Microtubule- and actin filament-dependent motors are distributed on pollen tube mitochondria and contribute differently to their movement

The pollen tube exhibits cytoplasmic streaming of organelles, which is dependent on the actin-myosin system. Although microtubule-based motors have also been identified in the pollen tube, many uncertainties exist regarding their role in organelle transport. As part of our attempt to understand the role of microtubule-based movement in the pollen tube of tobacco, we investigated the cooperation between microtubules and actin filaments in the transport of mitochondria and Golgi vesicles, which are distributed differently in the growing pollen tube. The analysis was performed using in vitro motility assays in which organelles move along both microtubules and actin filaments. The results indicated that the movement of mitochondria and Golgi vesicles is slow and continuous along microtubules but fast and irregular along actin filaments. In addition, the presence of microtubules in the motility assays forces organelles to use lower velocities. Actin- and tubulin-binding tests, immunoblotting and immunogold labeling indicated that different organelles bind to identical myosins but associate with specific kinesins. We found that a 90 kDa kinesin (previously known as 90 kDa ATP-MAP) is associated with mitochondria but not with Golgi vesicles, whereas a 170 kDa myosin is distributed on mitochondria and other organelle classes. In vitro and in vivo motility assays indicate that microtubules and kinesins decrease the speed of mitochondria, thus contributing to their positioning in the pollen tube.     

Age and nutrient limitation enhance polyunsaturated aldehyde production in marine diatoms

Skeletonema marinoi produces 2,4-heptadienal, 2,4-octadienal, and 2,4,7-octatrienal, the latter only in traces. In nutrient-replete cultures, the production of potentially defensive polyunsaturated aldehydes (PUA) increases from the exponential to the stationary phase of growth from 1.2 fmol cell(-1) (+/-0.4 fmol cell(-1) SD) to 4.2 fmol cell(-1) (+/-1.0 fmol cell(-1) SD), with 2,4-heptadienal as the dominant aldehyde. The plasticity of PUA production with age of the culture supports the hypothesis of a direct link between toxin production and cell physiological state. N- and P-limited cells in stationary phase produced 1.4 and 1.8 fold higher amounts of PUA than control cultures and 10.7 and 4.6 times higher PUAs when compared to their own exponential growth phase, respectively. The increase in PUA production in the nutrient-limited cultures was not paralleled by an increase in the total amount of precursor fatty acids indicating that physiological stress might trigger an enhanced expression or activity of the enzymes responsible for PUA production, i.e. chemical defense increase in aged and nutrient-stressed diatoms. If this holds true during blooms, grazers feeding at the end of a bloom would be more affected than early-bloom grazers.     

Anisocotyly and meristem initiation in an unorthodox plant, <Emphasis Type="Italic">Streptocarpus rexii</Emphasis> (Gesneriaceae)

In common with most Old World Gesneriaceae; Streptocarpus Lindl. shows anisocotylous growth, i.e., the continuous growth of one cotyledon after germination. Linked to this phenomenon is an unorthodox behaviour of the shoot apical meristem (SAM) that determines the growth pattern of acaulescent species (subgenus Streptocarpus). In contrast caulescent species develop a conventional central post-embryonic SAM (mainly subgenus Streptocarpella). We used S. rexii Lindl. as a model to investigate anisocotyly and meristem initiation in Streptocarpus by using histological techniques and analyses of the expression pattern of the meristematic marker SrSTM1 during ontogeny. In contrast to Arabidopsis thaliana (L.) Heynh., S. rexii does not establish a SAM during embryogenesis, and the first evidence of a SAM-like structure occurs during post-embryonic development on the axis (the petiolode) between the two cotyledons. The expression pattern of SrSTM1 suggests a function in maintaining cell division activity in the cotyledons before becoming localized in the basal meristem, initially at the proximal ends of both cotyledons, later at the base of the continuously growing macrocotyledon, and the groove meristem on the petiolode. The latter is equivalent to a displaced SAM seemingly originating de novo under the influence of endogenous factors. Applied cytokinin retains SrSTM1expression in the small cotyledon, thus promoting isocotyly and re-establishment of a central post-embryonic SAM. Hormone-dependent delocalization of the process of meristem development could underlie anisocotyly and the unorthodox SAM formation in Streptocarpus. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

On-line detection of atmospheric formaldehyde by a conductometric biosensor

Atmospheric formaldehyde (CH(2)O) was detected under continuous flow conditions by an on-line system comprising of a wet scrubber for a continuous transfer of the pollutant to an aqueous solution, a micro-reactor containing immobilized formaldehyde dehydrogenase (FDH) and a conductometric transducer. By this system atmospheric formaldehyde concentrations in the range 0.05-2 ppm were detected with a sensitivity of 20 microS/ppm. In this concentration range the immobilized enzyme oxidized all the sampled formaldehyde molecules to formic acid, avoiding cumbersome calibration procedures. The operational stability of the biosensor was at least 3 months, working continuously 10 h/day at room temperature.     

Twenty-four novel mutations in Wilson disease patients of predominantly Italian origin

Herein we report the results of mutation analysis of the ATP7B gene in a group of 134 Wilson disease (WD) families (268 chromosomes) prevalently of Italian origin. Using the SSCP and sequencing methods we identified 71 disease-causing mutations. Twenty-four were novel, while 19 more mutations already described, were identified in new populations in this study. A known mutation G591D showed a regional distribution, since it was only detected in 38.5% of the analyzed chromosomes in WD patients originating from Apulia, a region of South Italy. Detection of new mutations in the ATP7B gene increases our capability of molecular analysis that is essential for early diagnosis and treatment of WD.     

Action-related properties shape object representations in the ventral stream

The principles driving the organization of the ventral object-processing stream remain unknown. Here, we show that stimulus-specific repetition suppression (RS) in one region of the ventral stream is biased according to motor-relevant properties of objects. Quantitative analysis confirmed that this result was not confounded with similarity in visual shape. A similar pattern of biases in RS according to motor-relevant properties of objects was observed in dorsal stream regions in the left hemisphere. These findings suggest that neural specificity for "tools" in the ventral stream is driven by similarity metrics computed over motor-relevant information represented in dorsal structures. Support for this view is provided by converging results from functional connectivity analyses of the fMRI data and a separate neuropsychological study. More generally, these data suggest that a basic organizing principle giving rise to "category specificity" in the ventral stream may involve similarity metrics computed over information represented elsewhere in the brain.     

Heavy metal sorption by released polysaccharides and whole cultures of two exopolysaccharide-producing cyanobacteria

The metal removal capacity of cultures of two capsulated, exopolysaccharide-producing cyanobacteria, Cyanospira capsulata and Nostoc PCC7936, were tested using copper (II) as the model metal. C. capsulata cultures removed the greatest amount of copper, with a maximum per unit of biomass (q _max) of 115.0±5.1 mg copper g⁻¹ of protein, compared with 85.0±3.2 removed with Nostoc PCC7936 cultures. Water solutions of pure polysaccharides (RPSs) released into the culture medium by C. capsulata and Nostoc PCC7936 achieved q _max values of 20.2±0.8 mg g⁻¹ copper per polysaccharide dry weight with C. capsulata RPS and 11.0±1.5 mg g⁻¹ with Nostoc PCC7936 RPS. Cultures of the two cyanobacteria also removed Zn (II) and Ni (II), in both single-metal systems and in multimetal systems with Cu; in the various single-metal systems more copper was removed than Zn or Ni, while in the multimetal systems a smaller amount of each individual metal was removed but the overall amount of all metal ions sorbed or the amount of copper sorbed in the copper-only system was almost the same with C. capsulata, and slightly higher with Nostoc PCC7936.     

GATA elements control repression of cardiac troponin I promoter activity in skeletal muscle cells

Background  

We reported previously that the cardiac troponin I (cTnI) promoter drives cardiac-specific expression of reporter genes in cardiac muscle cells and in transgenic mice, and that disruption of GATA elements inactivates the cTnI promoter in cultured cardiomyocytes. We have now examined the role of cTnI promoter GATA elements in skeletal muscle cells.