Subcellular Compartmentation of Metabolites in Plant Cells

Redox changes of the reaction-center chlorophyll of photosystem I (P700) and chlorophyll fluorescence yield were measured in bundle sheath strands (BSS) isolated from maize (Zea mays L.) leaves. Oxidation of P700 in BSS by actinic light was suppressed by nigericin, indicating the generation of a proton gradient across the thylakoid membranes of BSS chloroplasts. Methyl viologen, which transfers electrons from photosystem I (PSI) to O2, caused a considerable decrease in the reduction rate of P700+ in BSS after turning off actinic light, showing that electron flow from the acceptor side of PSI to stromal components is critical for this reduction. Ascorbate (Asc), and to a lesser extent malate (Mal), caused a lower level of P700+ in BSS under aerobic conditions in far-red light, implying electron donation from these substances to the intersystem carriers. When Asc or Mal was added to BSS during pre-illumination under anaerobic conditions in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), the far-red-induced level of P700+ was lowered. The results suggest Asc and Mal can cause reduction of stromal donors, which in turn establishes conditions for rapid PSI-driven P700+ reduction. Addition of these metabolites also strongly stimulated the development of a proton gradient in thylakoids under aerobic conditions in the absence of DCMU, i.e. under conditions analogous to those in vivo. Ascorbate was a much more effective electron donor than Mal, suggesting it has a physiological role in activation of cyclic electron flow around PSI.

Section: Resultsmentioning

confidence: 99%

Characterization of photosynthetic electron transport in bundle sheath cells of maize. I. Ascorbate effectively stimulates cyclic electron flow around PSI

Иванов

Asada

Kramer

et al. 2004

“…In potato leaves, hexoses are nearly exclusively located in the vacuole, whereas sucrose is mainly compartmented in the cytosol (Leidreiter et al 1995). One possible explanation is that the increase in hexose content in the vacuolar transformants leads to an increase in vacuolar osmotic pressure.…”

Section: Discussionmentioning

confidence: 99%

Solute accumulation and decreased photosynthesis in leaves of potato plants expressing yeast-derived invertase either in the apoplast, vacuole or cytosol

Büssis

Heineke

Sonnewald

et al. 1997

Potato (Solanum tuberosum cv. Désirée) plants expressing yeast invertase directed either to the apoplast, vacuole or cytosol were biochemically and physiologically characterised. All lines of transgenic plants showed similarities to plants growing under water stress. Transformants were retarded in growth, and accumulated hexoses and amino acids, especially proline, to levels up to 40-fold higher than those of the wild types. In all transformants rates of CO2 assimilation and leaf conductance were reduced. From the unchanged intercellular partial pressure of CO2 and apoplastic cis-abscisic acid (ABA) content of transformed leaves it was concluded that the reduced rate of CO2 assimilation was not caused by a limitation in the availability of CO2 for the ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco). In the transformants the amount of Rubisco protein was not reduced, but both activation state and carboxylation efficiency of photosynthesis were lowered. In vacuolar and cytosolic transformants this inhibition of Rubisco might be caused by a changed ratio of organic bound and inorganic phosphate, as indicated by a doubling of phosphorylated intermediates. But in apoplastic transformants the pattern of phosphorylated intermediates resembled that of leaves of water-stressed potato plants, although the cause of inhibition of photosynthesis was not identical. Whereas in water-stressed plants increased contents of the phytohormone ABA are supposed to mediate the adaptation to water stress, no contribution of ABA to reduction of photosynthesis could be detected in invertase transformants.

“…The relative subcellular distributions of ABA and scFv antibody were calculated from the distribution of the marker enzymes as described in BuÈ ssis et al (1998). The subcellular concentrations were calculated using the volumes determined by Leidreiter et al (1995).…”

Section: Non-aqueous Fractionation Of Potato Leavesmentioning

confidence: 99%

“…This observation was not in accordance with the aniontrap concept. To test this concept further, BuÈ ssis et al (1998) used the method of non-aqueous fractionation (Leidreiter et al 1995) to determine the subcellular localisation of ABA in leaves. They found that in non-treated potato plants, ABA accumulated not in the chloroplast but in the cytosol, and PEG treatment led to an increase in ABA in the cytosol of old leaves or in the vacuole of the newly developed leaves.…”

Section: Introductionmentioning

confidence: 99%

“…Subcellular distribution was calculated from leaf material of 4-week-old plants separated by the method of non-aqueous fractionation of potato leaves. Subcellular concentrations are calculated from the subcellular volumes described byLeidreiter et al (1995). Means of three gradients SE Continuous record of stomatal conductance of leaves from 4-week-old wild-type potato plants and from scFvantibody plants (D1 9/7 = anti Oxazolone, RAK 25, 26 and 27 = anti-ABA) during the transition from light (quantum¯ux: 140 lmol m ±2 s ±1 ) to darkness at 140 lbar CO 2 .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Expression of an abscisic acid-binding single-chain antibody influences the subcellular distribution of abscisic acid and leads to developmental changes in transgenic potato plants

Strauss¹,

Kauder²,

Peisker³

et al. 2001

Potato (Solanum tuberosum L. cv. Désirée) plants were transformed to express a single-chain variable-fragment antibody against abscisic acid (ABA), and present in the endoplasmic reticulum at to up to 0.24% of the soluble leaf protein. The resulting transgenic plants were only able to grow normally at 95% humidity and moderate light. Four-week-old plants accumulated ABA to high extent, were retarded in growth and their leaves were smaller than those of control plants. Leaf stomatal conductivity was increased due to larger stomates. The subcellular concentrations of ABA in the chloroplast, cytoplasm and vacuole, and the apoplastic space of leaves were determined. In the 4-week-old transgenic plants the concentration of ABA not bound to the antibody was identical to that of control plants and the stomates were able to close in response to lower humidity of the atmosphere. A detailed analysis of age-dependent changes in plant metabolism showed that leaves of young transformed plants developed in ABA deficiency and leaves of older plants in ABA excess. Phenotypic changes developed in ABA deficiency partly disappeared in older plants.