Flagellar, cellular and organismal polarity in Volvox carteri

It has previously been shown that the flagellar apparatus of the mature Volvox carteri somatic cell lacks the 180° rotational symmetry typical of most unicellular green algae. This asymmetry has been postulated to be the result of rotation of each half of the flagellar apparatus. Here it is shown that V. carteri axonemes contain polarity markers that are similar to those found in Chlamydomonas, except that in V. carteri the number one doublets do not face each other as they do in Chlamydomonas but are oriented in parallel and at approximately right angles to the line that connects the flagella. Thus, the rotational orientations of the axonemes are consistent with the postulate that the flagella of V. carteri have rotated in opposite directions, as was predicted earlier from the positions of the basal fibers and microtubular rootlets. Moreover, high-speed cinephotomicrographic analysis shows that the V. carteri flagellar effective strokes are also oriented in approximately the same direction, and in parallel planes. These results suggest that the direction of the effective stroke in both Chlamydomonas and Volvox is fixed, and that rotation of the axoneme is the cause of the differences in flagellar motility observed between Chlamydomonas and Volvox. These differences are probably essential for effective organismal motility. Cellular polarity of V. carteri can be related to that of Chlamydomonas after taking into account the developmental reorientation of flagellar apparatus components. This reorientation also results in the movement of the eyespot from a position nearer one of the flagellar bases to a position approximately equidistant between them. By analogy to Chlamydomonas, the anti side of the V. carteri somatic cell faces the spheroid anterior, the syn side faces the spheroid posterior. The cis side of the cell is to the cell\u27s left (the right to an outside observer), although it cannot be described solely on the basis of eyespot position as it can in Chlamydomonas, while the trans side is to the cell\u27s right. It follows that if the direction of the effective flagellar stroke is specified by structural features, then effective organismal motility in V. carteri, will be accomplished only if the cells are held in the proper orientation with respect to one another. The simplest arrangement that will yield both progression and rotation in ovoid or spherical colonies composed of biflagellate isokont cells is one in which the cells are arranged with rotational symmetry about the anterior-posterior axis of the spheroid. Analysis of the polarity of somatic cells from throughout the spheroid shows that it is constructed with just such symmetry. This symmetry probably originates with the very first divisions

Ultrastructure and development of the flagellar apparatus and flagellar motion in the colonial graeen alga Astrephomene gubernaculifera.

Immediately following embryonic cleavage, the cells of Astrephomene have four equal-sized basal bodies, two of which are connected by a striated distal fibre and two striated proximal fibres. The four microtubular rootlets, which alternate between having 3/1 and 2 members, are arranged cruciately. The two basal bodies that are connected by the striated fibres then extend into flagella, while the two accessory basal bodies are now markedly shorter. At this stage the flagellar apparatus has 180 degrees rotational symmetry and is very similar to the flagellar apparatus of the unicellular Chlamydomonas and related algae. Development proceeds with a number of concurrent events. The basal bodies begin to separate at their proximal ends and become nearly parallel. Each striated proximal fibre detaches at one end from one of the basal bodies. Each half of the flagellar apparatus, which consists of a flagellum and attached basal body, an accessory basal body, two rootlets and a striated fibre (formerly one of the proximal striated fibres), rotates about 90 degrees, the two halves rotating in opposite directions. An electron-dense strut forms near one two-membered rootlet and grows past both basal bodies. During this time a fine, fibrous component appears between newly developed spade-like structures and associated amorphous material connected to each basal body. The basal bodies continue to separate as the distal fibre stretches and finally detaches from one of them. These processes result in the loss of the 180 degree rotational symmetry present in previous stages. Although the flagella continue to separate, there is no further reorganization of the components of the flagellar apparatus. In the mature cell of Astrephomene, the two flagella are inserted separately and are parallel. The four microtubular rootlets are no longer arranged cruciately. Three of the rootlets are nearly parallel, while the fourth is approximately perpendicular to the other three. A straited fibre connects each basal body to the underside of the strut. These fibres run in the direction of the effective stroke of the flagella and might be important either in anchoring the basal bodies or in the initiation of flagellar motion. Unlike the case in the unicellular Chlamydomonas, the two flagella beat in the same direction and in parallel planes. The flagella of a given cell may or may not beat in synchrony. The combination of this type of flagellar motion and the parallel, separate flagella appears to be suited to the motion of this colonial organism

Both German and Russian: Second-Generation Russian-German Identities in Germany

The article was submitted on 25.01.2021.Приведены результаты квалитативного исследования, включающего интервью с молодыми людьми российско-немецкого происхождения, рожденными в Германии, то есть потомками поздних переселенцев из стран бывшего СССР. Базируясь на постструктуралистских теориях, постулирующих лингвистическую практику и дискурсивную атрибуцию социальных категорий как способ конституирования субъективности и соответствующей идентичности, авторы исследования сосредоточены на процессах формирования национально-этнокультурной идентичности у второго поколения поздних переселенцев и их опыте внешней аскрипции (приписывания) к национально-этнокультурным категориям. Заявленная тема подробно освещена с точки зрения первого поколения поздних переселенцев. Второе же поколение до определенной степени было обделено вниманием исследовательского сообщества. Однако условия формирования его идентичности в Германии значительно отличались в силу не настолько ярко выраженной заметности или даже невидимости миграционного опыта второго поколения граждан российско-немецкого происхождения в обществе. Для первого поколения поздних переселенцев характерен опыт двойной эксклюзии – из-за немецкого происхождения в России и из-за русского в Германии. Именно такая эксклюзия стала причиной так называемой неопределенности идентичности, особенно с учетом того, что отнесение их к категории «русских» немецкими согражданами воспринималось ими как ложная аскрипция. Второе же поколение не испытало двойной эксклюзии. Окружающее общество в целом воспринимает его представителей как немцев, тем самым усиливая и их самоидентификацию именно в этой роли. При этом они демонстрируют некоторую позитивную самоидентификацию как «русских», которая не активируется внешней аскрипцией, а поддерживается наличием в семейной среде национальных обычаев. Представители второго поколения, таким образом, могут с успехом совмещать обе идентификации. Для этого поколения неустойчивая промежуточная категория «российских немцев» как способ идентификации выходит из употребления, в то время как для первого поколения она служила и до сих пор служит стратегией преодоления двойной эксклюзии и происходящей из нее неспособности идентифицировать себя ни как «немцев», ни как «русских». В то же время мы видим, как семантическая категория «российских немцев» утрачивает свое значение и сливается с категорией «русских». Это обусловлено тем, что второе поколение не имеет опыта осознания своей «инородности» как не-русских (до эмиграции) и не-немцев (после эмиграции), а только лишь как русских в Германии.This essay presents the results of a qualitative interview study with young people of Russian-German origin born in Germany, i. e., the descendants of resettlers (Spätaussiedler) from the successor states of the former Union of Soviet Socialist Republics. Using poststructuralist theories that understand the linguistic practices and discursive attribution of social categories as modes of constituting subjectivity and corresponding identities, this study focuses on processes of natio-ethno-cultural identity formation among the second generation of Spätaussiedler and their experiences of being externally ascribed to certain natio-ethno-cultural categories. In the existing literature, this topic has been extensively addressed with regard to the first generation of Spätaussiedler, but not the second generation, whose conditions for identity formation in Germany are quite different due to their relative inconspicuousness, i. e., the invisibility of their migration background. For the first generation of Spätaussiedler, the dual exclusion as German in Russia and Russian in Germany was the cause of a persistent identity uncertainty, especially given that the labeling as “Russian” by supposed fellow Germans was perceived as a hurtful mis-ascription. The second generation, in contrast, is not subject to this dual exclusion. Surrounding society generally perceives them as German, thus reinforcing their corresponding self-identification as German. At the same time, there is a limited but positive identification with the category of Russian as well, which is less often activated by external ascriptions and rather fed by the presence of customs in the family context that are perceived as Russian. Members of the second generation are thus able to identify satisfactorily as both “German” and “Russian”. For this generation, the evasive intermediate category “Russian-German” therefore becomes obsolete as a source of identification, while it served and still serves as a first-generation strategy for coping with dual exclusion and the resulting inability to identify as either German or Russian. At the same time, a semantic emptying and a conflation of the category “Russian-German” with the category “Russian” takes place, which results from the second generation never having perceived its own cultural otherness both as non-Russian (before migration) and non-German (after migration), but only as Russian in Germany

Software that goes with the flow in systems biology

A recent article in BMC Bioinformatics describes new advances in workflow systems for computational modeling in systems biology. Such systems can accelerate, and improve the consistency of, modeling through automation not only at the simulation and results-production stages, but also at the model-generation stage. Their work is a harbinger of the next generation of more powerful software for systems biologists

The yeast homologue of the microtubule-associated protein Lis1 interacts with the sumoylation machinery and a SUMO-targeted ubiquitin ligase

Microtubules and microtubule-associated proteins are fundamental for multiple cellular processes, including mitosis and intracellular motility, but the factors that control microtubule-associated proteins (MAPs) are poorly understood. Here we show that two MAPs - the CLIP-170 homologue Bik1p and the Lis1 homologue Pac1p - interact with several proteins in the sumoylation pathway. Bik1p and Pac1p interact with Smt3p, the yeast SUMO; Ubc9p, an E2; and Nfi1p, an E3. Bik1p interacts directly with SUMO in vitro, and overexpression of Smt3p and Bik1p results in its in vivo sumoylation. Modified Pac1p is observed when the SUMO protease Ulp1p is inactivated. Both ubiquitin and Smt3p copurify with Pac1p. In contrast to ubiquitination, sumoylation does not directly tag the substrate for degradation. However, SUMO-targeted ubiquitin ligases (STUbLs) can recognize a sumoylated substrate and promote its degradation via ubiquitination and the proteasome. Both Pac1p and Bik1p interact with the STUbL Nis1p-Ris1p and the protease Wss1p. Strains deleted for RIS1 or WSS1 accumulate Pac1p conjugates. This suggests a novel model in which the abundance of these MAPs may be regulated via STUbLs. Pac1p modification is also altered by Kar9p and the dynein regulator She1p. This work has implications for the regulation of dynein\u27s interaction with various cargoes, including its off-loading to the cortex. © 2012 Alonso et al

Two- and three-body photodissociation of gas phase I(-)(3)

The photodissociation dynamics of gas phase I-3 by using a fast beam photofragment translational spectrometer was examined. It was stated that the photofragment translational spectrometer was coupled to a coincidence imaging detector that enabled the direct detection and analysis of two and three neutron or anion fragments from single dissociation events. The three-body dissociation yielding I-+2I(2P3/2) photofragments was also seen throughout the energy range probed. Analysis shows that the three-body decay dynamics was dominated by synchronous concerted dissociation.Alexandra A. Hoops, Jason R. Gascooke, Ann Elise Faulhaber, Kathryn E. Kautzman, and Daniel M. Neumar

Evidence for concerted and mosaic brain evolution in dragon lizards

The brain plays a critical role in a wide variety of functions including behaviour, perception, motor control, and homeostatic maintenance. Each function can undergo different selective pressures over the course of evolution, and as selection acts on the outputs of brain function, it necessarily alters the structure of the brain. Two models have been proposed to explain the evolutionary patterns observed in brain morphology. The concerted brain evolution model posits that the brain evolves as a single unit and the evolution of different brain regions are coordinated. The mosaic brain evolution model posits that brain regions evolve independently of each other. It is now understood that both models are responsible for driving changes in brain morphology; however, which factors favour concerted or mosaic brain evolution is unclear. Here, we examined the volumes of the 6 major neural subdivisions across 14 species of the agamid lizard genus Ctenophorus (dragons). These species have diverged multiple times in behaviour, ecology, and body morphology, affording a unique opportunity to test neuroevolutionary models across species. We assigned each species to an ecomorph based on habitat use and refuge type, then used MRI to measure total and regional brain volume. We found evidence for both mosaic and concerted brain evolution in dragons: concerted brain evolution with respect to body size, and mosaic brain evolution with respect to ecomorph. Specifically, all brain subdivisions increase in volume relative to body size, yet the tectum and rhombencephalon also show opposite patterns of evolution with respect to ecomorph. Therefore, we find that both models of evolution are occurring simultaneously in the same structures in dragons, but are only detectable when examining particular drivers of selection. We show that the answer to the question of whether concerted or mosaic brain evolution is detected in a system can depend more on the type of selection measured than on the clade of animals studied. (C) 2017 S. Karger AG, Base

PlantSimLab - a modeling and simulation web tool for plant biologists.

BACKGROUND: At the molecular level, nonlinear networks of heterogeneous molecules control many biological processes, so that systems biology provides a valuable approach in this field, building on the integration of experimental biology with mathematical modeling. One of the biggest challenges to making this integration a reality is that many life scientists do not possess the mathematical expertise needed to build and manipulate mathematical models well enough to use them as tools for hypothesis generation. Available modeling software packages often assume some modeling expertise. There is a need for software tools that are easy to use and intuitive for experimentalists. RESULTS: This paper introduces PlantSimLab, a web-based application developed to allow plant biologists to construct dynamic mathematical models of molecular networks, interrogate them in a manner similar to what is done in the laboratory, and use them as a tool for biological hypothesis generation. It is designed to be used by experimentalists, without direct assistance from mathematical modelers. CONCLUSIONS: Mathematical modeling techniques are a useful tool for analyzing complex biological systems, and there is a need for accessible, efficient analysis tools within the biological community. PlantSimLab enables users to build, validate, and use intuitive qualitative dynamic computer models, with a graphical user interface that does not require mathematical modeling expertise. It makes analysis of complex models accessible to a larger community, as it is platform-independent and does not require extensive mathematical expertise

MRI atlas of a lizard brain

Magnetic resonance imaging (MRI) is an established technique for neuroanatomical analysis, being particularly useful in the medical sciences. However, the application of MRI to evolutionary neuroscience is still in its infancy. Few magnetic resonance brain atlases exist outside the standard model organisms in neuroscience and no magnetic resonance atlas has been produced for any reptile brain. A detailed understanding of reptilian brain anatomy is necessary to elucidate the evolutionary origin of enigmatic brain structures such as the cerebral cortex. Here, we present a magnetic resonance atlas for the brain of a representative squamate reptile, the Australian tawny dragon (Agamidae: Ctenophorus decresii), which has been the subject of numerous ecological and behavioral studies. We used a high-field 11.74T magnet, a paramagnetic contrasting-enhancing agent and minimum-deformation modeling of the brains of thirteen adult male individuals. From this, we created a high-resolution three-dimensional model of a lizard brain. The 3D-MRI model can be freely downloaded and allows a better comprehension of brain areas, nuclei, and fiber tracts, facilitating comparison with other species and setting the basis for future comparative evolution imaging studies. The MRI model and atlas of a tawny dragon brain (Ctenophorus decresii) can be viewed online and downloaded using the Wiley Biolucida Server at wiley.biolucida.net.Government of Australia, Grant/Award Numbers: APA#31/2011, IPRS#1182/2010; National Science and Engineering Research Council of Canada, Grant/Award Number: PGSD3-415253-2012; Quebec Nature and Technology Research Fund, Grant/AwardNumber: 208332; National Imaging Facility of Australia; Spanish Ministerio de Economía y Competitividad and Fondo Europeo de Desarrollo Regional, Grant/Award Number:BFU2015-68537-