Properties of a host range and coat protein variant of broad bean true mosaic comovirus from Vicia faba

Unlike other described isolates of broad bean true mosaic comovirus (BBTMV), a variant, code name SB, infected some non-leguminous plant species and, in N. benthamiana, induced systemic mottling and puckering of the leaves. However, like other described BBTMV isolates, purified SB particle preparations contained isometric particles c. 28 nm in diameter that sedimented as two nucleoprotein components with S_{20, w} values of 90S and 109S; some preparations occasionally contained a component of c. 50S. Virus particles contained two ssRNA species which, when denatured in glyoxal, had estimated M_T values of 2.1 × 10⁶ and 1.3 × 10⁶ and co-electrophoresed with cowpea mosaic virus RNA-1 and RNA-2 respectively. Isolate SB was serologically indistinguishable from British and German isolates of BBTMV. However, SB virus particles contained a major polypeptide (L) of M_r between c. 31 000 and up to three minor ones (S) or M_r between c. 20 000 and 24 000. This contrasts with protein preparations from other BBTMV isolates that typically contain only two polypeptides of M_r c. 37 000 (L) and 21 000 (S). Following isopycnic centrifugation in CsCl, SB particles purified from pea separated into two major components with densities of 1.39 and 1.44 g cm^-3 and a minor component of estimated density 1.43 g cm^-3. In Cs₂SO₄, virus preparations separated into three major components with densities of 1.30, 1.32 and 1.36 g cm^-3 and a minor one of density 1.27 g cm^-3. In CsCl isopycnic gradients, SB particles purified from TV. benthamiana separated into two components with densities of 1.38 and 1.43 g cm^-3. During immuno-electrophoresis in agarose gels, freshly prepared virus and preparations stored for up to 4 days at 4°C contained a single component that migrated rapidly to the anode, whereas similar preparations of an English isolate of BBTMV migrated as a single component that moved only slowly toward the anode but which, within 48 h, contained an additional component with a migration rate similar to that of isolate SB. Isolate SB is therefore a host range variant of BBTMV which, in comparison with previously described isolates of BBTMV, has an increased negative charge of its particles prior to any appreciable degradation of its S protein, and S protein that is degraded less rapidly. These features probably account for the anomalies observed in isopycnic centrifugation.     

Description of electrophysiological data using a microcomputer*

ABSTRACT. Customization of an inexpensive microcomputer and peripherals to produce hard copy outputs of electrophysiological data is described. The system uses any of the Apple II series computers and a common A/D+D/A card together with a digital plotter. For the 1–2 s recordings normally used in studies of insect chemoreception, this computer configuration can replace more laborious permanent hard copy production techniques. Additional analytical programs can easily use the three data files produced by the current sytem.     

Sensory inhibition as a mechanism of feeding deterrence: effects of three alkaloids on leaf beetle feeding

ABSTRACT. Effects of three alkaloids, sparteine, nicotine and quinine on galeal sensilla of larvae and adults of Entomoscelis americana Brown (Coleoptera: Chrysomelidae) are described. Each of these deterrent compounds stimulates a cell which is stimulated also by glucosinolates (Mitchell & Gregory, 1979; Sutcliffe & Mitchell, 1980) which are feeding stimulants. They inhibit also the response of the sugar-sensitive cell. It is suggested that the latter effect may be mainly responsible for the observed feeding deterrence caused by sparteine and implicated in the other two compounds. Possible mechanisms for the actions of these compounds are discussed with reference to work on other invertebrates. The results also lead us to suggest modification of recent interpretations of the role of secondary plant compounds in the evolution of insect chemosensitive systems.     

Characterization of galeal chemosensilla in the adult Colorado beetle, Leptinotarsa decemlineata

ABSTRACT. Approximately fifteen gustatory sensilla are present on the galeae of adult Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae). In the SEM, these sensilla are not distinguishable morphologically, but some of them differ physiologically. All are sensitive to sucrose, while only a few respond to gamma amino butyric acid (GABA). One, called the alpha sensillum, is significantly more sensitive to GABA than the others. The same sensory cell predominates in the alpha sensillum responses to GABA and sucrose. This example of differential specificity among sensilla, in an apparently uniform sensory field, is discussed.     

The Effect of 3-Aminobenzamide on Thymidine Incorporation in Ultra-Violet Irradiated Chick Pigment Epithelium Cells

The addition of 3-aminobenzamide (3-AB) to cultures of chick embryo pigmented epithelium rescues these cells after high doses of ultraviolet treatment. The addition of 3-AB prevents cells from losing pre-formed protein and DNA and stimulates thymidine incorporation by the cells after ultraviolet irradiation. Since 3-AB is an inhibitor of poly (ADP) ribosylation, these observations support the conclusion that death of these cells after ultra-violet irradiation depends upon poly (ADP) ribosylation and may be an apoptotic response.     

Response of Leaf Spectral Reflectance in Loblolly Pine to Increased Atmospheric Ozone and Precipitation Acidity

Leaf reflectance responses to increased ozone and precipitationacidity were determined at visible (400–720 nm) and infra-red(720–2500 nm) wavelengths for field-grown seedlings ofloblolly pine (Pinus taeda L.). Treatments were maintained continuouslyfrom 3 April to 3 November. In a relatively ozone-sensitivevariety of pine, increased ozone decreased visible and infra-redreflectance by late May. By late August, continued exposureto ozone increased visible and infra-red reflectance. As oflate November, ozone at 17ambient or greater concentrationshad increased visible reflectance substantially in an ozone-insensitiveas well as the ozone-sensitive variety. Acidic precipitationdecreased visible and infra-red reflectances in both varietiesin May and decreased infra-red reflectances in the ozone-sensitivevariety in August, but did not produce significant reflectanceresponses in November. Visible reflectance responses to ozoneand acidic precipitation, particularly those near 700 nm, werespectrally similar to reflectance responses reported previouslyfor other deleterious environmental influences. Key words: Pinus taeda, reflectance, ozone, acidic precipitation     

Phylogeny of Trichomonads Inferred from Small-Subunit rRNA Sequences

ABSTRACT. Small subunit (16S-like) ribosomal RNA sequences were obtained from representatives of all four families constituting the order Trichomonadida. Comparative sequence analysis revealed that the Trichomonadida are a monophyletic lineage and a deep branch of the eukaryotic tree. Relative to other early divergent eukaryotic assemblages the branching pattern within the Trichomonadida is very shallow. This pattern suggests the Trichomonadida radiated recently, perhaps in conjunction with their animal hosts. From a morphological perspective the Devescovinidae and Calonymphidae are considered more derived than the Monocercomonadidae and Trichomonadidae. Molecular trees inferred by distance, parsimony and likelihood techniques consistently show the Devescovinidae and Calonymphidae are the earliest diverging lineages within the Trichomonadida, however bootstrap values do not strongly support a particular branching order. In an analysis of all known 16S-like ribosomal RNA sequences, the Trichomonadida share most recent common ancestry with unidentified protists from the hindgut of the termite Reticulitermes flavipes. The position of two putative free-living trichomonads in the tree is indicative of derivation from symbionts rather than direct descent from some free-living ancestral trichomonad.