Secretion of Acid Phosphatase by x4xenic Entamoeba histolytica NIH-200 and Properties of the Extracellular Enzyme

Entamoeba histolytica (NIH-200) secreted large amounts of acid phosphatase in its external environment when grown axenically in modified TPS-II medium. Fractionation by DEAE-cellulose chromatography of the precipitate obtained from the cell-free medium at 60% ammonium sulfate saturation yielded 3 distinct peaks of enzyme activity. The enzyme in all the peaks showed resistance to tartrate but was inhibited by fluoride, cupnc chloride, ethylene diamine-tetra acetic acid, ammonium molybdale and cysteine: however, enzyme associated with different peaks differed in its polyacrylamide gel electrophoretic profiles and behavior towards concanavalin A.     

Leishmania donovani: A Chemically Defined Medium Suitable for Cultivation and Cloning of Promastigotes and Transformation of Amastigotes to Promastigotes

A chemically defined medium using commercially available α-MEM supplemented with HEPES, L-glutamine, D-glucose, folic acid, D-biotin and adenine supports the luxuriant growth and propagation of Leishmania donovani promastigotes. A peak parasite population of about 7.0 × 10⁷/ml at stationary phase and a population doubling time of 11.4 h for high-subpassage promastigotes were obtained. The medium was suitable for transformation of isolated amastigotes from infected hamster spleen. Promastigotes could be detected by culturing kala-azar patients’bone-marrow aspirate or spleen puncture material in this medium. Four out of six freshly transformed isolates gradually adapted and grew well in this medium. Macroscopic colonies appeared on agar plates prepared with the medium within 16–20 days after inoculation. The cloning efficiency was increased about five-fold by glycerol supplementation.     

Transformation of Vicia faba Cotyledon and Stem Tissues7Agrobacterium rhizogenes: Infectivity and Cytological Studies

Transformation of Vicia faba cotyledon and stem tissues by Agrobacteriumrhizogenes has been demonstrated. Hormone autotrophy and NPTIIdot blot assays were used to confirm the transgenic nature ofroot clones, and to show the co-transfer of the T-DNA from theRi plasmid and the NPTII gene from pBIN 19. An effect of plantgenotype on susceptibility to A. rhizogenes was observed. Theresponse to infection depended on tissue type in addition toplant genotype. Cytological analysis of transformed root clonesuncovered variation in ploidy up to the octoploid level andstructural rearrangements of chromosomes. The possible originsof these karyotype changes and their implications are discussed. Key words: Vicia faba, Agrobacterium rhizogenes, transformed roots, genotypic effects, chromosomes     

SGT1 positively regulates the process of plant cell death during both compatible and incompatible plant–pathogen interactions

SGT1 (suppressor of G2 allele of Skp1), an interactor of SCF (Skp1‐Cullin‐F‐box) ubiquitin ligase complexes that mediate protein degradation, plays an important role at both G1–S and G2–M cell cycle transitions in yeast, and is highly conserved throughout eukaryotes. Plant SGT1 is required for both resistance (R) gene‐mediated disease resistance and nonhost resistance to certain pathogens. Using virus‐induced gene silencing (VIGS) in Nicotiana benthamiana, we demonstrate that SGT1 positively regulates the process of cell death during both host and nonhost interactions with various pathovars of Pseudomonas syringae. Silencing of NbSGT1 in N. benthamiana plants delays the induction of hypersensitive response (HR)‐mediated cell death against nonhost pathogens and the development of disease‐associated cell death caused by the host pathogen P. syringae pv. tabaci. Our results further demonstrate that NbSGT1 is required for Erwinia carotovora‐ and Sclerotinia sclerotiorum‐induced disease‐associated cell death. Overexpression of NbSGT1 in N. benthamiana accelerates the development of HR during R gene‐mediated disease resistance and nonhost resistance. Our data also indicate that SGT1 is required for pathogen‐induced cell death, but is not always necessary for the restriction of bacterial multiplication in planta. Therefore, we conclude that SGT1 is an essential component affecting the process of cell death during both compatible and incompatible plant–pathogen interactions.     

Microclimatic factors associated with elevational changes in army ant density in tropical montane forest

Abstract.  1. The density (rate of encountering foraging raids) and species richness of army ants (Formicidae: Ecitoninae, and behaviourally convergent Ponerinae) was measured in montane tropical forest. Above-ground and subterranean army ant raids were sampled using standard protocols at four sites across an elevational gradient (1200–1650 m above mean sea level) in and near cloud forest in the area of Monteverde, Costa Rica.
2. Mean ambient temperature differed among sites, and decreased with elevation. For the above-ground foraging army ant species, raid rates also declined with elevation. Surface army ant raid rates, however, were not affected by day to day weather variation within sites (temperature, cloud cover, or precipitation).
3. For the underground foraging army ant species, raid rates did not vary directionally with elevation, and subterranean raid rates were not affected by day to day weather variation within sites.
4. Army ant species richness was not directionally related to elevation, and species sharing among sites was generally high.
5. Army ant community structure changes with elevation in Neotropical montane forest, and the results suggest that the strongest effects are of temperature regimes on the density of raids. These findings provide a baseline against which to detect changes in army ant communities that may accompany directional climate change in tropical cloud forests.     

EFFECT OF VARIETAL DIFFERENCES AND POLISHING OF RICE ON QUALITY PARAMETERS OF IDLI

The effect of varietal differences and polishing of rice on quality parameters of “idli,” an Indian fermented product, were studied. In addition, the functional properties of decorticated (whole and split) black gram (Phaseolus mungo Roxb.), were also determined. Two varieties of raw rice, “Jaya” and “Minilong,” and one variety of parboiled rice “Ponni” with two degrees of polishing (high and low) were selected. Idlis were prepared following standard procedures. Variations were observed in water and fat absorption capacities of two black gram samples. Emulsification capacity ranged from 102 to 110 mL/100 g. Foam capacities at different pH range were similar, but foam stability differed as a function of time. The pH of the fermented batter was between 4.1 and 4.8. Rice with a lesser degree of polishing fermented better with higher batter volume and microbial count, lesser shear value and gave softer idlis. However, sensory analysis revealed that idlis prepared with low‐polish rice scored significantly lower for appearance and color quality compared with products prepared with high‐polish rice. Significant differences were observed in the quality of flavor of all products. It can be concluded that the quality characteristics of Idli were influenced by the variety of rice and the degree of polishing, but the two types of black gram used, whole and split, had no effect.     

Roles,and establishment,maintenance and erasing of the epigenetic cytosine methylation marks in plants

Heritable information in plants consists of genomic information in DNA sequence and epigenetic information superimposed on DNA sequence. The latter is in the form of cytosine methylation at CG, CHG and CHH elements (where H = A, T or C) and a variety of histone modifications in nucleosomes. The epialleles arising from cytosine methylation marks on the nuclear genomic loci have better heritability than the epiallelic variation due to chromatin marks. Phenotypic variation is increased manifold by epiallele comprised methylomes. Plants (angiosperms) have highly conserved genetic mechanisms to establish, maintain or erase cytosine methylation from epialleles. The methylation marks in plants fluctuate according to the cell/tissue/organ in the vegetative and reproductive phases of plant life cycle. They also change according to environment. Epialleles arise by gain or loss of cytosine methylation marks on genes. The changes occur due to the imperfection of the processes that establish and maintain the marks and on account of spontaneous and stress imposed removal of marks. Cytosine methylation pattern acquired in response to abiotic or biotic stress is often inherited over one to several subsequent generations. Cytosine methylation marks affect physiological functions of plants via their effect(s) on gene expression levels. They also repress transposable elements that are abundantly present in plant genomes. The density of their distribution along chromosome lengths affects meiotic recombination rate, while their removal increases mutation rate. Transposon activation due to loss of methylation causes rearrangements such that new gene regulatory networks arise and genes for microRNAs may originate. Cytosine methylation dynamics contribute to evolutionary changes. This review presents and discusses the available evidence on origin, removal and roles of cytosine methylation and on related processes, such as RNA directed DNA methylation, imprinting, paramutation and transgenerational memory in plants.     

印度小圆胸小蠹的一种新寄主植物

自然条件下印度小圆胸小蠹Euwallacea fornicatus(Eichhoff,1868)在茶树枝条虫瘿内取食,是茶的重要害虫之一,以茶蛀虫著称.2010年5-8月,在印度Muga Eri研究中心3号农场(Lahdoigarh,Jorhat-Assam)的黄心树Persea bombycina Kost.(樟科)...