Tap Roots

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Arnd Sturm - One of the best experts on this subject based on the ideXlab platform.

  • Antisense repression of sucrose synthase in carrot (Daucus carota L.) affects growth rather than sucrose partitioning.
    Plant Molecular Biology, 1999
    Co-Authors: Guo-qing Tang, Arnd Sturm
    Abstract:

    To unravel the roles of sucrose synthase in carrot, we reduced its activity in transgenic carrot plants by an antisense approach. For this purpose, the cDNA for the main form of carrot sucrose synthase was expressed in antisense orientation behind the 35S promoter of cauliflower mosaic virus. In independent antisense plant lines grown in soil, sucrose synthase activity was reduced in Tap Roots but not in leaves. In the sink organs, sucrose utilization was markedly decreased and higher levels of sucrose but lower levels of UDP-glucose, glucose, fructose, starch and cellulose were found. The phenotype of the antisense plants clearly differed from that of control plants. Both leaves and Roots were markedly smaller, and the antisense line with the lowest sucrose synthase activity also developed the smallest plants. In most of the plant lines, the leaf-to-root dry weight ratios were not changed, suggesting that sucrose synthase in carrot is a major determinant of plant growth rather than of sucrose partitioning. In contrast to the acid invertases, which are critical for partitioning of assimilated carbon between source leaves and Tap Roots (Tang et al., Plant Cell 11: 177–189 (1999)), sucrose synthase appears to be the main sucrose-cleaving activity, feeding sucrose into metabolism.

  • Tissue-specific expression of two genes for sucrose synthase in carrot (Daucus carota L.).
    Plant Molecular Biology, 1999
    Co-Authors: Arnd Sturm, Susanne Lienhard, Stephan Schatt, Markus Hardegger
    Abstract:

    Sucrose synthase, which cleaves sucrose in the presence of uridine diphosphate (UDP) into UDP-glucose and fructose, is thought to be a key determinant of sink strength of heterotrophic plant organs. To determine the roles of the enzyme in carrot, we characterized carrot sucrose synthase at the molecular level. Two genes (Susy*Dc1 and Susy*Dc2) were isolated. The deduced amino acid sequences are 87% identical. However, the sequences upstream of the translation initiation codons are markedly different, as are the expression patterns of the two genes. Susy*Dc2 was exclusively expressed in flowers. Transcripts for Susy*Dc1 were found in stems, in Roots at different developmental stages, and in flower buds, flowers and maturing seeds, with the highest levels in strong utilization sinks for sucrose such as growing stems and Tap root tips. Expression of Susy*Dc1 was regulated by anaerobiosis but not by sugars or acetate. The carrot sucrose synthase protein is partly membrane-associated and this insoluble form may be directly involved in cellulose biosynthesis. Tap Roots of the carrot cultivar used accumulated starch in the vicinity of the vascular bundles, which correlated with high sucrose synthase transcript levels. This finding suggests that soluble sucrose synthase in Tap Roots channels sucrose towards starch biosynthesis. Starch accumulation appears to be transient and may be involved in sucrose partitioning to developing Tap Roots.

  • Molecular characterization and functional analysis of sucrose-cleaving enzymes in carrot (Daucus carota L.)
    Journal of Experimental Botany, 1996
    Co-Authors: Arnd Sturm
    Abstract:

    The amount of carbon transported into storage organs of crop plants to a large degree determines crop yield. The role of sucrose-cleaving enzymes in this process is not clear and it is the main goal of our work to tackle this question. Sucrose cleavage is catalysed either by invertase or sucrose synthase both of which exist in several isoforms with different subcellular locations. Carrot (Daucus carota L.) contains three major isoenzymes of acid invertase, which either accumulate as soluble polypeptides in the vacuole (isoenzymes I and II) or are ionically bound to the cell wall. Carrot sucrose synthase is thought to be a cytoplasmic enzyme encoded by two genes. cDNA clones have been isolated and characterized for cell wall invertase, for isoenzymes I and II of vacuolar invertase, and for sucrose synthase. Gene-specific fragments of these clones were used to determine the steady-state levels of transcripts in the prominent sink and source organs of developing carrot plants. The expression patterns of each gene were different and were organ- and development-specific. Developing Tap Roots contained only transcripts for isoenzyme II of vacuolar invertase and sucrose synthase. The source/sink balance of these plants was manipulated and only the expression of these two genes was markedly altered, indicating their importance in sucrose partitioning. Based on these results, a model is proposed for sucrose partitioning in carrot plants with developing Tap Roots in which sucrose synthase regulates sucrose utilization, whereas isoenzyme II of vacuolar invertase controls sucrose storage and sugar composition.

  • Development- and organ-specific expression of the genes for sucrose synthase and three isoenzymes of acid β-fructofuranosidase in carrot
    Planta, 1995
    Co-Authors: Arnd Sturm, Susanne Lienhard, Markus Hardegger, Veronika Šebková, Kathrin Lorenz, Christoph Unger
    Abstract:

    The steady-state levels of transcripts for cellwall β-fructofuranosidase (cwβF), for isoenzymes I and II of soluble acid β-fructofuranosidase (sI, sII), and for sucrose synthase (ss) were determined in the sink and source organs of developing carrot (Daucus carota L.) plants. The expression patterns of the four genes clearly differed. The expression of the gene for cwβF was development-specific but not organ-specific; high transcript levels were only found in plants with primary Roots, with about equal amounts in leaf lamina, petioles and Roots. The genes for sI and sII were mainly expressed in Roots, sI predominating in primary Roots and sII in developing Tap Roots. Transcripts for ss were found at a low level in all developing plant organs and were markedly up-regulated during the development of young leaves and during the transition of primary Roots to Tap Roots. Developing Tap Roots contained only transcripts for sII and for ss. Marked alterations in the expression of these two genes after manipulation of the source/sink balance of these plants indicates their importance in sucrose partitioning. We suggest that ss regulates sucrose utilization in developing Tap Roots, whereas sII located in the vacuole controls sucrose storage and sugar composition.

  • Structural organization and differential expression of carrot β-fructofuranosidase genes: identification of a gene coding for a flower bud-specific isozyme
    Plant molecular biology, 1995
    Co-Authors: Kathrin Lorenz, Susanne Lienhard, Arnd Sturm
    Abstract:

    Three genomic clones (Inv*Dc1, Inv*Dc2 and Inv*Dc3) were isolated by using the cDNA for carrot cell wall beta-fructofuranosidase as a probe. The expression patterns of the three genes differed markedly. High levels of Inv*Dc1 transcripts were found in leaves and Roots of young carrot, whereas in plants with developing Tap Roots no transcripts were detected. A high level of mRNA of Inv*Dc1 was also present in suspension-cultured cells. In developing reproductive organs, only low levels of transcripts of Inv*Dc1 were found in flower buds and flowers and none at later stages of development. In contrast, Inv*Dc2 and Inv*Dc3 were not expressed in vegetative plant organs. Invb1*Dc1 was exclusively and strongly expressed in flower buds, and Inv*Dc3 at a very low level in suspension-cultured cells.

Markus Hardegger - One of the best experts on this subject based on the ideXlab platform.

  • Tissue-specific expression of two genes for sucrose synthase in carrot (Daucus carota L.).
    Plant Molecular Biology, 1999
    Co-Authors: Arnd Sturm, Susanne Lienhard, Stephan Schatt, Markus Hardegger
    Abstract:

    Sucrose synthase, which cleaves sucrose in the presence of uridine diphosphate (UDP) into UDP-glucose and fructose, is thought to be a key determinant of sink strength of heterotrophic plant organs. To determine the roles of the enzyme in carrot, we characterized carrot sucrose synthase at the molecular level. Two genes (Susy*Dc1 and Susy*Dc2) were isolated. The deduced amino acid sequences are 87% identical. However, the sequences upstream of the translation initiation codons are markedly different, as are the expression patterns of the two genes. Susy*Dc2 was exclusively expressed in flowers. Transcripts for Susy*Dc1 were found in stems, in Roots at different developmental stages, and in flower buds, flowers and maturing seeds, with the highest levels in strong utilization sinks for sucrose such as growing stems and Tap root tips. Expression of Susy*Dc1 was regulated by anaerobiosis but not by sugars or acetate. The carrot sucrose synthase protein is partly membrane-associated and this insoluble form may be directly involved in cellulose biosynthesis. Tap Roots of the carrot cultivar used accumulated starch in the vicinity of the vascular bundles, which correlated with high sucrose synthase transcript levels. This finding suggests that soluble sucrose synthase in Tap Roots channels sucrose towards starch biosynthesis. Starch accumulation appears to be transient and may be involved in sucrose partitioning to developing Tap Roots.

  • Development- and organ-specific expression of the genes for sucrose synthase and three isoenzymes of acid β-fructofuranosidase in carrot
    Planta, 1995
    Co-Authors: Arnd Sturm, Susanne Lienhard, Markus Hardegger, Veronika Šebková, Kathrin Lorenz, Christoph Unger
    Abstract:

    The steady-state levels of transcripts for cellwall β-fructofuranosidase (cwβF), for isoenzymes I and II of soluble acid β-fructofuranosidase (sI, sII), and for sucrose synthase (ss) were determined in the sink and source organs of developing carrot (Daucus carota L.) plants. The expression patterns of the four genes clearly differed. The expression of the gene for cwβF was development-specific but not organ-specific; high transcript levels were only found in plants with primary Roots, with about equal amounts in leaf lamina, petioles and Roots. The genes for sI and sII were mainly expressed in Roots, sI predominating in primary Roots and sII in developing Tap Roots. Transcripts for ss were found at a low level in all developing plant organs and were markedly up-regulated during the development of young leaves and during the transition of primary Roots to Tap Roots. Developing Tap Roots contained only transcripts for sII and for ss. Marked alterations in the expression of these two genes after manipulation of the source/sink balance of these plants indicates their importance in sucrose partitioning. We suggest that ss regulates sucrose utilization in developing Tap Roots, whereas sII located in the vacuole controls sucrose storage and sugar composition.

G. Schilling - One of the best experts on this subject based on the ideXlab platform.

  • Behaviour of Sugar-beet Plants (Beta vulgaris L. ssp. vulgaris var. altissima [Doell]) under Conditions of Changing Water Supply: Abscisic Acid as Indicator
    Journal of Agronomy and Crop Science, 1998
    Co-Authors: L. Wittenmayer, G. Schilling
    Abstract:

    Moderate drought stress increases the root-to-shoot ratio in sugar-beet plants. The question arises whether abscisic acid occurs in these plants and whether it plays a role in their adaptation to limited water supply. Thus, after identification by GC/MS, the content of free ABA and its alkaline hydrolysable conjugates was determined by capillary GLC in sugar-beet plants of pot and field experiments with differentiated water supply. It was shown that leaves had a higher content of free ABA than Tap Roots. Within the leaf apparatus the young organs contained more ABA than the fully developed leaves. Moderate drought stress increased both free and alkaline hydrolysable ABA contents in leaves of intact plants, whereas the ABA content of Tap Roots was not demonstrably influenced. In contrast, severe and rapid osmotic stress treatment of detached leaves by dipping the petioles in mannitol solutions increased the free ABA content at the expense of the hydrolysable conjugates. This suggests an ABA release by the latter. Therefore, sugar-beet plants seem to have two mechanisms for increasing the free ABA content under drought stress conditions: the gradual synthesis of ABA including its conjugates and the release of free ABA from ABA conjugates.

Susanne Lienhard - One of the best experts on this subject based on the ideXlab platform.

  • Tissue-specific expression of two genes for sucrose synthase in carrot (Daucus carota L.).
    Plant Molecular Biology, 1999
    Co-Authors: Arnd Sturm, Susanne Lienhard, Stephan Schatt, Markus Hardegger
    Abstract:

    Sucrose synthase, which cleaves sucrose in the presence of uridine diphosphate (UDP) into UDP-glucose and fructose, is thought to be a key determinant of sink strength of heterotrophic plant organs. To determine the roles of the enzyme in carrot, we characterized carrot sucrose synthase at the molecular level. Two genes (Susy*Dc1 and Susy*Dc2) were isolated. The deduced amino acid sequences are 87% identical. However, the sequences upstream of the translation initiation codons are markedly different, as are the expression patterns of the two genes. Susy*Dc2 was exclusively expressed in flowers. Transcripts for Susy*Dc1 were found in stems, in Roots at different developmental stages, and in flower buds, flowers and maturing seeds, with the highest levels in strong utilization sinks for sucrose such as growing stems and Tap root tips. Expression of Susy*Dc1 was regulated by anaerobiosis but not by sugars or acetate. The carrot sucrose synthase protein is partly membrane-associated and this insoluble form may be directly involved in cellulose biosynthesis. Tap Roots of the carrot cultivar used accumulated starch in the vicinity of the vascular bundles, which correlated with high sucrose synthase transcript levels. This finding suggests that soluble sucrose synthase in Tap Roots channels sucrose towards starch biosynthesis. Starch accumulation appears to be transient and may be involved in sucrose partitioning to developing Tap Roots.

  • Development- and organ-specific expression of the genes for sucrose synthase and three isoenzymes of acid β-fructofuranosidase in carrot
    Planta, 1995
    Co-Authors: Arnd Sturm, Susanne Lienhard, Markus Hardegger, Veronika Šebková, Kathrin Lorenz, Christoph Unger
    Abstract:

    The steady-state levels of transcripts for cellwall β-fructofuranosidase (cwβF), for isoenzymes I and II of soluble acid β-fructofuranosidase (sI, sII), and for sucrose synthase (ss) were determined in the sink and source organs of developing carrot (Daucus carota L.) plants. The expression patterns of the four genes clearly differed. The expression of the gene for cwβF was development-specific but not organ-specific; high transcript levels were only found in plants with primary Roots, with about equal amounts in leaf lamina, petioles and Roots. The genes for sI and sII were mainly expressed in Roots, sI predominating in primary Roots and sII in developing Tap Roots. Transcripts for ss were found at a low level in all developing plant organs and were markedly up-regulated during the development of young leaves and during the transition of primary Roots to Tap Roots. Developing Tap Roots contained only transcripts for sII and for ss. Marked alterations in the expression of these two genes after manipulation of the source/sink balance of these plants indicates their importance in sucrose partitioning. We suggest that ss regulates sucrose utilization in developing Tap Roots, whereas sII located in the vacuole controls sucrose storage and sugar composition.

  • Structural organization and differential expression of carrot β-fructofuranosidase genes: identification of a gene coding for a flower bud-specific isozyme
    Plant molecular biology, 1995
    Co-Authors: Kathrin Lorenz, Susanne Lienhard, Arnd Sturm
    Abstract:

    Three genomic clones (Inv*Dc1, Inv*Dc2 and Inv*Dc3) were isolated by using the cDNA for carrot cell wall beta-fructofuranosidase as a probe. The expression patterns of the three genes differed markedly. High levels of Inv*Dc1 transcripts were found in leaves and Roots of young carrot, whereas in plants with developing Tap Roots no transcripts were detected. A high level of mRNA of Inv*Dc1 was also present in suspension-cultured cells. In developing reproductive organs, only low levels of transcripts of Inv*Dc1 were found in flower buds and flowers and none at later stages of development. In contrast, Inv*Dc2 and Inv*Dc3 were not expressed in vegetative plant organs. Invb1*Dc1 was exclusively and strongly expressed in flower buds, and Inv*Dc3 at a very low level in suspension-cultured cells.

Per Hofvander - One of the best experts on this subject based on the ideXlab platform.

  • Starch biosynthetic genes and enzymes are expressed and active in the absence of starch accumulation in sugar beet Tap-root.
    BMC plant biology, 2014
    Co-Authors: Helle Turesson, Mariette Andersson, Salla Marttila, Ingela Thulin, Per Hofvander
    Abstract:

    Background Starch is the predominant storage compound in underground plant tissues like Roots and tubers. An exception is sugar beet Tap-root (Beta vulgaris ssp altissima) which exclusively stores sucrose. The underlying mechanism behind this divergent storage accumulation in sugar beet is currently not fully known. From the general presence of starch in Roots and tubers it could be speculated that the lack in sugar beet Tap-Roots would originate from deficiency in pathways leading to starch. Therefore with emphasis on starch accumulation, we studied Tap-Roots of sugar beet using parsnip (Pastinaca sativa) as a comparator.