Light/Dark profiles of sucrose phosphate synthase, sucrose synthase, and Acid invertase in leaves of sugar beets

The activity of sucrose phosphate synthase, sucrose synthase, and acid invertase was monitored in 1- to 2-month-old sugar beet (Beta vulgaris L.) leaves. Sugar beet leaves achieve full laminar length in 13 days. Therefore, leaves were harvested at 2-day intervals for 15 days. Sucrose phosphate synthase activity was not detectable for 6 days in the dark-grown leaves. Once activity was measurable, sucrose phosphate synthase activity never exceeded half that observed in the light-grown leaves. After 8 days in the dark, leaves which were illuminated for 30 minutes showed no significant change in sucrose phosphate synthase activity. Leaves illuminated for 24 hours after 8 days in darkness, however, recovered sucrose phosphate synthase activity to 80% of that of normally grown leaves. Sucrose synthase and acid invertase activity in the light-grown leaves both increased for the first 7 days and then decreased as the leaves matured. In contrast, the activity of sucrose synthase oscillated throughout the growth period in the dark-grown leaves. Acid invertase activity in the dark-grown leaves seemed to be the same as the activity found in the light-grown leaves.     

Production and utilization of sugar beets

Processing of sugar beets has become a major chemical industry in the United States. About one-quarter of the country’s sugar requirement is obtained from about 12 million tons of beets grown on 700 thousand acres of land. This industry has succeeded through the combined efforts of scientists in many fields, who have improved resistance to diseases, sugar content of beets, methods of farming and processing procedures. Feed pulp, molasses, glutamic acid, potassium salts and betaine are by-products of the industry.     

Estimating genetic variation in sugar beets and wild beets using pools of individuals.

The study describes the genetic structure in sugar beets and in wild beets (Beta vulgaris) using 30 RFLP markers. Samples consisting of pooled plant material of 100 individuals from each line and population were used to analyse 120 sugar beet breeding lines and 91 wild beet populations. Greater variation was found among the wild populations than among the breeding lines. Although the two major groups of breeding lines, monogerm and multigerm, had approximately equal amounts of genetic variation, in the monogerm group more of this variation was partitioned among the lines than within the lines. Furthermore, despite most of the variation being shared by the two groups, the two groups were found to be separated along the first two components in a principal component analysis. Computer simulations were carried out to evaluate the usefulness of the pooled-sample strategy employed in the investigation. These simulations showed the use of pooled samples to be a better alternative than that of analysing a few plants individually.     

Aneuploids from the progeny of triploid sugar beets]

The crossing of sugar beet triploids with triploids (3x X 3x) produced 25.1 +/- 5.16% of aneuploids, the crossing of triploids with tetraploids (3x X 4x) resulted in 17.7 +/- +/- 2.66% of aneuploids, and the crossing of triploids with diploids (3x X 2x) yielded 12.4 +/- 2.36% of aneuploids. In the combinations 3x X 2x and 3x X 4x all the theoretically possible forms of aneuploids were observed. After free pollination of aneuploids with different numbers of chromosomes their progenies comprise 71.4 +/- 2.18% of euploids and 28.6 +/- 3.31% of aneuploids.     

Time course and temperature dependence of the membrane translocation of tetanus and botulinum neurotoxins C and D in neurons

Tetanus and botulinum neurotoxins act inside nerve terminals and, therefore, they have to translocate across a membrane to reach their targets. This translocation is driven by a pH gradient, acidic on the cis side and neutral on the cytosol. Recently, a protocol to induce translocation from the plasma membrane was established. Here, we have used this approach to study the temperature dependence and time course of the entry of the L chain of tetanus neurotoxin and of botulinum neurotoxins type C and D across the plasma membrane of cerebellar granular neurons. The time course of translocation of the L chain varies for the three neurotoxins, but it remains in the range of minutes at 37 °C, whilst it takes much longer at 20 °C. BoNT/C does not enter neurons at 20 °C. Translocation also depends on the dimension of the pH gradient. These data are discussed with respect to the contribution of the membrane translocation step to the total time to paralysis and to the low toxicity of these neurotoxins in cold-blood vertebrates.     

Magnesium deficiency in sugar beets alters sugar partitioning and phloem loading in young mature leaves

Magnesium deficiency has been reported to affect plant growth and biomass partitioning between root and shoot. The present work aims to identify how Mg deficiency alters carbon partitioning in sugar beet (Beta vulgaris L.) plants. Fresh biomass, Mg and sugar contents were followed in diverse organs over 20 days under Mg-sufficient and Mg-deficient conditions. At the end of the treatment, the aerial biomass, but not the root biomass, of Mg-deficient plants was lower compared to control plants. A clear inverse relationship between Mg and sugar contents in leaves was found. Mg deficiency promoted a marked increase in sucrose and starch accumulation in the uppermost expanded leaves, which also had the lowest content of Mg among all the leaves of the rosette. The oldest leaves maintained a higher Mg content. [¹⁴C]Sucrose labelling showed that sucrose export from the uppermost expanded leaves was inhibited. In contrast, sucrose export from the oldest leaves, which are close to, and export mainly to, the roots, was not restricted. In response to Mg deficiency, the BvSUT1 gene encoding a companion cell sucrose/H⁺ symporter was induced in the uppermost expanded leaves, but without further enhancement of sucrose loading into the phloem. The observed increase in BvSUT1 gene expression supports the idea that sucrose loading into the phloem is defective, resulting in its accumulation in the leaf.     

Anomalies in cytoskeletal microtubules in a mutant line of sugar beets

The morphological phenotype of meimutation acd (abnormal cytoskeleton dynamics) in Beta vulgaris was analysed using a classic method of achromatic figure visualization (Navashin fixative). The mutation demonstrates two different phenotypes under different growth conditions. The first variant is characterized by formation of chaotic network of microtubule bundles instead of two bipolar spindles at metaphase II. Such abnormality leads to the formation of polyads and monads. The second variant of phenotype demonstrates desorientation of spindles at metaphase II and partial asynapsis of homologous chromosomes.     

Sucrose phosphate synthase and sucrose accumulation at low temperature

The influence of growth temperature on the free sugar and sucrose phosphate synthase content and activity of spinach (Spinacia oleracea) leaf tissue was studied. When plants were grown at 25°C for 3 weeks and then transferred to a constant 5°C, sucrose, glucose, and fructose accumulated to high levels during a 14-d period. Predawn sugar levels increased from 14- to 20-fold over the levels present at the outset of the low-temperature treatment. Sucrose was the most abundant free sugar before, during, and after exposure to 5°C. Leaf sucrose phosphate synthase activity was significantly increased by the low-temperature treatment, whereas sucrose synthase and invertases were not. Synthesis of the sucrose phosphate synthase subunit was increased during and after low-temperature exposure and paralleled an increase in the steady-state level of the subunit. The increases in sucrose and its primary biosynthetic enzyme, sucrose phosphate synthase, are discussed in relation to adjustment of metabolism to low nonfreezing temperature and freezing stress tolerance.     

Transposition of the maize transposable element dSpm in transgenic sugar beets

Transgenic plants and cell lines of sugar beet carrying Spm/dSpm system of maize transposable elements have been obtained by Agrobacterium-mediated transformation. A heterologous system of mobile elements Spm/dSpm remains active in the genome of sugar beet that permit of transposon-based gene tagging and obtaining of marker-free transgenic sugar beet.     

Cytogenetics of autotetraploid sugar beets (Beta vulgaris L.)

Summary Variety seed samples, samples of eutetraploid plant progenies and samples of aneutetraploid or tetraploid population progenies were investigated for chromosome numbers. Genomal and chromosomal deviations from the artificially induced 4x genome level were encountered. Though deviations from the genome level were found to be exceptional, their impact on the reproduction of chromosome numbers may not be underestimated because sugar beets cross readily between genome levels. In general eutetraploid plants remained stable at the 4x genome level, but produced a high percentage of aneutetraploid plants. The chromosomal deviations on the 4x genome level ranged from –2 to +3 chromosomes. In cytogenetic terms chromosome reproduction of eutetraploid plants is characterized by incomplete selection pressure for euploidy. The type of chromosome reproduction differs from the diploid type in as much as eutetraploid plants do not precisely reproduce the chromosome number and gene content, fundamentals on which are based the Mendelian laws of inheritance. In propagation and selection of tetraploid sugar beets the mode of reproduction of chromosome numbers described has to be taken into account.

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Zusammenfassung Samenproben von Sorten, von eutetraploiden Pflanzennachkommenschaften und von aneutetraploiden oder tetraploiden Populationsnachkommenschaften wurden auf Chromosomenzahlen untersucht. Es wurden genomale und chromosomale Abweichungen von der künstlich induzierten 4x Genomzahl festgestellt. Obwohl nur wenige Abweichungen von der Genomstufe gefunden wurden, darf ihr Einfluß auf die Chromosomenzahlreproduktion wegen der leichten Kreuzbarkeit der Rüben zwischen den Genomstufen nicht unterschätzt werden. Eutetraploide Pflanzen zeigten im allgemeinen eine Stabilisierung auf der 4x Genomstufe, produzierten aber einen hohen Prozentsatz von aneuploiden Pflanzen. Die chromosomalen Abweichungen von der 4x Genomstufe betrugen bis zu –2 und +3 Chromosomen. In cytogenetischem Sinne ist die zahlenmäßige Chromosomenproduktion tetraploider Pflanzen durch unvollständigen Selektionsdruck für Euploidie gekennzeichnet. Die Art der zahlenmäßigen Chromosomenreproduktion unterscheidet sich von der diploiden insofern, als eutetraploide Pflanzen sich in Chromosomenzahl und Geninhalt nicht genau reproduzieren, Voraussetzungen, auf denen die Regeln der Mendelvererbung beruhen. Bei der Vermehrung und Auslese tetraploider Zuckerrüben muß die beschriebene Art der zahlenmäßigen Chromosomenreproduktion berücksichtigt werden.

     

Toxin production by Fusarium species from sugar beets and natural occurrence of zearalenone in beets and beet fibers.

Fifty-five Fusarium isolates belonging to nine species were collected from fungus-invaded tissue of stored sugar beets and identified as F. acuminatum (11 isolates), F. avenaceum (1 isolate), F. culmorum (1 isolate), F. equiseti (23 isolates), F. graminearum (4 isolates), F. oxysporum (1 isolate), F. solani (4 isolates), F. sporotrichioides (7 isolates), and F. subglutinans (2 isolates). All isolates were cultured on autoclaved rice grains and assayed for toxicity by feeding weanling female rats the ground-rice cultures of the isolates in a 50% mixture with a regular diet for 5 days. Fifty-eight percent of the isolates were acutely toxic to rats, 26% caused hematuria, 18% caused hemorrhages, and 29% caused uterine enlargement. In most cases, toxicity could not be accounted for by the known toxins found. The following mycotoxins were found in extracts of the rice cultures: zearalenone (22 to 6,282 micrograms/g), chlamydosporol (HM-8) (68 to 4,708 micrograms/g), moniliformin (45 to 400 micrograms/g), deoxynivalenol (10 to 34 micrograms/g), 15-acetyldeoxynivalenol (5 to 10 micrograms/g), diacetoxyscirpenol (22 to 63 micrograms/g), monoacetoxyscirpenol (21 to 26 micrograms/g), scirpenetriol (24 micrograms/g), T-2 toxin (4 to 425 micrograms/g), HT-2 toxin (2 to 284 micrograms/g), neosolaniol (2 to 250 micrograms/g), and T-2 tetraol (4 to 12 micrograms/g). F. equiseti was the predominant species found on visibly molded beets in the field. Six of 25 moldy sugar beet root samples collected in the field contained zearalenone in concentrations ranging between 12 and 391 ng/g, whereas 10 samples from commercial stockpiles were negative for zearalenone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Toxin production by Fusarium species from sugar beets and natural occurrence of zearalenone in beets and beet fibers.

Fifty-five Fusarium isolates belonging to nine species were collected from fungus-invaded tissue of stored sugar beets and identified as F. acuminatum (11 isolates), F. avenaceum (1 isolate), F. culmorum (1 isolate), F. equiseti (23 isolates), F. graminearum (4 isolates), F. oxysporum (1 isolate), F. solani (4 isolates), F. sporotrichioides (7 isolates), and F. subglutinans (2 isolates). All isolates were cultured on autoclaved rice grains and assayed for toxicity by feeding weanling female rats the ground-rice cultures of the isolates in a 50% mixture with a regular diet for 5 days. Fifty-eight percent of the isolates were acutely toxic to rats, 26% caused hematuria, 18% caused hemorrhages, and 29% caused uterine enlargement. In most cases, toxicity could not be accounted for by the known toxins found. The following mycotoxins were found in extracts of the rice cultures: zearalenone (22 to 6,282 micrograms/g), chlamydosporol (HM-8) (68 to 4,708 micrograms/g), moniliformin (45 to 400 micrograms/g), deoxynivalenol (10 to 34 micrograms/g), 15-acetyldeoxynivalenol (5 to 10 micrograms/g), diacetoxyscirpenol (22 to 63 micrograms/g), monoacetoxyscirpenol (21 to 26 micrograms/g), scirpenetriol (24 micrograms/g), T-2 toxin (4 to 425 micrograms/g), HT-2 toxin (2 to 284 micrograms/g), neosolaniol (2 to 250 micrograms/g), and T-2 tetraol (4 to 12 micrograms/g). F. equiseti was the predominant species found on visibly molded beets in the field. Six of 25 moldy sugar beet root samples collected in the field contained zearalenone in concentrations ranging between 12 and 391 ng/g, whereas 10 samples from commercial stockpiles were negative for zearalenone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Time course of pump inhibition by ouabain in amphibian epithelia

Inhibition by ouabain of rheogenic Na⁺ transport across the basolateral membranes of frog skin is found to be manifest within 3–4 min. This rate of pump inhibition is not different from the rate of diffusion through extracellular tissue layers between the serosal bath and the actual site of action, i.e., the epithelial cell layers. It is concluded that the well-known slow time course of decrease in transepithelial current flow is due ionic redistribution and conductance changes of the epithelial membranes secondary to pump inhibition.     

Variation in mitochondrial translation products in fertile and cytoplasmic male-sterile sugar beets

Summary Intact and functional mitochondria were isolated from sugar beet plants (Beta vulgaris L.) containing normal fertile (F) or cytoplasmic male-sterile (S₁–S₄) cytoplasms. Incorporation of ³⁵S-methionine by mitochondria isolated from both roots and leaves showed approximately 20 major and ten minor translation products. Comparison of the polypeptide synthesis patterns produced by leaf mitochondria from fertile plants of three different species within the genus Beta revealed several taxonomically related differences. Contrary to this, the patterns of polypeptides synthesized by mitochondria from roots and leaves of sugar beet plants containing the F and S₁–S₄ cytoplasms were very similar; in the S₁ and S₂ cytoplasms no qualitative, and only a few quantitative, differences from the F cytoplasm were observed. Thus, in these cases, cytoplasmic male sterility in sugar beet is not correlated with the constitutive expression of variant polypeptides. In the S₃ cytoplasm, however, an additional 6 kDa polypeptide was synthesized and in the S₄ cytoplasm an additional 10 kDa polypeptide was observed when compared with the F cytoplasm. The expression of cytoplasmic male sterility in sugar beet may be associated with these variant polypeptides. The mitochondrial polypeptides synthesized were identical in plants with different nuclear backgrounds but with identical S₁ cytoplasms. Mitochondria from plants with variants of the S₄ cytoplasm in the same nuclear genotype also showed identical patterns of polypeptide synthesis, including the synthesis of the 10 kDa S₄-specific polypeptide. Pulse-chase experiments did not affect the synthesis of this polypeptide.     

The origin and evolution of weed beets: consequences for the breeding and release of herbicide-resistant transgenic sugar beets

Populations of weed beets have expanded into European sugar beet production areas since the 1970s, thereby forming a serious new weed problem for this crop. We sampled seeds in different French populations and studied mitochondrial DNA, chloroplast DNA and life-cycle variability. Given the maternal inheritance of the mitochondrial and chloroplastic genomes and the nuclear determinism of the annual habit, we were able to determine the maternal origin and evolution of these weed beet populations. Our study shows that they carry the dominant allele B for annual habit at high frequency. The main cytoplasmic DNA type found in northern weed beet populations is the cytoplasmic male-sterile type characteristic of sugar beets. We were able to determine that these populations arise from seeds originating from the accidental pollinations of cultivated beets by adventitious beets in the seed production area, which have been transported to the regions where sugar beets are cultivated. These seeds are supposedly the origin of the weed forms and a frequently disturbed cultivated environment has selected for annual habit and early flowering genotypes. We discuss the consequences of the weed beet populations for the breeding, seed production and release of herbicide-resistant transgenic sugar beets.     

Time course of photosynthetic temperature acclimation in Carex eleocharis Bailey

Abstract Photosynthetic temperature acclimation in Carex eleocharis has been demonstrated in a previous study in which warm grown (35/15°C) plants were shown to have photosynthetic temperature optima approximately 14°C higher than cool grown (20/15°C) plants (Monson, Littlejohn & Williams, 1983). The current study examined the time course of this acclimation by determining photo-synthetic temperature optima as a function of time, of cool grown plants moved to warm growing conditions. Leaves which had developed under cool conditions were capable of an upward adjustment of 6–8°C of their optimum photosynthetic temperature within a time span of 6–14 d. For greatest photosynthetic temperature acclimation it was necessary for leaves to form and develop entirely under warm conditions. These leaves exhibited a 14–15°C upward adjustment of their optimum temperature for photosynthesis within 20–31 d since moving plants from cool to warm growing conditions. Thus, the time course of this acclimation is of short enough duration to be significant during the growing season and presumably contributes toward the ability of this species to maintain active growth during the cool and warm portions of the growing season. It is also noted that the plant with its capacity to form new leaves, has a much wider acclimation capacity than any single leaf.     

Nucleic acid and protein elimination during the sugar manufacturing process of conventional and transgenic sugar beets

The fate of cellular DNA during the standard purification steps of the sugar manufacturing process from conventional and transgenic sugar beets was determined. Indigenous nucleases of sugar beet cells were found to be active during the first extraction step (raw juice production) which was carried out at 70°C. This and the consecutive steps of the manufacturing process were validated in terms of DNA degradation by competitive PCR of added external DNA. Each step of the process proved to be very efficient in the removal of nucleic acids. Taken together, the purification steps have the potential to reduce the amount of DNA by a factor of >10¹⁴, exceeding by far the total amount of DNA present in sugar beets. Furthermore, the gene products of the transgenes neomycin phosphotransferase and BNYVV (rhizomania virus) coat protein CP21 were shown to be removed during the purification steps, so that they could not be detected in the resulting white sugar. Thus, sugar obtained from conventional and transgenic beets is indistinguishable or substantially equivalent with respect to purity.     

Purification and properties of starch hydrolyzing enzymes in mature roots of sugar beets

Mature roots of sugar beets, which accumulate large amounts of sucrose but not starch, nevertheless contained acid and neutral amylases, judging from their pH optima, as well as pullulanase. Acid and neutral amylases were partially purified by procedures including fractionation with ammonium sulfate, ion exchange column chromatography, and gel filtration. Acid amylase was classified as an exoamylase, since it produced only glucose from soluble starch, amylopectin. β-limit dextrin, and rabbit liver glycogen. Neutral amylase was classified as an endoamylase, since it liberated maltose as the main product plus a small amount of glucose and oligosaccharides, and was capable of hydrolyzing β-limit dextrin. Pullulanase was purified to apparent homogeneity by procedures including fractionation with ammonium sulfate, Diethylaminoethyl-cellulose column chromatography and affinity chromatography. Pullulanase was capable of hydrolyzing soluble starch, amylopectin, β-limit-dextrin, and pullulan. Debranching of amylopectin was further evident by an increase in extinction coefficient, and by a shift of λ_max from 530 to 560 nm when the debranched amylopectin formed a complex with I₂-KI.