What Do Eye Gaze Metrics Tell Us about Motor Imagery?

Many of the brain structures involved in performing real movements also have increased activity during imagined movements or during motor observation, and this could be the neural substrate underlying the effects of motor imagery in motor learning or motor rehabilitation. In the absence of any objective physiological method of measurement, it is currently impossible to be sure that the patient is indeed performing the task as instructed. Eye gaze recording during a motor imagery task could be a possible way to “spy” on the activity an individual is really engaged in. The aim of the present study was to compare the pattern of eye movement metrics during motor observation, visual and kinesthetic motor imagery (VI, KI), target fixation, and mental calculation. Twenty-two healthy subjects (16 females and 6 males), were required to perform tests in five conditions using imagery in the Box and Block Test tasks following the procedure described by Liepert et al. Eye movements were analysed by a non-invasive oculometric measure (SMI RED250 system). Two parameters describing gaze pattern were calculated: the index of ocular mobility (saccade duration over saccade + fixation duration) and the number of midline crossings (i.e. the number of times the subjects gaze crossed the midline of the screen when performing the different tasks). Both parameters were significantly different between visual imagery and kinesthesic imagery, visual imagery and mental calculation, and visual imagery and target fixation. For the first time we were able to show that eye movement patterns are different during VI and KI tasks. Our results suggest gaze metric parameters could be used as an objective unobtrusive approach to assess engagement in a motor imagery task. Further studies should define how oculomotor parameters could be used as an indicator of the rehabilitation task a patient is engaged in.     

Evolution and maintenance of haploid–diploid life cycles in natural populations: The case of the marine brown alga Ectocarpus

The evolutionary stability of haploid–diploid life cycles is still controversial. Mathematical models indicate that niche differences between ploidy phases may be a necessary condition for the evolution and maintenance of these life cycles. Nevertheless, experimental support for this prediction remains elusive. In the present work, we explored this hypothesis in natural populations of the brown alga Ectocarpus. Consistent with the life cycle described in culture, Ectocarpus crouaniorum in NW France and E. siliculosus in SW Italy exhibited an alternation between haploid gametophytes and diploid sporophytes. Our field data invalidated, however, the long‐standing view of an isomorphic alternation of generations. Gametophytes and sporophytes displayed marked differences in size and, conforming to theoretical predictions, occupied different spatiotemporal niches. Gametophytes were found almost exclusively on the alga Scytosiphon lomentaria during spring whereas sporophytes were present year‐round on abiotic substrata. Paradoxically, E. siliculosus in NW France exhibited similar habitat usage despite the absence of alternation of ploidy phases. Diploid sporophytes grew both epilithically and epiphytically, and this mainly asexual population gained the same ecological advantage postulated for haploid–diploid populations. Consequently, an ecological interpretation of the niche differences between haploid and diploid individuals does not seem to satisfactorily explain the evolution of the Ectocarpus life cycle.     

Species-specific duplications driving the recent expansion of NBS-LRR genes in five Rosaceae species

Background

Disease resistance (R) genes from different Rosaceae species have been identified by map-based cloning for resistance breeding. However, there are few reports describing the pattern of R-gene evolution in Rosaceae species because several Rosaceae genome sequences have only recently become available.

Results

Since most disease resistance genes encode NBS-LRR proteins, we performed a systematic genome-wide survey of NBS-LRR genes between five Rosaceae species, namely Fragaria vesca (strawberry), Malus × domestica (apple), Pyrus bretschneideri (pear), Prunus persica (peach) and Prunus mume (mei) which contained 144, 748, 469, 354 and 352 NBS-LRR genes, respectively. A high proportion of multi-genes and similar Ks peaks (Ks = 0.1- 0.2) of gene families in the four woody genomes were detected. A total of 385 species-specific duplicate clades were observed in the phylogenetic tree constructed using all 2067 NBS-LRR genes. High percentages of NBS-LRR genes derived from species-specific duplication were found among the five genomes (61.81% in strawberry, 66.04% in apple, 48.61% in pear, 37.01% in peach and 40.05% in mei). Furthermore, the Ks and Ka/Ks values of TIR-NBS-LRR genes (TNLs) were significantly greater than those of non-TIR-NBS-LRR genes (non-TNLs), and most of the NBS-LRRs had Ka/Ks ratios less than 1, suggesting that they were evolving under a subfunctionalization model driven by purifying selection.

Conclusions

Our results indicate that recent duplications played an important role in the evolution of NBS-LRR genes in the four woody perennial Rosaceae species. Based on the phylogenetic tree produced, it could be inferred that species-specific duplication has mainly contributed to the expansion of NBS-LRR genes in the five Rosaceae species. In addition, the Ks and Ka/Ks ratios suggest that the rapidly evolved TNLs have different evolutionary patterns to adapt to different pathogens compared with non-TNL resistant genes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1291-0) contains supplementary material, which is available to authorized users.     

Sphingolipids involvement in plant endomembrane differentiation: the BY2 case

Sphingolipids play an essential role in the functioning of the secretory pathway in eukaryotic organisms. Their importance in the functional organization of plant cells has not been studied in any detail before. The sphingolipid synthesis inhibitor fumonisin B1 (FB1), a mycotoxin acting as a specific inhibitor of ceramide synthase, was tested for its effects on cell growth, cell polarity, cell shape, cell cycle and on the ultrastructure of BY2 cells. We used cell lines expressing different GFP-tagged markers for plant cell compartments, as well as a Golgi marker fused to the photoconvertible protein Kaede. Light and electron microscopy, combined with flow cytometry, were applied to analyse the morphodynamics and architecture of compartments of the secretory pathway. The results indicate that FB1 treatment had severe effects on cell growth and cell shape, and induced a delay in cell division processes. The cell changes were accompanied by the formation of the endoplasmic reticulum (ER)-derived tubular aggregates (FB1-induced compartments), together with an inhibition of cargo transport from the ER to the Golgi apparatus. A change in polar localization of the auxin transporter PIN1 was also observed, but endocytic processes were little affected. Electron microscopy studies confirmed that molecular FB1 targets were distinct from brefeldin A (BFA) targets. We propose that the reported effects of inhibition of ceramide biosynthesis reflect the importance of sphingolipids during cell growth and establishment of cell polarity in higher plant cells, notably through their contribution to the functional organization of the ER or its differentiation into distinct compartments.     

Tumor delivery of ultrasound contrast agents using Shiga toxin B subunit

The present study demonstrates the targeting of ultrasound contrast agents to human xenograft tumors by exploiting the overexpression of the glycolipid Gb3 in neovasculature. To this end, microbubbles were functionalized with a natural Gb3 ligand, the B subunit of the Shiga toxin (STxB). The targeting of Gb3-expressing tumor cells by STxB microbubbles was first shown by flow cytometry and fluorescence microscopy. A significantly higher proportion of STxB microbubbles were associated with Gb3-expressing tumor cells compared to cells in which Gb3 expression was inhibited. Moreover, ultrasonic imaging of culture plates showed a 12 dB contrast enhancement in average backscattered acoustic intensity on the surface of Gb3-expressing cells compared to Gb3-negative cells. Also, a 18 dB contrast enhancement was found in favor of STxB microbubbles compared to unspecific microbubbles. Microbubble signal intensity in subcutaneous tumors in mice was more than twice as high after the injection of STxB-functionalized microbubbles compared to the injection of unspecific microbubbles. These in vitro and in vivo experiments demonstrated that STxB-functionalized microbubbles bind specifically to cells expressing the Gb3 glycolipid. The cell-binding moieties of toxins thus appear as a new group of ligands for angiogenesis imaging with ultrasound.     

Functional ultrasound imaging of the brain

We present functional ultrasound (fUS), a method for imaging transient changes in blood volume in the whole brain at better spatiotemporal resolution than with other functional brain imaging modalities. fUS uses plane-wave illumination at high frame rate and can measure blood volumes in smaller vessels than previous ultrasound methods. fUS identifies regions of brain activation and was used to image whisker-evoked cortical and thalamic responses and the propagation of epileptiform seizures in the rat brain.     

Genetic diversity of the genus Malus and implications for linkage mapping with SNPs

Knowledge about the sequence-based genetic diversity of a crop species is important in order to develop highly informative genotyping assays, which will eventually positively impact breeding practice. Diversity data were obtained from two pools of 185 and 75 accessions each, representing most of the species belonging to the genus Malus, by re-sequencing 27 gene-specific amplicons and by screening 237 Malus × domestica SNPs using the multiplex genotyping technology SNPlex™. Nucleotide diversity and insertion/deletion rates in M. × domestica were estimated as π = 0.0037 and 1/333 bp, respectively. The SNP frequency was estimated as 0.0194 (1 SNP/52 bp) while within a single apple cultivar an average of one SNP in every 455 bp was found. We also investigated transferability (T _SNP) of the heterozygous state of SNPs across the species M. × domestica and the genus Malus. Raw re-sequencing showed that 12–15% of M. × domestica SNPs are transferable to a second M. × domestica cultivar, however T _SNP rose to ∼41% with SNPs selected for high minor allele frequency. T _SNP of chosen SNPs averaged ∼27% in the two M. × domestica-related species, Malus sieversii and Malus sylvestris, but was much lower in more distantly related species. On the basis of T _SNP, simulations, and empirical results, we calculated that a close-design, multiplexed genotyping array with at least 2,000 SNPs is required for building a highly saturated linkage maps within any M. × domestica cross. The same array would gradually lose informativeness in increasingly phylogenetically distant Malus species.     

Inner-membrane proteins PMI/TMEM11 regulate mitochondrial morphogenesis independently of the DRP1/MFN fission/fusion pathways

Mitochondria are highly dynamic organelles that can change in number and morphology during cell cycle, development or in response to extracellular stimuli. These morphological dynamics are controlled by a tight balance between two antagonistic pathways that promote fusion and fission. Genetic approaches have identified a cohort of conserved proteins that form the core of mitochondrial remodelling machineries. Mitofusins (MFNs) and OPA1 proteins are dynamin-related GTPases that are required for outer- and inner-mitochondrial membrane fusion respectively whereas dynamin-related protein 1 (DRP1) is the master regulator of mitochondrial fission. We demonstrate here that the Drosophila PMI gene and its human orthologue TMEM11 encode mitochondrial inner-membrane proteins that regulate mitochondrial morphogenesis. PMI-mutant cells contain a highly condensed mitochondrial network, suggesting that PMI has either a pro-fission or an anti-fusion function. Surprisingly, however, epistatic experiments indicate that PMI shapes the mitochondria through a mechanism that is independent of drp1 and mfn. This shows that mitochondrial networks can be shaped in higher eukaryotes by at least two separate pathways: one PMI-dependent and one DRP1/MFN-dependent.