Teratocytes growth pattern reflects host suitability in a host–parasitoid assemblage

Abstract.  In some parasitoid species, the serosa membrane breaks apart at hatching and produces teratocyte cells that assume various functions (immunossupression, secretion and nutrition) mediating host–parasitoid relationships. Teratocyte growth pattern may thus reflect the host suitability for a parasitoid. The teratocyte growth pattern (increase in size and number of teratocytes as a function of time) is studied and used as an indirect measure of fitness to compare the development of the endoparasitoid Dinocampus coccinellae in a marginal host, the coccinellid Harmonia axyridis , and in a suitable host, Coleomegilla maculata . Indirect measures of fitness recorded in both host species confirm that C. maculata is a suitable host for D. coccinellae contrary to the marginal host H. axyridis. According to regression analysis, teratocyte numbers decrease linearly whereas teratocyte size increases linearly with time in the suitable host C. maculata (larvae or adults). In the marginal host, parasitism occurs only in the larval stage where a delay in the parasitoid larval development is observed. Increase in teratocyte size is also highly variable. The teratocyte growth pattern of the parasitoid in the marginal host does not follow the linear model found in the suitable host. Teratocyte growth pattern may be a useful criterion to evaluate host-suitability and host range of parasitoids.     

Wounding and the Regulation of Apoplasmic Retrieval in Source Leaf Tissue 5Spinacia oleracea L.

Kinetic studies were performed on fresh-cut and aged leaf discsof Spinacia oleracea L. in order to investigate the regulatoryprocesses involved in sugar transport across the mesophyll plasmamembrane. A comparison of the kinetic profiles for fructose,glucose, sucrose and arginine obtained on freshly-cut and ageddiscs revealed that during wound-recovery, uptake is enhanced,but that this enhancement varies considerably for the differentsubstrates tested. Variation in the saturable and first-orderkinetic components of uptake was also observed. The involvementof a phosphoinositide-signalling mechanism in the wounding processwas examined by pretreating spinach leaves with lithium. Lithiuminhibited the enhancement of uptake and this effect was reversedby the addition of miro-inositol. However, in some experimentsthe tissue appeared to be insensitive to Li⁺. Gas chromatographicanalyses performed on cut discs indicated that ethylene wasproduced in response to wounding and that the addition of cobaltto the ageing media inhibited this ethylene production. Comparativekinetic studies of control and cobalt-treated discs indicatedthat ethylene was essential for the enhancement of transportacross the plasma membrane. However, addition of ethylene touncut tissue caused only a partial increase in the uptake offructose, which indicates that some additional wound-signallingcomponent is involved. Addition of cycloheximide to the recoverymedia completely inhibited this enhancement phenomenon. Thecycloheximide-response was not due to an inhibition of ACC synthasesynthesis nor to a reduction of ATP levels. We concluded thatthe effect of cycloheximide was on protein synthesis. Our resultsare discussed in terms of possible cellular and molecular mechanismsregulating sugar transport. Key words: Sugar transport, wounding, ethylene production, spinach leaves     

Hydroxyl- and Bicarbonate-Associated Transport Processes in Chara corallina: Studies on the Light-Dark Regulation Mechanism

Lucas, W. J. and Ogata, K. 1985. Hydroxyl– and bicarbonate–associatedtransport processes in Chara corallintr. Studies on the light–darkregulation mechanism.—J. exp. Bot. 36: 1947–1958.Experiments were undertaken on the fresh water alga Chara corallinato investigate the nature of the coupling between the chloroplastsand the light–dependent OH^– and -associated plasmalemma transport systems. Electrophysiologicalexperiments, in which DCMU was employed, revealed that thischemical could elicit a hyperpolarization of the membrane potentialthat was identical to that normally obtained by turning offthe light. This DCMU–induced hyperpolarization was obtainedunder control () and phosphate–decoupled conditions (). Measurements of the extracellular electric potentialswhich are associated with the acidic () and alkaline (OH^–) regions, indicated that, in the presenceof control ()or phosphate–decoupled conditions, normal profiles were established under air, oxygenor nitrogen environments. These results indicate that the generationof the control signal(s) is related to events associated withchloroplast electron transport, rather than to changes in theflow or levels of carbon intermediates within the reductivepentose phosphate or photorespiratory cycles. Although the levelof oxygen was found to have no effect on the light–inducedactivation of the OH regions, we found that in pure oxygen thedark–induced inactivation of the OH^– efflux systemwas delayed, and that partial transport function could be maintainedin the dark. The possible involvement of changes in either theratio of oxidized to reduced ferridoxin or NADP^? to NADPH, aspart of this light–mediated control signal, is discussed. Key words: Chara corallina, Plasma membrance transport, OH^– and , regulation     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.      

Characterisation of a 34 kD protein from potato cyst nematodes, using monoclonal antibodies with potential for species diagnosis

Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations.     

Gap junction structures: Analysis of the x-ray diffraction data

Models for the spatial distribution of protein, lipid and water in gap junction structures have been constructed from the results of the analysis of X-ray diffraction data described here and the electron microscope and chemical data presented in the preceding paper (Caspar, D. L. D., D. A. Goodenough, L. Makowski, and W.C. Phillips. 1977. 74:605-628). The continuous intensity distribution on the meridian of the X-ray diffraction pattern was measured, and corrected for the effects of the partially ordered stacking and partial orientation of the junctions in the X-ray specimens. The electron density distribution in the direction perpendicular to the plane of the junction was calculated from the meridional intensity data. Determination of the interference function for the stacking of the junctions improved the accuracy of the electron density profile. The pair-correlation function, which provides information about the packing of junctions in the specimen, was calculated from the interference function. The intensities of the hexagonal lattice reflections on the equator of the X-ray pattern were used in coordination with the electron microscope data to calculate to the two-dimensional electron density projection onto the plane of the membrane. Differences in the structure of the connexons as seen in the meridional profile and equatorial projections were shown to be correlated to changes in lattice constant. The parts of the junction structure which are variable have been distinguished from the invariant parts by comparison of the X-ray data from different specimens. The combination of these results with electron microscope and chemical data provides low resolution three- dimensional representations of the structures of gap junctions.     

甘肃省被子植物分布新记录

报道了甘肃省分布的玄参科(Scrophulariaceae)水茫草属(Limosella Linn.)1个新记录属,以及玄参科(Scrophulariaceae)、木兰科(Magnoliaceae)、蓼科(Polygonaceae)、胡颓子科(Elaeagnaceae)、百合科(Liliaceae)5个新记录种——水茫草(Limosella aquatica Linn.)、峨眉含笑(Michelia wilsonii Finet et Gagnep.)、叉分蓼(Polygonum divaricatum L.)、棱果沙棘(Hippophae goniocarpa Y.S.Lian et al.ex SwensonBartish)、青海黄精(Polygontum qinghaiense Z.L.Wu et Y.C.Yang)。其中,峨眉含笑是国家二级重点保护野生植物。     

上海环城林带景观美学评价及优化策略

选取上海环城林带7种植物群落,采用美景度评判法,从林内景观和林外景观2个空间层次和春、夏、秋、冬4个季节,应用数量化理论Ⅰ建立了美景度和各景观因子类目之间的景观评价与预测的多元回归模型,分析了群落的结构特征和季相特征对林内景观以及外貌特征对林外景观的影响,并提出相应的优化对策。结果表明:(1)群落结构特征对林内景观的影响主要因子为胸径(平均胸径和胸径变异系数)、郁闭度和疏透度。在春季,林内美景度随着树木胸径增大而增加;在夏季,郁闭度增大会提升林内美景度;在秋季,胸径变异小的群落具有更高的林内观赏性;在冬季,疏透度对林内景观美景度影响最大。(2)群落季相特征对林内景观的影响,在各季节表现亦不同。在春季,黄色、紫色等明度较高的色相和开花量适中的群落美景度最佳;在夏季,生长势好、林冠层变化小以及树干清晰度高的群落具较高的美景度,且观花可显著提高夏季林内美景度;在秋季,色彩越纯美景度越高;而在冬季,树皮颜色深的群落美景度高。(3)群落外貌特征对林外景观有显著影响,其中林冠线对林外景观美景度影响最大,其次为林缘线。具有起伏不大林冠线和自然流畅林缘线的植物群落美景度高。旨在通过对典型植被群落不同季相的美景度评价,对上海环城林带的群落景观进行定量的评价,进而为不同情景下的群落结构优化提出相应的对策,为城市森林的群落建构与管理提供科学依据。