Isolation and Characterisation of Chemotactic Mutants of Chlamydomonas reinhardtii obtained by Insertional Mutagenesis

The swimming behaviour of the green flagellated protist Chlamydomonas reinhardtii is influenced by several different external stimuli including light and chemical attractants. Common components are involved in both the photo- and chemo-sensory transduction pathways, although the nature and organisation of these pathways are poorly understood. To learn more about the mechanism of chemotaxis in Chlamydomonas, we have generated nonchemotactic strains by insertional mutagenesis. The arginine-requiring strain arg7-8 was transformed with DNA carrying the wild-type ARG7 gene. Of the 8630 arginine-independent transformants obtained, five are defective in their chemotaxis towards various sugars. Two of the mutants (CTX2 and CTX3) are blocked only in their response to xylose. Mutant CTX1 is blocked in its response to xylose, maltose and mannitol, but displays normal taxis to sucrose. Mutants CTX4 and CTX5 lack chemotactic responses to all sugars tested. CTX1, CTX4 and CTX5 represent novel chemotactic phenotypes not previously obtained using ultra-violet or chemical mutagenesis. Genetic analysis confirms that each mutation maps to a single nuclear locus that is unlinked to the mating-type locus. Further analysis of CTX4 indicates that the mutant allele is tagged by the transforming ARG7 DNA. CTX4 appears to be defective in a component specific for chemotactic signal transduction since it exhibits wild-type photobehavioural responses (phototaxis and photoshock) as well as the wild-type responses of EGTA-induced trans-flagellum inactivation and acid-induced deflagellation. Insertional mutagenesis has thus permitted the generation of novel chemotactic mutants that will be of value in the molecular dissection of the signalling machinery.     

Conserved sequences in bacterial and viral sialidases

The genes of the bacterial sialidases fromClostridium sordellii G12,C. perfringens A99,Salmonella typhimurium LT-2 andVibrio cholerae 395 sequenced so far were examined for homologies and were compared with sequences of viral sialidases.Each of the bacterial sialidases contains a short sequence of twelve amino-acids, which is repeated at four positions in the protein. All these sequences exhibit significant similarities. Comparing the repeated sequences of the four sialidases, five amino-acids were found to be highly conserved at defined positions: Ser-X-Asp-X-Gly-X-Thr-Trp. Additionally, most of the distances betweeen the four repeated regions are also conserved among the different sialidases. The conserved bacterial sequences show similarity with sialidases of influenza A H7N1 and H13N9.     

Role of calonyctin on free sugars in relation to starch accumulation in developing sweet potatoes

Calonyctin, a natural plant growth regulator extracted from the leaves of Calonyction aculeatum (L.) House, can promote crop growth and increase crop yield. The specific reasons for this response are unknown. This study was conducted to determine the effect of calonyctin treatment on the free sugars of sweet potato [Ipomoea batatas (L.) Lam.] as related to starch accumulation. The sweet potatoes were grown in the field in 1992, treated by foliar spray with Calonyctin concentrations of 0 (control) and 0.1 activity unit (CTSP) at 20 days after planting (DAP) at the rate of 190 liters of diluted solution/ha., and sampled periodically to determine free sugars. The response of sweet potato to calonyctin was first detected at 40 days after treatment (on 60 DAP). Data indicated that calonyctin treatment significantly increased starch synthesis in storage roots, decreased the fluctuation tendency of total sugar level during the growth period, and kept the sugar level relatively constant with a gradual rise regardless of variations in weather. The level of the reducing sugars in CTSP leaves was higher at 60 and 160 DAP and lower at 100, 120, and 140 DAP. During rainy days (100 DAP), the reducing sugars in CTSP storage roots remained at a lower level when those in controls reached high levels. The sucrose content in CTSP leaves was 40–138% greater than that in controls except at 80 and 120 DAP, and the ratio of sucrose to total nonreducing sugars remained at 100% in CTSP leaves even on rainy and cool days and above 96% in CTSP storage roots except on cool days (140 and 160 DAP), suggesting that calonyctin treatment promoted the synthesis and transfer of sucrose and supplied abundant sugar precursors for starch accumulation in storage roots.Abbreviations DAP days after planting - CTSP calonyctin-treated sweet potato with 0.1 activity unit     

Synthesis ofO-glycopyranosyl-N-hydroxysuccinimides of glucose and lactose and their opening by nucleophiles into prespacer glycosides

O-Glycopyranosyl-N-hydroxysuccinimides of glucose and lactose have been synthesized. Peracetylated sugars, acetobromo sugars and benzoylated thioethyl glycosides have been used as precursors. With boron trifluoride etherate in dichloromethane, peracetylated sugars gave predominantly the anomer. Trimethylsilyl trifluoromethanesulfonate in nitromethane, however, gave predominantly the anomer. Treatment of the acetylatedO-glucopyranosyl-N-hydroxysuccinimide with various nucleophiles (methoxide, hydroxide and pentylamine) gave the corresponding deacetylatedN-(succinyl)glucopyranosylhydroxylamines in almost quantitative yield. These derivatives are suitable for the formation of glycoconjugates or attachment of carbohydrates to solid phases using the opened succinimide as linking arm.     

Typologie de bactéries prélevées devant le delta du Rhöne. Classification hiérarchique par une méthode d'agrégation suivant la variance. Clustering of Bacteria Isolated Seaward from the Rhǒne Outlet. Hierarchical Classification Using the Method of Aggregation According to Variance

Bacteria isolated from surface sea waters, brackish waters and from algal cultures were studied to attempt a nutritional clustering. A hierarchical method, using aggregation according to variance, was used to compute the data. Six nutritional groups had been separated by differences in genus composition and nutritional characteristics. Groups range from one with bacteria which are poorly versatile, i.e. attach few different substances, and which grow on sugars, amino-acids and organic acids without any selectivity, to one with bacteria which are versatile, and which attack numerous organic acids and amino-acids, but only a few sugars. Bacteria from different origins are not spread randomly in the different clusters. Strains isolated from algal cultures are mainly associated with the lowest versatility; those isolated from the undiluted sea water are associated with the highest versatility. Bacteria from diluted sea waters appear to be intermediate in regard to their capability of using organic substances as their sole source of carbon. It also appears that organic acids provide individually the most discriminating substrates, i.e. the most useful for separating individual groups, but amino-acids and organic acids, as a whole, are not easy to use in classification, because they are too heterogeneous. Sugar contribution to classification is almost nil.     

Chemical composition of the peptidoglycan-free cell envelopes of budding bacteria of the Pirella/Planctomyces group

Cell envelopes were prepared from freeze-dried cells of 8 strains of budding bacteria belonging to the Pirella/Planctomyces group. Treatment with 10% sodium dodecylsulfate (SDS) (30 min, 100°C) allowed the isolation of stable cell sacculi which still maintained the original cell shape. The chemical analysis showed, as the main component, protein which was unusually rich in proline and cystine. Except for Planctomyces maris IFAM 1317 (where this protein comprised 62.6% of the total envelope dry weight) the corresponding values for the other strains varied from 75 to 82%. Amino sugars and neutral sugars were present only in small amounts and uronic acids were not found. The ash content varied from 5 to 10% of the dry weight, except for IFAM 1317 which had 19% ash. The high content of cystine indicated a high degree of crosslinking of the cell envelopes through disulfide bonds. Our data show that bacteria of the Pirella/Planctomyces group possess a similar cell wall composition.     

Comparative field studies of various traps and attractants of the olive fruit fly,Bactrocera oleae

In the framework of an ongoing testing and refining process of a mass trapping method, using a combination of semiochemicals, for the control of the olive fruit fly,Bactrocera (Dacus) oleae, four trap designs, three trap colors, six different food attractants, and two pheromone formulations were compared under field conditions. No differences were observed between the trap designs and the food attractants tested. Trap color had a significant effect in preference tests only. Traps combining food attractants and pheromones attracted higher numbers of both male and female flies but the differences became statistically significant only in cases of low trap densities. Pheromones enclosed in cyclodextrenes were not as attractive as standard pheromone formulations. The findings of these tests allow a choice among trap types and semiochemicals for cost reduction and convenience, but not for enhancement of the efficacy of the method.     

Comparison of sampling tabanids (Diptera: Tabanidae) by four different potential attractants

Synthetic and natural attractants in traps are used in many parts of the world to attract female tabanids. Certain attractants in different geographic regions may be ineffective or effective under different environmental conditions for horseflies. One‐octen‐3‐ol, as a compound present in bovine emanations, has a behavioural effect on many horsefly species and together with other phenolic compounds makes very effective attractant for this group of insects. As the attractiveness of the mixture of three chemicals (1‐octen‐3‐ol, acetone and ammonia solution in the proportions 5 : 3 : 2), aged donkey urine, lactic acid and fresh human urine is not yet known, it was studied in Eastern Croatia. The combination of those three chemicals and efficiency of natural attractants offers promising results. Tabanus was the most represented genus with 83% of the total collected tabanids. The chi‐squared analyses of the trapping data for canopy traps revealed that each of the attractants (mixture of three chemicals, aged donkey urine, lactic acid and fresh human urine) significantly increased the number of collected horseflies in comparison to those collected in unbaited canopy traps. Some species differences in relative response to different attractants were noted. Significantly, more specimens of Haematopota pluvialis were collected from canopy traps baited with the mixture of three chemicals when compared with traps baited with other attractants. Canopy traps baited with aged donkey urine collected significantly more Atylotus loewianus females than did traps baited with the mixture. The F‐test analysis of the trapping data for the genus Tabanus showed that there is significant difference between average number of collected specimens between mixture of three chemicals and other used attractants (lactic acid and human urine) except aged donkey urine. Finally, traps baited with the mixture of three chemicals (1‐octen‐3‐ol, acetone and ammonia solution) collected 14.5 times more tabanids than unbaited traps, whereas aged donkey urine, lactic acid, and fresh human urine‐baited traps collected 12, 3.9 and 2.5 times as many tabanids, respectively, than did unbaited traps. The mixture of three chemicals (1‐octen‐3‐ol, acetone and ammonia solution) and aged donkey urine appear to be very effective attractants for tabanids.     

Photosynthesizing Leaves and Nodulated Roots as Donors of Carbon to Protein of the Shoot of the Field Pea (Pisum arvense L.)

In Pisum arvense, the amides and amino-acids normally suppliedto the shoot in the transpiration stream transfer carbon toprotein largely throught the amino-acids, aspartic acid (+asparagine),glutarnic acid (+glutamine), threonine, lysine, arginine, andproline. Carbon from carbon dioxide enters the protein of photosynthesizingtissues through an essentially complementary set of amino-acidsincluding glycine, alanine, serine, valine, and the aromaticamino-acids tyrosine, phenylalnine, and histidine. Young tissuesof the shoot synthesize certain amino-acids de novo by metabolismof sugars supplied from photosynthesizing leaves. Each mature leaf on a shoot contributes carbon to current synthesisof protein at the shoot apex. Sucrose accounts for more than90 per cent of the labelled carbon leaving any age of leaf whichhas been fed with ¹⁴CO₂. Upper leaves supply labelled assimilatesdirectly to the shoot apex, and the radiocarbon from these assimilatesis subsequently incorporated into a wide range of amino-acidunits of protein. The majority of the labelled assimilates exportedfrom a lower leaf move downwards to the root and nodules and,in consequence, the amino-acids and amides associated with rootmetabolism are strongly represented among the compounds eventuallylabelled in the apical region of the shoot.     

A gene encoding a truncated large subunit of Rubisco is transcribed and salt-inducible in rice

Using the rice salt-tolerant mutant 20 as material, a cDNA library was constructed and two salt-inducible clones, SIR5.5 and SIR8.1, were isolated by differential screening. Homology analysis revealed that the two clones together constituted a chimeric rbcL which encoded a truncated large subunit of Rubisco with 337 amino-acids, plus 64 amino-acids of unknown origin. The expressions of both the normal and the chimeric locus appeared to be developmentally regulated and salt-inducible in shoots of the salt-tolerant mutant 20 and its original variety 77–170. In roots, their expressions were salt-inducible in the salt-tolerant mutant 20 whereas no, or only premature, forms were present in the salt-treated original variety 77–170. Higher concentrations of salt reduced the expressions of both normal rbcL and the chimeric locus. ABA showed no effect on their expression.     

Chemotaxis of a motile Streptococcus toward sugars and amino acids.

A motile Streptococcus was isolated and its chemotactic behavior toward sugars and amino acids was studied. Motility was optimal in the presence of an exogenous energy source and a nonionic detergent, e.g., Tween 80 or Brij-36. Both glucose and pyruvate could serve as energy source. Chemotaxis toward leucine was optimal at pH 7 to 8.5 and a temperature between 30 and 37 C. The Streptococcus showed a chemotactic response toward a variety of sugars. All commonly occurring L-amino acids, except alanine, asparagine, aspartate, glutamate, arginine, and lysine, were attractants. From concentration response curves the thresholds, peak concentrations, and optimal responses were determined.     

Chemotaxis toward carbohydrates and amino acids in Physarum polycephalum

A method is described for assaying chemotaxis in the acellular slime mold Physarum polycephalum. It consists of measuring the amount of plasmodium that moves on a strip of nitrocellulose membrane filter Millipore in response to a gradient of an attractant. Time course of chemotactic response of the slime mold is described. Different factors that affect chemotaxis in the slime mold such as: culture care and stage of growth of microplasmodia, substratum used for cell movement, nature of the gradient, effect of salts, pH and temperature are described. From concentration-response curves for different attractants several parameters of the chemotactic effect, such as threshold concentration, half maximal concentration, and maximal effective concentration can be determined. As a group, sugars are more effective chemotactic agents than amino acids. Glucose and galactose, which support the growth of the slime mold, are shown to have high positive chemotactic effect. 3-O-Methyl- -glucose and 2-deoxy- -glucose are two sugars that do not support growth but are very effective attractants. Conversely, fructose which supports slime mold growth is at best a weak attractant. The results support the view that the chemotactic effects of different sugars are not dependent on their growth-supporting value.     

Some Constituents of Xylem Sap and their Possible Relationship to Xylem Differentiation

Bleeding sap of Actinidia chinensis and Betula populifolia andguttation fluidof Avena sativa were analysed for sugars, amino-acids,auxin, and certain enzymes. A wide range of amino-acids wasfound in all three. Auxin was not detected in the bleeding sap,but was present in Avena guttation fluid (5.1 µg IAA equivalent/l).‘IAA oxidase’, acid phosphatase, ribonuclease, deoxyribonuclease,and protease were detected in the bleeding sap and guttationfluid. The possibility that some of the substances found insap and guttation fluid are products of autolysing, differentiatingxylem cells in the roots is discussed.     

Floral biology and pollination in stapeliads — new results and a literature review

The myiophilous pollination syndrome of stapeliads is investigated. Olfactory stimuli, imitating dung or decaying organic (zoogenic or phytogenic) matter, are used as attractants, together with mimetic colouration and, sometimes mimetic sculpturing. In most species nectar is present. The nectar mainly serves as optical attractant causing brilliance effects, and as visitor guide. However, nectar obviously is also a reward in many species. Flies (Cyclorrhapha:Calyptratae) constitute the most important pollinating group. In the pollination process they carry pollinaria only at the distal parts of their proboscis, never on their legs. No fundamental differences between the pollinator spectra of flowers in habitat and cultivated ones were observed.     

Nodulation,nitrogen fixation,leaf area,and sugars content inLablab purpureus as affected by sulfur nutrition

Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N₂ fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N₂ fixation, possibly by improving sugars supply and N metabolism.In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 M for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 M S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo.Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots.     

A preliminary study on pollination biology of Omphalogramma souliei Franch. (Primulaceae), a species endemic to China

The pollination biology of Omphalogramma souliei Franch., a species endemic to southwestern China, was investigated. Floral phenology, flower visitors, pollen/ovule ratio, attractants and rewards to the visitors were observed, measured, and recorded. Bagging experiments to exclude pollinators were carried out in the wild for two years. Our results revealed five important aspects of the reproductive biology of Omphalogramma souliei. 1) The pollen-ovule ratio was 1748±233. The breeding system was self-compatible, with facultative xenogamy. 2) The pollination syndrome is entomophily, and this species could not be pollinated by wind if the pollinators were unavailable. 3) Six insect species were observed visiting the flowers of Omphalogramma souliei in the wild, of them, three species of hymenoptera, Lasioglossum sp., Heriades parvula Cockerell and Micrapis florae Fabricius, are the principal floral visitors and effective pollinators. 4) The visual attractants to the visitors are floral color and shape, the large yellow anthers, and the rewards for visitors are pollen and nectar. 5) Cleistogamy may also occur, since the anthers of some flowers dehisced before opening of the corolla. The results of floral biology and pollination characters suggest that xenogamy predominated and autogamy played an assistant role in the evolution of reproduction and breeding system of O. souliei.     

Change in the amino-acid content during male gametophyte formation of Datura metel in Situ

Summary Determination of the free and bound aminoacids during microsporogenesis of Datura metel showed that the principal amino-acids were proline, glutamic acid, aspartic acid, threonine-serine and alanine. Of these, only proline showed a consistent increment during pollen development. In contrast, aspartic acid and lysine decreased in the later stages of microsporogenesis. The amounts of other amino-acids did not show any consistent pattern. Four amino-acids, namely proline, glutamic acid and threonine-serine constituted nearly 85% of the free amino-acid pool in the developed anther (stage IV). Proline accumulation, relative to the total free amino-acid pool in mature anthers, was correlated with the water-content. The results were discussed in view of possible relationships between metabolic activity and free and bound amino-acid concentrations.Abbreviations ABA -Aminobutyric acid - mol/g micromoles of each amino-acid per gram of dry material     

Glucose transport into the extremely halophilic archaebacteria

Penetration of glucose into cells of several extremely halophilic archaebacteria of the Halobacterium and Haloferax genera (Halobacterium saccharovorum and Halobacterium salinarium, Haloferax volcanii and Haloferax mediterranei) has been studied. Some characteristics of transport systems of carbohydrate-utilizing halobacteria Halobacterium saccharovorum, Haloferax mediterranei and Haloferax volcanii (pH and temperature optima, stereospecificity, kinetic parameters) have been determined. Inability of H. salinarium cells for active glucose transport has been shown. The dependence of glucose transport on the Na⁺ ions gradient (on the whole cells and membrane vesicles) has been demonstrated. Cells or membrane vesicles of carbohydrate-utilizing halobacteria grown in media containing this sugar indicated the activation of glucose transport, whereas cells grown in media without sugars did not. This fact has allowed us to conclude that corresponding transport systems are inducible.     

Combined effect of salicylic acid and salinity on some antioxidant activities,oxidative stress and metabolite accumulation in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>

It has been shown that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing abiotic stress tolerance in plants. The effect of SA and sodium chloride (NaCl) on growth, metabolite accumulation, oxidative stress and enzymatic and non-enzymatic antioxidant responses on common bean plants (Phaseolus vulgaris, cv. F-15) was studied. Results revealed that either SA or NaCl decrease, shoot, root and total plant dry weights. SA treatments decreased the contents of proline, and reduced forms of ascorbate and glutathione, however, the content of soluble sugars (TSS), thiobarbituric acid-reactive substances (TBARs) and oxidized ascorbate remained unaffected. On the other hand, salinity significantly reduced the levels of endogenous SA but increased the content of proline, soluble sugars, TBARs, ascorbate and glutathione, as well as all increasing the levels of antioxidant enzyme activities assayed, except CAT. The application of SA improved the response of common bean plants to salinity by increasing plant dry weight and decreasing the content of organic solutes (proline and TSS) and damage to the membrane (TBARs). Moreover, SA application under saline conditions decreased the levels of antioxidant enzyme activities POX, APX and MDHAR which could indicate successful acclimatization of these plants to saline conditions.     

Some physiological observations on the uptake of d-glucose and 2-deoxy-d-glucose by starving and exponentially-growing yeasts

Some methods for measuring the uptake of sugars by yeasts were investigated critically. A study was made of the effects of starvation of Pichia pinus, Candida utilis, Saccharomyces cerevisiae and Rhodosporidium toruloides on their uptake of d-glucose and 2-deoxy-d-glucose. Marked changes in the rates of uptake of these sugars occurred during 10 h of starvation, including (a) an immediate increase of up to 75% above that for growing cells and (b) a continuous decline to as little as 4%. Each yeast behaved differently. The rates did not remain constant during the periods of starvation often used for studies on the transport of sugars into yeasts. For Pichia pinus, there were striking differences, associated with starvation, between the transport of 2-deoxy-d-glucose and d-glucose, despite evidence that the two sugars enter this yeast by means of the same carrier. Some physiological explanations for these findings are discussed.