Latest Articles Include:
- Embryonic developments
- Curr Biol 19(11):R427-R428 (2009)
As the UK updates its pioneering Human Fertilisation and Embryology Act, legal boundaries for research in the life sciences are redrawn in other countries as well. Michael Gross reports. - Swallow surprise
- Curr Biol 19(11):R428-R429 (2009)
It's the centenary of the first bird ringing that led to information about the extraordinary migration of the swallow. Nigel Williams reports. - Coral fears
- Curr Biol 19(11):R429-R430 (2009)
The rich coral reefs of south-east Asia are under increasing threat from human activity and climate change. Nigel Williams reports. - Fruit heartland threatened
- Curr Biol 19(11):R431-R432 (2009)
Many fruit tree species in a recently discovered Asian garden of Eden are increasingly endangered. Nigel Williams reports. - Science first
- Curr Biol 19(11):R432 (2009)
Major explorations remain off the menu for one society. Nigel Williams reports. - Knocking birds
- Curr Biol 19(11):R433 (2009)
- Matthew Cobb
- Curr Biol 19(11):R434-R435 (2009)
- Ocelli
Krapp HG - Curr Biol 19(11):R435-R437 (2009)
- The natural history of antibiotics
Clardy J Fischbach MA Currie CR - Curr Biol 19(11):R437-R441 (2009)
- A neural basis for unique hues?
Mollon JD - Curr Biol 19(11):R441-R442 (2009)
The four perceptually simple colors — red, green, yellow and blue — are a challenge to neuroscience, because no one has found cortical cells that represent color in terms of these 'unique hues' [1]. The chromatically selective cells at early stages of the primate visual system do not map on to the unique hues [2] and [3]. Recently, however, Stoughton and Conway [4] have reported that the peak sensitivities of color cells in posterior inferior temporal cortex do cluster near the unique hues. The authors plot their results as a polar histogram: at each position on a hue circle, they show the number of cells that are maximally excited by that hue. There are three peaks in the histogram: one (the largest) falls close to unique red and another falls close to unique blue, while the third (less well-defined) lies in the yellow-green region. In fact, however, if the stimuli used in the experiment are plotted in a physiological color space, they form not a circle but an! obtuse triangle. The peaks identified by Stoughton and Conway [4] fall at the apices of this triangle. Because these stimuli maximize the ratios of cone signals, they would maximally excite cells earlier in the visual system. So Stoughton and Conway's polar plot does not in itself show that cells of the posterior inferior temporal cortex represent unique hues, nor that they differ qualitatively in their behavior from chromatic cells at an earlier level. - Response: Towards a neural representation for unique hues
- Curr Biol 19(11):R442-R443 (2009)
We recently reported that a population of color-tuned neurons in posterior inferior temporal cortex of macaque monkey represents all colors and that this population shows a bias towards certain colors: we found that many cells were tuned to red, followed by peaks to green, blue, and an indistinct peak corresponding to yellow [1]. This appears to be the closest explicit neural representation of unique hues found in the primate. John Mollon suggests that the distribution is what one would expect of neurons found earlier in the visual pathway, in lateral geniculate nucleus (LGN), if tested with the colors we used to measure tuning. Previous work has shown that LGN cells respond linearly to changes in cone contrast and do not represent unique hues. While we acknowledge that our stimuli would constrain the population's color-tuning distribution if the neurons were linear, the recorded cells have narrow nonlinear color tuning, quite unlike LGN cells. Thus, the population tun! ing is consistent with our initial interpretation. - CNS Regeneration: Only on One Condition
Silver J - Curr Biol 19(11):R444-R446 (2009)
The mammalian CNS is usually not capable of regeneration. However, conditioning dorsal root ganglion neurons by first lesioning their peripheral axons allows for regeneration of their central axons later on within the spinal cord. New work shows that, even if the sequence of lesioning is reversed, regeneration through the CNS lesion can rapidly occur under certain conditions. - Insect Bioacoustics: Mosquitoes Make an Effort to Listen to Each Other
Robert D - Curr Biol 19(11):R446-R449 (2009)
As they encounter each other in flight, male and female mosquitoes alter their wing beat to bring their flight tones closer together. Two recent studies provide new insights into the complex auditory processing required for this behaviour. - Nuclear Dimorphism: Two Peas in a Pod
Goldfarb DS Gorovsky MA - Curr Biol 19(11):R449-R452 (2009)
The macro- and micronuclei of Tetrahymena reside in the same cytoplasm but are about as different as night and day. This extreme case of nuclear dimorphism can now be partially attributed to differences in the subunit compositions of their nuclear pore complexes. - Bacterial Development: Evidence for Very Short Umbilical Cords
Kroos L - Curr Biol 19(11):R452-R453 (2009)
Higher eukaryotes have channels, such as gap junctions and plasmodesmata, that allow intercellular communication. Recent studies on endospore formation in Bacillus subtilis suggest that an analogous structure may exist in prokaryotes. - Intracellular Signaling: Peripatetic Ras
Fehrenbacher N Philips M - Curr Biol 19(11):R454-R457 (2009)
Ras proteins traffic between the plasma membrane and endomembranes and signal from the cytosolic face of a variety of organelles. Palmitoylated N-Ras and H-Ras signal from early endosomes. A recent study reports that K-Ras resides on and signals from various types of endosomes, including late endosomes/lysosomes and multivesicular bodies. - Gut Microbiology: Fitting into the Intestinal Neighbourhood
Willing BP Finlay BB - Curr Biol 19(11):R457-R459 (2009)
Microbes inhabiting the gut affect our health in profound and unexpected ways: new studies now show that these effects depend on synergistic and competitive interactions between the bacteria, which are influenced by diet. - Meristems: The Root of Stem Cell Regulation
Dolan L - Curr Biol 19(11):R459-R460 (2009)
The stem cells from which the plant body develops are located in shoot and root meristems, and new research shows that the balance between proliferation and differentiation in each is controlled by related proteins that interact in a similar feedback network. - Circadian Rhythms: A Tale of Two Nuclei
Schwartz WJ - Curr Biol 19(11):R460-R462 (2009)
Uncoupling the oscillators in the dorsal and ventral subdivisions of the rat suprachiasmatic nucleus reveals which one of them regulates the circadian rhythm of rapid eye movement sleep. - Highly Selective Tuning of a Silkworm Olfactory Receptor to a Key Mulberry Leaf Volatile
Tanaka K Uda Y Ono Y Nakagawa T Suwa M Yamaoka R Touhara K - Curr Biol 19(11):881-890 (2009)
Background The olfactory system plays an important role in the recognition of leaf volatiles during the search of folivore insects for a suitable plant host. For example, volatiles emitted by mulberry leaves trigger chemotaxis behavior in the silkworms Bombyx mori, and as a consequence, they preferentially reside on and consume mulberry leaves. Here, we aimed to identify natural chemoattractants and their corresponding olfactory receptors (Ors) involved in silkworm behavior to mulberry leaves. Results Chemotaxis behavioral assays for headspace volatiles detected by gas chromatography-mass spectroscopy analysis revealed that among the volatiles that were emitted by mulberry leaves, cis-jasmone was the most potent attractant for silkworms, working at a threshold of 0.3 pg from a 20 cm distance. Among a total of 66 Ors identified in the B. mori genome, we found that 23 were expressed in the olfactory organs during larval stages. Functional analysis of all the larvae-expressed Ors in Xenopus oocytes revealed that one Or, termed BmOr-56, showed a high sensitivity to cis-jasmone. In addition, the ligand-receptor activity of BmOr-56 reflected the chemotaxis behavioral response of silkworms. Conclusions We identified cis-jasmone as a potent attractant in mulberry leaves for silkworms and provide evidence that a highly tuned receptor, BmOr-56, may mediate this behavioral attraction. The current study sheds light on the mechanism of the correlation between olfactory perception in folivore insects and chemotaxis behavior to a natural volatile emitted by green leaves. - Mechanistic Plasticity of Sexual Reproduction and Meiosis in the Candida Pathogenic Species Complex
Reedy JL Floyd AM Heitman J - Curr Biol 19(11):891-899 (2009)
Background Candida species are microbial pathogens originally thought to be asexual, but several are now recognized as sexual or parasexual. Candida albicans, the most common fungus infecting humans, is an obligate diploid with a parasexual cycle involving mating, recombination, and genome reduction but no recognized meiosis. Others (C. lusitaniae, C. guilliermondii) are haploid, and their mating produces spores, suggestive of complete meiotic sexual cycles. However, comparative genomic analysis reveals that these species lack key meiotic components, including the recombinase Dmc1 and cofactors (Mei5/Sae3), synaptonemal-complex proteins (Zip1-Zip4/Hop1), and the crossover interference pathway (Msh4/5). Results Here we elucidate the structure and functions of the mating-type (MAT) locus and establish that C. lusitaniae undergoes meiosis during its sexual cycle. The MAT-encoded a2 (high-mobility group) and α1 (α domain) factors specify a and α cell identity, whereas the a1 homeodomain protein drives meiosis and sporulation and functions without its canonical heterodimeric partner, α2. Despite the apparent loss of meiotic genes, C. lusitaniae undergoes meiosis during sexual reproduction involving diploid intermediates, frequent SPO11-dependent recombination, and whole-genome reduction generating haploid progeny. The majority of meiotic progeny are euploid, but approximately one-third are diploid/aneuploid. Conclusions The cell identity and meiotic pathways have been substantially rewired, and meiotic generation of both recombinant and aneuploid progeny may expand genetic diversity. These findings inform our understanding of sexual reproduction in pathogenic microbes and the evolutionary plasticity of the meiotic machinery, with implications for the sexual nature of C. albicans and the generation and consequences of aneuploidy in biology and medicine. - A Novel Conus Snail Polypeptide Causes Excitotoxicity by Blocking Desensitization of AMPA Receptors
Walker CS Jensen S Ellison M Matta JA Lee WY Imperial JS Duclos N Brockie PJ Madsen DM Isaac JT Olivera B Maricq AV - Curr Biol 19(11):900-908 (2009)
Background Ionotropic glutamate receptors (iGluRs) are glutamate-gated ion channels that mediate excitatory neurotransmission in the central nervous system. Based on both molecular and pharmacological criteria, iGluRs have been divided into two major classes, the non-NMDA class, which includes both AMPA and kainate subtypes of receptors, and the NMDA class. One evolutionarily conserved feature of iGluRs is their desensitization in the continued presence of glutamate. Thus, when in a desensitized state, iGluRs can be bound to glutamate, yet the channel remains closed. However, the relevance of desensitization to nervous system function has remained enigmatic. Results Here, we report the identification and characterization of a novel polypeptide (con-ikot-ikot) from the venom of a predatory marine snail Conus striatus that specifically disrupts the desensitization of AMPA receptors (AMPARs). The stoichiometry of con-ikot-ikot appears reminiscent of the proposed subunit organization of AMPARs, i.e., a dimer of dimers, suggesting that it acts as a molecular four-legged clamp that holds the AMPAR channel open. Application of con-ikot-ikot to hippocampal slices caused a large and rapid increase in resting AMPAR-mediated current leading to neuronal death. Conclusions Our findings provide insight into the mechanisms that regulate receptor desensitization and demonstrate that in the arms race between prey and predators, evolution has selected for a toxin that blocks AMPAR desensitization, thus revealing the fundamental importance of desensitization for regulating neural function. - A Signaling Module Controlling the Stem Cell Niche in Arabidopsis Root Meristems
Stahl Y Wink RH Ingram GC Simon R - Curr Biol 19(11):909-914 (2009)
The niches of the Arabidopsis shoot and root meristems, the organizing center (OC) and the quiescent center (QC), orchestrate the fine balance of stem cell maintenance and the provision of differentiating descendants. They express the functionally related homeobox genes WUSCHEL (WUS) and WOX5, respectively, that promote stem cell fate in adjacent cells [1]. Shoot stem cells signal back to the OC by secreting the CLAVATA3 (CLV3) dodecapeptide [2], which represses WUS expression [3]. However, the signals controlling homeostasis of the root stem cell system are not identified to date. Here we show that the differentiating descendants of distal root stem cells express CLE40, a peptide closely related to CLV3. Reducing CLE40 levels delays differentiation and allows stem cell proliferation. Conversely, increased CLE40 levels drastically alter the expression domain of WOX5 and promote stem cell differentiation. We report that the receptor kinase ACR4, previously shown to cont! rol cell proliferation [4], is an essential component, and also a target, of CLE40 signaling. Our results reveal how, in contrast to the shoot system, signals originating from differentiated cells, but not the stem cells, determine the size and position of the root niche. - The Global Stock of Domesticated Honey Bees Is Growing Slower Than Agricultural Demand for Pollination
Aizen MA Harder LD - Curr Biol 19(11):915-918 (2009)
The prospect that a global pollination crisis currently threatens agricultural productivity has drawn intense recent interest among scientists, politicians, and the general public [1], [2], [3], [4] and [5]. To date, evidence for a global crisis has been drawn from regional or local declines in pollinators themselves [6], [7], [8] and [9] or insufficient pollination for particular crops [9] and [10]. In contrast, our analysis of Food and Agriculture Organization (FAO) [11] data reveals that the global population of managed honey-bee hives has increased 45% during the last half century and suggests that economic globalization, rather than biological factors, drives both the dynamics of the global managed honey-bee population and increasing demands for agricultural pollination services [12]. Nevertheless, available data also reveal a much more rapid (>300%) increase in the fraction of agriculture that depends on animal pollination during the last half century, which may ! be stressing global pollination capacity. Although the primary cause of the accelerating increase of the pollinator dependence of commercial agriculture seems to be economic and political and not biological, the rapid expansion of cultivation of many pollinator-dependent crops has the potential to trigger future pollination problems for both these crops and native species in neighboring areas. Such environmental costs merit consideration during the development of agriculture and conservation policies. - Bidirectional Flower Color and Shape Changes Allow a Second Opportunity for Pollination
Willmer P Stanley DA Steijven K Matthews IM Nuttman CV - Curr Biol 19(11):919-923 (2009)
Flowers act as "sensory billboards" with multiple signals (color, morphology, odor) attracting and manipulating potential pollinators [1]. Many use changing signals as indicators that visitation and/or pollination have occurred [2] and [3]). Floral color change is commonly used to transmit this information [3], [4], [5], [6] and [7] (often correlated with reduced nectar reward [8] and [9]) and can be specifically triggered by pollination or visitation. By retaining color-changed flowers, plants benefit from larger floral displays but also indicate at close range which flowers are still rewarding (and still unpollinated), so that visitors forage more efficiently [5] and [6]. However, the legume Desmodium setigerum shows a unique ability, if inadequately pollinated, to reverse its flowers' color and shape changes. Single visits by bees mechanically depress the keel and expose stigma and anthers (termed "tripping"); visits also initiate a rapid color change from l! ilac to white and turquoise and a slower morphological change, the upper petal folding downwards over the reproductive parts. But flowers receiving insufficient pollen can partially reopen, re-exposing the stigma, with a further color change to deeper turquoise and/or lilac. Thus, most flowers achieve pollination from one bee visit, but those with inadequate pollen receipt can reverse their signals, earning a "second chance" by eliciting attention from other potential pollinators. - The PCP Pathway Instructs the Planar Orientation of Ciliated Cells in the Xenopus Larval Skin
Mitchell B Stubbs JL Huisman F Taborek P Yu C Kintner C - Curr Biol 19(11):924-929 (2009)
Planar cell polarity (PCP) is a property of epithelial tissues where cellular structures coordinately orient along a two-dimensional plane lying orthogonal to the axis of apical-basal polarity [1]. PCP is particularly striking in tissues where multiciliate cells generate a directed fluid flow, as seen, for example, in the ciliated epithelia lining the respiratory airways or the ventricles of the brain. To produce directed flow, ciliated cells orient along a common planar axis in a direction set by tissue patterning, but how this is achieved in any ciliated epithelium is unknown [2]. Here, we show that the planar orientation of Xenopus multiciliate cells is disrupted when components in the PCP-signaling pathway are altered non-cell-autonomously. We also show that wild-type ciliated cells located at a mutant clone border reorient toward cells with low Vangl2 or high Frizzled activity and away from those with high Vangl2 activity. These results indicate that the PCP pathw! ay provides directional non-cell-autonomous cues to orient ciliated cells as they differentiate, thus playing a critical role in establishing directed ciliary flow. - Chronically CNS-Injured Adult Sensory Neurons Gain Regenerative Competence upon a Lesion of Their Peripheral Axon
Ylera B Ertürk A Hellal F Nadrigny F Hurtado A Tahirovic S Oudega M Kirchhoff F Bradke F - Curr Biol 19(11):930-936 (2009)
Several experimental manipulations result in axonal regeneration in the central nervous system (CNS) when applied before or at the time of injury [1], [2], [3], [4], [5] and [6] but not when initiated after a delay [5], [6], [7], [8], [9] and [10], which would be clinically more relevant. As centrally injured neurons show signs of atrophy and degeneration [11], [12] and [13], it raises the question whether chronically injured neurons are able to regenerate. To address this question, we used adult rodent primary sensory neurons that regenerate their central axon when their peripheral axon is cut (called conditioning) beforehand but not afterwards. We found that primary sensory neurons express regeneration-associated genes and efficiently regrow their axon in cell culture two months after a central lesion upon conditioning. Moreover, conditioning enables central axons to regenerate through a fresh lesion independent of a previous central lesion. Using in vivo imaging we ! demonstrated that conditioned neurons rapidly regrow their axons through a fresh central lesion. Finally, when single sensory axons were cut with a two-photon laser, they robustly regenerate within days after attaining growth competence through conditioning. We conclude that sensory neurons can acquire the intrinsic potential to regenerate their axons months after a CNS lesion, which they implement in the absence of traumatic tissue. - Centrocortin Cooperates with Centrosomin to Organize Drosophila Embryonic Cleavage Furrows
Kao LR Megraw TL - Curr Biol 19(11):937-942 (2009)
In the Drosophila early embryo, the centrosome coordinates assembly of cleavage furrows [1], [2] and [3]. Currently, the molecular pathway that links the centrosome and the cortical microfilaments is unknown. In centrosomin (cnn) mutants, in which the centriole forms but the centrosome pericentriolar material (PCM) fails to assemble [4] and [5], actin microfilaments are not organized into furrows at the syncytial cortex [6]. Although CNN is required for centrosome assembly and function [4], [6] and [7], little is known of its molecular activities. Here, we show the novel protein Centrocortin (CEN), which associates with centrosomes and also with cleavage furrows in early embryos, is required for cleavage furrow assembly. CEN binds to CNN within CNN Motif 2 (CM2), a conserved 60 amino acid domain at CNN's C terminus. The cnnB4 allele, which contains a missense mutation at a highly conserved residue within CM2, blocks the binding of CEN and disrupts cleavage furrow assem! bly. Together, these findings show that the C terminus of CNN coordinates cleavage furrow formation through binding to CEN, thereby providing a molecular link between the centrosome and cleavage furrow assembly. - Decoding the Representation of Multiple Simultaneous Objects in Human Occipitotemporal Cortex
Macevoy SP Epstein RA - Curr Biol 19(11):943-947 (2009)
Previous work using functional magnetic resonance imaging has shown that the identities of isolated objects viewed by human subjects can be extracted from distributed patterns of brain activity [1]. Outside the laboratory, however, objects almost never appear in isolation; thus it is important to understand how multiple simultaneously occurring objects are encoded by the visual system. We used multivoxel pattern analysis to examine this issue, testing whether activity patterns in the lateral occipital complex (LOC) evoked by object pairs showed an ordered relationship to patterns evoked by their constituent objects. Applying a searchlight analysis [2] to identify voxels with the highest signal-to-noise ratios, we found that responses to object pairs within these informative voxels were well predicted by the averages of responses to their constituent objects. Consistent with this result, we were able to classify object pairs by using synthetic patterns created by averag! ing single-object patterns. These results indicate that the representation of multiple objects in LOC is governed by a response normalization mechanism similar to that reported in visual areas of several nonhuman species [[3], [4], [5] and [6]]. They also suggest a population coding scheme that preserves information about multiple objects under conditions of distributed attention, facilitating fast object and scene recognition during natural vision. - Conical Epidermal Cells Allow Bees to Grip Flowers and Increase Foraging Efficiency
Whitney HM Chittka L Bruce TJ Glover BJ - Curr Biol 19(11):948-953 (2009)
The plant surface is by default flat, and development away from this default is thought to have some function of evolutionary advantage. Although the functions of many plant epidermal cells have been described, the function of conical epidermal cells, a defining feature of petals in the majority of insect-pollinated flowers, has not [1] and [2]. The location and frequency of conical cells have led to speculation that they play a role in attracting animal pollinators [1], [3] and [4]. Snapdragon (Antirrhinum) mutants lacking conical cells have been shown to be discriminated against by foraging bumblebees [4]. Here we investigated the extent to which a difference in petal surface structure influences pollinator behavior through touch-based discrimination. To isolate touch-based responses, we used both biomimetic replicas of petal surfaces and isogenic Antirrhinum lines differing only in petal epidermal cell shape. We show that foraging bumblebees are able to discriminate! between different surfaces via tactile cues alone. We find that bumblebees use color cues to discriminate against flowers that lack conical cells—but only when flower surfaces are presented at steep angles, making them difficult to manipulate. This facilitation of physical handling is a likely explanation for the prevalence of conical epidermal petal cells in most flowering plants. - Effects of Confinement on the Self-Organization of Microtubules and Motors
Pinot M Chesnel F Kubiak JZ Arnal I Nedelec FJ Gueroui Z - Curr Biol 19(11):954-960 (2009)
The regulation of the cytoskeleton is essential for the proper organization and function of eukaryotic cells. For instance, radial arrays of microtubules (MTs), called asters, determine the intracellular localization of organelles [1] and [2]. Asters can be generated through either MT organizing center (MTOC)-dependent regulation or self-organization processes [1], [3] and [4]. In vivo, this occurs within the cell boundaries. How the properties of these boundaries affect MT organization is unknown. To approach this question, we studied the organization of microtubules inside droplets of eukaryotic cellular extracts with varying sizes and elastic properties. Our results show that the size of the droplet determined the final steady-state MT organization, which changed from symmetric asters to asymmetric semi-asters and, finally, to cortical bundles. A simple physical model recapitulated these results, identifying the main physical parameters of the transitions. The use o! f vesicles with more elastic boundaries resulted in very different morphologies of microtubule structures, such as asymmetrical semi-asters, "Y-branching" organizations, cortical-like bundles, "rackets," and bundled organizations. Our results highlight the importance of taking into account the physical characteristics of the cellular confinement to understand the formation of cytoskeleton structures in vivo. - Spatial Control of Cytokinesis by Cdr2 Kinase and Mid1/Anillin Nuclear Export
Almonacid M Moseley JB Janvore J Mayeux A Fraisier V Nurse P Paoletti A - Curr Biol 19(11):961-966 (2009)
Maintaining genome integrity and cellular function requires proper positioning of the cell division plane. In most eukaryotes, cytokinesis relies on a contractile actomyosin ring positioned by intrinsic spatial signals that are poorly defined at the molecular level. Fission yeast cells assemble a medial contractile ring in response to positive spatial cues from the nucleus at the cell center [1] and [2] and negative spatial cues from the cell tips [3] and [4]. These signals control the localization of the anillin-like protein Mid1, which defines the position of the division plane at the medial cortex, where it recruits contractile-ring components at mitosis onset [5], [6], [7], [8], [9] and [10]. Here we show that Cdr2 kinase anchors Mid1 at the medial cortex during interphase through association with the Mid1 N terminus. This association underlies the negative regulation of Mid1 distribution by cell tips. We also demonstrate that the positive signaling from the nucleu! s is based on Mid1 nuclear export, which links division-plane position to nuclear position during early mitosis. After nuclear displacement, Mid1 nuclear export is dominant over Cdr2-dependent positioning of Mid1. We conclude that Cdr2- and nuclear export-dependent positioning of Mid1 constitute two overlapping mechanisms that relay cell polarity and nuclear positional information to ensure proper division-plane specification. - A Novel Form of Motility in Filopodia Revealed by Imaging Myosin-X at the Single-Molecule Level
Kerber ML Jacobs DT Campagnola L Dunn BD Yin T Sousa AD Quintero OA Cheney RE - Curr Biol 19(11):967-973 (2009)
Although many proteins, receptors, and viruses are transported rearward along filopodia by retrograde actin flow [1], [2] and [3], it is less clear how molecules move forward in filopodia. Myosin-X (Myo10) is an actin-based motor hypothesized to use its motor activity to move forward along actin filaments to the tips of filopodia [4]. Here we use a sensitive total internal reflection fluorescence (TIRF) microscopy system to directly visualize the movements of GFP-Myo10. This reveals a novel form of motility at or near the single-molecule level in living cells wherein extremely faint particles of Myo10 move in a rapid and directed fashion toward the filopodial tip. These fast forward movements occur at 600 nm/s over distances of up to 10 μm and require Myo10 motor activity and actin filaments. As expected for imaging at the single-molecule level, the faint particles of GFP-Myo10 are diffraction limited, have an intensity range similar to single GFP molecules, and exhib! it stepwise bleaching. Faint particles of GFP-Myo5a can also move toward the filopodial tip, but at a slower characteristic velocity of 250 nm/s. Similar movements were not detected with GFP-Myo1a, indicating that not all myosins are capable of intrafilopodial motility. These data indicate the existence of a novel system of long-range transport based on the rapid movement of myosin molecules along filopodial actin filaments.
No comments:
Post a Comment