Genetic analysis of tomato golden mosaic virus: the coat protein is not required for systemic spread or symptom development

The geminiviruses are a unique group of higher plant viruses that are composed of twin isometric particles which contain circular, single-stranded DNA. Tomato golden mosaic virus (TGMV), a whitefly-transmitted agent, belongs to the subgroup of geminiviruses whose members possess a bipartite genome. The TGMV A genome component has the capacity to encode at least four proteins. One of these is the viral coat protein, as inferred by homology with coat-protein, genes of other geminiviruses and by the observation of typical geminate particles in transgenic plants that contain inserts of TGMV A DNA. We have investigated the role of the coat protein in TGMV replication and report here that its coding sequence may be interrupted or substantially deleted without loss of infectivity. However, certain coat-protein mutants showed reproducible delays in time of symptom appearance as well as reduced symptom development, when inoculated onto transgenic Nicotiana benthamiana plants containing the TGMV B component. The most attenuated symptoms were seen with a mutant in which the coat-protein coding sequence was almost entirely deleted. The significance of these findings for the development of plant vectors from TGMV DNA is discussed.     

Multiracial Facial Golden Ratio and Evaluation of Facial Appearance

This study aimed to investigate the association of facial proportion and its relation to the golden ratio with the evaluation of facial appearance among Malaysian population. This was a cross-sectional study with 286 randomly selected from Universiti Sains Malaysia (USM) Health Campus students (150 females and 136 males; 100 Malaysian Chinese, 100 Malaysian Malay and 86 Malaysian Indian), with the mean age of 21.54 ± 1.56 (Age range, 18–25). Facial indices obtained from direct facial measurements were used for the classification of facial shape into short, ideal and long. A validated structured questionnaire was used to assess subjects’ evaluation of their own facial appearance. The mean facial indices of Malaysian Indian (MI), Malaysian Chinese (MC) and Malaysian Malay (MM) were 1.59 ± 0.19, 1.57 ± 0.25 and 1.54 ± 0.23 respectively. Only MC showed significant sexual dimorphism in facial index (P = 0.047; P<0.05) but no significant difference was found between races. Out of the 286 subjects, 49 (17.1%) were of ideal facial shape, 156 (54.5%) short and 81 (28.3%) long. The facial evaluation questionnaire showed that MC had the lowest satisfaction with mean score of 2.18 ± 0.97 for overall impression and 2.15 ± 1.04 for facial parts, compared to MM and MI, with mean score of 1.80 ± 0.97 and 1.64 ± 0.74 respectively for overall impression; 1.75 ± 0.95 and 1.70 ± 0.83 respectively for facial parts. In conclusion: 1) Only 17.1% of Malaysian facial proportion conformed to the golden ratio, with majority of the population having short face (54.5%); 2) Facial index did not depend significantly on races; 3) Significant sexual dimorphism was shown among Malaysian Chinese; 4) All three races are generally satisfied with their own facial appearance; 5) No significant association was found between golden ratio and facial evaluation score among Malaysian population.     

川金丝猴食谱的地域性差异比较

对不同地区川金丝猴食物组成的比较有助于了解其对不同生境食物供应的适应性。本研究通过对陕西川金丝猴猴群食谱的长期记录,并汇集了国内对四川-甘肃和湖北的川金丝猴食性研究结果,集成了这三个地理种群川金丝猴各自的地域性食谱,共计有136 种植物(隶属35 科)被该物种作为采食对象。对来自这三个不同区域(陕西、四川-甘肃、湖北)的川金丝猴食谱组成的比较,发现有近半数的植物是三个地理种群共同的采食对象,但其食谱组成差异明显。这可能源于各地植物本身的多样性差异,及不同地理种群对各种食物采食偏好的不同所致。对其相关聚类分析结果显示,陕西和湖北的猴群在食谱组成上相近,但四川-甘肃的猴群与前两个地区猴群的食谱组成差异极大。然而湖北和四川-甘肃种群在食物的选择上采用了近乎相同的偏好倾向,而陕西的猴群与它们明显不同。我们初步分析认为造成食谱组成和采食偏好差异的原因可能是各地理种群活动地海拔带重叠度不同、森林类型不同、它们在不同林型中活动的时间分配不一。很明显,就我们目前所掌握的有关川金丝猴食谱组成来看,该物种不应该仅仅被认为是一个叶食性灵长类动物,而应该是一个泛化采食者。     

Nestling sex ratio of golden‐winged warblers Vermivora chrysoptera in an introgressed population

Sex ratio biases in avian species remain controversial, although several studies have documented apparent facultative adjustment of offspring sex ratios. While hybridizing pied and collared flycatchers have exhibited sex ratio skews that may be a response to sex‐based costs associated with hybridization, this appears not to be true of a hybridized population of blue‐winged Vermivora pinus and golden‐winged V. chrysoptera warblers. We examined the primary sex ratio of nestlings in a population of hybrid and introgressed golden‐winged warblers. The sex ratio of 298 nestlings from 81 nests in the population was approximately 50:50. We conducted paternity assignments and analyzed groups of nestlings with shared genetic parents (“genetic broods”) and found no difference from the expected binomial distribution, and no statistically significant relationship between parental species phenotype and nestling sex ratio. We saw no evidence of preferential production of male or female nestlings, and female hybrids were found to mate and breed in the population. This suggests that heterogametic (female) hybrids are both viable and fertile, and thus that Haldane's Rule does not apply to this system. While populations of hybridizing golden‐winged warblers should be monitored for evidence of costs of heterospecific pairings, it is unlikely that adjustment of sex ratios would be the form of compensation for sub‐optimal mating conditions. Our results provide support for the emerging hypothesis that hybrids suffer no disadvantage relative to golden‐winged and blue‐winged warblers.     

Early vascular land plants: proof and conjecture

Megafossil evidence does not fill the 'evolutionary gap' between land plants and their hypothetical green algal ancestors. Rare Late Silurian vascular plant megafossils provide little information about the morphological, physiological, biochemical, and ecological steps that preceded their evolution. Dissociated trilete spores, spore tetrads, cuticle- and tracheid-like structures far exceed the abundance and diversity of Silurian vascular plant megafossils, and appear millions of years before them. In reference to whole-bodied organisms, these or analogous structures belong to land plants or emergent aquatics; they may represent plants evolutionarily intermediate between green algae and descendent vascular plants at the bryophyte or pre-bryophyte stages. Changes in the cellular biochemistry of pre-Devonian land plants in response to the selective pressures of terrestrial life may have led to the origin of lignin and cutin, neither of which has any counterpart among the algae, and to the evolutionary surge of the vascular plants in the Early Devonian represented by the plant megafossil record. Positive correlation between abundance and diversity of trilete spores and shallow-water, nearshore sites reinforces conclusions based on morphology that a terrestrial flora existed well prior to the appearance of vascular plant megafossils.     

Pore-forming properties of elicitors of plant defense reactions and cellulolytic enzymes.

Using the planar lipid bilayer technique, it is shown that a yeast elicitor as well as several cellulolytic enzymes used in protoplasting plant cells contain components which strongly interact with the bilayers. This results in the appearance of transmembrane ion fluxes which may pass through membrane defect structures and even large conductance pores with unitary conductances above 400 pS. Since membrane depolarization is an immediate response in the process of defense elicitation in plant cells, elicitors may act directly with the lipid phase of cell membranes, causing depolarizations and thus initiating the process of elicitation. When using enzymatically prepared protoplasts in electrophysiological work, contributions to electrical activity by membrane active constituents originating from the enzymes used must be expected.     

Senescence induced structural reorganization of thylakoid membranes in Cucumis sativus cotyledons; LHC II involvement in reorganization of thylakoid membranes

We report the formation and appearance of loosely stacked extended grana like structures along with plastoglobuli in the chloroplasts isolated from 27-day old senescing cucumber cotyledons. The origin and the nature of these extended grana structures have not been elucidated earlier. We isolated Photosystem I complexes from 6-day-old control and 27-day-old senescing cotyledons. The chlorophyll a/b ratio of the isolated Photosystem I complex obtained from 6-day cotyledons was 5–5.5 as against a ratio of 2.9 was found in Photosystem I complexes obtained from 27-day-old senescing cotyledons. We also found that the presence of LHC II in the Photosystem I complexes isolated from 27-day cotyledonary chloroplasts. The presence of LHC II in Photosystem I complexes in senescing and not in control samples, clearly suggest the detachment and diffusion of LHC II complexes from stacked grana region to Photosystem I enriched stroma lamellar region thereby, forming loose disorganized extended grana structures seen in the transmission electron microscope. Furthermore, we show that under in vitro condition the senescing cotyledon chloroplasts exhibited lower extent of light induced phosphorylation of LHC II than the control samples suggesting a possible irreversible phosphorylation and diffusion of LHC II in vivo during the progress of senescence in Cucumis cotyledons. From these findings, we suggest that the senescence induced phosphorylation of LHC II and its migration towards Photosystem I may be a programmed one some how causing the destruction of the thylakoid membrane. The released membrane components may be stored in the plastoglobuli prior to their mobilization to the younger plant parts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Functional morphology of the middle ear in Chlorotalpa golden moles (Mammalia, Chrysochloridae): predictions from three models

The ossicular apparatus of golden moles in the genus Chlorotalpa has received comparatively little attention in the literature, although the malleus is known to be intermediate in size between the "unmodified" malleus of Amblysomus and the hypertrophied mallei found in some other golden moles. In the present study, the middle ear structures of three Chlorotalpa species (C. duthieae, C. sclateri, and C. arendsi) are described. Measurements of middle ear structures were applied into three existing models of middle ear function. The predictions from the models suggest that the airborne hearing of Chlorotalpa species is limited to relatively low frequencies, but the impedance transformation by the middle ear apparatus is expected to be reasonably efficient. The sensitivity of the middle ear apparatus to inertial bone conduction is intermediate between that predicted for Amblysomus and that predicted for species with hypertrophied mallei. Hearing in fossorial mammals may be limited by factors other than the middle ear apparatus: the predictions for Chlorotalpa must therefore be treated with caution. However, a consideration of the "intermediate" middle ear morphology of Chlorotalpa species sheds some light on the origin of ossicular hypertrophy in golden moles. The limited enlargement of the malleus seen in Chlorotalpa is expected to have improved seismic sensitivity by bone conduction significantly at low frequencies, while airborne hearing might not have been adversely affected.     

冠层部位对金叶女贞叶片结构的影响

金叶女贞是一种在园林绿化上广泛应用的彩叶植物,上层叶金黄色,下层叶深绿色。本文利用常规植物制片技术,研究了叶绿素缺少的金叶女贞上层金叶和下层绿叶的解剖结构。结果表明:(1)金叶女贞上层金叶和下层绿叶的上表皮无显著差异,但是下层绿叶的下表皮细胞较小,气孔密度较低;(2)下层绿叶的叶肉组织较薄,细胞较大,排列疏松;(3)在下层绿叶中叶绿体类囊体片层排列密集,叶肉组织内单位体积叶绿体数量较少;(4)冠层部位对光合色素的积累有明显影响。叶绿素缺少的金叶女贞叶片结构显著受到冠层部位的影响,光合色素的变化幅度较一般植物更大,不同冠层部位叶片叶色有明显差异,可以作为研究植物冠层部位对叶形态、结构和生理生化影响的好材料。     

Tissue specificity of geminivirus infection is genetically determined

The types of cells and tissues infected by a virus define its tissue tropism. Determinants of tissue tropism in animal-infecting viruses have been extensively investigated, but little is known about plant viruses in this regard. Some geminiviruses in the genus Begomovirus exhibit phloem limitation and are restricted to cells of the vascular system, whereas others can invade mesophyll tissue. To identify viral genetic determinants of tissue tropism, we established a model system using two begomoviruses and their common host plant, Nicotiana benthamiana. Analysis by DNA in situ hybridization confirmed that tomato golden mosaic virus invades mesophyll tissues in systemically infected leaves, whereas bean golden mosaic virus remains phloem limited. Through genetic complementation and analysis of recombinant hybrid viruses, we demonstrated that three genetic elements of tomato golden mosaic virus determine its mesophyll tissue tropism. A noncoding region of the viral genome is essential for the phenotype, but it must be accompanied by one of two different coding regions. To our knowledge, this is the first example documented in a plant virus of noncoding DNA sequences that determine tissue tropism.     

Fine structure of the epithelial reticular cells of the medulla of the thymus in the golden hamster

Summary The epithelial reticular cells of the thymic medulla of the golden hamster were studied by electron microscopy. On the basis of their structural details two cell types are distinguished, although the two types are similar in basic structure. The cells of one type are more extended in shape and darker in appearance. They are connected with one another by their cytoplasmic processes, forming a reticulum in the medulla. Thus they appear to play a supporting role as do the cortical epithelial reticular cells. The other cell type is larger, more rounded and lighter. The characteristic feature of this cell type is an abundance of vesicular structures, which occur as vesicles or vacuoles of varying sizes. In addition, an enormous, intracytoplasmic ciliated cyst is occasionally encountered in the latter cell type. The cyst may be regarded as representing a specialized form of the vesicular structures. The possible functional significance of the latter cell type is discussed in relation to recent concepts concerning the mechanism of thymic function.Dedicated to Professor W. Bargmann, under whose guidance my thymus studies were begun, in honor of his 60th birthday (T. Ito).     

Foraging site use and interspecific competition between bluegills and golden shiners

Synopsis Laboratory experiments examined the foraging performances of a dietary generalist, bluegill,Lepomis macrochirus, and a dietary specialist, golden shiner,Notemigonus crysoleucas, as they fed from devices simulating four foraging sites (bottom substrate, water column, submerged macrophytes, and water surface). Fishes foraged in monospecific and mixed-species groups of two and four individuals. For monospecific groups, foraging rates of bluegills did not differ among the four sites, but golden shiners had significantly higher rates on bottom and midwater sites than on plant and surface sites. The size of monospecific groups did not affect foraging rates of either species. In mixed-species trials, bluegills removed more food items than golden shiners from plant and surface sites in two- and four-fish groups and from bottom sites in two-fish groups. Bluegills' foraging performances improved with experience, golden shiners' performances did not. Experimental results are discussed with respect to interactions between bluegills and golden shiners in natural assemblages.     

Morphology of the middle ear of golden moles (Chrysochloridae)

The middle ear structures of nine species of golden moles (family Chrysochloridae) were examined under the light microscope. Auditory structures of several of these species are described here for the first time in detail, the emphasis being on the ossicular apparatus. Confirming previous observations, some golden moles (e.g. Amblysomus species) have ossicles of a morphology typical of mammals, whereas others ( Chrysospalax , Chrysochloris , Cryptochloris and Eremitalpa species) have enormously hypertrophied mallei. Golden moles differ in the nature and extent of the interbullar connection, the shape of the tympanic membrane and that of the manubrium. The stapes has an unusual orientation, projecting dorsomedially from the incus. It has been proposed that hypertrophied ossicles in golden moles are adapted towards the detection of seismic vibrations. The functional morphology of the middle ear apparatus is reconsidered in this light, and it is proposed that adaptations towards low-frequency airborne hearing might have predisposed golden moles towards the evolution of seismic sensitivity through inertial bone conduction. The morphology of the middle ear apparatus sheds little light on the disputed ordinal position of the Chrysochloridae.     

Pathogen‐induced conditioning of the primary xylem vessels – a prerequisite for the formation of bacterial emboli by Pectobacterium atrosepticum

Representatives of Pectobacterium genus are some of the most harmful phytopathogens in the world. In the present study, we have elucidated novel aspects of plant–Pectobacterium atrosepticum interactions. This bacterium was recently demonstrated to form specific ‘multicellular’ structures – bacterial emboli in the xylem vessels of infected plants. In our work, we showed that the process of formation of these structures includes the pathogen‐induced reactions of the plant. The colonisation of the plant by P. atrosepticum is coupled with the release of a pectic polysaccharide, rhamnogalacturonan I, into the vessel lumen from the plant cell wall. This polysaccharide gives rise to a gel that serves as a matrix for bacterial emboli. P. atrosepticum‐caused infection involves an increase of reactive oxygen species (ROS) levels in the vessels, creating the conditions for the scission of polysaccharides and modification of plant cell wall composition. Both the release of rhamnogalacturonan I and the increase in ROS precede colonisation of the vessels by bacteria and occur only in the primary xylem vessels, the same as the subsequent formation of bacterial emboli. Since the appearance of rhamnogalacturonan I and increase in ROS levels do not hamper the bacterial cells and form a basis for the assembly of bacterial emboli, these reactions may be regarded as part of the susceptible response of the plant. Bacterial emboli thus represent the products of host–pathogen integration, since the formation of these structures requires the action of both partners.     

The biological essence of golden sections

Using the examples of phyllotaxis and the process of graduated development of plant photosynthetic apparatus the author shows that the principle of golden section is an implication of the principle of optimal construction (maximal simplicity). The principle of optimal construction is characterized by minimum of numerical relations between integer and its parts, that indicate the fractal character of studied objects and processes organized according to the golden section principle.     

The duration of capture and restraint during anesthesia and euthanasia influences glucocorticoid levels in male golden hamsters

Deep litter has been shown to decrease stereotypic wire-gnawing in male golden hamsters, suggesting that increased litter depth may be associated with decreased chronic stress levels. To determine the relationship between litter depth and stress levels in hamsters, the authors measured serum levels of corticosterone, cortisol, and ACTH in male golden hamsters kept in cages with three different depths of litter. The duration of handling the hamsters significantly increased the concentrations of corticosterone, cortisol, and the ratio of cortisol/corticosterone. It took longer to catch hamsters housed in cages with deep litter and the ACTH levels were higher in these hamsters. The positive effect of the enrichment (deep litter) was diminished by methodological problems during handling/anesthesia.     

川金丝猴血象和血液生物化学指标的研究

测定了１２只川金丝猴的血象和血液生物化学指标。结果发现;在各项血象指标中,只有白细胞总数和白细胞分类计数与滇金丝猴的有较大判别;在各项生物化学指标中,血清尿酸含量比滇金猴的高,血清总胆固醇和尿素氮的含量比滇金丝猴的低,血清白收白和球蛋白比值与人的差异明显;其余各项指标与滇金丝猴和人的十分接近。     

Golden: a novel coat color mutant in the wild mouse Mus caroli

We identified a spontaneous pigmentation mutant in the wild mouse species Mus caroli. Mutant mice exhibit a golden coat color on the agouti background, easily distinguishable from the darker wild type. The golden phenotype segregates as an autosomal recessive, showing no linkage to the sex-linked enzyme marker glucose-6-phosphate dehydrogenase. Obligate heterozygotes are phenotypically indistinguishable from the wild type. At birth, homozygotes have poorly pigmented eyes, which darken with age to become indistinguishable from the wild type. Pigmentation of the ears, tail, and footpads is reduced in intensity. Preliminary studies indicate that the phenotype may be due to an alteration in the shape and pigmentation of the eumelanosomes. The viability and fertility of both heterozygotes and homozygotes, as measured by litter size, sex ratio, or frequency of survival to weaning, appear to be normal for M. caroli. Spectrophotometric analysis of hair samples from the mouse variant at the putative golden locus (gdn) suggests that this mutant is not homologous to at least six independent pigment mutants previously identified in M. musculus.     

Correlation between dynamic tomato fruit-set and source–sink ratio: a common relationship for different plant densities and seasons?

Background and Aims

It is widely accepted that fruit-set in plants is related to source–sink ratio. Despite its critical importance to yield, prediction of fruit-set remains an ongoing problem in crop models. Functional–structural plant models are potentially able to simulate organ-level plasticity of plants. To predict fruit-set, the quantitative link between source–sink ratio and fruit-set probability is analysed here via a functional–structural plant model, GreenLab.

Methods

Two experiments, each with four plant densities, were carried out in a solar greenhouse during two growth seasons (started in spring and autumn). Dynamic fruit-set probability was estimated by frequent observation on inflorescences. Source and sink parameter values were obtained by fitting GreenLab outputs for the biomass of plant parts (lamina, petiole, internode, fruit), at both organ and plant level, to corresponding destructive measurements at six dates from real plants. The dynamic source–sink ratio was calculated as the ratio between biomass production and plant demand (sum of all organ sink strength) per growth cycle, both being outputs of the model.

Key Results and Conclusions

Most sink parameters were stable over multiple planting densities and seasons. From planting, source–sink ratio increased in the vegetative stage and reached a peak after fruit-set commenced, followed by a decrease of leaf appearance rate. Fruit-set probability was correlated with the source–sink ratio after the appearance of flower buds. The relationship between fruit-set probability and the most correlated source–sink ratio could be quantified by a single regression line for both experiments. The current work paves the way to predicting dynamic fruit-set using a functional structure model.     

Use of green fluorescent protein to quantify the growth of Colletotrichum during infection of tobacco

To develop a quantitative assay of fungal growth inside plant tissues, strains of Colletotrichum destructivum and Colletotrichum orbiculare were transformed with a modified green fluorescent protein (GFP) gene fused with a glyceraldehyde-3-phosphate dehydrogenase promoter from Aspergillus nidulans. Transformants expressed GFP in culture and had the same growth rate and general appearance as the wild type. GFP was observed in all fungal structures during infection of leaves of Nicotiana benthamiana, except for the melanized appressoria and setae. The timing and appearance of the fungal structures in the host appeared to be identical to that of the wild type. GFP accumulation in inoculated leaves of N. benthamiana was quantified in leaf extracts using a fluorescence microplate reader, and the quantity of fluorescence was strongly correlated with the growth of the fungus as measured by the amount of fungal actin gene expression using Northern blot hybridizations. These results demonstrated that assaying green fluorescence levels from a GFP-transformed fungus is an accurate, fast and easy means of quantifying fungal growth inside host plant cells.