‐β‐d‐ribofuranosyl zeatin and its monophosphate, demonstrating the presence of a functional isopentenyl transferase enzyme. Theiptgene was transcribed at different levels in different transformed callus lines. The absence of shoot differntiation is apparently not due to a lack of zeatin‐type cytokinins in the transforme

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01357.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Photoinhibition of photosynthesis and its reactivation was studied in the cyanobateriumA. nidulansin the presence of the respiratory inhibitor sodium azide, the uncouplers carbonyl cyanidep‐(trifluoromethoxy)‐phenylhydrazone (FCCP) and carbonyl cyanidem‐chlorophenylhydrazone (CCCP) and the photosystem I elicitor phenazine methosulphate (PMS). Inhibition of dark respiration by azide increased the susceptibility of the cyanobacterium to photoinhibition. Both FCCP and CCCP also remarkably affected the process of photoinhibition inA. nidulans.The PMS at lower photoinhibitory light intensity partially protectedA. nidulansfrom photoinhibition. The recovery from photoinhibition in the presence of azide or FCCP was slow and normal photosynthesis could not be resumed even after a longer period of incubation under suitable reactivating condition. Thus dark respiration has a key function in the process of photoinhibition of photosynthesis and its reactivation in the cyanobacteriumA. nid

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01358.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Effects of CO2on stomatal movements ofCommelina communisL. were studied with plants, epidermal strips and guard cell protoplasts. With plants, the stomatal response induced by a blue light pulse was studied for different ambient CO2concentration ranging from CO2‐deprived air to 100 Pa in darkness or under red light. It was observed that the blue light response could be obtained not only under a red light background but also in darkness and CO2‐free air, the two responses being quite similar.With epidermal strips, the effect of CO2on ferricyanide reductase activity at the guard cell plasmalemma was studied by transmission electron microscopy. In the presence of ferric ions, reduced ferricyanide gives an electron dense precipitate of Prussian Blue. In darkness and air, no precipitate was observed. In darkness and CO2‐free air as well as under light and normal air, a precipitate was found along the plasmalemma of the guard cells, indicating a ferricyanide reductase activity. With guard cell protoplasts suspended in a medium either in equilibrium with air or in a CO2‐free medium the H+extrusion induced by a blue light pulse added to a red light background was measured. A low CO2content was obtained by adding photosynthetic algae to the suspension of guard cell protoplasts. In a CO2‐free medium the rate of H+extrusion was enhanced.The results are discussed on the basis of a possible competition for reducing power between CO2fixation and a putative blue light dependent redox chain located on the plasma

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01359.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY