Duplication and Divergence of Grass Genomes: Integrating the Chloridoids

Expressed Sequence Tags from a variety of plant species have been useful for comparative genomics. The evolution of the Chloridoideae subfamily, previously lacking sequence data, was clarified by analysis of Bermudagrass (Cynodon dactylon) ESTs generated from a normalized cDNA library. Using EST collections, we generated unigene sets and analyzed them to further elucidate the evolutionary history of grass subfamilies. A total of eight grasses (C. dactylon, Sorghum bicolor, Saccharum officinarum, Zea mays, Oryza sativa, Hordeum vulgare, Festuca arundinacea, and Triticum aestivum) in four subfamilies and five tribes were analyzed using two different approaches—synonymous substitution rates (Ks) and phylogenetic trees. Ks distributions of paralogous genes suggested several duplication events in C. dactylon, S. bicolor, H. vulgare, and T. aestivum. Phylogenetic analysis with the unigene sets indicated that the analyzed grasses diverged from a common ancestor after a shared ancient polyploidization (ca. 50.0?~?67.8 million years ago). Ks distributions of orthologous genes suggested that the Chloridoideae and Panicoideae subfamilies diverged about 34.6?~?38.5 million years ago. With the evidence described in this study, we found traces of genomic changes in some grass subfamilies after the divergence of the PACC and BEP clades as well as divergence of Chloridoideae subfamily.     

多巴胺系统调控鸣禽鸣唱相关神经核团及鸣唱行为

鸣禽的鸣唱与人类的语言产生相似,是一种复杂的习得性行为.因此,鸣禽可以作为研究人类语言学习与产生的重要模式动物.鸣禽鸣唱受到相互联系的鸣唱控制核团调控.多巴胺作为脑内重要的神经递质,参与调控哺乳动物多种活动.多巴胺及其受体在鸣禽鸣唱相关神经核团大量分布.近期研究表明,多巴胺通过调控鸣唱相关核团,促进鸣禽幼年期鸣曲学习、成年期鸣曲保持以及求偶性鸣唱的产生.本文结合本课题组的研究工作,对近年鸣禽多巴胺系统调控鸣唱相关神经核团及鸣唱行为的研究进展进行了综述,并提出了多巴胺信号调控鸣禽鸣唱学习行为的潜在机制.     

雄激素调控鸣禽鸣唱核团对鸣唱行为影响

鸣禽的鸣唱是一种习得性行为,它由脑内离散的神经核团所控制,这些核团相互关联构成鸣唱控制系统.鸣禽体内的性激素可以通过调控鸣唱系统来影响鸣唱行为.研究表明性激素中的雄激素在调节鸣唱稳定性方面发挥关键作用.雄激素可以通过调控细胞增殖、神经元电生理特性、突触传递及相关受体来影响鸣唱控制核团进而导致鸣唱行为改变.本文主要集中在雄激素对鸣禽鸣唱行为调控作用的神经机制研究进展进行论述.     

Integrating Proximate and Ultimate Causation in the Study of Vertebrate Behavior: Methods Considerations

SYNOPSIS. Methods issues are critical for the integration ofproximate and ultimate explanations of animal behavior. Understandingthat evolution of behavior may begin with changes in sensoryand perceptual systems is a first step. For example, advancesin neurobiology can trigger questions about social behavior.Variation in the size of particular brain areas, such as thehippocampus, can be related to variation in socio-spatial systems.Second, procedures, developed in recent years, provide new avenuesto understand behavior. Hormone assay techniques, such as RIAand ELISA, can be performed on some hormones from urine andfeces collected in the wild. Metabolic measurement, such asthe use of doublylabeled water, make it possible to measureenergy costs under field conditions. Advances in DNA technologiesprovide new perspectives, particularly with regard to measuringreproductive success. Third, current theories in behavior canbe tested with regard to physiological mechanisms; all thatis needed is some ingenuity to design and execute appropriatestudies. These include kin recognition, sex ratio variation,and foraging behavior. Fourth, cross—fertilization betweenlaboratory and field approaches produces new insights regardingbehavior. Organizational effects of hormones have now been exploredin field populations of mice and in domestic swine. Testingaspects of foraging behavior in the laboratory is another example.Fifth, simulation models have been used to produce new questionsabout both proximate and ultimate aspects of behavior. Exploringbehavioral phenomena may involve semi—natural settings.The suitability of semi—natural enclosures for the studyof house mouse behavior has been tested with regard to densityand home range size.     

Song Learning, Early Nutrition and Sexual Selection in Songbirds

SYNOPSIS. The developmental processes through which songbirdsacquire their species—typical songs have been well—studiedfrom a proximate perspective, but less attention has been givento the ultimate question of why birds learn to sing. We presenta new hypothesis for the adaptive significance of song learningin songbirds, suggesting that this specialized form of vocaldevelopment provides an indicator mechanism by which femalescan accurately assess the quality of potential mates. This hypothesisexpands on the established idea that song can provide an indicatorof male quality, but it explicitly links the variation in songexpression that females use to choose mates to the developmentalprocesses through which song is acquired. How well a male sings—reflectedin repertoire size or in other learned features of a male'ssinging behavior—provides an honest indicator of qualitybecause the timing of song learning and, more importantly, thetiming of the development of brain structures mediating learningcorresponds to a period in development during which young songbirdsare most likely to undergo nutritional stress. This correspondencemeans that song learning can provide a sensitive indicator ofearly developmental history in general, which in turn reflectsvarious aspects of the phenotypic and genotypic quality of apotential mate.     

鸣禽与人类发声器官及发声行为神经控制通路的比较

与人类语言学习或形成一样,鸣禽鸣唱也是一种发声学习行为,二者具有一定的相似性,例如发声学习过程均需听觉反馈的参与,幼年期具有更强的发声学习能力,可对复杂的声学结构和音节序列进行控制等。尽管鸣禽和人类的发声器官在结构上有很大差异,但二者发声的物理机制仍表现出很强的相似性。虽然相比于其他哺乳动物,鸣禽和人类的亲缘关系很远,但通过对比发声行为产生的基础通路——脑干先天发声控制通路,以及与发声学习相关的更高神经水平的发声运动和学习通路脑区位置、相互联系、功能及基因表达谱,提示鸣禽鸣唱和人类语言的神经控制具有一定的进化相似性。这些共同特征使得鸣禽成为了研究发声学习的理想模型。本文对鸣禽与人类的发声器官及发声行为的神经控制通路进行了比较,并对鸣禽模型在人类失语症治疗研究中潜在的应用前景进行了展望,以期为研究人类语言学习的神经机制及语言障碍的治疗带来理论参考和借鉴。     

Comparative Analysis of Protocadherin-11 X-Linked Expression among Postnatal Rodents,Non-Human Primates,and Songbirds Suggests Its Possible Involvement in Brain Evolution

Background

Protocadherin-11 is a cell adhesion molecule of the cadherin superfamily. Since, only in humans, its paralog is found on the Y chromosome, it is expected that protocadherin-11X/Y plays some role in human brain evolution or sex differences. Recently, a genetic mutation of protocadherin-11X/Y was reported to be associated with a language development disorder. Here, we compared the expression of protocadherin-11 X-linked in developing postnatal brains of mouse (rodent) and common marmoset (non-human primate) to explore its possible involvement in mammalian brain evolution. We also investigated its expression in the Bengalese finch (songbird) to explore a possible function in animal vocalization and human language faculties.

Methodology/Principal Findings

Protocadherin-11 X-linked was strongly expressed in the cerebral cortex, hippocampus, amygdala and brainstem. Comparative analysis between mice and marmosets revealed that in certain areas of marmoset brain, the expression was clearly enriched. In Bengalese finches, protocadherin-11 X-linked was expressed not only in nuclei of regions of the vocal production pathway and the tracheosyringeal hypoglossal nucleus, but also in areas homologous to the mammalian amygdala and hippocampus. In both marmosets and Bengalese finches, its expression in pallial vocal control areas was developmentally regulated, and no clear expression was seen in the dorsal striatum, indicating a similarity between songbirds and non-human primates.

Conclusions/Significance

Our results suggest that the enriched expression of protocadherin-11 X-linked is involved in primate brain evolution and that some similarity exists between songbirds and primates regarding the neural basis for vocalization.     

Integrating the Multiple Biological Causes of Human Behavior

I introduce a range of examples of different causal hypotheses about human mate selection. The hypotheses I focus on come from evolutionary psychology, fluctuating asymmetry research and chemical signaling research. I argue that a major obstacle facing an integrated biology of human behavior is the lack of a causal framework that shows how multiple proximate causal mechanisms can act together to produce components of our behavior.     

Rodent Brain Microinjection to Study Molecular Substrates of Motivated Behavior

Brain microinjection can aid elucidation of the molecular substrates of complex behaviors, such as motivation. For this purpose rodents can serve as appropriate models, partly because the response to behaviorally relevant stimuli and the circuitry parsing stimulus-action outcomes is astonishingly similar between humans and rodents. In studying molecular substrates of complex behaviors, the microinjection of reagents that modify, augment, or silence specific systems is an invaluable technique. However, it is crucial that the microinjection site is precisely targeted in order to aid interpretation of the results. We present a method for the manufacture of surgical implements and microinjection needles that enables accurate microinjection and unlimited customizability with minimal cost. Importantly, this technique can be successfully completed in awake rodents if conducted in conjunction with other JoVE articles that covered requisite surgical procedures. Additionally, there are many behavioral paradigms that are well suited for measuring motivation. The progressive ratio is a commonly used method that quantifies the efficacy of a reinforcer to maintain responding despite an (often exponentially) increasing work requirement. This assay is sensitive to reinforcer magnitude and pharmacological manipulations, which allows reinforcing efficacy and/ or motivation to be determined. We also present a straightforward approach to program operant software to accommodate a progressive ratio reinforcement schedule.     

Development of Auditory-Vocal Perceptual Skills in Songbirds

Songbirds are one of the few groups of animals that learn the sounds used for vocal communication during development. Like humans, songbirds memorize vocal sounds based on auditory experience with vocalizations of adult “tutors”, and then use auditory feedback of self-produced vocalizations to gradually match their motor output to the memory of tutor sounds. In humans, investigations of early vocal learning have focused mainly on perceptual skills of infants, whereas studies of songbirds have focused on measures of vocal production. In order to fully exploit songbirds as a model for human speech, understand the neural basis of learned vocal behavior, and investigate links between vocal perception and production, studies of songbirds must examine both behavioral measures of perception and neural measures of discrimination during development. Here we used behavioral and electrophysiological assays of the ability of songbirds to distinguish vocal calls of varying frequencies at different stages of vocal learning. The results show that neural tuning in auditory cortex mirrors behavioral improvements in the ability to make perceptual distinctions of vocal calls as birds are engaged in vocal learning. Thus, separate measures of neural discrimination and behavioral perception yielded highly similar trends during the course of vocal development. The timing of this improvement in the ability to distinguish vocal sounds correlates with our previous work showing substantial refinement of axonal connectivity in cortico-basal ganglia pathways necessary for vocal learning.     

基因组编码小分子蛋白质研究进展

不超过50个氨基酸组成的蛋白在所有生物体中表现的特征都不明显.对其相应的基进行确实可靠的注释非常具有挑战性.由从细胞中纯化和鉴定小分子蛋白产物极其困难,难以确切知道细胞内有多少小分子蛋白,更不用说研究它们的生物学功能了.但越来越多的例子表明,小分子蛋白在细胞中分布广泛,而且有着不同的细胞生理学功能.本文即是对小分子蛋白研究进展的简要总结.