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Hans J. Bohnert - One of the best experts on this subject based on the ideXlab platform.

  • Cell type-specific responses to salinity - the epidermal bladder cell transcriptome of Mesembryanthemum Crystallinum.
    The New phytologist, 2015
    Co-Authors: Bronwyn J. Barkla, Hans J. Bohnert, Rosario Vera-estrella, Omar Pantoja, Sang-yeol Lee, Maheshi Dassanayake
    Abstract:

    Mesembryanthemum Crystallinum (ice plant) exhibits extreme tolerance to salt. Epidermal bladder cells (EBCs), developing on the surface of aerial tissues and specialized in sodium sequestration and other protective functions, are critical for the plant's stress adaptation. We present the first transcriptome analysis of EBCs isolated from intact plants, to investigate cell type-specific responses during plant salt adaptation. We developed a de novo assembled, nonredundant EBC reference transcriptome. Using RNAseq, we compared the expression patterns of the EBC-specific transcriptome between control and salt-treated plants. The EBC reference transcriptome consists of 37 341 transcript-contigs, of which 7% showed significantly different expression between salt-treated and control samples. We identified significant changes in ion transport, metabolism related to energy generation and osmolyte accumulation, stress signalling, and organelle functions, as well as a number of lineage-specific genes of unknown function, in response to salt treatment. The salinity-induced EBC transcriptome includes active transcript clusters, refuting the view of EBCs as passive storage compartments in the whole-plant stress response. EBC transcriptomes, differing from those of whole plants or leaf tissue, exemplify the importance of cell type-specific resolution in understanding stress adaptive mechanisms.

  • Expression of water channel proteins in Mesembryanthemum Crystallinum
    Plant physiology, 2000
    Co-Authors: Hans-hubert Kirch, Christine B. Michalowski, Rosario Vera-estrella, Dortje Golldack, Françoise Quigley, Bronwyn J. Barkla, Hans J. Bohnert
    Abstract:

    We have characterized transcripts for nine major intrinsic proteins (MIPs), some of which function as water channels (aquaporins), from the ice plant Mesembryanthemum Crystallinum. To determine the cellular distribution and expression of these MIPs, oligopeptide-based antibodies were generated against MIP-A, MIP-B, MIP-C, or MIP-F, which, according to sequence and functional characteristics, are located in the plasma membrane (PM) and tonoplast, respectively. MIPs were most abundant in cells involved in bulk water flow and solute flux. The tonoplast MIP-F was found in all cells, while signature cell types identified different PM-MIPs: MIP-A predominantly in phloem-associated cells, MIP-B in xylem parenchyma, and MIP-C in the epidermis and endodermis of immature roots. Membrane protein analysis confirmed MIP-F as tonoplast located. MIP-A and MIP-B were found in tonoplast fractions and also in fractions distinct from either the tonoplast or PM. MIP-C was most abundant but not exclusive to PM fractions, where it is expected based on its sequence signature. We suggest that within the cell, MIPs are mobile, which is similar to aquaporins cycling through animal endosomes. MIP cycling and the differential regulation of these proteins observed under conditions of salt stress may be fundamental for the control of tissue water flux.

  • The expression of a Vp1-like gene and seed dormancy in Mesembryanthemum Crystallinum.
    Genes & genetic systems, 2000
    Co-Authors: Toshiyuki Fukuhara, Hans J. Bohnert
    Abstract:

    Seeds of the common ice plant (Mesembryanthemum Crystallinum) germinate in distinct sub-populations over a time period of more than 4 weeks following imbibition. Distinguishing early (E)- and late (L)-germinating seeds is the expression of a homologue of the transcriptional activator VP1. The deduced amino acid sequence of ice plant VP1 (MVP1) is 39% identical (50% similar) to the sequence of the Arabidopsis VP1 homologue, ABI3. The amount of Mvp1 mRNA, transcribed from a single gene, is different in E and L seeds after water uptake. The levels of the Mvp1 transcripts are very low in immature and mature seeds and they increased during 6 days of imbibition. This expression profile of Mvp1 is different from known Vp1/ABI3-like genes in other plants. Cycloheximide (at 35 μM) abolishes the increase of Mvp1, and L seeds are turned into E seeds, which develop normally when the inhibitor is applied for a short time during imbibition. E seeds treated for the same time period are developmentally impaired and show no radicle elongation. We suggest that the presence and late disappearance of Mvp1 in L seeds is responsible for dormancy and after-ripening of late-germinating ice plant seeds.

  • Na+/myo-inositol symporters and Na+/H+-antiport in Mesembryanthemum Crystallinum.
    The Plant journal : for cell and molecular biology, 2000
    Co-Authors: Sanjay Chauhan, Françoise Quigley, Donald E. Nelson, Nancy Forsthoefel, Yingquing Ran, Hans J. Bohnert
    Abstract:

    Mitr1 and Mitr2 from Mesembryanthemum Crystallinum (common ice plant) are members of a family of genes homologous to H + [or Na + /myo-inositol symporters (ITRs), not previously studied in plants. MITR1 complemented an Itr1-deficient yeast strain. Mitr1 is strongly expressed in roots, moderately in stems, and weakly in leaves. Its transcripts increased in all organs, most dramatically in roots, under salinity stress. Mitr2 constitutes a rare transcript, slightly upregulated by salt stress in leaves only. Mitr1 transcripts are present in all cells in the root tip, but become restricted to phloem-associated cells in mature roots. Peptide antibodies against the two proteins indicated the presence of MITR1 in all organs and of MITR2 in leaves. Both are located in the tonoplast. MITR1 acts in removing sodium from root vacuoles, correlated with findings of low root sodium, while leaf vacuoles accumulate sodium in the ice plant. Up-regulation in leaves and stems is also found for Na + /H + -antiporter (Nhx-type) transcripts. Under comparable stress conditions, Nhx-and Itr-like transcripts in Arabidopsis were regulated differently. In the ice plant, co-ordinate induction of Na + /H + -antiporters and Na + /myo-inositol symporters transfers sodium from vacuoles in root cells into the leaf mesophyll as a halophytic strategy that lowers the osmotic potential. The tissue-specific differential expression of Itr- and Nhx-type transcripts suggests that the vacuolar sodium/inositol symporters function to reduce sodium amounts in cells of the root and vascular tissue, while sodium/proton antiporters in leaf tissues function to partition sodium into vacuoles for storage.

  • The Expression of an Aquaporin Promoter from Mesembryanthemum Crystallinum in Tobacco
    Plant & cell physiology, 1997
    Co-Authors: Shigehiro Yamada, Donald E. Nelson, Eleazar Ley, Sheila Marquez, Hans J. Bohnert
    Abstract:

    The promoter region of the MipB gene encoding an aquaporin from Mesembryanthemum Crystallinum was isolated and used in a transcriptional fusion to control uidA expression in tobacco. The sequence of the promoter was determined for 2 kb upstream of the translation initiation site. Three start sites were utilized with approximately equal frequency, located 176, 170, and 161 bases, respectively, upstream of the translation initiation site. As judged by analysis of GUS expression, promoter MipB retains its specificity in transgenic tobacco. In germinating seedlings, all cells showed GUS expression of different intensities with the strongest signals in root meristems. In older seedlings, GUS staining was observed in rapidly expanding cells— root and apical meristem, and lateral root primordia. In mature plants, strong GUS activity was located to glandular trichomes, subepidermal cells of the stem and petioles, to cells surrounding vascular tissues as well as in xylem parenchyma cells. In immature floral organs, GUS expression was strong in sepals, petals, stamen, and pistil. The intensity declined as they matured. In general, this promoter was active in rapidly expanding cells and cells with high water flux capacity, especially in the xylem parenchyma.

John C. Cushman - One of the best experts on this subject based on the ideXlab platform.

Zbigniew Miszalski - One of the best experts on this subject based on the ideXlab platform.

  • Effects of NaCl on the response of Mesembryanthemum Crystallinum callus to Botrytis cinerea infection
    Biologia plantarum, 2011
    Co-Authors: Elżbieta Kuźniak, Barbara Gabara, Maria Skłodowska, Marta Libik-konieczny, Zbigniew Miszalski
    Abstract:

    Callus of the halophyte Mesembryanthemum Crystallinum was used to study the effect of NaCl on the response to Botrytis cinerea infection. The fungus easily colonized the callus surface and the intercellular spaces. However, in the NaCl-adapted tissues the incidence of penetration was 67 % lower than in the inoculated control tissue. The modification of the infection pattern found in the salt-adapted callus could be related to metabolic adaptations to salinity. This was manifested by the enhanced antioxidant potential of ascorbate, the up-regulated activities of ascorbate peroxidase, as well as guaiacol and syringaldazine peroxidases together with the increased detoxification capacity of glutathione transferase in the NaCl-adapted callus. The post-inoculation changes in NaCl-adapted and non-adapted calli were roughly similar and supported the prooxidative nature of B. cinerea infection.

  • CAM-related changes in chloroplastic metabolism of Mesembryanthemum Crystallinum L.
    Planta, 2010
    Co-Authors: Ewa Niewiadomska, Zbigniew Miszalski, Wolfgang Bilger, Magdalena Gruca, Maria Mulisch, Karin Krupinska
    Abstract:

    Crassulacean acid metabolism (CAM) is an intriguing metabolic strategy to maintain photosynthesis under conditions of closed stomata. A shift from C3 photosynthesis to CAM in Mesembryanthemum Crystallinum plants was induced by high salinity (0.4 M NaCl). In CAM-performing plants, the quantum efficiencies of photosystem II and I were observed to undergo distinct diurnal fluctuations that were characterized by a strong decline at the onset of the day, midday recovery, and an evening drop. The temporal recovery of both photosystems’ efficiency at midday was associated with a more rapid induction of the electron transport rate at PSII. This recovery of the photosynthetic apparatus at midday was observed to be accompanied by extreme swelling of thylakoids. Despite these fluctuations, a persistent effect of CAM was the acceptor side limitation of PSI during the day, which was accompanied by a strongly decreased level of Rubisco protein. Diurnal changes in the efficiency of photosystems were parallel to corresponding changes in the levels of mRNAs for proteins of PSII and PSI reaction centers and for rbcL, reaching a maximum in CAM plants at midday. This might reflect a high demand for new protein synthesis at this time of the day. Hybridization of run-on transcripts with specific probes for plastid genes of M. Crystallinum revealed that the changes in plastidic mRNA levels were regulated at the level of transcription.

  • interaction of botrytis cinerea with the intermediate c3 cam plant Mesembryanthemum Crystallinum
    Environmental and Experimental Botany, 2010
    Co-Authors: Elzbieta Kuźniak, Zbigniew Miszalski, Barbara Gabara, Andrzej Kornas, C Ullrich, Maria Sklodowska
    Abstract:

    Abstract The interaction between necrotrophic Botrytis cinerea and Mesembryanthemum Crystallinum , a C3/CAM intermediate plant, was followed macroscopically, microscopically, by analyzing CAM (Crassulacean Acid Metabolism) related and H 2 O 2 accumulation in leaf tissue. In response to infection, M. Crystallinum in both C3 and CAM states exhibited hypersensitive response (HR)-like defence response or soft-rot spreading lesions depending on the post-inoculation environmental conditions. Our results point out to the fact that light is required for plant resistance, and HR-like necrotic lesions are co-localized with thermal effects visible on the infrared images possibly related to water disturbances, stomatal closure and H 2 O 2 accumulation. In C3 plants, these changes were followed by metabolic shifts towards weak diurnal oscillations of malate content. We suppose that light-dependent processes related to CAM and H 2 O 2 accumulation are in parallel with resistance to B. cinerea . This may explain at least partly why CAM plants could be less sensitive to biotic stress factors.

  • Antioxidant response system in the short-term post-wounding effect in Mesembryanthemum Crystallinum leaves
    Journal of plant physiology, 2007
    Co-Authors: Ireneusz Ślesak, Halina Ślesak, Marta Libik, Zbigniew Miszalski
    Abstract:

    Summary Mechanical wounding of Mesembryanthemum Crystallinum leaves in planta induced a fast decrease in stomatal conductance, which was related to accumulation of hydrogen peroxide (H 2 O 2 ). Higher levels of H 2 O 2 were accompanied by an increase in total activity of superoxide dismutase (SOD) and a decrease in catalase (CAT) activity. Among SOD forms, manganese SOD (MnSOD) and copper/zinc SOD (Cu/ZnSOD) seem to be especially important sources of H 2 O 2 at early stages of wounding response. Moreover, NADP-malic enzyme (NADP-ME), one of the key enzymes of primary carbon metabolism, which is also involved in stress responses, showed a strong increase in activity in wounded leaves. All these symptoms: high accumulation of H 2 O 2 , high activities of Cu/ZnSOD and NADP-ME, together with the decrease of CAT activity, were also observed in the major veins of unwounded leaves. The potential role of veinal tissues as an important source of H 2 O 2 during wounding response is discussed.

  • Partial characterization and expression of leaf catalase in the CAM-inducible halophyte Mesembryanthemum Crystallinum L.
    Plant physiology and biochemistry : PPB, 2007
    Co-Authors: Ewa Niewiadomska, Zbigniew Miszalski
    Abstract:

    Abstract Catalase (CAT; EC 1.11.1.6) isolated from leaves of the halophytic plant Mesembryanthemum Crystallinum is characterized by a high apparent molecular mass of about 320 kDa, and high resistance to denaturing agents (10% ME). SDS-treatment breaks active oligomeric CAT into the less active and putatively dimeric form of 160 kDa apparent molecular mass. Three subunits are resolved after denaturing PAGE: 79, 74 and 62 kDa. Higher molecular masses of subunits coincide with increased activity of CAT. M. Crystallinum leaf CAT reveals a diel variation in the resistance to denaturing factors and the stability of CAT is increased in a light-dependent manner both in C 3 - and in CAM-induced plants. Unchanged level of leaf CAT transcripts is documented in the diurnal cycle of C 3 plants and after salinity-induced crassulacean acid metabolism (CAM).

John C. Thomas - One of the best experts on this subject based on the ideXlab platform.

  • Genetic responsiveness to copper in the Ice Plant, Mesembryanthemum Crystallinum
    Plant Science, 2004
    Co-Authors: John C. Thomas, Mike Perron, Elizabeth C. Davies
    Abstract:

    Abstract To better understand genetic responsiveness to stress, Mesembryanthemum Crystallinum plants were challenged with copper and then analyzed for mRNAs corresponding to the salt inducible and constitutive forms of phosphoenolpyruvate carboxylase (PEPCase) (Ppc1 and Ppc2 respectively), and a senescence inducible cysteine protease (Sep7). During the 200 μM copper stress of 6–7-week old adult plants, leaf transcripts of the CAM specific Ppc1 and Sep7 were approximately 5–10 times more abundant than those seen in unstressed plants. Constitutive Ppc2mRNA levels were unchanged relative to controls. Compared to unstressed plants, both Ppc1 and Sep7 transcripts were also quite abundant in leaves during NaCl and cytokinin treatment. Leaves of 800 μM copper sulfate treated plants did not contain detectable Ppc1, Ppc2 or Sep7 transcripts. Aerial tissues of 12–14-week old previously unstressed plants contained mostly flower buds and stems. Both these organs expressed Sep7 and Ppc2 transcripts at similar levels regardless of manipulation (no stress, salt or copper stress). As in younger tissues, mature bud and stem tissues responded to NaCl or copper stress by increasing Ppc1 mRNA levels. Only young copper stressed plants had enhanced copper sequestration and tissue lipid peroxidation, the latter indicative of free radical damage. Together, these results suggest that within a developmental context, the Ice Plant uses distinct genetic mechanisms quite akin to salt/drought stress in response to a moderate copper stress.

  • Distinct responses to copper stress in the halophyte Mesembryanthemum Crystallinum
    Physiologia Plantarum, 1998
    Co-Authors: John C. Thomas, Farah K. Malick, Charles Endreszl, Elizabeth C. Davies, Kent S. Murray
    Abstract:

    Selective gene expression allows the halophyte Mesembryanthemum Crystallinum to survive a salt stress. To broaden our understanding of the environmental cues initiating diverse stress responses in this higher plant, unstressed and 0.4 M NaCl-stressed plants were compared to plants treated with several concentrations of copper (CuSO 4 ), an increasingly relevant environmental heavy metal pollutant. Comparisons of control and copper-stressed plants included germination, chlorophyll content, accumulation of proline, heat shock protein (HSP) 60 and a Crassulacean acid metabolism (CAM)-specific marker enzyme, phosphoenolpyruvate carboxylase (PEPCase). In germination and whole plant tests, M. Crystallinum was significantly more tolerant to copper than Arabidopsis thaliana. Mature M. Crystallinum plants stressed with 50 ppm CuSO 4 for 48 h became dehydrated. These plants produced a 4-fold increase in proline concentration and accumulated both the CAM-specific PEPCase and HSP 60 compared to controls. Higher levels of copper stress resulted in a 10-fold increase in leaf proline content, 10-fold HSP 60 accumulation but no detectable PEPCase protein compared to unstressed controls. HSP 60 did not accumulate under NaCI stress. Concurrent with copper-induced genetic responses to stress, copper was accumulated and concentrated in leaves (3 500 ppm). Together, these results suggest that this halophyte copes with copper metal exposure through distinct genetic mechanisms.

  • Responses to Salt Stress in the Halophyte Mesembryanthemum Crystallinum
    Biochemical and Cellular Mechanisms of Stress Tolerance in Plants, 1994
    Co-Authors: Hans J. Bohnert, John C. Thomas, E. Jay Derocher, Christine B. Michalowski, Heimo Breiteneder, Dan M. Vernon, Wei Deng, Shigehiro Yamada, Richard G. Jensen
    Abstract:

    The halophyte Mesembryanthemum Crystallinum (common ice plant) has emerged as a model system suitable to advance our understanding of mechanisms that have evolved in a species adapted to harsh environments, characterized by drought and salt stress conditions. Here, we include a discussion of distinguishing factors of cellular and organismic responses to salt stress, the role of growth regulators, and a discussion of molecular and metabolic mechanisms employed by this plant for survival. Several mechanisms appear to be important, including acceleration of ontogeny, protection of the photosynthetic apparatus, the rapid induction of presumably osmoprotective substances, and the long-term establishment of Crassulacean Acid Metabolism (CAM). Our understanding of the causes for tolerance and resistance towards abiotic environmental stresses, salt stress in particular, has been extended to include the transfer of functionally characterized genes from M. Crystallinum into other plants. The use of transgenic plants will be an essential component of future work directed at the molecular dissection of mechanisms of transcription control, mRNA-stability and developmental competence in establishing salt stress tolerance.

  • Salt Stress Perception and Plant Growth Regulators in the Halophyte Mesembryanthemum Crystallinum.
    Plant physiology, 1993
    Co-Authors: John C. Thomas, Hans J. Bohnert
    Abstract:

    We selected indicators of four different metabolic processes (Crassulacean acid metabolism [CAM], amino acid and nitrogen mobilization metabolism, osmoprotection, and plant defense mechanisms) to study the relationship between salt-stress-mediated and plant growth regulator (PGR)-induced responses in Mesembryanthemum Crystallinum (ice plant). Nacl and PGRs (cytokinin and abscisic acid [ABA]) are efficient elicitors of the well-studied Nacl stress responses: induction of the CAM form of phosphoenolpyruvate carboxylase, proline pinitol accumulation, and the increase of an osmotin-like protein. NaCl and cytokinin are more effective than ABA in stimulating accumulation of proline and an osmotin-like protein before the plants are committed to flowering. The results are consistent with a plant defense-induction model, in which environmental stress and PGRs are distinct signals whose subsequent effects lead to overlapping responses, the magnitude of which depends on plant developmental status.

  • Regeneration of multiple shoots and plants from Mesembryanthemum Crystallinum.
    Plant cell reports, 1991
    Co-Authors: Michael S. Meiners, John C. Thomas, Hans J. Bohnert, John C. Cushman
    Abstract:

    Mesembryanthemum Crystallinum plants have been regenerated via organogenesis from hypocotyl, cotyledonary node, and leaf expiants with varying frequencies. The highest regeneration frequencies were obtained from either hypocotyls (23–34%) or cotyledonary nodes (21–41%). Leaf expiants yielded very poor regeneration frequencies (0–11%). Expiants were placed on Murashige and Skoog (MS) media supplemented with 3% sucrose, 0.8% bacto-agar and either, 10.8×10−6M NAA and 8.8×10−6M BA (MSmsh), 1×10−5M BA and 1×10−6M IAA, (MS4) or 1×10−6M BA and 1×10−6M IAA (MS5). Shoot formation frequencies were greater on MS4 and MS5 and lower on MSmsh, however, overall differences of regeneration frequency among media tested were not statistically significant. Regenerated plantlets were rooted on MS medium without growth regulators. Mature, regenerated plants were fertile and exhibited DNA content and ploidy profiles that were identical to wild type plants.

Bronwyn J. Barkla - One of the best experts on this subject based on the ideXlab platform.

  • Single-cell-type quantitative proteomic and ionomic analysis of epidermal bladder cells from the halophyte model plant Mesembryanthemum Crystallinum to identify salt-responsive proteins
    BMC plant biology, 2016
    Co-Authors: Bronwyn J. Barkla, Rosario Vera-estrella, Carolyn A Raymond
    Abstract:

    Background Epidermal bladder cells (EBC) are large single-celled, specialized, and modified trichomes found on the aerial parts of the halophyte Mesembryanthemum Crystallinum. Recent development of a simple but high throughput technique to extract the contents from these cells has provided an opportunity to conduct detailed single-cell-type analyses of their molecular characteristics at high resolution to gain insight into the role of these cells in the salt tolerance of the plant.

  • Cell type-specific responses to salinity - the epidermal bladder cell transcriptome of Mesembryanthemum Crystallinum.
    The New phytologist, 2015
    Co-Authors: Bronwyn J. Barkla, Hans J. Bohnert, Rosario Vera-estrella, Omar Pantoja, Sang-yeol Lee, Maheshi Dassanayake
    Abstract:

    Mesembryanthemum Crystallinum (ice plant) exhibits extreme tolerance to salt. Epidermal bladder cells (EBCs), developing on the surface of aerial tissues and specialized in sodium sequestration and other protective functions, are critical for the plant's stress adaptation. We present the first transcriptome analysis of EBCs isolated from intact plants, to investigate cell type-specific responses during plant salt adaptation. We developed a de novo assembled, nonredundant EBC reference transcriptome. Using RNAseq, we compared the expression patterns of the EBC-specific transcriptome between control and salt-treated plants. The EBC reference transcriptome consists of 37 341 transcript-contigs, of which 7% showed significantly different expression between salt-treated and control samples. We identified significant changes in ion transport, metabolism related to energy generation and osmolyte accumulation, stress signalling, and organelle functions, as well as a number of lineage-specific genes of unknown function, in response to salt treatment. The salinity-induced EBC transcriptome includes active transcript clusters, refuting the view of EBCs as passive storage compartments in the whole-plant stress response. EBC transcriptomes, differing from those of whole plants or leaf tissue, exemplify the importance of cell type-specific resolution in understanding stress adaptive mechanisms.

  • Protein profiling of epidermal bladder cells from the halophyte Mesembryanthemum Crystallinum
    Proteomics, 2012
    Co-Authors: Bronwyn J. Barkla, Rosario Vera-estrella, Omar Pantoja
    Abstract:

    Plant epidermal trichomes are as varied in morphology as they are in function. In the halophyte Mesembryanthemum Crystallinum, specialized trichomes called epidermal bladder cells (EBC) line the surface of leaves and stems, and increase dramatically in size and volume upon plant salt-treatment. These cells have been proposed to have roles in plant defense and UV protection, but primarily in sodium sequestration and as water reservoirs. To gain further understanding into the roles of EBC, a cell-type-specific proteomics approach was taken in which precision single-cell sampling of cell sap from individual EBC was combined with shotgun peptide sequencing (LC-MS/MS). Identified proteins showed diverse biological functions and cellular locations, with a high representation of proteins involved in H(+)-transport, carbohydrate metabolism, and photosynthesis. The proteome of EBC provides insight into the roles of these cells in ion and water homeostasis and raises the possibility that they are photosynthetically active and functioning in Crassulacean acid metabolism.

  • day night regulation of aquaporins during the cam cycle in Mesembryanthemum Crystallinum
    Plant Cell and Environment, 2012
    Co-Authors: Rosario Veraestrella, Bronwyn J. Barkla, Julio C Amezcuaromero, Omar Pantoja
    Abstract:

    Mesembryanthemum Crystallinum exhibits induction of Crassulacean acid metabolism (CAM) after a threshold stage of development, by exposure to long days with high light intensities or by water and salt stress. During the CAM cycle, fluctuations in carbon partitioning within the cell lead to transient drops in osmotic potential, which are likely stabilized/balanced by passive movement of water via aquaporins (AQPs). Protoplast swelling assays were used to detect changes in water permeability during the day/night cycle of CAM. To assess the role of AQPs during the same period, we followed transcript accumulation and protein abundance of four plasma membrane intrinsic proteins (PIPs) and one tonoplast intrinsic protein (TIP). CAM plants showed a persistent rhythm of specific AQP protein abundance changes throughout the day/night cycle, including changes in amount of McPIP2;1, McTIP1;2, McPIP1;4 and McPIP1;5, while the abundance of McPIP1;2 was unchanged. These protein changes did not appear to be coordinated with transcript levels for any of the AQPs analysed; however, they did occur in parrallel to alterations in water permeability, as well as variations in cell osmolarity, pinitol, glucose, fructose and phosphoenolpyruvate carboxylase (PEPc) levels measured throughout the day/night CAM cycle. Results suggest a role for AQPs in maintaining water balance during CAM and highlight the complexity of protein expression during the CAM cycle.

  • Day/night regulation of aquaporins during the CAM cycle in Mesembryanthemum Crystallinum.
    Plant cell & environment, 2011
    Co-Authors: Rosario Vera-estrella, Bronwyn J. Barkla, Julio C. Amezcua-romero, Omar Pantoja
    Abstract:

    Mesembryanthemum Crystallinum exhibits induction of Crassulacean acid metabolism (CAM) after a threshold stage of development, by exposure to long days with high light intensities or by water and salt stress. During the CAM cycle, fluctuations in carbon partitioning within the cell lead to transient drops in osmotic potential, which are likely stabilized/balanced by passive movement of water via aquaporins (AQPs). Protoplast swelling assays were used to detect changes in water permeability during the day/night cycle of CAM. To assess the role of AQPs during the same period, we followed transcript accumulation and protein abundance of four plasma membrane intrinsic proteins (PIPs) and one tonoplast intrinsic protein (TIP). CAM plants showed a persistent rhythm of specific AQP protein abundance changes throughout the day/night cycle, including changes in amount of McPIP2;1, McTIP1;2, McPIP1;4 and McPIP1;5, while the abundance of McPIP1;2 was unchanged. These protein changes did not appear to be coordinated with transcript levels for any of the AQPs analysed; however, they did occur in parrallel to alterations in water permeability, as well as variations in cell osmolarity, pinitol, glucose, fructose and phosphoenolpyruvate carboxylase (PEPc) levels measured throughout the day/night CAM cycle. Results suggest a role for AQPs in maintaining water balance during CAM and highlight the complexity of protein expression during the CAM cycle.