Association of the Red Ring Nematode and Other Nematode Species with the Palm Weevil,Rhynchophorus palmarum

The palm weevil, Rhynchophorus palmarum (L.), was collected in cocoons from red ring-diseased coconut palms (Cocos nucifera L.) in Trinidad and Tobago. Juveniles of five species of nematodes were extracted from the genitalia and macerated bodies of newly emerged adults of the palm weevil: Rhadinaphelenchus cocophilus (Cobb) Goodey (the red ring nematode), Teratorhabditis sp., Diplogasteritus sp., Mononchoides sp., and Bursaphelenchus sp. Over 90% of newly emerged weevil females and males were infested internally with red ring nematode juveniles, and over 47% of the weevils contained more than 1,000 red ring nematodes each. There was no significant correlation between weevil body length and the number of red ring nematodes carried internally by each weevil. Teratorhabditis sp. and Diplogasteritus sp. were extracted from over 50% of the palm weevils, and Monochoides sp. and Bursaphelenchus sp. were found in a small proportion of the weevils. Field-collected adult weevils were also internally and externally infested with a Rhabditis sp., which was not observed in or on weevils allowed to emerge from field-collected cocoons.     

Inositol 1,3,4,5-tetrakisphosphate is essential for sustained activation of the Ca2+-dependent K+ current in single internally perfused mouse lacrimal acinar cells

Summary We have examined the effects of various inositol polyphosphates, alone and in combination, on the Ca²⁺-activated K⁺ current in internally perfused, single mouse lacrimal acinar cells. We used the patch-clamp technique for whole-cell current recording with a set-up allowing exchange of the pipette solution during individual experiments so that control and test periods could be directly compared in individual cells. Inositol 1,4,5-trisphosphate (Ins 1,4,5 P₃) (10–100 m) evoked a transient increase in the Ca²⁺-sensitive K⁺ current that was independent of the presence of Ca²⁺ in the external solution. The transient nature of the Ins 1,4,5 P₃ effect was not due to rapid metabolic breakdown, as similar responses were obtained in the presence of 5mm 2,3-diphosphoglyceric acid, that blocks the hydrolysis of Ins 1,4,5 P₃, as well as with the stable analoguedl-inositol 1,4,5-trisphosphorothioate (Ins 1,4,5 P(S)₃) (100 m). Ins 1,3,4 P₃ (50 m) had no effect, whereas 50 m Ins 2,4,5 P₃ evoked responses similar to those obtained by 10 m Ins 1,4,5 P₃. A sustained increase in Ca²⁺-dependent K⁺ current was only observed when inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5 P₄) (10 m) was added to the Ins 1,4,5 P₃ (10 m)-containing solution and this effect could be terminated by removal of external Ca²⁺. The effect of Ins 1,3,4,5 P₄ was specifically dependent on the presence of Ins 1,4,5 P₃ as it was not found when 10 m concentrations of Ins 1,3,4 P₃ or Ins 2,4,5 P₃ were used. Ins 2,4,5 P₃ (but not Ins 1,3,4 P₃) at the higher concentration of 50 m did, however, support the Ins 1,3,4,5 P₄-evoked sustained current activation. Ins 1,3,4 P₃ could not evoke sustained responses in combination with Ins 1,4,5 P₃ excluding the possibility that the action of Ins 1,3,4,5 P₄ could be mediated by its breakdown product Ins 1,3,4 P₃. Ins 1,3,4,5 P₄ also evoked a sustained response when added to an Ins 1,4,5 P(S)₃-containing solution. Ins 1,3,4,5,6 P₅ (50 m) did not evoke any effect when administered on top of Ins 1,4,5 P₃. In the absence of external Ca²⁺, addition of Ins 1,3,4,5 P₄ to an Ins 1,4,5 P₃-containing internal solution evoked a second transient K⁺ current activation. Readmitting external Ca²⁺ in the continued presence internally of Ins 1,4,5 P₃ and Ins 1,3,4,5 P₄ made the response reappear. We conclude that both Ins 1,4,5 P₃ and Ins 1,3,4,5 P₄ play crucial and specific roles in controlling intracellular Ca²⁺ homeostasis.     

Physical mapping of the von Recklinghausen neurofibromatosis region on chromosome 17

The von Recklinghausen neurofibromatosis (NF1) locus has been linked to chromosome 17, and recent linkage analyses place the gene on the proximal long arm. NF1 probably resides in 17q11.2, since two unrelated NF1 patients have been identified who possess constitutional reciprocal translocations involving 17q11.2 with chromosomes 1 and 22. We have used a somatic-cell hybrid from the t(17;22) individual, along with other hybrid cell lines, to order probes around the NF1 locus. An additional probe, 17L1, has been isolated from a NotI linking library made from flow-sorted chromosome 17 material and has been mapped to a region immediately proximal to the translocation breakpoint. While neither NF1 translocation breakpoint has yet been identified by pulse-field gel analysis, an overlap between two probes, EW206 and EW207, has been detected. Furthermore, we have identified the breakpoint in a non-NF1 translocation, SP-3, on the proximal side of the NF1 locus. This breakpoint has been helpful in creating a 1,000-kb pulsed-field map, which includes the closely linked NF1 probes HHH202 and TH17.19. The combined somatic-cell hybrid and pulsed-field gel analysis we report here favors the probe order D17Z1-HHH202-TH17.19-CRYB1-17L1-NF1- (EW206, EW207, EW203, L581, L946)-(ERBB2, ERBA1). The agreement in probe ordering between linkage analysis and physical mapping is excellent, and the availability of translocation breakpoints in NF1 should now greatly assist the cloning of this locus.     

Rice hull and caryopsis discoloration diseases

In West Africa, rice is grown in three constrasting ecosystems, upland, phreatic, and lowland, which is characterized by differing water availability and soil properties. These ecosystems influence the predisposition of rice to disease problems, including the grain discoloration complex. Discoloration of the hull was found to be most severe in the upland, less in the phreatic, and least in the water-saturated lowland ecosystem. Caryopsis discoloration, however, showed no consistent pattern in relation to the three ecosystems and was not correlated with hull discoloration, indicating that other factors are involved.     

Crown ether mediated cadmium halide dimers and polymers

The reactions of cadmium halides with the 15-membered macrocyclic crown ethers, 15-crown-5 and benzo-15-crown-5, have been carried out and six new complexes have been isolated and structurally characterized. Metal to ligand stoichiometries of 1:1, 2:1, 3:1 and 3:2 have been observed with a variety of different formulations. Examples of charge separated ion pairs ([(NH₄)(benzo-15-crown-5)₂]₂[Cd₂I₆]), halogen bridged monomers, dimers or polymers ([Cd(15-crown-5)(OHMe)(μ-Br)CdBr₃], [Cd(15-crown-5)(μ-Br)₂CdBr(μ-Br)]₂(isolated from the same reaction mixture) and [(CdCl₂)₂CdCl₂(15-crown-5)]_n), and hydrogen bonded finite chains or polymers ([(Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN and [CdI₂(OH₂)₂(THF)]·benzo-15-crown-5) have been isolated. Three different types of 15-crown-5 coordination modes have been observed in these complexes. In-cavity coordination resulting in pentagonal bipyramidal geometries about Cd²⁺ was observed in [(CdCl₂)₂CdCl₂(15-crown-5)]_n, [Cd(15-crown-5)(OHMe)(μ-Br)CdBr₃], and [Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN, [Cd(15-crown-5)(μ-Br)₂CdBr(μ-Br)]₂ displays out-of-cavity coordination with one etheric donor distorted into an axial position of a distorted pentagonal bipyramid. The third coordination mode is secondary sphere coordination via hydrogen bonding which is observed for [Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN. The good fit of Cd²⁺ within the cavity of 15-crown-5 results in shorter bonding contacts and a more narrow distribution in Cd---O values (2.273(7)-2.344(6) Å) than observed for cadmium halide complexes of 18-crown-6 (Cd---O = 2.69(1)–2.81(1) Å).     

Diet composition influences the fitness of the herbivorous crab Grapsus albolineatus

The tropical rocky shore crab Grapsus albolineatus feeds primarily on filamentous algae but eats animal matter whenever it is available. During the summer the crab's diet switches to encrusting algae due to a die-off of filamentous algae. As a result of the switch the nutrients in the diet of the crab vary seasonally and may influence the fitness of the crab. Maintenance, growth, reproductive performance and nutrient storage of crabs were examined under four dietary regimes of increasing nutritional value ranging from low organic to high protein content. The nutritional quality of these diets significantly affected crab survival and moulting. Crabs fed on the nutritionally superior diet of algae and meat exhibited enhanced growth, higher levels of energy in the reproductive organs and stored more energy in the hepatopancreas than did individuals on the shore and crabs fed only on algal diets in the laboratory. Filamentous algae were a better food source than other algae, resulting in fewer deaths and superior levels of maintenance and growth. Growth and maintenance can occur on a pure algal diet, but reproductive performance and nutrient storage require some degree of added nutrients in the form of animal matter in the diet. Crabs fed coralline or foliose algae had higher mortality and fewer successful moults than crabs fed the other two diets. The fitness of G. albolineatus appears to be limited by the amount of extra nutrients obtained from animal matter. The opportunistic consumption of animal material in the form of carrion, or of animals associated with dietary algae, could be a key factor in the reproductive success of this crab.     

Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat

A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur, Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg⁻¹ of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg⁻¹ live chaff-inoculum and control having 0.1 g kg⁻¹ dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg⁻¹ applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg⁻¹ for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05 mg Zn kg⁻¹ soil) and medium (0.5 mg Zn kg⁻¹ soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg⁻¹ soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana     

Catabolism of caffeine and related purine alkaloids in leaves ofCoffea arabica L.

In a study of purine alkaloid catabolism pathways in coffee,¹⁴C-labelled theobromine, caffeine, theophylline and xanthine were incubated with leaves ofCoffea arabica. Incorporation of label into¹⁴CO₂ was determined and methanol-soluble metabolites were analysed by high-performance liquid chromatography-radiocounting. The data obtained demonstrate catabolism of caffeine theophylline 3-methylxanthine xanthine. Xanthine is degraded further by the conventional purine catabolism pathway to CO₂ and NH₃ via uric acid, allantoin and allantoic acid. The conversion of caffeine to theophylline is the rate-limiting step in purine alkaloid catabolism and provides a ready explanation for the high concentration of endogenous caffeine found inC. arabica leaves. Although theobromine is converted primarily to caffeine, a small portion of the theobromine pool appears to be degraded to xanthine by a caffeine-independent pathway. In addition to being broken down to CO₂, via the purine catabolism pathway, xanthine is metabolised to 7-methylxanthine. Metabolism of [2-¹⁴C]xanthine byC. arabica leaves in the presence of 5 mM allopurinol results in very large increases in incorporation of radioactivity into 7-methylxanthine as degradation of the substrate via the purine catabolism pathway is blocked. The identity of 7-methylxanthine in these studies was confirmed by gas chromatography-mass spectrometry analysis.Abbreviations HPLC-RC high-performance liquid chromatography-radiocounting This work was supported by the British Council which provided H.A. with Japan-UK travel grants. F.M.G. was supported by a Biotechnology and Biological Sciences Research Council grant to A.C.