Therizinosauria are an unusual group of theropod dinosaurs, found mostly in the Cretaceous deposits in Mongolia, China and western USA. The basal forms of this group are represented by incomplete or disarticulated material. Here, we report a nearly complete, articulated skeleton of a new basal therizinosaur from the Early Cretaceous Yixian Formation of Jianchang County, western part of Liaoning Province, which sheds light on our understanding of anatomy of basal therizinosaurs. This new dinosaur shows some typical therizinosaur features, such as neural spines of the anterior caudal vertebrae that possess anterior and posterior alae, a rectangular buttress on the ventrolateral side of the proximal end of metacarpal I, and appressed metatarsal shafts. Our phylogenetic analysis suggests that it is a basal therizinosaur (sister taxon to Therizinosauroidea) because it bears many basal therizinosaur characters in the dentition, pelvis and hind limbs. The new therizinosaur described here has unique tooth and jaw characters such as the offsetting of the tooth row by a shelf and dentary teeth with labially concave and lingually convex dentary teeth, similar to ornithopods and ceratopsians.

BackgroundN fixation is one of the most important microbially driven ecosystem processes on Earth, allowing N to enter the soil from the atmosphere, and regulating plant productivity. A question that remains to be answered is whether such a fundamental process would still be that important in an over-fertilized world, as the long-term effects of fertilization on N fixation and associated diazotrophic communities remain to be tested. Here, we used a 35-year fertilization experiment, and investigated the changes in N fixation rates and the diazotrophic community in response to long-term inorganic and organic fertilization.ResultsIt was found that N fixation was drastically reduced (dropped by 50%) after almost four decades of fertilization. Our results further indicated that functionality losses were associated with reductions in the relative abundance of keystone and phylogenetically clustered N fixers such as Geobacter spp.ConclusionsOur work suggests that long-term fertilization might have selected against N fixation and specific groups of N fixers. Our study provides solid evidence that N fixation and certain groups of diazotrophic taxa will be largely suppressed in a more and more fertilized world, with implications for soil biodiversity and ecosystem functions.

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Cap-adjacent nucleotides of animal, protist and viral mRNAs can be O-methylated at the 2‘ position of the ribose (cOMe). The functions of cOMe in animals, however, remain largely unknown. Here we show that the two cap methyltransferases (CMTr1 and CMTr2) of Drosophila can methylate the ribose of the first nucleotide in mRNA. Double-mutant flies lack cOMe but are viable. Consistent with prominent neuronal expression, they have a reward learning defect that can be rescued by conditional expression in mushroom body neurons before training. Among CMTr targets are cell adhesion and signaling molecules. Many are relevant for learning, and are also targets of Fragile X Mental Retardation Protein (FMRP). Like FMRP, cOMe is required for localization of untranslated mRNAs to synapses and enhances binding of the cap binding complex in the nucleus. Hence, our study reveals a mechanism to co-transcriptionally prime mRNAs by cOMe for localized protein synthesis at synapses.

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Reversal learning has been widely used to probe the implementation of cognitive flexibility in the brain. Previous studies in monkeys identified an essential role of the orbitofrontal cortex (OFC) in reversal learning. However, the underlying circuits and molecular mechanisms are poorly understood. Here, we use the T-maze to investigate the neural mechanism of olfactory reversal learning in Drosophila. By adding a reversal training cycle to the classical learning protocol, we show that wildtype flies are able to reverse their choice according to the alteration of conditioned stimulus (CS)-unconditioned stimulus (US) contingency. The reversal protocol induced a specific suppression of the initial memory, an effect distinct from memory decay or extinction. GABA down-regulation in the anterior paired lateral (APL) neurons, which innervate the mushroom bodies (MBs), eliminates this suppression effect and impairs normal reversal. These findings reveal that inhibitory regulation from the GABAergic APL neurons facilitates olfactory reversal learning by suppressing initial memory in Drosophila.[Supplemental material is available for this article.]Cognitive flexibility is one of the most salient characteristics of biological intelligence. Even for insects, the ability to respond flexibly to an ever-changing environment is vital for survival. The reversal learning paradigm is often used to study the neural basis of cognitive flexibility. A typical reversal learning process involves establishing and then altering an association between a conditioned stimulus (CS) and an unconditioned stimulus (US, either reward or punishment) (Kringelbach 2005;Murray et al. 2007). One of the most significant findings regarding reversal learning was the identification of the importance of the orbitofrontal cortex (OFC) for reversal acquisition in monkeys (Iversen and Mishkin 1970). Furthermore, the role of OFC in reversal learning seems to be conserved across species: rats, cats, mice, monkeys, and humans with OFC damage acquire reversals more slowly (Murray et al. 2007), which suggests the existence of a general underlying mechanism. In addition, work in honeybees has shown that the mushroom bodies (MBs), the brain structures strongly associated with olfactory learning and memory, are required for the normal acquisition of reversal learning (Devaud et al. 2007).In Drosophila, olfactory reversal learning is usually assayed using the T-maze platform initially designed to study olfactory classical learning (Quinn et al. 1974;Tully and Quinn 1985;Tully et al. 1990;Dubnau et al. 2001;Wu et al. 2007;Shuai et al. 2010). Basically, a reversal training cycle (cycle 2) with reversed CS-US contingency is added after the normal classical training cycle (cycle 1) and before the testing period. The flies selectively avoid the odor more recently paired with shock, regardless of what they learned during cycle 1 (Tully and Quinn 1985). Furthermore, the cycle 2 training interacts nonadditively with the cycle 1 memory (Tully et al. 1990), which indicates an ...

Inflexible cognition and behavior are prominent features of prefrontal cortex damage and several neuropsychiatric disorders. The ability to flexibly adapt cognitive processing and behavior to dynamically changing environmental contingencies has been studied using the reversal learning paradigm in mammals, but the complexity of the brain circuits precludes a detailed analysis of the underlying neural mechanism. Here we study the neural circuitry mechanism supporting flexible behavior in a genetically tractable model organism, Drosophila melanogaster. Combining quantitative behavior analysis and genetic manipulation, we found that inhibition from a single pair of giant GABAergic neurons, the anterior paired lateral (APL) neurons, onto the mushroom bodies (MBs) selectively facilitates behavioral flexibility during visual reversal learning. This effect was mediated by ionotropic GABA A receptors in the MB. Moreover, flies with perturbed MB output recapitulated the poor reversal performance of flies with dysfunctional APL neurons. Importantly, we observed that flies with dysfunctional APL-MB circuit performed normally in simple forms of visual learning, including initial learning, extinction, and differential conditioning. Finally, we showed that acute disruption of the APL-MB circuit is sufficient to impair visual reversal learning. Together, these data suggest that the APL-MB circuit plays an essential role in the resolution of conflicting reinforcement contingencies and reveals an inhibitory neural mechanism underlying flexible behavior in Drosophila.

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