| 1. |
- Andersson, Jan O, 1971-, et al.
(författare)
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A cyanobacterial gene in nonphotosynthetic protists : an early chloroplast acquisition in eukaryotes?
- 2002
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445. ; 12:2, s. 115-119
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Tidskriftsartikel (refereegranskat)abstract
- Since the incorporation of mitochondria and chloroplasts (plastids) into the eukaryotic cell by endosymbiosis, genes have been transferred from the organellar genomes to the nucleus of the host, via an ongoing process known as endosymbiotic gene transfer. Accordingly, in photosynthetic eukaryotes, nuclear genes with cyanobacterial affinity are believed to have originated from endosymbiotic gene transfer from chloroplasts. Analysis of the Arabidopsis thaliana genome has shown that a significant fraction (2%-9%) of the nuclear genes have such an endosymbiotic origin. Recently, it was argued that 6-phosphogluconate dehydrogenase (gnd)-the second enzyme in the oxidative pentose phosphate pathway-was one such example. Here we show that gnd genes with cyanobacterial affinity also are present in several nonphotosynthetic protistan lineages, such as Heterolobosea, Apicomplexa, and parasitic Heterokonta. Current data cannot definitively resolve whether these groups acquired the gnd gene by primary and/or secondary endosymbiosis or via an independent lateral gene transfer event. Nevertheless, our data suggest that chloroplasts were introduced into eukaryotes much earlier than previously thought and that several major groups of heterotrophic eukaryotes have secondarily lost photosynthetic plastids.
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| 2. |
- Andersson, Jan O, 1971-
(författare)
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Evolutionary genomics : is Buchnera a bacterium or an organelle?
- 2000
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445. ; 10:23, s. R866-R868
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Tidskriftsartikel (refereegranskat)abstract
- The first genome sequence of an intracellular bacterial symbiont of a eukaryotic cell has been determined. The Buchnera genome shares features with the genomes of both intracellular pathogenic bacteria and eukaryotic organelles, and it may represent an intermediate between the two.
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| 3. |
- Andersson, Jan O, 1971-, et al.
(författare)
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Phylogenetic analyses of diplomonad genes reveal frequent lateral gene transfers affecting eukaryotes
- 2003
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445. ; 13:2, s. 94-104
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Lateral gene transfer (LGT) is an important evolutionary mechanism among prokaryotes. The situation in eukaryotes is less clear; the human genome sequence failed to give strong support for any recent transfers from prokaryotes to vertebrates, yet a number of LGTs from prokaryotes to protists (unicellular eukaryotes) have been documented. Here, we perform a systematic analysis to investigate the impact of LGT on the evolution of diplomonads, a group of anaerobic protists.RESULTS: Phylogenetic analyses of 15 genes present in the genome of the Atlantic Salmon parasite Spironucleus barkhanus and/or the intestinal parasite Giardia lamblia show that most of these genes originated via LGT. Half of the genes are putatively involved in processes related to an anaerobic lifestyle, and this finding suggests that a common ancestor, which most probably was aerobic, of Spironucleus and Giardia adapted to an anaerobic environment in part by acquiring genes via LGT from prokaryotes. The sources of the transferred diplomonad genes are found among all three domains of life, including other eukaryotes. Many of the phylogenetic reconstructions show eukaryotes emerging in several distinct regions of the tree, strongly suggesting that LGT not only involved diplomonads, but also involved other eukaryotic groups.CONCLUSIONS: Our study shows that LGT is a significant evolutionary mechanism among diplomonads in particular and protists in general. These findings provide insights into the evolution of biochemical pathways in early eukaryote evolution and have important implications for studies of eukaryotic genome evolution and organismal relationships. Furthermore, "fusion" hypotheses for the origin of eukaryotes need to be rigorously reexamined in the light of these results.
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| 4. |
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| 5. |
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| 6. |
- Carlen, M., et al.
(författare)
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Functional integration of adult-born neurons
- 2002
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445. ; 12:7, s. 606-608
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Tidskriftsartikel (refereegranskat)abstract
- Over the past decade, it has become clear that neural stem cells in the adult mammalian brain continuously generate new neurons, predominantly in the hippocampus and olfactory bulb [1]. However, the central issue of whether these new neurons participate in functional synaptic circuitry has yet to be resolved. Here, we use virus-based transsynaptic neuronal tracing and c-Fos mapping of odor-induced neuronal activity to demonstrate that neurons generated in the adult functionally integrate into the synaptic circuitry of the brain.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Flanagan, J Randall, et al.
(författare)
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Prediction precedes control in motor learning
- 2003
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 13:2, s. 146-150, Article Number: PII S0960-9822(03)00007-1
-
Tidskriftsartikel (refereegranskat)abstract
- Skilled motor behavior relies on the brain learning both to control the body and predict the consequences of this control. Prediction turns motor commands into expected sensory consequences, whereas control turns desired consequences into motor commands. To capture this symmetry, the neural processes underlying prediction and control are termed the forward and inverse internal models, respectively. Here, we investigate how these two fundamental processes are related during motor learning. We used an object manipulation task in which subjects learned to move a hand-held object with novel dynamic properties along a prescribed path. We independently and simultaneously measured subjects' ability to control their actions and to predict their consequences. We found different time courses for predictor and controller learning, with prediction being learned far more rapidly than control. In early stages of manipulating the object, subjects could predict the consequences of their actions, as measured by the grip force they used to grasp the object, but could not generate appropriate actions for control, as measured by their hand trajectory. As predicted by several recent theoretical models of sensorimotor control, our results indicate that people can learn to predict the consequences of their actions before they can learn to control their actions.
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| 11. |
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| 12. |
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| 13. |
- Holmgren, Claes, et al.
(författare)
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CpG methylation regulates the Igf2/H19 insulator
- 2001
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445. ; 11:14, s. 1128-1130
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Tidskriftsartikel (refereegranskat)abstract
- The differentially methylated 5'-flank of the mouse H19 gene unidirectionally regulates the communication between enhancer elements and gene promoters and presumably represses maternal Igf2 expression in vivo [1-6]. The specific activation of the paternally inherited Igf2 allele has been proposed to involve methylation-mediated inactivation of the H19 insulator function during male germline development [1-4, 6]. Here, we addressed the role of methylation by inserting a methylated fragment of the H19-imprinting control region (ICR) into a nonmethylated episomal H19 minigene construct, followed by the transfection of ligation mixture into Hep3B cells. Individual clones were expanded and analyzed for genotype, methylation status, chromatin conformation, and insulator function. The results show that the methylated status of the H19 ICR could be propagated for several passages without spreading into the episomal vector. Moreover, the nuclease hypersensitive sites, which are typical for the maternally inherited H19 ICR allele [1], were absent on the methylated ICR, underscoring the suggestion that the methylation mark dictates parent of origin-specific chromatin conformations [1] that involve CTCF [2]. Finally, the insulator function was strongly attenuated in stably maintained episomes. Collectively, these results provide the first experimental support that the H19 insulator function is regulated by CpG methylation.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Kiesler, Eva, et al.
(författare)
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HEL/UAP56 Binds Cotranscriptionally to the Balbiani Ring Pre-mRNA in an Intron-Independent Manner and Accompanies the BR mRNP to the Nuclear Pore
- 2002
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Ingår i: Current Biology. - : Current Biology Limited. - 0960-9822. ; 12, s. 859-862
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Tidskriftsartikel (refereegranskat)abstract
- The splicing factor UAP56/HEL/Sub2p is essential for mRNA export [1], [2], [3] and [4]. It has been proposed [1] and [2] that UAP56/HEL/Sub2p interacts with the pre-mRNA during splicing and recruits the export factor Aly/REF/Yra1 (reviewed in [5]) to the spliced mRNA. However, UAP56/HEL/Sub2p also participates in the transport of intronless mRNAs, and thus its role in export is not necessarily coupled to splicing [2], [3] and [4]. Here, we characterize the HEL protein of Chironomus tentans and we analyze in situ the interaction of HEL with a natural export substrate, the Balbiani ring pre-messenger ribonucleoprotein (BR pre-mRNP, reviewed in [6]). Using immunoelectron microscopy, we show that HEL binds to the BR pre-mRNP cotranscriptionally and that incorporation of HEL into the pre-mRNP is independent of the location of introns along the BR pre-mRNA. We also show that HEL accompanies the BR mRNP to the nuclear pore and is released from the BR mRNP during translocation to the cytoplasm. Aly/REF is also released from the BR mRNP during translocation but after dissociation of HEL. In summary, we have shown that binding of HEL to the BR pre-mRNA occurs independently of splicing, and we have established the point in the export pathway at which HEL and Aly/REF interact with the mRNP.
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| 18. |
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| 19. |
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| 20. |
- Norlin, Marianne, et al.
(författare)
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Vomeronasal Phenotype and Behavioral Alterations in Gαi2 Mutant Mice
- 2003
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 13:14, s. 1214-1219
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Tidskriftsartikel (refereegranskat)abstract
- Several social and reproductive behaviors are under the influence of the vomeronasal (VN) organ; VN neurons detect odorous molecules emitted by individuals of the same species. There are two types of VN neurons, and these differ in their expression of chemosensory receptors and G protein subunits. The significance of this dichotomy is largely unknown. VN neurons express high levels of either G alpha i2 or G alpha o. A mouse line carrying a targeted disruption of the G alpha i2 gene offered the opportunity for studying the effects of a lack of receptor signaling through the heterotrimeric Gi2 protein in one VN cell type. As a consequence of this deficiency, the number of VN neurons that normally express G alpha i2 is decreased by half. These residual neurons are defective in eliciting a response in their target neurons in the accessory olfactory bulb. Moreover, G alpha i2 mutant mice show alterations in behaviors for which an intact VN organ is known to be important. Display of maternal aggressive behavior is severely blunted, and male mice show significantly less aggression toward an intruder. However, male mice show unaltered sexual-partner preference. This suggests that the two types of VN neurons may have separate functions in mediating behavioral changes in response to chemosensory information.
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| 21. |
- Silverstein, Rebecka A., et al.
(författare)
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A new role for the transcriptional corepressor SIN3; Regulation of centromeres
- 2003
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445. ; 13:1, s. 68-72
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Tidskriftsartikel (refereegranskat)abstract
- Centromeres play a vital role in maintaining the genomic stability of eukaryotes by coordinating the equal distribution of chromosomes to daughter cells during mitosis and meiosis. Fission yeast (S. pombe) centromeres consist of a 4-9 kb central core region and 30-100 kb of flanking inner (imr/B) and outer (otr/K) repeats [1-3]. These sequences direct a laminar kinetochore structure similar to that of human centromeres [4, 5]. Centromeric heterochromatin is generally underacetylated [6, 7]. We have previously shown that inhibition of histone deacetylases (HDACs) caused hyperacetylation of centromeres and defective chromosome segregation [8]. SIN3 is a HDAC corepressor that has the ability to mediate HDAC targeting in the repression of promoters. In this study, we have characterized S. pombe sin three corepressors (Pst1p and Pst2p) to investigate whether SIN3-HDAC is required in the regulation of centromeres. We show that only pst1-1 and not pst2Delta cells displayed anaphase defects and thiabendazole sensitivity. pst1-1 cells showed reduced centromeric silencing, increased histone acetylation in centromeric chromatin, and defective centromeric sister chromatid cohesion. The HDAC Clr6p and Pst1p coimmunoprecipitated, and Pst1p colocalized with centromeres, particularly in binucleate cells. These data are consistent with a model in which Pst1 pClr6p temporally associate with centromeres to carry out the initial deacetylation necessary for subsequent steps in heterochromatin formation.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Nordström, Karin, 1973-, et al.
(författare)
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Invertebrate vision : Peripheral adaptation to repeated object motion
- 2013
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 23:15, s. R655-R656
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Visual systems adapt rapidly to objects moving repeatedly within the visual field, because such objects are likely irrelevant. In the crab, the neural switch for such adaptation has been found to take place at a surprisingly early stage of the visual processing pathway.
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| 26. |
- Smolka, Jochen, et al.
(författare)
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A new galloping gait in an insect
- 2013
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Ingår i: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 23:20, s. 913-915
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Tidskriftsartikel (refereegranskat)abstract
- An estimated three million insect species all walk using variations of the alternating tripod gait. At any one time, these animals hold one stable triangle of legs steady while swinging the opposite triangle forward. Here, we report the discovery that three different flightless desert dung beetles use an additional gallop-like gait, which has never been described in any insect before. Like a bounding hare, the beetles propel their body forward by synchronously stepping with both middle legs and then both front legs. Surprisingly, this peculiar galloping gait delivers lower speeds than the alternating tripod gait. Why these beetles have shifted so radically away from the most widely used walking style on our planet is as yet unknown.
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| 27. |
- Aguilera-Campos, Karla Iveth, et al.
(författare)
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Hydrogen metabolism : A eukaryote taps into the electron sink
- 2022
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Ingår i: Current biology : CB. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 32:1, s. 49-51
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Tidskriftsartikel (refereegranskat)abstract
- The ability to harvest reducing power from molecular hydrogen was once considered a prokaryotic trait. New research challenges this notion by finding the first eukaryotic organism capable of oxidizing hydrogen.
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| 28. |
- Aikens, Ellen O., et al.
(författare)
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Wave-like Patterns of Plant Phenology Determine Ungulate Movement Tactics
- 2020
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Ingår i: Current Biology. - Cambridge : Cell Press. - 0960-9822 .- 1879-0445. ; 30:17, s. 3444-3449
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Tidskriftsartikel (refereegranskat)abstract
- Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called "green-wave surfing" [3-5]. Yet general principles describing how the dynamic nature of resources determine movement tactics are lacking [6]. We tested an emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of green-up facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change [10], our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.© 2020 Elsevier Inc.
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| 29. |
- Alerstam, Thomas, et al.
(författare)
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Ecology of animal migration
- 2018
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 28:17, s. 968-972
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Forskningsöversikt (refereegranskat)abstract
- Billions of animals are adapted to a travelling life, making regular return migrations between more or less distant living stations on Earth by swimming, flying, running or walking (Figure 1). Extremely long migrations are completed annually by whales between calving areas in warmer waters and feeding areas at higher latitudes in either hemisphere. The longest oceanic migrations among sea turtles and fish are often undertaken by younger immature individuals during a period of several years before they start their more regular return visits to breeding and spawning sites. Among adult leatherback turtles, intervals of several years between successive breeding events leave enough time for extremely long journeys. Famous among bird migrants are arctic terns, showing the longest known annual migration circuit of about 50,000 km. Bar-tailed godwits breed in Alaska and winter in New Zealand and make the longest known non-stop flapping flights, lasting more than two hundred hours and covering up to 12,000 km across the Pacific Ocean. Their total annual migration circuit extends over 30,000 km covered in three main flights (Figure 1). Although diapause with hibernation as egg, pupae, larvae or adult is an important strategy among insects, there are also examples of impressive migrations. Monarch butterflies complete an annual circuit up to 9,000 km in North America in four generations (for more detail, see the review by Steven Reppert in this issue), and the globe skimmer (a dragonfly) presumably exploits the monsoon rains in India and rainy seasons in southern and equatorial Africa in a 15,000 km circuit in four generations (Figure 1). In comparison with swimmers and flyers, animals that migrate by running or walking cover shorter distances. Caribous migrate between boreal forest and tundra over a total distance of not much more than 1000—2000 km per year. Zebras make the longest migrations in Africa, covering at least 500 km, which is just a little bit longer than the well-known wildebeest migration circuit in Serengeti. Alerstam and Bäckman introduce the ecological factors influencing the way animals migrate and how this branch of ecology has developed and grown.
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| 30. |
- Allen, John
(författare)
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Photosynthesis: The Processing of Redox Signals in Chloroplasts
- 2005
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Ingår i: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 15:22, s. 929-932
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Tidskriftsartikel (refereegranskat)abstract
- Recent work identifies two kinases required for phosphorylation of proteins of chloroplast thylakoid membranes. One kinase, STN7, is required for phosphorylation of light-harvesting complex II; another, STN8, is required for phosphorylation of photosystem II. How do these kinases interact, what do they do, and what are they for?
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| 31. |
- Alva, Omar, et al.
(författare)
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The loss of biodiversity in Madagascar is contemporaneous with major demographic events
- 2022
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Ingår i: Current Biology. - : Elsevier. - 0960-9822 .- 1879-0445. ; 32:23, s. 4997-
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Tidskriftsartikel (refereegranskat)abstract
- Only 400 km off the coast of East Africa, the island of Madagascar is one of the last large land masses to have been colonized by humans. While many questions surround the human occupation of Madagascar, recent studies raise the question of human impact on endemic biodiversity and landscape transformation. Previous genetic and linguistic analyses have shown that the Malagasy population has emerged from an admixture that happened during the last millennium, between Bantu-speaking African populations and Austronesian-speaking Asian populations. By studying the sharing of chromosome segments between individuals (IBD determination), local ancestry information, and simulated genetic data, we inferred that the Malagasy ancestral Asian population was isolated for more than 1,000 years with an effective size of just a few hundred individuals. This isolation ended around 1,000 years before present (BP) by admixture with a small African population. Around the admixture time, there was a rapid demographic expansion due to intrinsic population growth of the newly admixed population, which coincides with extensive changes in Madagascar's landscape and the extinction of all endemic large- bodied vertebrates. Therefore, our approach can provide new insights into past human demography and associated impacts on ecosystems.
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| 32. |
- Andersson, Jan O
(författare)
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Convergent evolution: gene sharing by eukaryotic plant pathogens.
- 2006
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Ingår i: Curr Biol. - 0960-9822. ; 16:18, s. R804-6
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Forskningsöversikt (populärvet., debatt m.m.)abstract
- Oomycetes and filamentous parasitic fungi are plant pathogens that have undergone convergent evolution. A recent study has shown that these microbial eukaryotes have exchanged metabolic genes, which might explain some of their phenotypic similarities.
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| 33. |
- André, Domenique, et al.
(författare)
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FLOWERING LOCUS T paralogs control the annual growth cycle in Populus trees
- 2022
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 32:13, s. 2988-2996.e4
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Tidskriftsartikel (refereegranskat)abstract
- In temperate and boreal regions, perennials adapt their annual growth cycle to the change of seasons. These adaptations ensure survival in harsh environmental conditions, allowing growth at different latitudes and altitudes, and are therefore tightly regulated. Populus tree species cease growth and form terminal buds in autumn when photoperiod falls below a certain threshold.1 This is followed by establishment of dormancy and cold hardiness over the winter. At the center of the photoperiodic pathway in Populus is the gene FLOWERING LOCUS T2 (FT2), which is expressed during summer and harbors significant SNPs in its locus associated with timing of bud set.1–4 The paralogous gene FT1, on the other hand, is hyper-induced in chilling buds during winter.3,5 Even though its function is so far unknown, it has been suggested to be involved in the regulation of flowering and the release of winter dormancy.3,5 In this study, we employ CRISPR-Cas9-mediated gene editing to individually study the function of the FT-like genes in Populus trees. We show that while FT2 is required for vegetative growth during spring and summer and regulates the entry into dormancy, expression of FT1 is absolutely required for bud flush in spring. Gene expression profiling suggests that this function of FT1 is linked to the release of winter dormancy rather than to the regulation of bud flush per se. These data show how FT duplication and sub-functionalization have allowed Populus trees to regulate two completely different and major developmental control points during the yearly growth cycle.
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| 34. |
- Appeltans, W., et al.
(författare)
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The Magnitude of Global Marine Species Diversity
- 2012
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 22:23, s. 2189-2202
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Tidskriftsartikel (refereegranskat)abstract
- Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are similar to 226,000 eukaryotic marine species described. More species were described in the past decade (similar to 20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are similar to 170,000 synonyms, that 58,000-72,000 species are collected but not yet described, and that 482,000-741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7-1.0 million marine species. Past rates of description of new species indicate there may be 0.5 +/- 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
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| 35. |
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| 36. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Habitat complexity affects microbial growth in fractal maze
- 2023
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Ingår i: Current biology : CB. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 33:8, s. 4-1458
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Tidskriftsartikel (refereegranskat)abstract
- The great variety of earth's microorganisms and their functions are attributed to the heterogeneity of their habitats, but our understanding of the impact of this heterogeneity on microbes is limited at the microscale. In this study, we tested how a gradient of spatial habitat complexity in the form of fractal mazes influenced the growth, substrate degradation, and interactions of the bacterial strain Pseudomonas putida and the fungal strain Coprinopsis cinerea. These strains responded in opposite ways: complex habitats strongly reduced fungal growth but, in contrast, increased the abundance of bacteria. Fungal hyphae did not reach far into the mazes and forced bacteria to grow in deeper regions. Bacterial substrate degradation strongly increased with habitat complexity, even more than bacterial biomass, up to an optimal depth, while the most remote parts of the mazes showed both decreased biomass and substrate degradation. These results suggest an increase in enzymatic activity in confined spaces, where areas may experience enhanced microbial activity and resource use efficiency. Very remote spaces showing a slower turnover of substrates illustrate a mechanism which may contribute to the long-term storage of organic matter in soils. We demonstrate here that the sole effect of spatial microstructures affects microbial growth and substrate degradation, leading to differences in local microscale spatial availability. These differences might add up to considerable changes in nutrient cycling at the macroscale, such as contributing to soil organic carbon storage.
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| 37. |
- Arias, Pablo, et al.
(författare)
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Facial mimicry in the congenitally blind
- 2021
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 31:19, s. 1112-1114
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Tidskriftsartikel (refereegranskat)abstract
- Imitation is one of the core building blocks of human social cognition, supporting capacities as diverse as empathy, social learning, and knowledge acquisition1. Newborns’ ability to match others’ motor acts, while quite limited initially, drastically improves during the first months of development2. Of notable importance to human sociality is our tendency to rapidly mimic facial expressions of emotion. Facial mimicry develops around six months of age3, but because of its late emergence, the factors supporting its development are relatively unknown. One possibility is that the development of facial mimicry depends on seeing emotional imitative behavior in others4. Alternatively, the drive to imitate facial expressions of emotion may be independent of visual learning and be supported by modality-general processes. Here we report evidence for the latter, by showing that congenitally blind participants facially imitate smiles heard in speech, despite having never seen a facial expression.
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| 38. |
- Arshamian, Artin, et al.
(författare)
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The perception of odor pleasantness is shared across cultures
- 2022
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 32:9, s. 2061-2066, e1-e3
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Tidskriftsartikel (refereegranskat)abstract
- Humans share sensory systems with a common anatomical blueprint, but individual sensory experience nevertheless varies. In olfaction, it is not known to what degree sensory perception, particularly the perception of odor pleasantness, is founded on universal principles dictated by culture or merely a matter of personal taste. To address this, we asked 225 individuals from 9 diverse nonwestern cultures—hunter-gatherer to urban dwelling—to rank the monomolecular odorants from most to least pleasant. Contrary to expectations, culture explained only 6% of the variance in pleasantness rankings, whereas individual variability or personal taste explained 54%. Importantly, there was substantial global consistency, with molecular identity explaining 41% of the variance in odor pleasantness rankings. Critically, these universal rankings were predicted by the physicochemical properties of out-of-sample molecules and out-of-sample pleasantness ratings given by a tenth group of western urban participants. Taken together, this shows human olfactory perception is strongly constrained by universal principles.
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| 39. |
- Aryal, Bibek, et al.
(författare)
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Interplay between Cell Wall and Auxin Mediates the Control of Differential Cell Elongation during Apical Hook Development
- 2020
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 30, s. 1733-1739
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Tidskriftsartikel (refereegranskat)abstract
- Differential growth plays a crucial role during morphogenesis [1-3]. In plants, development occurs within mechanically connected tissues, and local differences in cell expansion lead to deformations at the organ level, such as buckling or bending [4, 5]. During early seedling development, bending of hypocotyl by differential cell elongation results in apical hook structure that protects the shoot apical meristem from being damaged during emergence from the soil [6, 7]. Plant hormones participate in apical hook development, but not how they mechanistically drive differential growth [8]. Here, we present evidence of interplay between hormonal signals and cell wall in auxin-mediated differential cell elongation using apical hook development as an experimental model. Using genetic and cell biological approaches, we show that xyloglucan (a major primary cell wall component) mediates asymmetric mechanical properties of epidermal cells required for hook development. The xxt1 xxt2 mutant, deficient in xyloglucan [9], displays severe defects in differential cell elongation and hook development. Analysis of xxt1 xxt2 mutant reveals a link between cell wall and transcriptional control of auxin transporters PINFORMEDs (PINs) and AUX1 crucial for establishing the auxin response maxima required for preferential repression of elongation of the cells on the inner side of the hook. Genetic evidence identifies auxin response factor ARF2 as a negative regulator acting downstream of xyloglucan-dependent control of hook development and transcriptional control of polar auxin transport. Our results reveal a crucial feedback process between the cell wall and transcriptional control of polar auxin transport, underlying auxin-dependent control of differential cell elongation in plants.
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| 40. |
- Azeez, Abdul, et al.
(författare)
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A Tree Ortholog of APETALA1 Mediates Photoperiodic Control of Seasonal Growth
- 2014
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 24, s. 717-724
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Tidskriftsartikel (refereegranskat)abstract
- Background: Photoperiodic control of development plays a key role in adaptation of plants to seasonal changes. A signaling module consisting of CONSTANS (CO) and FLOWERING LOCUS T (FT) mediates in photoperiodic control of a variety of developmental transitions (e. g., flowering, tuberization, and seasonal growth cessation in trees). How this conserved CO/FT module can mediate in the photoperiodic control of diverse unrelated developmental programs is poorly understood.Results: We show that Like-AP1 (LAP1), a tree ortholog of Arabidopsis floral meristem identity gene APETALA1 (AP1), mediates in photoperiodic control of seasonal growth cessation downstream of the CO/FT module in hybrid aspen. Using LAP1 overexpressors and RNAi-suppressed transgenic trees, we demonstrate that short day (SD)-mediated downregulation of LAP1 expression is required for growth cessation. In contrast with AP1 targets in flowering, LAP1 acts on AINTEGUMENTA-like 1 transcription factor, which is implicated in SD-mediated growth cessation. Intriguingly, unlike AP1 in Arabidopsis, ectopic expression of LAP1 fails to induce early flowering in hybrid aspen trees.Conclusions: These results indicate that AP1 ortholog in trees has acquired a novel function in photoperiodic regulation of seasonal growth. Thus, photoperiodic signaling pathway may have diverged downstream of AP1/LAP1 rather than the CO/FT module during evolution. Moreover, control of flowering by the CO/FT module can be uncoupled from its role in photoperiodic control of seasonal growth in trees. Thus, our findings can explain mechanistically how a conserved signaling module can mediate in the control of a highly diverse set of developmental transitions by a similar input signal, namely photoperiod.
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| 41. |
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| 42. |
- Bach, Dominik R., et al.
(författare)
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Human Hippocampus Arbitrates Approach-Avoidance Conflict
- 2014
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 24:5, s. 541-547
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Tidskriftsartikel (refereegranskat)abstract
- Animal models of human anxiety often invoke a conflict between approach and avoidance [1, 2]. In these, a key behavioral assay comprises passive avoidance of potential threat and inhibition, both thought to be controlled by ventral hippocampus [2-6]. Efforts to translate these approaches to clinical contexts [7, 8] are hampered by the fact that it is not known whether humans manifest analogous approach-avoidance dispositions and, if so, whether they share a homologous neurobiological substrate [9]. Here, we developed a paradigm to investigate the role of human hippocampus in arbitrating an approach-avoidance conflict under varying levels of potential threat. Across four experiments, subjects showed analogous behavior by adapting both passive avoidance behavior and behavioral inhibition to threat level. Using functional magnetic resonance imaging (fMRI), we observe that threat level engages the anterior hippocampus, the human homolog of rodent ventral hippocampus [10]. Testing patients with selective hippocampal lesions, we demonstrate a causal role for the hippocampus with patients showing reduced passive avoidance behavior and inhibition across all threat levels. Our data provide the first human assay for approach-avoidance conflict akin to that of animal anxiety models. The findings bridge rodent and human research on passive avoidance and behavioral inhibition and furnish a framework for addressing the neuronal underpinnings of human anxiety disorders, where our data indicate a major role for the hippocampus.
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| 43. |
- Baden, Tom, et al.
(författare)
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Is our retina really upside down?
- 2022
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 32:7, s. 300-303
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Tidskriftsartikel (refereegranskat)
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| 44. |
- Baird, Emily, et al.
(författare)
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X-ray micro computed-tomography
- 2017
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822. ; 27:8, s. 289-291
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Tidskriftsartikel (refereegranskat)abstract
- Emily Baird and Gavin Taylor describe how you can make three-dimensional models of biological samples using x-ray micro-computed tomography
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| 45. |
- Barlow, Axel, et al.
(författare)
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Middle Pleistocene genome calibrates a revised evolutionary history of extinct cave bears
- 2021
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 31:8, s. 1771-1779
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Tidskriftsartikel (refereegranskat)abstract
- Palaeogenomes provide the potential to study evolutionary processes in real time, but this potential is limited by our ability to recover genetic data over extended timescales.1 As a consequence, most studies so far have focused on samples of Late Pleistocene or Holocene age, which covers only a small part of the history of many clades and species. Here, we report the recovery of a low coverage palaeogenome from the petrous bone of a 360,000 year old cave bear from Kudaro 1 cave in the Caucasus Mountains. Analysis of this genome alongside those of several Late Pleistocene cave bears reveals widespread mito-nuclear discordance in this group. Using the time interval between Middle and Late Pleistocene cave bear genomes, we directly estimate ursid nuclear and mitochondrial substitution rates to calibrate their respective phylogenies. This reveals postdivergence mitochondrial transfer as the dominant factor explaining their mito-nuclear discordance. Interestingly, these transfer events were not accompanied by large-scale nuclear introgression. However, we do detect additional instances of nuclear admixture among other cave bear lineages, and between cave bears and brown bears, which are not associated with mitochondrial exchange. Genomic data obtained from the Middle Pleistocene cave bear petrous bone has thus facilitated a revised evolutionary history of this extinct megafaunal group. Moreover, it suggests that petrous bones may provide a means of extending both the magnitude and time depth of palaeogenome retrieval over substantial portions of the evolutionary histories of many mammalian clades.
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| 46. |
- Barnett, Paul D, et al.
(författare)
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Motion adaptation and the velocity coding of natural scenes
- 2010
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 20:11, s. 994-999
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Tidskriftsartikel (refereegranskat)abstract
- Estimating relative velocity in the natural environment is challenging because natural scenes vary greatly in contrast and spatial structure. Widely accepted correlation-based models for elementary motion detectors (EMDs) are sensitive to contrast and spatial structure and consequently generate ambiguous estimates of velocity [1]. Identified neurons in the third optic lobe of the hoverfly can reliably encode the velocity of natural images largely independent of contrast [2], despite receiving inputs directly from arrays of such EMDs [3, 4]. This contrast invariance suggests an important role for additional neural processes in robust encoding of image motion [2, 5, 6]. However, it remains unclear which neural processes are contributing to contrast invariance. By recording from horizontal system neurons in the hoverfly lobula, we show two activity-dependent adaptation mechanisms acting as near-ideal normalizers for images of different contrasts that would otherwise produce highly variable response magnitudes. Responses to images that are initially weak neural drivers are boosted over several hundred milliseconds. Responses to images that are initially strong neural drivers are reduced over longer time scales. These adaptation mechanisms appear to be matched to higher-order natural image statistics reconciling the neurons' accurate encoding of image velocity with the inherent ambiguity of correlation-based motion detectors.
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| 47. |
- Barnett, Paul, et al.
(författare)
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Retinotopic organization of small-field-target-detecting neurons in the insect visual system.
- 2007
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 17:7, s. 569-578
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundDespite having tiny brains and relatively low-resolution compound eyes, many fly species frequently engage in precisely controlled aerobatic pursuits of conspecifics. Recent investigations into high-order processing in the fly visual system have revealed a class of neurons, coined small-target-motion detectors (STMDs), capable of responding robustly to target motion against the motion of background clutter. Despite limited spatial acuity in the insect eye, these neurons display exquisite sensitivity to small targets. ResultsWe recorded intracellularly from morphologically identified columnar neurons in the lobula complex of the hoverfly Eristalis tenax. We show that these columnar neurons with exquisitely small receptive fields, like their large-field counterparts recently described from both male and female flies, have an extreme selectivity for the motion of small targets. In doing so, we provide the first physiological characterization of small-field neurons in female flies. These retinotopically organized columnar neurons include both direction-selective and nondirection-selective classes covering a large area of visual space. ConclusionsThe retinotopic arrangement of lobula columnar neurons sensitive to the motion of small targets makes a strong case for these neurons as important precursors in the local processing of target motion. Furthermore, the continued response of STMDs with such small receptive fields to the motion of small targets in the presence of moving background clutter places further constraints on the potential mechanisms underlying their small-target tuning.
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| 48. |
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| 49. |
- Barnett, Ross, et al.
(författare)
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Genomic Adaptations and Evolutionary History of the Extinct Scimitar-Toothed Cat, Homotherium latidens
- 2020
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Ingår i: Current Biology. - 0960-9822 .- 1879-0445.
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Tidskriftsartikel (refereegranskat)abstract
- Summary Homotherium was a genus of large-bodied scimitar-toothed cats, morphologically distinct from any extant felid species, that went extinct at the end of the Pleistocene [1, 2, 3, 4]. They possessed large, saber-form serrated canine teeth, powerful forelimbs, a sloping back, and an enlarged optic bulb, all of which were key characteristics for predation on Pleistocene megafauna [5]. Previous mitochondrial DNA phylogenies suggested that it was a highly divergent sister lineage to all extant cat species [6, 7, 8]. However, mitochondrial phylogenies can be misled by hybridization [9], incomplete lineage sorting (ILS), or sex-biased dispersal patterns [10], which might be especially relevant for Homotherium since widespread mito-nuclear discrepancies have been uncovered in modern cats [10]. To examine the evolutionary history of Homotherium, we generated a ∼7x nuclear genome and a ∼38x exome from H. latidens using shotgun and target-capture sequencing approaches. Phylogenetic analyses reveal Homotherium as highly divergent (∼22.5 Ma) from living cat species, with no detectable signs of gene flow. Comparative genomic analyses found signatures of positive selection in several genes, including those involved in vision, cognitive function, and energy consumption, putatively consistent with diurnal activity, well-developed social behavior, and cursorial hunting [5]. Finally, we uncover relatively high levels of genetic diversity, suggesting that Homotherium may have been more abundant than the limited fossil record suggests [3, 4, 11, 12, 13, 14]. Our findings complement and extend previous inferences from both the fossil record and initial molecular studies, enhancing our understanding of the evolution and ecology of this remarkable lineage.
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| 50. |
- Bass, David, et al.
(författare)
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Ascetosporea
- 2019
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Ingår i: Current Biology. - : CELL PRESS. - 0960-9822 .- 1879-0445. ; 29:1, s. R7-R8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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