Immunocytochemical Localization of Wheat Storage Proteins in Endosperm Cells 30 Days After Anthesis

Antisera against seven different wheat (Triticum aestivum L.)storage protein subfractions were characterized using (1) ELISAwith gliadins and low- and high-molecular weight glutenin subunitsand (2) electrophoresis (SDS-PAGE and acidic buffer PAGE) andimmunoblotting. The specificities of these antisera (polyclonalantibodies) and 13 monoclonal antibodies covered various patternsof reactivity with alpha-, beta-, gamma- and omega-gliadinsand low- and high-molecular weight glutenins. The antisera andantibodies were applied to ultrathin sections of wheat endospermtissue, from kernels fixed 30 d after anthesis, and were detectedby secondary antibodies tagged with either 5 or 15 nm gold particlesusing transmission electron microscopy. Labelling was denserwhen the small gold particles were used but irrespective ofgold particle size, labelling of polyclonal antisera predominatedwhen the endosperm cells were subjected to both mono- and polyclonalantibodies. Each of the antisera and monoclonal antibodies thatlabelled the protein bodies, labelled them more or less uniformly.This indicates that only one kind of protein body, containingall gliadin and glutenin subfractions, exists during this stageof grain development. Electron-dense globular inclusions foundin many protein bodies were not labelled. Label was also foundon protein-like material present in the lumen of the rough endoplasmicreticulum and on vesicles of the Golgi apparatus. Thus concentrationof storage proteins takes place both at the site of synthesis,the lumen of the rough endoplasmic reticulum, and at the siteof processing and transport, the vesicles of the Golgi apparatus.Fusions between these proteinaceous materials give rise to largerprotein bodies and ultimately to the protein matrix. Key words: Wheat, immunocytochemistry, protein bodies, rough endoplasmic reticulum, Golgi apparatus     

Temperature-induced Changes in the Synthesis of Unsaturated Fatty Acids by Acanthamoeba castellanii

ABSTRACT. Major fatty acid components of Acanthamoeba castellanii lipids extracted after growth at 30°C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15°C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30°C to 15°C, increased lipid unsaturation occurred over a period of 24 h; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15°C to 30°C gave negligible alterations in fatty acid composition over a similar period. At 15°C organisms rapidly use [1-¹⁴C] acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30°C indicate only de novo synthesis and Δ9-desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1-¹⁴C] oleate at 30°C was not accompanied by metabolic conversion over two hours, whereas at 15°C n-6 desaturation to linoleate was observed. Temperature shift of organisms from 15°C to 30°C in the presence of [1-¹⁴C] acetate revealed that over half of the fatty acids in newly-synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 h. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n-6 desaturation in the low temperature adaptation of Acanthamoeba castellanii .     

Reproduction of Antarctic Benthic Marine Invertebrates: Tempos, Modes, and Timing

Work on the life histories of common antarctic benthic marineinvertebrates over the past several decades demands a revisionof several widely held paradigms. First, contrary to expectationsderived from work on temperate species, there is little or noevidence for temperature adaptation with respect to reproduction(gametogenesis), development, and growth. It remains to be determinedwhether the slow rates of these processes reflect some inherentinability to adapt to low temperatures, or are a response tofeatures of the antarctic marine environment not directly relatedto low temperature, such as low food resources. Secondly, contraryto the widely accepted opinion designated as "Thorson's rule,"pelagic development is common in many groups of shallow-watermarine invertebrates. In fact in some groups, such as asteroids,pelagicdevelopment is as prevalent in McMurdo Sound, the southern-mostopen-water marine environment in the world, as in central California.In other taxonomic groups, especially gastropods, there doesseem to be a genuine trend toward non-pelagic development fromtropical to antarctic latitudes. Although this trend has beenpredicted by theoretical models, its underlying causes appearto be group specific rather than general. Thirdly, pelagic lecithotrophicdevelopment, often considered to be of negligible importance,occurs in many shallow-water antarctic marine macroinvertebrates.Pelagic lecithotrophy may be an adaptation to a combinationof poor food conditions in antarctic waters most of the yearand slow rates of development. Nevertheless, some of the mostabundant and widespread antarctic marine invertebrates havepelagic planktotrophic larvae that take very long times to completedevelopment to metamorphosis. These species areparticularlyprevalent in productive regions of shallow water (<30 m),which are frequently disturbed by anchor ice formation, andthe production of numerous pelagic planktotrophic larvaemayrepresent a strategy for colonization. Although planktotrophiclarvae tend to be seasonal in occurrence, their production isnot linked particularly closely to the mid-summer pulse of phytoplanktonproduction. These larvae show no evidence of starvation, evenduring times when phytoplankton abundance is very low, and theymay depend on unusual sources of food, such as bacteria. Howthey escape the selective conditions that apparently led toa predominance of non-feeding modes of development in antarcticmarine invertebrates remains as a major challenge for antarcticmarine biology.     

Influence of Host Diet on the Fatty Acid Composition and Content of Rumen Protozoa in Cattle

The fatty acid profiles and contents of protozoa from the rumen fluid of cattle varied according to the type of diet consumed by their host. Changing from a high-quality hay diet to a low-quality hay diet (DA) decreased the proportions of saturated acids and increased the proportions of the unsaturated acids 18:1 cis-9, 18:2 and 18:3 in neutral lipids (NL) and phospholipids (PL). Adding sucrose, urea and sulphur (SUS) to DA increased the proportions of branched chain acids in PL while addition of safflower oil increased polyunsaturated acids in PL and 18:1 trans-11 in NL. Diet did not alter the PL fatty acid content of protozoa but oil supplement of DA resulted in a 10-fold increase in the content of free fatty acids. The defaunating effect of oil supplement was partly reversed by SUS suggesting that factors other than the fatty acid content of cells are important in determining the toxicity of oil to rumen protozoa. The results indicate that the amounts of individual long-chain fatty acids taken up by rumen ciliates are largely determined by their concentrations in rumen digesta.     

Symbiotic Performance of Supernoclulating Soybean (Glycine max (L.) Merrill) Mutants during Development on Different Nitrogen Regimes

Growth and symbiotic performance of soybean (Glycine max (L.)Merrill) cv. Bragg and three of its induced nodulation mutants(nod49, non-nodulating; ntsl 116, intermediate supernodulator;nts1007, extreme supernodulator) were compared throughout developmentunder different nitrogen regimes (0, 2, 5 and 10 mol nitratem^–3). Nitrogen fixation was assessed using ¹⁵N-isotopedilution and xylem sap analysis for ureide content. Both techniquesconfirmed a complete lack of N₂ fixation activity in nod49.Plant reliance on nitrogen fixation by the other genotypes wasdependent on the nitrate regime and the developmental stage.The ntsl007 and ntsl 116 mutants fixed more nitrogen than theparent cultivar in the presence of 10 mol m^–3 nitratein the nutrient solution, but higher input of symbioticallyderived nitrogen was still insufficient to offset the amountof nitrogen removed in the harvested seed. However, the mutantsutilized less nitrate for growth than Bragg. Comparison of estimatesof N₂ fixation derived from the ¹⁵N-dilution technique withthose based on relative ureide content of xylem sap indicatedthat the latter offered a simple and reliable procedure forevaluating the symbiotic performance of supernodulating plants. Key words: ¹⁵N-isotope dilution, supernodulation, ureides     

Heterostyly and gene-flow in Menyanthes trifoliata L. (Menyanthaceae)

NIC LUGHADHA, E. M. & PARNELL, J. A. N., 1989. Heterostyly and gene-flow in Menyanthes trifoliata L. (Menyanthaceae). Menyanthes trifoliata is shown to be a self-incompatible heterostylous species with a suite of associated pollen and gynoecium dimorphisms. These features may promote legitimate pollination. Analysis of a natural population showed substantial pollen inviability, a preponderance of illegitimate pollen on stigmas and a possible asymmetry of pollen flow. Mean pollen travel was estimated as 2.6 m by counting legitimate grains on stigmas whose distance from the nearest source of legitimate pollen was known. Direct field and laboratory measurement indicated mean seed travel of <0.2m. The density of flowering spikes varied greatly within the studied colony of Menyanthes , with a mean of 0.93 m^-2. Using suitable corrections the genetically effective density was estimated as between 0.04 and 4.4 m^-2. Crossing experiments indicated that Menyanthes is fully outcrossed (r=1). The neighbourhood area was estimated as 10–15 m² while neighbourhood size ranged from less than one to sixty-five. Some published neighbourhood estimates are revised with the results for Menyanthes being at the lower end of the range. If the genetically effective density were estimated more accurately, neighbourhood estimates would likely be lower still. It is concluded that what is generally referred to as a population of Menyanthes , may actually represent many evolutionary units.     

Phenology and life history of Belgica antarctica, an Antarctic midge (Diptera: Chironomidae)

ABSTRACT.

• 1 An account of the life-history with emphasis on phenology and number of instars is presented for Belgica antarctica Jacobs, the southernmost holometabolous insect.
• 2 Contrary to earlier reports, Belgica has four instars, in common with most other chironomids. Mean head capsule lengths varied between different populations but no overlap was found between discrete size classes of successive instars.
• 3 Belgica overwinters in all four instars.
• 4 Relative frequency of different instars from samples taken through the season indicates that a 2-year life-span is the commonest pattern.
• 5 Emergence of adults is relatively synchronous. Belgica exhibits protandry, which may be established at the time of pupation.

     

Role of two phoretic mites in transmission of bluestain fungus, Ceratocystis minor

ABSTRACT.

• 1 Tarsonemus mites phoretic on southern pine beetles were shown to be hypervectors of bluestain fungus, Ceratocystis minor (Hedgcock 1906).
• 2 Beetles with phoretic mites had significantly more C.minor than did mite-free beetles.
• 3 Over 90% of tarsonemid mites collected from beetle-infested inner bark and 59% of mites phoretic on emerging beetles carried C.minor spores.
• 4 This association is an interesting example of a three-way mutualism among insects, mites and fungi.

     

Hormonal and Structural Aspects of Fruit Development in the Orchid, Epidendrum

Endogenous cytokinin and gibberellin-like activity were measuredby bioassay in developing fruit of the orchid Epidendrum ibaguense.Cytokinins decline during the first 30 d after pollination,then begin to accumulate, with very high levels (1–13µ g zeatin eq. g^–1 dry wt. ) in the mature fruitand seed. The major structural change in developing fruit duringthe first 30 d is the ongoing cell division in the fruit wall.By day 30 most ovules have been fertilized and embryo developmentbegins. The increase in cytokinin activity thus coincides withthe onset of embryo development. Gibberellin levels declinein the fruit throughout development, although high activity(0.9 µ g GA₃ eq. g^–1 dry wt. ) is observed in themature seed. The mature embryo shows no obvious structural differentiationinto embryonic axis and cotyledon and no endosperm develops.     

The Osmotic Pressure of Concentrated Solutions of Polyethylene Glycol 6000, and its Variation with Temperature

The vapour pressures of aqueous solutions of polyethylene glycol6000 have been measured (by equilibration with sucrose solutions)up to the saturation point at 25 °C (1.45 g g^–1 water).The reduced-osmotic-pressure (/c), when plotted versus concentration(c), rapidly and linearly increased up to a concentration ofabout 0.8 g g^–1 (crossing the similar plot for sucrose).Above this concentration, the reduced-osmotic-pressure rosemore slowly, but still more rapidly than sucrose. The maximumosmotic pressure achieved at saturation was nearly 18 MPa. Usingthe virial equation: /c= RT/M + RTA₂c, the calculated secondvirial coefficient (A₂) for the linear part is 4.5 x 10^–3mol g^–1, a value slightly greater than most literaturevalues at 25 °C. Data are cited showing that A₂ varies linearlyfrom 5–6 x 10^x3 at 0 °C, to zero at 80–90 °C