Import oligomers induce positive feedback to promote peroxisome differentiation and control organelle abundance

A fundamental question in cell biology is how cells control organelle composition and abundance. Woronin bodies are fungal peroxisomes centered on a crystalline core of the self-assembled HEX protein. Despite using the canonical peroxisome import machinery for biogenesis, Woronin bodies are scarce compared to the overall peroxisome population. Here, we show that HEX oligomers promote the differentiation of a subpopulation of peroxisomes, which become enlarged and highly active in matrix protein import. HEX physically associates with the essential matrix import peroxin, PEX26, and promotes its enrichment in the membrane of differentiated peroxisomes. In addition, a PEX26 mutant that disrupts differentiation produces increased numbers of aberrantly small Woronin bodies. Our data suggest a mechanism where HEX oligomers recruit a key component of the import machinery, which promotes the import of additional HEX. This type of positive feedback provides a basic mechanism for the production of an organelle subpopulation of distinct composition and abundance.     

Abnormal mitochondrial dynamics and synaptic degeneration as early events in Alzheimer's disease: implications to mitochondria-targeted antioxidant therapeutics

Synaptic pathology and mitochondrial oxidative damage are early events in Alzheimer's disease (AD) progression. Loss of synapses and synaptic damage are the best correlates of cognitive deficits found in AD patients. Recent research on amyloid beta (Aβ) and mitochondria in AD revealed that Aβ accumulates in synapses and synaptic mitochondria, leading to abnormal mitochondrial dynamics and synaptic degeneration in AD neurons. Further, recent studies using live-cell imaging and primary neurons from amyloid beta precursor protein (AβPP) transgenic mice revealed reduced mitochondrial mass, defective axonal transport of mitochondria and synaptic degeneration, indicating that Aβ is responsible for mitochondrial and synaptic deficiencies. Tremendous progress has been made in studying antioxidant approaches in mouse models of AD and clinical trials of AD patients. This article highlights the recent developments made in Aβ-induced abnormal mitochondrial dynamics, defective mitochondrial biogenesis, impaired axonal transport and synaptic deficiencies in AD. This article also focuses on mitochondrial approaches in treating AD, and also discusses latest research on mitochondria-targeted antioxidants in AD. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.     

Centenary commemorations or centenary contestations?—Celebrating a hundred years of cinema in Bombay

The commemorations of the hundredth year of the arrival of cinema in India staged by the Government of Maharashtra were a combination of public and semi‐public rituals inscribing the history of cinema in India onto the urban landscape of Bombay. This article examines those commemorations to show how the history of cinema becomes an arena for the state to proclaim its distinct cultural identity. The centenary commemorations are an example of how a world‐historical moment like the Lumière screenings is appropriated by the state government to assert a particular cultural claim over the city of Bombay.     

Review in vitro-induced flowering in bamboos

Summary The majority of bamboos (Graminae) are arborescent and perennial. The erect stems (culms) of woody bamboos are useful for a wide variety of purposes. Most bamboos flower only once at the end of very long vegetative growth phases and die afterwards. Flowering in bamboos is thought to be under genetic control, occurring somewhat like an alarm clock, going off at a preset time. The nature of this genetic clock and any interaction between the ‘internal clock’ and the environment are not yet known. Because of this ‘peculiar’ flowering behavior, bamboo seeds are available only at very long intervals. Obtaining concurrent flowering in two or more species (or varieties) in space and time is difficult, making perennial seed propagation and genetic improvement by breeding nearly impossible. Besides, this peculiar flowering behavior of bamboos is also believed to have brought the giant pandas to the verge of extinction. One of the spectacular developments in the area of bamboo genetic improvement has been the precocious in vitro induction of flowering. By this method it has been possible to rapidly accelerate the reproductive development (within 3–6 mo. versus 30–60 yr in nature). This has opened the possibility of perennial seed propagation and hybridization. In vitro induction of flowering can be obtained by diverse methods which show some similarities and differences. Induction of flowering is possible in cultures derived from both juvenile and mature explants. The proportion of seedlings induced to flower is possibly influenced by genotypic variation, though the role of methods used cannot be ruled out. A cytokinin or a shift in the auxin-cytokinin equilibrium is believed to bring about in vitro induction of flowering. The pH of the media also has an influence. Induction of flowering and rhizogenesis is considered to be an antagonistic phenomenon in vitro. A comparison between in vitro and in vivo flowering in Bambusa arundinacea has shown that though smaller, in vitro-induced florets are comparable to normal florets. There is reduced pollen fertility and some impairment in pollen wall development. Biochemical studies on the in vitro-induced flowering in bamboos have shown (1) selective expression of esterase and peroxidase isozymes during transition of nonembryogenic calluses to embryogenic calluses, somatic embryo development, germination and subsequent flowering of somatic embryo derived shoots, and (2) minimal peroxidase activity before rhizogenesis and induction of flowering in vitro. There are reports of published and comparable methods having failed to induce flowering in vitro.     

Le gisement acheuléen de plein air de La Garde (Loire). Remarques sur une série lithique acheuléenne entre Rhône et Loire

The lithic assemblage of La Garde offers the opportunity to observe a Final Acheulean series located in the Loire department (south-east France). The site was probably a multi-activity place asking large tools and flakes, according to the strategies used by humans. Three main categories of large bifacial tools mainly made of flint can be described, with a triangular or oval shape and with a transversal cutting edge. These tools are more bifacial-tools than bifaces through the kind of shaping and the retouches on the cutting edges. The Levallois flaking is associated to various other types of knapping. The site, located along a small valley, suggests a human circulating between the Saône-Rhône corridor and the interior basins of the Massif Central Mountains. The Rhodanian corridor yielded little evidence of Acheulean settlements while in the Centre of France, they are numerous. La Garde proves that systematic prospecting in this area will permit in future to complete the map of the Acheulean occupations in south-east France.     

Bud break and multiple shoot formation from tissues of mature trees ofPinus caribaea andPinus kesiya

Summary Proliferation of terminal and axillary buds of 20 yr-oldPinus caribaea andP. kesiya trees was obtained on half strength DCR medium supplemented with 0.5 mg·liter^−1 6-benzylaminopurine (BA). These sprouts further elongated with the formation of multiple shoots with the ratio of 1:3, on transfer to medium in which the 0.25 mg·liter^−1 BA of the initiation medium was replaced by 0.25 mg·liter^−1 kinetin. Rooting was obtained on the same medium. Plantlets thus formed were transferred to perlite:peat:vermiculite mixture (1:1:1) in polybags (10×5 cm) under 80±5% humidity in a polyhouse. Plantlets ofP. caribaea andP. kesiya were established with 72.5 and 83.3% survival, respectively.     

Purification of a Class B1 platelet aggregation inhibitor phospholipase A2 from Indian cobra (Naja Naja) venom

A platelet aggregation inhibitor phospholipase A(2) (NND-IV-PLA(2)) was isolated from Naja naja (Eastern India) venom by a combination of cation and anion exchange chromatography. NND-IV-PLA(2) is the most catalytically active enzyme isolated from the Indian cobra venom. The acidic PLA(2) profile of Eastern regional Indian cobra venom is distinctly different from that of the western regional venom. However the acidic PLA(2)s from both the regions follow the pattern of increasing catalytic activity with increase in acidic nature of the PLA(2) isoform. NND-IV-PLA(2) is a Class B1 platelet aggregation inhibitor and inhibits platelet aggregation induced by ADP, collagen and epinephrine. Modification of active site histidine abolishes both catalytic activity and platelet aggregation inhibition activities while aristolochic acid, a phospholipase A(2) inhibitor has only partial effect on the two activities.     

Identification of prosaposin and transgelin as potential biomarkers for gallbladder cancer using quantitative proteomics

Gallbladder cancer is an uncommon but lethal malignancy with particularly high incidence in Chile, India, Japan and China. There is a paucity of unbiased large-scale studies investigating molecular basis of gallbladder cancer. To systematically identify differentially regulated proteins in gallbladder cancer, iTRAQ-based quantitative proteomics of gallbladder cancer was carried out using Fourier transform high resolution mass spectrometry. Of the 2575 proteins identified, proteins upregulated in gallbladder cancer included several lysosomal proteins such as prosaposin, cathepsin Z and cathepsin H. Downregulated proteins included serine protease HTRA1 and transgelin, which have been reported to be downregulated in several other cancers. Novel biomarker candidates including prosaposin and transgelin were validated to be upregulated and downregulated, respectively, in gallbladder cancer using tissue microarrays. Our study provides the first large scale proteomic characterization of gallbladder cancer which will serve as a resource for future discovery of biomarkers for gallbladder cancer.     

In vitro plantlet regeneration from mature zygotic embryos of Pinus wallichiana A.B. Jacks

 Plantlet regeneration was achieved in blue pine (Pinus wallichiana A.B. Jacks) by organogenesis of mature zygotic embryos. The effect of various basal media and five cytokinins on adventitious bud induction, development and elongation was investigated. Half-strength Douglas fir cotyledon revised medium (DCR) supplemented with 2.5 μm N⁶-benzyladinine (BA) and 0.025 μM thidiazuron was found to be most effective in inducing adventitious buds. The effect of a BA pulse treatment was also tested, and the bud-forming capacity of each treatment was quantified. The elongation of adventitious buds was achieved on hormone-free half-strength DCR medium containing 2% sucrose and 0.05% activated charcoal. Rooting was induced in the elongated shoots with a 6-h treatment of indoleacetic acid and indolebutyric acid solutions (1 mM each). Rooted shoots were transplanted in the greenhouse for hardening and their survival percentage was 64.4 after 5 weeks and 45.7 after 6 months. Received: 11 September 1998 / Revision received: 10 February 1999 / Accepted: 26 February 1999