Recent evidence suggests that the P-proteins of Cucurbita maxima exist in at least two structural states: large polymers that are immobilized in individual sieve elements and small polymers or individual subunits that are translocated over long distances. We investigated variation in the structure of the phloem filament protein (phloem protein 1 or PP1) to determine the translocated form of the protein and its relationship to the polymerized state. It was demonstrated that the stability, folding state and assembly of the phloem filament protein rely on distinct intramolecular disulfide bonds. Acid trapping experiments combined with intergeneric grafts revealed that the phloem filament protein is translocated as an 88 kDa globular protein. By altering the pH of the collection buffer (pH 2-10), four individual conformational isoforms of PP1 with molecular masses of 81, 83, 85 and 88 kDa were consistently observed. The 81 kDa isoform represents the totally reduced phloem filament protein, the 83 and 85 kDa isoforms folding intermediates, and the 88 kDa its native soluble translocated form. The 83 and 85 kDa folding intermediates are susceptible to aggregation causing the gelation and formation of P-protein filaments in oxidized phloem sap. In contrast to the 88 kDa globular transport form, the 81, 83 and 85 kDa isoforms possibly exhibit lower stability, and therefore a higher sensitivity to proteolytic digestion.
{"title":"Dynamic transitions in the translocated phloem filament protein","authors":"K. Leineweber, A. Schulz, G. Thompson","doi":"10.1071/PP99161","DOIUrl":"https://doi.org/10.1071/PP99161","url":null,"abstract":"Recent evidence suggests that the P-proteins of Cucurbita maxima exist in at least two structural states: large polymers that are immobilized in individual sieve elements and small polymers or individual subunits that are translocated over long distances. We investigated variation in the structure of the phloem filament protein (phloem protein 1 or PP1) to determine the translocated form of the protein and its relationship to the polymerized state. It was demonstrated that the stability, folding state and assembly of the phloem filament protein rely on distinct intramolecular disulfide bonds. Acid trapping experiments combined with intergeneric grafts revealed that the phloem filament protein is translocated as an 88 kDa globular protein. By altering the pH of the collection buffer (pH 2-10), four individual conformational isoforms of PP1 with molecular masses of 81, 83, 85 and 88 kDa were consistently observed. The 81 kDa isoform represents the totally reduced phloem filament protein, the 83 and 85 kDa isoforms folding intermediates, and the 88 kDa its native soluble translocated form. The 83 and 85 kDa folding intermediates are susceptible to aggregation causing the gelation and formation of P-protein filaments in oxidized phloem sap. In contrast to the 88 kDa globular transport form, the 81, 83 and 85 kDa isoforms possibly exhibit lower stability, and therefore a higher sensitivity to proteolytic digestion.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83610357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Fernie, J. Riesmeier, Annette Martiny, S. Ramalingam, L. Willmitzer, R. Trethewey
The aim of this work was to further define the metabolic factors that regulate carbohydrate metabolism in potato (Solanum tuberosum L. cv. Desiree) tubers. We previously found that glycolysis is induced (and starch accumulation reduced) in transgenic tubers in which a yeast invertase and a glucokinase from Zymomonas mobilis were expressed in the cytosol, whereas potato tuber size is dramatically increased when invertase expression is targeted to the apoplast. In this study we describe the further characterisation of potato tubers expressing a yeast invertase in the apoplast. We also report the generation of two novel transgenic plants in which the Z. mobilis glucokinase gene is expressed tuber-specifically (either in the wild type or apoplastic invertase-expressing back- ground). We evaluated the influence that increasing the glucokinase activity, independent of invertase activity, had on the shift in carbon partitioning, and assessed if the hexoses produced by the apoplastic cleavage of sucrose could be brought into metabolism. We found that expression of glucokinase either in the wild type or in the apoplastic invertase-expressing background led to changes in the levels of glucose and glucose 6-phosphate. However, these changes had little effect on carbon partitioning or tuber size with respect to the parent line. We conclude that neither the accumulation nor the phosphorylation of glucose play a pivotal role in the regulation of metabolism or morphology in the potato tuber.
{"title":"Consequences of the expression of a bacterial glucokinase in potato tubers, both in combination with and independently of a yeast-derived invertase","authors":"A. Fernie, J. Riesmeier, Annette Martiny, S. Ramalingam, L. Willmitzer, R. Trethewey","doi":"10.1071/PP99152","DOIUrl":"https://doi.org/10.1071/PP99152","url":null,"abstract":"The aim of this work was to further define the metabolic factors that regulate carbohydrate metabolism in potato (Solanum tuberosum L. cv. Desiree) tubers. We previously found that glycolysis is induced (and starch accumulation reduced) in transgenic tubers in which a yeast invertase and a glucokinase from Zymomonas mobilis were expressed in the cytosol, whereas potato tuber size is dramatically increased when invertase expression is targeted to the apoplast. In this study we describe the further characterisation of potato tubers expressing a yeast invertase in the apoplast. We also report the generation of two novel transgenic plants in which the Z. mobilis glucokinase gene is expressed tuber-specifically (either in the wild type or apoplastic invertase-expressing back- ground). We evaluated the influence that increasing the glucokinase activity, independent of invertase activity, had on the shift in carbon partitioning, and assessed if the hexoses produced by the apoplastic cleavage of sucrose could be brought into metabolism. We found that expression of glucokinase either in the wild type or in the apoplastic invertase-expressing background led to changes in the levels of glucose and glucose 6-phosphate. However, these changes had little effect on carbon partitioning or tuber size with respect to the parent line. We conclude that neither the accumulation nor the phosphorylation of glucose play a pivotal role in the regulation of metabolism or morphology in the potato tuber.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79344657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent studies support the concept that long-distance signals are involved in the regulation of resource allocation among the various plant organs. Following the finding that viral movement proteins (MPs) can exert an effect on sugar metabolism and resource allocation at sites distant from their expression, we suggested that the MPs interfere with an element(s) involved in the plant's endogenous long-distance signal network. To provide experi- mental support for this hypothesis, several unique procedures were employed to identify interactions between viral MPs and phloem sap proteins (PSPs) collected from cut petioles of squash (Cucurbita pepo L. subsp. pepo) and melon (Cucumis melo L.) plants. Far-western experiments with blotted PSPs, using both bacteria-overexpressed and in vitro-translated CMV- and TMV-MPs, revealed that the two virally encoded proteins react specifically with more than one PSP. Moreover, isolation of the naturally folded phloem protein in an affinity column containing a TMV-MP-maltose-binding protein indicated, once again, an interaction between the viral protein and similar PSPs. Two melon PSPs with molecular masses of 8 and 23 kDa were found to specifically interact with both the CMV- and TMV-MPs. The possible effects of this interaction in terms of altering the process of phloem transport and resource allocation are discussed.
最近的研究支持了远距离信号参与植物各器官间资源分配调节的观点。在发现病毒运动蛋白(MPs)可以在远离其表达的位点对糖代谢和资源分配产生影响之后，我们认为MPs干扰了植物内源性长距离信号网络中的一个元件。为了对这一假设提供实验支持，采用了几种独特的方法来鉴定从南瓜(Cucurbita pepo L. subsp)切下的叶柄中收集的病毒MPs与韧皮部汁液蛋白(PSPs)之间的相互作用。人和甜瓜(Cucumis melo L.)植物。利用细菌过表达和体外翻译的CMV-和TMV-MPs对斑点化PSP进行的远西部实验表明，这两种病毒编码的蛋白与不止一种PSP发生特异性反应。此外，在含有tmv - mp -麦芽糖结合蛋白的亲和柱中分离出自然折叠的韧皮部蛋白，再次表明病毒蛋白与类似的psp之间存在相互作用。发现分子质量分别为8和23 kDa的两种甜瓜PSPs与CMV-和TMV-MPs特异性相互作用。讨论了这种相互作用在改变韧皮部运输和资源分配过程方面可能产生的影响。
{"title":"Interaction between phloem proteins and viral movement proteins","authors":"D. Shalitin, S. Wolf","doi":"10.1071/PP99153","DOIUrl":"https://doi.org/10.1071/PP99153","url":null,"abstract":"Recent studies support the concept that long-distance signals are involved in the regulation of resource allocation among the various plant organs. Following the finding that viral movement proteins (MPs) can exert an effect on sugar metabolism and resource allocation at sites distant from their expression, we suggested that the MPs interfere with an element(s) involved in the plant's endogenous long-distance signal network. To provide experi- mental support for this hypothesis, several unique procedures were employed to identify interactions between viral MPs and phloem sap proteins (PSPs) collected from cut petioles of squash (Cucurbita pepo L. subsp. pepo) and melon (Cucumis melo L.) plants. Far-western experiments with blotted PSPs, using both bacteria-overexpressed and in vitro-translated CMV- and TMV-MPs, revealed that the two virally encoded proteins react specifically with more than one PSP. Moreover, isolation of the naturally folded phloem protein in an affinity column containing a TMV-MP-maltose-binding protein indicated, once again, an interaction between the viral protein and similar PSPs. Two melon PSPs with molecular masses of 8 and 23 kDa were found to specifically interact with both the CMV- and TMV-MPs. The possible effects of this interaction in terms of altering the process of phloem transport and resource allocation are discussed.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76311618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The distance between sites of synthesis of assimilates and the site of phloem loading can be large, and specialized leaf cell layers such as the paraveinal mesophyll (PVM) might act to enhance the efficiency of transport. A number of techniques were used to analyse PVM of legume leaves with respect to a hypothesized function in transfer of assimilates between tissues. Of 39 legume species examined, PVM was found in 22. Leaves of all PVM- containing species had multiple palisade parenchyma layers, while non-PVM species generally had only one distinct palisade layer. Morphometric analysis identified a significant correlation between PVM presence and greater numbers of palisade cells per unit leaf surface area. Comparison of photosynthetic rates of four PVM and four non- PVM species showed the PVM species had higher rates on a leaf area basis than all but one of the non-PVM species. Microautoradiography of 14 CO2 pulse-chase studies in soybean demonstrated PVM is an intermediary tissue in transfer of assimilates to vascular bundles. In addition, PVM cells but not mesophyll cells, were enriched in a sucrose binding protein previously found to be associated with sucrose-transporting tissues. The structural, positional and transport data support the hypothesis that the PVM acts as a transport pathway between the vascular system and photoassimilatory cells of the leaf, and has probably evolved to overcome diffusion limitations imposed by multiple palisade layers.
{"title":"The paraveinal mesophyll: a specialized path for intermediary transfer of assimilates in legume leaves","authors":"A. Lansing, V. Franceschi","doi":"10.1071/PP99167","DOIUrl":"https://doi.org/10.1071/PP99167","url":null,"abstract":"The distance between sites of synthesis of assimilates and the site of phloem loading can be large, and specialized leaf cell layers such as the paraveinal mesophyll (PVM) might act to enhance the efficiency of transport. A number of techniques were used to analyse PVM of legume leaves with respect to a hypothesized function in transfer of assimilates between tissues. Of 39 legume species examined, PVM was found in 22. Leaves of all PVM- containing species had multiple palisade parenchyma layers, while non-PVM species generally had only one distinct palisade layer. Morphometric analysis identified a significant correlation between PVM presence and greater numbers of palisade cells per unit leaf surface area. Comparison of photosynthetic rates of four PVM and four non- PVM species showed the PVM species had higher rates on a leaf area basis than all but one of the non-PVM species. Microautoradiography of 14 CO2 pulse-chase studies in soybean demonstrated PVM is an intermediary tissue in transfer of assimilates to vascular bundles. In addition, PVM cells but not mesophyll cells, were enriched in a sucrose binding protein previously found to be associated with sucrose-transporting tissues. The structural, positional and transport data support the hypothesis that the PVM acts as a transport pathway between the vascular system and photoassimilatory cells of the leaf, and has probably evolved to overcome diffusion limitations imposed by multiple palisade layers.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81469610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O. Koroleva, A. D. Tomos, J. Farrar, P. Roberts, C. Pollock
In order to investigate the roles of different cell types, metabolite compartmentation in barley (Hordeum vulgare L.) leaf tissue was mapped at the single-cell level, using single-cell sampling and analysis (SiCSA) tech- niques. The partitioning of recently fixed photoassimilate was investigated for the first time at single-cell resolution, using BAMS (biological accelerator mass spectroscopy) for precise measurement of 14 C in femtomole quantities. The data obtained by BAMS qualitatively reflect concentrations of sugars in different cell types measured by SiCSA. Calculation of 14 C-specific activities showed that the radioactive label saturated the mesophyll and parenchymatous bundle sheath (PBS) pools within the 45-min labelling period. During the photoperiod, sucrose concentration increased to 200 mM in mesophyll cells. The concentration of malate also increased during the photoperiod in meso- phyll and PBS cells. Epidermal cells contained very low concentrations of sugar but high concentrations of malate (120-180 mM) and did not show significant diurnal changes. Accumulation of sugars and fructan synthesis could be induced in mesophyll and PBS cells by reduced export of sugars from leaves or, alternatively, when sugars were sup- plied from excised leaf blade bases immersed in a sucrose solution in the dark. The epidermis accumulated addi- tional malate in step with the accumulation of sugar by the mesophyll/PBS cells during the long-term reduction of export. Immunolocalisation of Rubisco and cytochrome oxidase proteins was used to analyse the distribution of enzymes of photoassimilation and respiration between functionally different cells in mature leaves of barley.
{"title":"Tissue distribution of primary metabolism between epidermal, mesophyll and parenchymatous bundle sheath cells in barley leaves","authors":"O. Koroleva, A. D. Tomos, J. Farrar, P. Roberts, C. Pollock","doi":"10.1071/PP99156","DOIUrl":"https://doi.org/10.1071/PP99156","url":null,"abstract":"In order to investigate the roles of different cell types, metabolite compartmentation in barley (Hordeum vulgare L.) leaf tissue was mapped at the single-cell level, using single-cell sampling and analysis (SiCSA) tech- niques. The partitioning of recently fixed photoassimilate was investigated for the first time at single-cell resolution, using BAMS (biological accelerator mass spectroscopy) for precise measurement of 14 C in femtomole quantities. The data obtained by BAMS qualitatively reflect concentrations of sugars in different cell types measured by SiCSA. Calculation of 14 C-specific activities showed that the radioactive label saturated the mesophyll and parenchymatous bundle sheath (PBS) pools within the 45-min labelling period. During the photoperiod, sucrose concentration increased to 200 mM in mesophyll cells. The concentration of malate also increased during the photoperiod in meso- phyll and PBS cells. Epidermal cells contained very low concentrations of sugar but high concentrations of malate (120-180 mM) and did not show significant diurnal changes. Accumulation of sugars and fructan synthesis could be induced in mesophyll and PBS cells by reduced export of sugars from leaves or, alternatively, when sugars were sup- plied from excised leaf blade bases immersed in a sucrose solution in the dark. The epidermis accumulated addi- tional malate in step with the accumulation of sugar by the mesophyll/PBS cells during the long-term reduction of export. Immunolocalisation of Rubisco and cytochrome oxidase proteins was used to analyse the distribution of enzymes of photoassimilation and respiration between functionally different cells in mature leaves of barley.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85652431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There is evidence that calcium (Ca2+) activity in sieve elements is much higher than in adjacent cells, which raises questions about Ca2+ exchange across the sieve element plasma membrane. We looked for the presence of Ca2+ channels in tobacco (Nicotiana tabacum L.) and Pistia stratiotes (L.) using a monoclonal antibody to a dihydropyridine (DHP)-type Ca channel (MAB427). Immunolabeling at the light microscope level gave strong signals along the sieve element of both species, and with the transmission electron microscope this label was found associated with the plasma membrane. Western blot analysis using the MAB427 antibody detects a protein between 175 and 220 kDa (approximately the size expected of the α-1 subunit of the Ca2+ channel protein in mammals) in blots containing either Pistia or tobacco leaf microsomal membrane protein extracts. As a further test for Ca2+ channels, hand-sectioned young Pistia leaves were treated with the fluorescent-tagged Ca2+ channel blocker 4,4difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-3-(indacene)propionic acid (DM-BODIPY)-DHP. The phloem, as well as calcium oxalate idioblast cells, exhibited strong fluorescence compared to general parenchyma cells. The binding of DM-BODIPY-DHP was inhibited by pre-treatment of sections with nifedipine, a competitive inhibitor of DHP-type Ca2+ channels in animal systems. The results indicate that sieve elements may be enriched with Ca2+ channels which might be partly responsible for the high Ca2+ activities observed in sieve sap, and also for rapid phloem responses, such as Ca2+ activated callose deposition.
{"title":"Localization of a calcium channel-like protein in the sieve element plasma membrane","authors":"G. Volk, V. Franceschi","doi":"10.1071/PP99192","DOIUrl":"https://doi.org/10.1071/PP99192","url":null,"abstract":"There is evidence that calcium (Ca2+) activity in sieve elements is much higher than in adjacent cells, which raises questions about Ca2+ exchange across the sieve element plasma membrane. We looked for the presence of Ca2+ channels in tobacco (Nicotiana tabacum L.) and Pistia stratiotes (L.) using a monoclonal antibody to a dihydropyridine (DHP)-type Ca channel (MAB427). Immunolabeling at the light microscope level gave strong signals along the sieve element of both species, and with the transmission electron microscope this label was found associated with the plasma membrane. Western blot analysis using the MAB427 antibody detects a protein between 175 and 220 kDa (approximately the size expected of the α-1 subunit of the Ca2+ channel protein in mammals) in blots containing either Pistia or tobacco leaf microsomal membrane protein extracts. As a further test for Ca2+ channels, hand-sectioned young Pistia leaves were treated with the fluorescent-tagged Ca2+ channel blocker 4,4difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-3-(indacene)propionic acid (DM-BODIPY)-DHP. The phloem, as well as calcium oxalate idioblast cells, exhibited strong fluorescence compared to general parenchyma cells. The binding of DM-BODIPY-DHP was inhibited by pre-treatment of sections with nifedipine, a competitive inhibitor of DHP-type Ca2+ channels in animal systems. The results indicate that sieve elements may be enriched with Ca2+ channels which might be partly responsible for the high Ca2+ activities observed in sieve sap, and also for rapid phloem responses, such as Ca2+ activated callose deposition.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82232196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Roitsch, R. Ehness, M. Goetz, B. Hause, M. Hofmann, A. Sinha
Carbohydrates are synthesised in photosynthetically active source tissues and exported, in most species in the form of sucrose, to photosynthetically less active or inactive sink tissues. Sucrose hydrolysis at the site of utili- sation contributes to phloem unloading. This phenomenon links sink metabolism with phloem transport to, and par- titioning between, sinks. Invertases catalyse the irreversible hydrolysis of sucrose and thus are expected to contribute to carbohydrate partitioning. Different invertase isoenzymes may be distinguished based on their intracellular loca- tion, their isoelectric points and pH optima. Extracellular, cell-wall-bound invertase is uniquely positioned to supply carbohydrates to sink tissues via an apoplasmic pathway, and links the transport sugar sucrose to hexose transporters. A number of studies demonstrate an essential function of this invertase isoenzyme for phloem unloading, carbo- hydrate partitioning and growth of sink tissues. Extracellular invertases were shown to be specifically expressed under conditions that require a high carbohydrate supply to sink tissues. Further, their expression is upregulated by a number of stimuli that affect source-sink relations. Substrate and reaction products of invertases are not only nutri- ents, but also signal molecules. Like hormones and in combination with hormones and other stimuli, they can regu- late many aspects of plant development from gene expression to long-distance nutrient allocation. Based on studies in Chenopodium rubrum, tomato (Lycopersicon esculentum) and tobacco (Nicotiana tabacum), the regulation of extracellular invertase and its function in assimilate partitioning, defence reactions and sugar signal transduction pathways are discussed.
{"title":"Regulation and function of extracellular invertase from higher plants in relation to assimilate partitioning, stress responses and sugar signalling","authors":"T. Roitsch, R. Ehness, M. Goetz, B. Hause, M. Hofmann, A. Sinha","doi":"10.1071/PP00001","DOIUrl":"https://doi.org/10.1071/PP00001","url":null,"abstract":"Carbohydrates are synthesised in photosynthetically active source tissues and exported, in most species in the form of sucrose, to photosynthetically less active or inactive sink tissues. Sucrose hydrolysis at the site of utili- sation contributes to phloem unloading. This phenomenon links sink metabolism with phloem transport to, and par- titioning between, sinks. Invertases catalyse the irreversible hydrolysis of sucrose and thus are expected to contribute to carbohydrate partitioning. Different invertase isoenzymes may be distinguished based on their intracellular loca- tion, their isoelectric points and pH optima. Extracellular, cell-wall-bound invertase is uniquely positioned to supply carbohydrates to sink tissues via an apoplasmic pathway, and links the transport sugar sucrose to hexose transporters. A number of studies demonstrate an essential function of this invertase isoenzyme for phloem unloading, carbo- hydrate partitioning and growth of sink tissues. Extracellular invertases were shown to be specifically expressed under conditions that require a high carbohydrate supply to sink tissues. Further, their expression is upregulated by a number of stimuli that affect source-sink relations. Substrate and reaction products of invertases are not only nutri- ents, but also signal molecules. Like hormones and in combination with hormones and other stimuli, they can regu- late many aspects of plant development from gene expression to long-distance nutrient allocation. Based on studies in Chenopodium rubrum, tomato (Lycopersicon esculentum) and tobacco (Nicotiana tabacum), the regulation of extracellular invertase and its function in assimilate partitioning, defence reactions and sugar signal transduction pathways are discussed.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90600481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Majnik, J. Weinman, M. Djordjevic, B. Rolfe, G. Tanner, R. Joseph, P. Larkin
This study presents the first evidence of heterologous anthocyanin regulatory genes altering anthocyanin expression in stably transformed leguminous plants. Two families of anthocyanin regulatory genes, myc (delila, B-Peru) and myb (myb.Ph2, C1), are involved in the activation of the phenylpropanoid pathway. White clover (Trifolium repens cv. Haifa) plants were transformed with dicotyledonous and monocotyledonous myb or myc genes. Some of these transformed plants exhibited enhanced anthocyanin accumulation in a range of tissues. One plant, transformed with the B-Peru gene driven by the Cauliflower Mosaic Virus 35S promoter, displayed a unique pattern of anthocyanin accumulation in the leaf. The accumulation of anthocyanin in this plant was closely associated with the crescent of leaves, which is normally white. The red pigmentation declined in intensity in the oldest leaf stage. The B-Peru message was detected in all leaf stages of this white clover plant. This anthocyanin pattern was shown to be heritable.
{"title":"Anthocyanin regulatory gene expression in transgenic white clover can result in an altered pattern of pigmentation","authors":"J. Majnik, J. Weinman, M. Djordjevic, B. Rolfe, G. Tanner, R. Joseph, P. Larkin","doi":"10.1071/PP99115","DOIUrl":"https://doi.org/10.1071/PP99115","url":null,"abstract":"This study presents the first evidence of heterologous anthocyanin regulatory genes altering anthocyanin expression in stably transformed leguminous plants. Two families of anthocyanin regulatory genes, myc (delila, B-Peru) and myb (myb.Ph2, C1), are involved in the activation of the phenylpropanoid pathway. White clover (Trifolium repens cv. Haifa) plants were transformed with dicotyledonous and monocotyledonous myb or myc genes. Some of these transformed plants exhibited enhanced anthocyanin accumulation in a range of tissues. One plant, transformed with the B-Peru gene driven by the Cauliflower Mosaic Virus 35S promoter, displayed a unique pattern of anthocyanin accumulation in the leaf. The accumulation of anthocyanin in this plant was closely associated with the crescent of leaves, which is normally white. The red pigmentation declined in intensity in the oldest leaf stage. The B-Peru message was detected in all leaf stages of this white clover plant. This anthocyanin pattern was shown to be heritable.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89645844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Fischer-Schliebs, M. Drobny, E. Ball, R. Ratajczak, U. Lüttge
The tonoplast V-type H + -ATPase (V-ATPase; EC 3.6.1.34) of higher plants responds by its activity and molecular-subunit fine structure to environmental parameters, such as temperature and salinity, or to the mode of photosynthesis in C3-CAM intermediate plants. To test the hypothesis that the enzyme is responding to varied mineral nutrition in similar ways, tobacco plants were grown at low (2 mM) and high (40 mM) nitrate supply, and a group of plants was also transferred from the low to the high nitrate concentration for 48 h before analysis. Direct correlation of V-ATPase properties with nitrate regimes and leaf nitrate content were not found, but indirect effects related to nitrate-affected growth were obtained. Although the ATP-hydrolysis of isolated tonoplast vesicles was similar under all three conditions, H + -transport activity and hence the apparent H + -transport activity/ATP-hydroly- sis coupling ratio of the V-ATPase in native tonoplast vesicles was high at low growth-limiting nitrate supply and after growth acceleration following the transfer of plants from low to high nitrate. Immunological differences of the V-ATPase suggested that the membrane-integral proteolipid subunit c showed structural differences related to nitrate nutrition. These differences were revealed by differential cross-reactions with two polyclonal antisera directed against the V-ATPase of Kalanchoe daigremontiana, respectively. The immunological differences could possibly be due to the expression of different forms of subunit c correlated with actual growth rates of leaves, which were high at 40 mM and after the transfer from 2 mM to 40 mM, and low at 2 mM nitrate. These complex responses to variation in nitrogen nutrition of plants are consistent with the notion in the literature that nitrate is both a nutrient and a signal for plant growth.
{"title":"Variation in nitrate nutrition leads to changes in the performance of the V-ATPase and immunological differences of proteolipid subunit c in tobacco (Nicotiana tabacum) leaves.","authors":"E. Fischer-Schliebs, M. Drobny, E. Ball, R. Ratajczak, U. Lüttge","doi":"10.1071/PP98085","DOIUrl":"https://doi.org/10.1071/PP98085","url":null,"abstract":"The tonoplast V-type H + -ATPase (V-ATPase; EC 3.6.1.34) of higher plants responds by its activity and molecular-subunit fine structure to environmental parameters, such as temperature and salinity, or to the mode of photosynthesis in C3-CAM intermediate plants. To test the hypothesis that the enzyme is responding to varied mineral nutrition in similar ways, tobacco plants were grown at low (2 mM) and high (40 mM) nitrate supply, and a group of plants was also transferred from the low to the high nitrate concentration for 48 h before analysis. Direct correlation of V-ATPase properties with nitrate regimes and leaf nitrate content were not found, but indirect effects related to nitrate-affected growth were obtained. Although the ATP-hydrolysis of isolated tonoplast vesicles was similar under all three conditions, H + -transport activity and hence the apparent H + -transport activity/ATP-hydroly- sis coupling ratio of the V-ATPase in native tonoplast vesicles was high at low growth-limiting nitrate supply and after growth acceleration following the transfer of plants from low to high nitrate. Immunological differences of the V-ATPase suggested that the membrane-integral proteolipid subunit c showed structural differences related to nitrate nutrition. These differences were revealed by differential cross-reactions with two polyclonal antisera directed against the V-ATPase of Kalanchoe daigremontiana, respectively. The immunological differences could possibly be due to the expression of different forms of subunit c correlated with actual growth rates of leaves, which were high at 40 mM and after the transfer from 2 mM to 40 mM, and low at 2 mM nitrate. These complex responses to variation in nitrogen nutrition of plants are consistent with the notion in the literature that nitrate is both a nutrient and a signal for plant growth.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73101089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Measurements of the hydraulic conductance (L0) of roots of melon plants (Cucumis melo L.) derived from roots grown under saline conditions were performed to determine the effect of NaCl and which ion, Na + or Cl – , is involved. Root hydraulic conductance of plants treated with a 50 mM NaCl, 47 mM Na + or 45 mM Cl – salts mixture was reduced, but the reduction was less when 10 mM CaCl2 was added before the salts, except in the case of the Cl – salt mixture. Only when CaCl2 was applied before NaCl was there an ameliorative effect on L0 (25.8% increase). Addition of HgCl2 reduced theL0 of control plants, but the reduction progressively decreased as the NaCl concentration was increased (from 0 to 50 mM). Osmotic water permeability (Pf) values were calculated in root protoplasts treated with 90 mM NaCl. Large reductions were observed with the NaCl treatment (10.38 mm s –1 for the control and 3.31 mm s –1 for the NaCl treatment). In addition, Pfmeasurements were carried out for protoplasts treated with 100 mM NaCl plus the phosphatase inhibitor, okadaic acid (5 mM). The effect of okadaic acid on Pf values before and after NaCl addition was similar (6.61 and 7.01 mm s –1 , respectively), showing a smaller decrease of Pf than with NaCl alone with respect to control protoplasts. The results showed that the negative effect of NaCl on water channel activity was not due to a high ion concentration effect on channel pores or to the increase in osmotic pressure. We suggest that it was due to a direct action of NaCl on protein regulation.
通过对甜瓜(Cucumis melo L.)根系的水力导度(L0)测定，确定了NaCl的影响以及Na +和Cl -离子的影响。50 mM NaCl、47 mM Na +和45 mM Cl -盐混合处理的植株根系水力导度均有所降低，但除Cl -盐混合处理外，先添加10 mM CaCl2的植株根系水力导度降低幅度较小。只有先施用CaCl2再施用NaCl, L0才有改善作用(提高25.8%)。HgCl2的添加降低了对照植株的theL0，但随着NaCl浓度的增加(从0到50 mM)，其还原程度逐渐降低。计算了90 mM NaCl处理根原生质体的渗透透水性(Pf)值。NaCl处理显著降低(对照10.38 mm s -1, NaCl处理3.31 mm s -1)。此外，原生质体经100 mM NaCl加磷酸酶抑制剂冈田酸(5 mM)处理后，进行了Pfmeasurements。与对照原生质体相比，添加NaCl前后冈田酸对Pf值的影响相似(分别为6.61和7.01 mm s -1)，但Pf的降低幅度小于单独添加NaCl。结果表明，NaCl对水通道活性的负面影响不是由于高离子浓度对通道孔隙的影响或渗透压的增加。我们认为这可能是NaCl对蛋白质调控的直接作用。
{"title":"Regulation of water channel activity in whole roots and in protoplasts from roots of melon plants grown under saline conditions","authors":"M. C. Martínez-Ballesta, V. Martínez, M. Carvajal","doi":"10.1071/PP99203","DOIUrl":"https://doi.org/10.1071/PP99203","url":null,"abstract":"Measurements of the hydraulic conductance (L0) of roots of melon plants (Cucumis melo L.) derived from roots grown under saline conditions were performed to determine the effect of NaCl and which ion, Na + or Cl – , is involved. Root hydraulic conductance of plants treated with a 50 mM NaCl, 47 mM Na + or 45 mM Cl – salts mixture was reduced, but the reduction was less when 10 mM CaCl2 was added before the salts, except in the case of the Cl – salt mixture. Only when CaCl2 was applied before NaCl was there an ameliorative effect on L0 (25.8% increase). Addition of HgCl2 reduced theL0 of control plants, but the reduction progressively decreased as the NaCl concentration was increased (from 0 to 50 mM). Osmotic water permeability (Pf) values were calculated in root protoplasts treated with 90 mM NaCl. Large reductions were observed with the NaCl treatment (10.38 mm s –1 for the control and 3.31 mm s –1 for the NaCl treatment). In addition, Pfmeasurements were carried out for protoplasts treated with 100 mM NaCl plus the phosphatase inhibitor, okadaic acid (5 mM). The effect of okadaic acid on Pf values before and after NaCl addition was similar (6.61 and 7.01 mm s –1 , respectively), showing a smaller decrease of Pf than with NaCl alone with respect to control protoplasts. The results showed that the negative effect of NaCl on water channel activity was not due to a high ion concentration effect on channel pores or to the increase in osmotic pressure. We suggest that it was due to a direct action of NaCl on protein regulation.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85551698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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