Characterization of Chromosome Stability in Diploid,Polyploid and Hybrid Yeast Cells

Chromosome instability is a key component of cancer progression and many heritable diseases. Understanding why some chromosomes are more unstable than others could provide insight into understanding genome integrity. Here we systematically investigate the spontaneous chromosome loss for all sixteen chromosomes in Saccharomyces cerevisiae in order to elucidate the mechanisms underlying chromosome instability. We observed that the stability of different chromosomes varied more than 100-fold. Consistent with previous studies on artificial chromosomes, chromosome loss frequency was negatively correlated to chromosome length in S. cerevisiae diploids, triploids and S. cerevisiae-S. bayanus hybrids. Chromosome III, an equivalent of sex chromosomes in budding yeast, was found to be the most unstable chromosome among all cases examined. Moreover, similar instability was observed in chromosome III of S. bayanus, a species that diverged from S. cerevisiae about 20 million years ago, suggesting that the instability is caused by a conserved mechanism. Chromosome III was found to have a highly relaxed spindle checkpoint response in the genome. Using a plasmid stability assay, we found that differences in the centromeric sequence may explain certain aspects of chromosome instability. Our results reveal that even under normal conditions, individual chromosomes in a genome are subject to different levels of pressure in chromosome loss (or gain).     

The Effect of Organic Solvents on the Appearance of Bacterial Nuclei

Treatment of bacterial smears with organic solvents was found to produce a typical appearing nuclei which could lead to false interpretation of nuclear events. The crystal violet nuclear stain, which does not utilize organic solvents or acid hydrolysis, was used as a basis of comparison. Acid hydrolysis also was observed to affect the appearance of the nucleus. It is concluded that caution should be used in interpreting nuclear structure and activity in bacterial cells, especially when organic solvents or acid hydrolysis are involved in the staining technic.     

Parasitism of Hoplolaimus galeatus on Diploid and Polyploid St. Augustine grasses

''Floratam'' and ''FX-313'' St. Augusfinegrasses (Stenotaphrum secundatum) were compared in a time-course experiment for host suitability and susceptibility to the lance nematode, Hoplolaimus galeatus. Nematode densities were determined in the soil and acid-fuchsin stained roots 42, 84, 126, 168, and 210 days after pots containing 230 cm³ of autoclaved native Margate fine sand/pot were infested with 104 ± 9 nematodes and maintained at 25 ± 2 C in the laboratory. ''FX-313'' was a more suitable host for H. galeatus. Numbers of H. galeatus reached a maximum at 210 days after inoculation, with 5,550 and 4,120 nematodes (adults plus juveniles)/pot for ''FX-313'' and ''Floratam,'' respectively. Root and shoot dry weights of both grasses were not affected by H. galeatus throughout the experiment. Three polyploid, 2n = 30 to 32 (''Floratam,'' ''FX-10,'' and ''Bitterblue'') and three diploid, 2n = 18 (''FX-313,'' ''Florida Common,'' and ''Seville'') S. secundatum genotypes were inoculated with H. galeatus (99 ± 9/pot) and compared with uninoculated controls 210 days after inoculation. St. Augustinegrass genotypes differed as hosts of H. galeatus. ''FX-313'' and ''Florida Common'' represented the high and low extremes, respectively, for nematode reproduction (9,750 and 5,490 nematodes/pot or 4,239 and 2,387 nematodes/100 cm³ of soil). However, differences in root and shoot growth were not detected 210 days after inoculation with H. galeatus.     

广东省被子植物 2个新记录

在广东大亚湾海岛植物调查中,发现广东省被子植物新记录2个物种——芸香科(Rutaceae)光叶山小橘[Glycosmis craibii var. glabra (Craib) Tanaka]和山茶科(Theaceae)保亭杨桐(Adinandra howii Merrill & Chun)。凭证标本存放于厦门大学生命科学学院植物标本室(AU)。新记录既丰富了广东省植物多样性,也为海岛植物研究提供了基础资料。     

Regeneration of Diploid and Polyploid Plants from the Stem Pith Explants of Diploid Marrow Stem Kale (Brassica oleracea L.)

Viable plants of kale (Brassica oleracea L.) have been regeneratedfrom stem pith explants grown on complex agar media. About 80per cent of kale plants cv. Krasa gave explants which differentiatedroots and shoots. Analysis of stomatal length, pollen grainmorphology and estimation of chromosome number in PMC and somaticcells showed that a set of 71 regenerated plants derived fromfive diploid mother plants contained 6 di-, 54 tetra-, and 11octoploid regenerates. Utilization of this method in plant breedingis discussed.     

Rhinovirus RNA Polymerase: Products and Kinetics of Appearance in Human Diploid Cells

The kinetics of appearance of an RNA-dependent RNA polymerase activity obtained from human embryo lung cells infected with rhinovirus type 2 have been followed by analysis of the RNA synthesized by the polymerase preparation in vitro. Little single-stranded RNA was synthesized and the proportion of replicative intermediate to replicative form was over threefold greater than obtained in vivo. The polymerase activity in vivo declined in the presence of cycloheximide showing that continued protein synthesis was necessary to maintain RNA replication.     

Physiology of Polyploid Plants: Water Balance in Autotetraploid and Diploid Tomato under Low and High Salinity

Diploid and autotetraploid plants of the cultivated tomato Lycopersicon esculentum cv. Lukullus (Luk) were studied under low and high salinity. Polyploids had a higher water content than diploid plants. Water content in both plant types decreased under salinity, the decrease being smaller in the polyploid plants. Dry weight of whole young plants decreased in both diploid and polyploid plants under salinity, the decrease being smaller in the latter. Transpiration of whole plants, grown in control solution, was lower in polyploid than in diploid plants and decreased more under salinity in the latter. Rate of change of water loss of detached drying leaves was similar in diploid and polyploid plants. Leaves of control diploid plants, however, lost more water per unit leaf area during the phase of stomatal closure apparently due to higher stomatal density. Polyploid plants had fewer but more open stomata per unit leaf area, under both control and saline conditions. Root pressure, determined only under control conditions, seemed to be higher in polyploid plants. No difference in Cl^? concentration per unit leaf dry weight was found between diploid and polyploid plants grown in either control or NaCl solution.     

Intraplant Nuclear DNA Content Variation in Diploid Nuclei of Maize (Zea mays L.)

Diploid nuclei from stem, mesocotyl, nodal root and root tiptissue of two maize hybrids were examined with respect to theirDNA content. The nuclei were isolated and stained with DAPIand passed through a flow cytometer-cell sorter. The titrationcurve for each tissue was determined. Significant variationwas observed among nuclei of different tissue types. Stem androot tips had the highest diploid nuclear DNA amounts while2-week-old mesocotyl had the lowest diploid nuclear DNA amount.These results provide evidence that during plant developmentand differentiation, the amount of DNA within a diploid nucleuschanges through loss of specific DNA sequences. This study alsodemonstrates the sensitivity of flow cytometry in detectingsmall intraplant variation in nuclear DNA. Key words: Flow cytometry, fluorochrome DAPI, DNA content, tissue differentiation, plant development     

阿拉伯半乳糖蛋白在被子植物中的功能

阿拉伯半乳糖蛋白(arabinogalactan proteins,AGPs)是一类富含羟脯氨酸/脯氨酸的高度糖基化的蛋白分子,在高等植物的细胞壁、质膜和胞外基质中广泛存在。AGPs是一类重要的糖蛋白,它在被子植物营养生长和生殖发育的各个环节都可能发挥作用,涉及体细胞胚胎发生、细胞增殖、细胞膨大、细胞程序性死亡、损伤防御、根形态建成、花粉管生长以及植物激素信号传导等。植物结构基因组学及功能基因组学的快速发展,使得人们对AGPs的表达模式和功能特点有了更深入的认识。本文首先就AGPs的分子结构和分类,然后重点就利用基因组序列信息分析以及正、反向遗传学等手段进行的AGPs在植物营养生长、生殖发育、细胞程序性死亡,以及分子互作和信号传导等方面的作用的研究进行了综述。     

Evidence for the Transfer of Rhizobial Metabolites to the Polyploid Nuclei of Young Clover Nodules

Autoradiography was used to provide evidence for the transfer of Rhizobium produced moieties to the host nuclei of young clover nodule cells. Cells of Rhizobium trifolii Dangeard were labeled with ³H-adenine or 4,5-³H-l -leucine and 3,4-³H-l .-proline, washed free of external label, and allowed to nodulate young seedlings of white clover (Trifolium repens L. cv. White Dutch). Sections (0.5–1.0 μm) of young nodules up to four days old were autoradiographed using the dipping technique. Grain counts indicated movement of tritium from the leucine-proline labeled rhizobia to the polyploid nuclei of two day old clover nodule cells. Acetylene reduction was not detected until approximately 24 hours after the transfer of tritium was observed. No transfer of tritium was observed with ³H-adenine labeled rhizobia. It is hypothesized that nodulating rhizobia may induce clover nodule cells to initiate leghemoglobin synthesis by the transfer of a bacterially produced inducer.     

Both Nucleolar Organizers Are Replicated in Dipteran Polyploid Tissues: A Study at the Level of Individual Nuclei

Working with the Dipteran Calliphora erythrocephala, we have tested the hypothesis that only one nucleolar organizer region (NO) is replicated during polyploidization. NO replication was examined in two very different highly polyploid nuclear types: salivary gland nuclei and nurse cell nuclei. Two strains of the organism containing NO regions with highly diagnostic nontranscribed spacer (NTS) polymorphisms were prepared and reciprocal single pair-matings between members of the strains were performed. The representation of the two distinguishable NOs in diploid and polyploid DNAs of individual F1 progeny from each cross was then examined. DNA from a total polyploid nuclear DNA preparation and from individual polyploid nuclei of both tissue types was analyzed. Our results show conclusively that both genomic NOs are replicated in individual polyploid nuclei of both types. Further, evidence for variation in the relative replication of cistrons from the two NOs by individual nuclei was obtained. The cistron types present in the NOs of both strains showed differential replication upon polyploidization. In general, the patterns of differential cistron replication seen in salivary gland and nurse cell nuclei were similar.     

The Importance of Roots in Regulating the Senescence of Soybean Primary Leaves

The role of roots in regulating primary leaf senescence of 14-day-old soybean seedlings was investigated. Compared with intact seedlings, the senescence of primary leaves is accelerated by removal of the root system but delayed if apical bud and the first trifoliate leaf are removed. No difference in senescence was found between intact seedlings and seedlings without roots, apical bud, and first trifoliate leaf. Lateral roots seem to play a predominant role in regulating primary leaf senescence. However, neither root nodules nor primary root play any function in senescence. Results indicate that benzyladenine (BA) at optimal concentration (2 mg/1) completely replaces the roots to prevent the senescence of primary leaves, whereas gibberellic acid (GA) and abscisic acid (ABA) accelerate. The effect of indole-3-acetic acid (IAA) to replace roots in preventing senescence depends on the season the young seedlings are grown. Additional, though indirect, information of acropetal transport of ABA is provided. In conclusion, it seems that cytokinins in lateral roots play a predominant role in leaf senescence and the normal supply of root cytokinins is important in leaf metabolism.     

Sonographic Appearance of Primary Thyroid Lymphoma-Preliminary Experience

Objective

Primary thyroid lymphoma (PTL) is an uncommon thyroid malignancy. Despite the rarity of PTL, it is important to recognize PTL promptly because its management differs from that of all the other thyroid neoplasms. This study was designed to investigate the sonographic features of PTL.

Methods

Twenty-seven pathologically confirmed PTLs were categorized into diffuse and non-diffuse type. Sonographic features including thyroid size, thyroid background echotexture, lesion size, echogenecity, calcification, vascularity, cervical lymphadenopathy of each type were retrospectively analyzed.

Results

All 27 PTLs were diffuse large B-cell lymphomas and were accompanied by diffuse Hashimoto''s thyroiditis. Ten were diffuse type and seventeen were non-diffuse type sonographically. The observations in diffuse group included goiter (10/10, 100.0%), marked echogenesity (10/10, 100.0%), heterogeneous echotexture (10/10, 100.0%), and cervical lymphadenopathy (4/10, 40.0%). The observations in non-diffuse group included marked hypoechogenicity (17/17, 100.0%), heterogeneous background thyroid gland (17/17, 100.0%), goiter (15/17, 88.2%), increased vascularity (8/13, 61.5%), mulifocality (10/17, 58.8%), and cervical lymphadenopathy (7/17, 41.2%).

Conclusions

Although some common features were found, the sonographic appearance of PTL is unspecific, especially for the diffuse type. Therefore, interventional diagnostic procedures should be warranted in the clinical settings when PTL is suspected.     

Tritiated-thymidine Labelled Nuclei in Primordia and Newly-emerged Lateral Roots of Vicia faba L.

The utilization of ³H-TdR in DNA synthesis and the distributionof labelled nuclei have been determined in large primordia (LP)and newly emerged lateral roots (JE) of Vicia faba followingdifferent exposure periods. This nucleoside appears to reachLP and the more basal, unemerged parts of JE by way of the vasculartissue of the primary root, while those parts of JE which projectout from the epidermis of the primary obtain ³H-TdR directlyfrom the surrounding medium. The utilization of ³H-TdR in thesynthesis of DNA in basal segments of JE is also complicatedby the temporary quiescence of nuclei in this part of thesemeristems as LP elongate to form lateral roots.     

Genetic Polymorphism and Evolution in Parthenogenetic Animals. II. Diploid and Polyploid SOLENOBIA TRIQUETRELLA (Lepidoptera: Psychidae)

Genic polymorphism at sixteen enzyme loci of four different chromosomal races of Solenobia triquetrella (bisexual, two diploid parthenogenetic races and tetraploid parthenogenetic) has been studied by starch gel electrophoresis. Isolated small diploid bisexual populations have rather uniform allele frequencies at all loci which we have studied. Diploid and tetraploid parthenogenetic individuals of this species are in general as heterozygous as bisexual ones. All parthenogenetic local populations are different from each other in the Alps. These parthenogenetic genotypes cannot be derived from a common ancestor through single mutations but rather bear evidence for a polyphyletic origin of parthenogenesis in Solenobia triquetrella. In the marginal distribution areas of the species in northern Europe single genotypes are spread over far larger areas than in the mountain regions of central Europe. This may be due to the old origin of parthenogenesis and polyploidy in northern Europe. No new parthenogenetic and polyploid strains have lately arisen in the regions outside of the Alps.     

Mating System and Clonal Architecture: A Comparative Study in Two Marine Angiosperms

In the present study, we compared the clonal architecture between two seagrass species, the dioecious Cymodocea nodosa and the hermaphroditic, self-compatible Zostera noltii, in order to verify the hypothesis that clonal growth strategies and resulting genet architecture are associated with mating system in clonal plants. It is expected that self-incompatible species should be associated to a guerrilla growth form, because of pollen limitation due to obligate outbreeding, while the ecologically advantageous phalanx strategy can be adopted in self-compatible species. Genotypic diversity and heterozygosity were also assessed in the two species. Sampling has been conducted in mixed stands, collecting shoots of the two species at the same points of the sampling grid, in order to even out any effects of environmental heterogeneity. Species-specific microsatellite loci have been used as molecular markers to identify clones and assess their spatial distribution in both species. As expected, we found an intermingled configuration of genets in the dioecious C. nodosa while Z. noltii was characterized by a clumped, `phalanx-type' distribution of clones. C. nodosa was characterized by higher genotypic diversity with regard to Z. noltii, while heterozygosity levels were comparable in the two species. Coordinating Editor: Dr J. Tuomi