ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractConjugatophycean green algae, such asMougeotiaandMesotaenium, are presumably the most ancient organisms to show phytochrome‐mediated photomodulatory processes, i.e. chloroplast reorientational movements. Experiments have provided striking evidence for a dichroic mode of light absorption by the phytochrome molecules located at the periphery of the cylindrical cell; in addition, the transition moment of the chromophoric group of phytochrome has been shown to change by a fixed angle upon conversion of Prto Pfrandvice versa. Consequently, a hypothesis has been put forward involving a tetrapolar phytochrome gradient at the plasmalemma. This presumed pigment pattern precisely controls chloroplast reorientation in the low‐irradiance response. Intriguingly, a blue‐light absorbing pigment is expressed inMougeotiaas well, which also mediates low‐irradiance response via a presumed tetrapolar gradient, apparently independent of the phytochrome.Two hypotheses for the controlling mechanism of chloroplast reorientation have been put forward:a)Coupling of the influx of calcium through the plasmalemma to the tetrapolar gradient of the sensor pigment proper, resulting in a tetrapolar gradient of calcium in the cytoplasm. This is the “reorientation via calcium” hypothesis.b)Coupling of actin anchorage sites on the plasmalemma to the tetrapolar gradient of the sensor pigment proper, resulting in a tetrapolar gradient of actin anchorage sites. Cytoplasmic calcium, released from internal stores or taken up through the plasmalemma, triggers actomyosin interaction. This is the “reorientation via anchorage sites” hypothesis.Consistent with the latter hypothesis, photoregulation by two steps seems to be indicated, (i) cytoplasmic initiation of actomyosin interaction, (ii) the graded formation of plasmalemma anchorage sites for

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe electrical properties of the tonoplast from a large variety of plant materials such as mesophyll cells, storage cells, tumor cells, suspension cultured cells, guard cells, coleoptile cells, and liverwort cells have been investigated using the patch‐clamp technique. Whole‐vacuole recordings were employed to study the dynamics of an ATP‐dependent proton pump by directly measuring the electrogenic currents. The addition of Mg‐ATP induced an inwardly directed current which depolarized the tonoplast (the vacuole becoming positive inside). Furthermore, voltage‐dependent passive ion fluxes were analyzed using whole vacuoles and isolated membrane patches. Whole‐vacuolar currents and single‐channel currents were induced at hyperpolarizing potentials, whereas currents decreased at positive trans‐tonoplast potentials. The electrical properties of the tonoplast of vacuoles from various plant tissues were similar and it was concluded that ion fluxes across the tonoplast follow the same gen

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe prasinophycean algaMantoniellacontains, in addition to Chl a and b, at least a third green pigment which is functionally active in the light‐harvesting antenna. This third Chl was isolated in order to elucidate its chemical structure. The absorption and fluorescence spectra were measured not only from the purified pigment but also from its pheophytin and its methylpheophorbide. The spectra were compared with those of authentic Chl c‐1 and c‐2, which were isolated from the diatomNitzschiasp. and with Mg‐DVPP (purified fromRhodobacter).The results show that the pigment fromMantoniellacompares best with Chl c‐1. In order to clarify the spectral data, Chl c‐1 and c‐2, Mg‐DVPP, and the pigment fromMantoniellawere subjected to a chromatographic system that is able to separate these porphyrins. The chromatographic analysis clearly shows that the pigment fromMantoniellaco‐migrates with Chl c‐1 and not with the bacterial pigment.Mantoniellais the first organism which has been demonstrated to contain Chl a,

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effects of calcium ions and of the calcium channel blockers verapamil, diltiazem and nifedipine on galvanotaxis inChlamydomonashave been investigated using a fully automated and computerized population system. Galvanotaxis is a function of the voltage applied to the cell population. However, the galvanotactic orientation also depends on the external calcium concentration. In a calcium‐deprived nutrient medium which still contains 6 × 10−7M calcium, galvanotactic orientation is about 20% of orientation at optimal calcium concentration of 10−4M at 9 V. The higher the external calcium concentration is, the lower is the voltage necessary for optimal galvanotactic orientation. The calcium channel blockers diltiazem and nifedipine likewise inhibit galvanotaxis ofChlamydomonasvery specifically without impairing motility. Verapamil is effective, but also inhibits motility by causing detachment or shortening of the flagella. Nevertheless, inhibition of galvanotaxis by verapamil is not the only result of decreased motility, because the galvanotactic orientation is impaired to a greater extent than motility. The effectiveness of the three blockers tested in inhibiting galvanotaxis depends on the concentration and on the voltage applied. At 10−5M, verapamil causes maximal inhibition of galvanotaxis at 9 V. At increasing concentrations up to 10−4M, diltiazem inhibits galvanotaxis more strongly than the other blockers. If the voltage is varied at a constant blocker concentration of 2 × 10−5M, nifedipine causes maximal inhibition at 3 V–6 V, diltiazem at 9 V and verap

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effects of extracellular K+concentration ([K+]o) on the pH of cell sap, “bulk cytoplasm” and vacuole have been investigated inElodea densaleaves under conditions of either low or high activity of the plasmalemma electrogenic H+pump. Cell sap pH was evaluated directly in the cell sap expressed after freezing and thawing. Cytoplasmic and vacuolar pH were calculated by the weak base and weak acid distribution method, DMO and benzylamine appearing to be a suitable acid and base, respectively, for this purpose in this material.When added to the basal medium (no rapidly permeating ions present), 5 mM K+induced an increase in intracellular pH, larger for the cell sap and the vacuole (about 0.2 units), and smaller but still significant for the cytoplasm (0.07 units). This alkalinizing effect of K+was thus associated with a significant decrease in the pH difference across the tonoplast. The alkalinizing effect of K+was markedly and synergistically enhanced by the presence of fusicoccin, a condition inducing a marked activation of H+extrusion and of K+uptake.The correlation between these effects of [K+]oon intracellular pH and those on H+extrusion indicates that changes in extracellular K+concentration, and thus in K+influx, can influence cytoplasmic and vacuolar pH by modulating the rate of H+extrusion by the plasmalemma H+p

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractDay — and night‐forms of phosphoenolpyruvate carboxylase (EC 4.1.1.31) (PEP‐C) were extracted from leaves of the CAM plantKalanchoë daigremontiana. During storage after extraction, the day‐form spontaneously lost its sensitivity towards the allosteric inhibitorl‐malate. This effect was accelerated by inorganic phosphate, PEP, 3‐PGA and G‐6‐P.l‐Malate however stabilized the malate sensitivity of the day‐form of PEP‐C.Crude desalted extracts of the day‐form and of the night‐form of PEP‐C were subjected to ultracentrifugation on a continuous sucrose gradient in the presence of malate and of marker enzymes. Both forms of PEP‐C were found to have relative molecular masses of about 200,000. This suggests that both forms represent the dimers of the enzyme protein. The result also suggests that reversible dissociation and association of enzyme subunits is not the mechanism which brings about the interconversion of the two PEP‐C forms dur

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractNAD(P)H is rapidly oxidized in the presence of peroxidase, a substituted monophenol such asp‐coumaric acid, and Mn2+ions. As recently reported by Miller (1985), this NAD(P)H oxidation at the expense of molecular oxygen is inhibited by submicromolar concentrations of Cu2+ions. This inhibition by cupric ions is counteracted by micromolar concentrations of cytokinins. We now show that NAD(P)H‐oxidation by the above system is under the control of superoxide dismutase, where in the absence of cytokinin‐copper, superoxide dismutase stimulates NAD(P)H‐oxidation. In the presence of unribosylated cytokinins and copper, however, superoxide dismutase acts as an inhibitor. Thus cytokinins and superoxide dismutase may interact in the control of the redox state of plan

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA nitrate‐sensitive, azide‐insensitive ATPase isolated fromM. crystallinumin the C3and in the CAM state has been solubilized in active form using octylglucoside and Zwittergent 3–14. Like the membrane‐bound tonoplast ATPase, the solubilized ATPase showed an increase in ATP‐hydrolysis activity after transition from the C3to the CAM mode of photosynthesis. The characteristics of the membrane‐bound and the solubilized tonoplast ATPase were comparable with respect to salt stimulation, inhibitor effects, and MgATP2–‐concentration dependence. Differing from the membrane‐bound ATPases, the solubilized ATPase from C3‐ and CAM‐M. crystallinumshowed a pH optimum between pH 6.5 and 7.0.In order to compare the solubilized ATPases immunologically, antibodies were prepared against the tonoplast fraction of C3‐ and CAM‐M. crystallinum. A cross‐reaction was observed between antibodies against the tonoplast ATPase from C3‐ and CAM‐M. crystallinumand the solubilized ATPase from C3‐ and CAM‐M. crystallinum. A cross‐reaction was also observed between antibodies against the tonoplast ATPase from C3‐ and CAM‐M. crystallinumand the solubilized tonoplast ATPase fromKalanchoë daigremontiana. However, there was no cross‐reaction with the solu

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe stromal pH of chloroplasts contained in wheat leaf protoplasts was determined by incubating the protoplast suspension with radioactively labelled DMO, followed by rapid subcellular fractionation and measurement of the radioactivity in the separated chloroplast fraction. The stromal pH was found to be about 8.0 upon illumination and 7.6 in darkness. These results demonstrate that light‐dependent stromal pH changes, which have been found earlier in isolated chloroplasts, also occur in a plant cel

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1988.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY