GTPase activity and biochemical characterization of a recombinant cotton fiber annexin.
A cDNA encoding annexin was isolated from a cotton (Gossypium hirsutum) fiber cDNA library. The cDNA was expressed in Escherichia coli, and the resultant recombinant protein was purified. We then investigated some biochemical properties of the recombinant annexin based on the current understanding of plant annexins. An "add-back experiment" was performed to study the effect of the recombinant annexin on beta-glucan synthase activity, but no effect was found. However, it was found that the recombinant annexin could display ATPase/GTPase activities. The recombinant annexin showed much higher GTPase than ATPase activity. Mg2+ was essential for these activities, whereas a high concentration of Ca2+ was inhibitory. A photolabeling assay showed that this annexin could bind GTP more specifically than ATP. The GTP-binding site on the annexin was mapped into the carboxyl-terminal fourth repeat of annexin from the photolabeling experiment using domain-deletion mutants of this annexin. Northern-blot analysis showed that the annexin gene was highly expressed in the elongation stages of cotton fiber differentiation, suggesting a role of this annexin in cell elongation. (+info)
A GroEL homologue from endosymbiotic bacteria of the whitefly Bemisia tabaci is implicated in the circulative transmission of tomato yellow leaf curl virus.
Evidence for the involvement of a Bemisia tabaci GroEL homologue in the transmission of tomato yellow leaf curl geminivirus (TYLCV) is presented. A approximately 63-kDa protein was identified in B. tabaci whole-body extracts using an antiserum raised against aphid Buchnera GroEL. The GroEL homologue was immunolocalized to a coccoid-shaped whitefly endosymbiont. The 30 N-terminal amino acids of the whitefly GroEL homologue showed 80% homology with that from different aphid species and GroEL from Escherichia coli. Purified GroEL from B. tabaci exhibited ultrastructural similarities to that of the endosymbiont from aphids and E. coli. In vitro ligand assays showed that tomato yellow leaf curl virus (TYLCV) particles displayed a specific affinity for the B. tabaci 63-kDa GroEL homologue. Feeding whiteflies anti-Buchnera GroEL antiserum before the acquisition of virions reduced TYLCV transmission to tomato test plants by >80%. In the haemolymph of these whiteflies, TYLCV DNA was reduced to amounts below the threshold of detection by Southern blot hybridization. Active antibodies were recovered from the insect haemolymph suggesting that by complexing the GoEL homologue, the antibody disturbed interaction with TYLCV, leading to degradation of the virus. We propose that GroEL of B. tabaci protects the virus from destruction during its passage through the haemolymph. (+info)
Histological changes in the rat common carotid artery induced by aneurysmal wrapping and coating materials.
Histological changes in and around the arterial walls of rats were investigated following topical application of aneurysmal wrapping and coating materials, including a fibrin glue, a cyanoacrylate glue (Biobond), and cotton fibers (Bemsheet). Bilateral common carotid arteries were exposed using sterile techniques, and one of the test materials was applied to the right artery. The left artery was used as the control. Changes in arterial histology were evaluated at 2 weeks, 1 month, 2 months, and 3 months after surgery. The fibrin glue was surrounded by intense inflammation at 2 weeks after surgery. Both the fibrin glue and inflammation had disappeared at 2 months, but the glue had induced mild inflammation in the adventitia. Biobond caused chronic inflammation, necrosis of the media, and thickening of the arterial wall due to fibrosis in both the media and adventitia. Bemsheet produced chronic inflammation, progressive fibrosis, and granuloma. Connective tissue increased in the adventitia, but no major changes were observed in the media. The Bemsheet fibers remained unchanged, and adhered to the arterial wall. Although arterial stenoses were not observed in the present study, the results suggest that cyanoacrylate glue can cause the arterial occlusive lesions observed following aneurysm surgery. (+info)
Toxicity of combustion products from burning polymers: development and evaluation of methods.
Laboratory and room-scale experiments were conducted with natural and synthetic polymers: cotton, paper, wood, wool, acetate, acrylic, nylon, and urethane. Smoke and off-gases from single materials were generated in a dual-compartment 110-liter exposure chamber. Multicomponent, composite fuel loads were burned within a 100 m(3) facility subdivided into rooms. In chamber experiments, mortality depended on the amount of material burned, i.e., fuel consumption (FC). Conventional dose (FC)/mortality curves were obtained, and the amount of fuel required to produce 50% mortality (FC(50)) was calculated. With simple flame ignition, cotton was the only material that produced smoke concentrations lethal to rats; FC(50) values for cotton ranged from 2 g to 9 g, depending on the configuration of the cotton sample burned. When supplemental conductive heat was added to flame ignition, the following FC(50) values were obtained; nylon, 7 g; acrylic, 8 g; newsprint, 9 g; cotton, 10 g; and wood, 11 g. Mortality resulting from any given material depended upon the specific conditions employed for its thermal decomposition. Toxicity of off-gasses from pyrolysis of phosphorus-containing trimethylol propane-polyurethane foams was markedly decreased by addition of a flame ignition source. Further studies are needed to determine the possible relevance of single-material laboratory scale smoke toxicity experiments. Room-scale burns were conducted to assess the relative contributions of single materials to toxicity of smoke produced by a multicomponent self-perpetuating fire. Preliminary results suggest that this approach permits a realistic evaluation of the contribution of single materials to the toxicity of smoke from residential fires. (+info)
Low levels of nucleotide diversity at homoeologous Adh loci in allotetraploid cotton (Gossypium L.).
Levels of genetic diversity within and among populations and species are shaped by both external (population-level) and internal (genomic and genic) evolutionary forces. To address the effect of internal pressures, we estimated nucleotide diversity for a pair of homoeologous Adh loci in an allotetraploid species, Gossypium hirsutum. These data represent the first such estimates for a pair of homoeologous nuclear loci in plants. Estimates of nucleotide diversity for AdhA in Gossypium are lower than those for any plant nuclear gene yet described. This low diversity appears to reflect primarily a history of repeated, severe genetic bottlenecks associated with both speciation and recent domestication, supplemented by an unusually slow nucleotide substitution rate and an autogamous breeding system. While not statistically supportable, the sum of the observations also suggest differential evolutionary dynamics at each of the homoeologous loci. (+info)
Identification of a novel circular single-stranded DNA associated with cotton leaf curl disease in Pakistan.
Recent reports have suggested that cotton leaf curl virus (CLCuV), a geminivirus of the genus Begomovirus, may be responsible for cotton leaf curl disease in Pakistan. However, the causal agent of the disease remains unclear as CLCuV genomic components resembling begomovirus DNA A are unable to induce typical disease symptoms when reintroduced into plants. All attempts to isolate a genomic component equivalent to begomovirus DNA B have been unsuccessful. Here, we describe the isolation and characterisation of a novel circular single-stranded (ss) DNA associated with naturally infected cotton plants. In addition to a component resembling DNA A, purified geminate particles contain a smaller unrelated ssDNA that we refer to as DNA 1. DNA 1 was cloned from double-stranded replicative form of the viral DNA isolated from infected cotton plants. Blot hybridisation using probes specific for either CLCuV DNA or DNA 1 was used to demonstrate that both DNAs co-infect naturally infected cotton plants from different geographical locations. DNA 1 was detected in viruliferous Bemisia tabaci and in tobacco plants infected under laboratory conditions using B. tabaci, indicating that it is transmitted by whiteflies. Sequence analysis showed that DNA 1 is approximately half the size of CLCuV DNA but shares no homology, indicating that it is not a defective geminivirus component. DNA 1 has some homology to a genomic component of members of Nanoviridae, a family of DNA viruses that are normally transmitted by aphids or planthoppers. DNA 1 encodes a homologue of the nanovirus replication-associated protein (Rep) and has the capacity to autonomously replicate in tobacco. The data suggest that a nanovirus-like DNA has become whitefly-transmissible as a result of its association with a geminivirus and that cotton leaf curl disease may result from a mutually dependent relationship that has developed between members of two distinct DNA virus families that share a similar replication strategy. (+info)
Gene-specific changes in alpha-tubulin transcript accumulation in developing cotton fibers.
The fibers of cotton (Gossypium hirsutum) are single-cell trichomes that undergo rapid and synchronous elongation. Cortical microtubules provide spatial information necessary for the alignment of cellulose microfibrils that confine and regulate cell elongation. We used gene-specific probes to investigate alpha-tubulin transcript levels in elongating cotton fibers. Two discrete patterns of transcript accumulation were observed. Whereas transcripts of alpha-tubulin genes GhTua2/3 and GhTua4 increased in abundance from 10 to 20 d post anthesis (DPA), GhTua1 and GhTua5 transcripts were abundant only through to 14 DPA, and dropped significantly at 16 DPA with the onset of secondary wall synthesis. This is the first report, to our knowledge, of gene-specific changes in tubulin transcript levels during the development of a terminally differentiated plant cell. The decrease in abundance of GhTua1 and GhTua5 transcripts was correlated with pronounced changes in cell wall structure, suggesting that alpha-tubulin isoforms may be functionally distinct in elongating fiber cells. Although total alpha-tubulin transcript levels were much higher in fiber than several other tissues, including the hypocotyl and pollen, none of the alpha-tubulins was specific to fiber cells. (+info)
Respiratory symptoms in Lancashire textile weavers.
OBJECTIVES: To investigate a large population of cotton textile weavers for reported respiratory symptoms relative to occupational factors, smoking, and exposure to dust. Cotton processing is known to produce a respiratory disease known as byssinosis particularly in the early processes of cotton spinning. Relatively little is known about the respiratory health of the cotton weavers who produce cloth from spun cotton. By the time cotton is woven many of the original contaminants have been removed. METHODS: 1295 operatives from a target population of 1428 were given an interviewer led respiratory questionnaire. The presence of upper and lower respiratory tract symptoms were sought and the work relatedness of these symptoms determined by a stem questionnaire design. Also occupational and demographic details were obtained and spirometry and personal dust sampling performed. RESULTS: Byssinosis was present in only four people (0.3%). Chronic bronchitis had a moderate overall prevalence of about 6% and was related predominantly to smoking. There were several other work related respiratory symptoms (persistent cough 3.9%, chronic production of phlegm 3.6%, chest tightness 4.8%, wheezing 5.4%, and breathlessness 2.3%). All of these were predicted predominantly by smoking (either past or present), with no consistent independent effect of exposure to dust. Work related eye and nasal symptoms were more common (10.4% and 16.9% respectively). CONCLUSION: Byssinosis is a rare respiratory symptom in cotton weaving. Other work related respiratory symptoms were reported but their presence was predominantly related to smoking with no consistent effects of exposure to dust. (+info)