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991.
To study the minimal length required for the secretion of recombinant proteins and silkproteins in posterior silk gland,the signal peptide(SP)of the fibroin heavy chain(FibH)of silkwormBombyx mori was systematically shortened from the C-terminal.Its effect on the secretion of protein wasobserved using enhanced green fluorescent protein(EGFP)as a reporter.Secretion of EGFP fusion proteinswas examined under fluorescence microscope.FibH SPs with lengths of 20,18,16 and 12 a.a.can directthe secretion of the reporter,yet those with lengths of 11, 10, 9, 8 and 1 a.a. can not. When the FibH SP wasshortened to 12a.a., the secretion efficiency was decreased slightly and cleavage occurred within EGFP.When 16a.a.of the FibH SP were used,the secretion of fusion protein was normal and the cleavage sitewas between the Gly-Ser linker and Met,the starting amino acid of EGFP. These findings are applicable forthe expression of foreign proteins in silkworm silk gland.The cleavage site of the SP is discussed andcompared with the predictive results of the SignalP 3.0 online prediction program. 相似文献
992.
Regulation of phosphate starvation responses in higher plants 总被引:8,自引:0,他引:8
Background
Phosphorus (P) is often a limiting mineral nutrient for plant growth. Many soils worldwide are deficient in soluble inorganic phosphate (Pi), the form of P most readily absorbed and utilized by plants. A network of elaborate developmental and biochemical adaptations has evolved in plants to enhance Pi acquisition and avoid starvation.Scope
Controlling the deployment of adaptations used by plants to avoid Pi starvation requires a sophisticated sensing and regulatory system that can integrate external and internal information regarding Pi availability. In this review, the current knowledge of the regulatory mechanisms that control Pi starvation responses and the local and long-distance signals that may trigger Pi starvation responses are discussed. Uncharacterized mutants that have Pi-related phenotypes and their potential to give us additional insights into regulatory pathways and Pi starvation-induced signalling are also highlighted and assessed.Conclusions
An impressive list of factors that regulate Pi starvation responses is now available, as is a good deal of knowledge regarding the local and long-distance signals that allow a plant to sense and respond to Pi availability. However, we are only beginning to understand how these factors and signals are integrated with one another in a regulatory web able to control the range of responses demonstrated by plants grown in low Pi environments. Much more knowledge is needed in this agronomically important area before real gains can be made in improving Pi acquisition in crop plants. 相似文献993.
Alison L. Hill David G. Rand Martin A. Nowak Nicholas A. Christakis 《Proceedings. Biological sciences / The Royal Society》2010,277(1701):3827-3835
Human populations are arranged in social networks that determine interactions and influence the spread of diseases, behaviours and ideas. We evaluate the spread of long-term emotional states across a social network. We introduce a novel form of the classical susceptible–infected–susceptible disease model which includes the possibility for ‘spontaneous’ (or ‘automatic’) infection, in addition to disease transmission (the SISa model). Using this framework and data from the Framingham Heart Study, we provide formal evidence that positive and negative emotional states behave like infectious diseases spreading across social networks over long periods of time. The probability of becoming content is increased by 0.02 per year for each content contact, and the probability of becoming discontent is increased by 0.04 per year per discontent contact. Our mathematical formalism allows us to derive various quantities from the data, such as the average lifetime of a contentment ‘infection’ (10 years) or discontentment ‘infection’ (5 years). Our results give insight into the transmissive nature of positive and negative emotional states. Determining to what extent particular emotions or behaviours are infectious is a promising direction for further research with important implications for social science, epidemiology and health policy. Our model provides a theoretical framework for studying the interpersonal spread of any state that may also arise spontaneously, such as emotions, behaviours, health states, ideas or diseases with reservoirs. 相似文献
994.
Simon Levin 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1537):13-18
Two conflicting tendencies can be seen throughout the biological world: individuality and collective behaviour. Natural selection operates on differences among individuals, rewarding those who perform better. Nonetheless, even within this milieu, cooperation arises, and the repeated emergence of multicellularity is the most striking example. The same tendencies are played out at higher levels, as individuals cooperate in groups, which compete with other such groups. Many of our environmental and other global problems can be traced to such conflicts, and to the unwillingness of individual agents to take account of the greater good. One of the great challenges in achieving sustainability will be in understanding the basis of cooperation, and in taking multicellularity to yet a higher level, finding the pathways to the level of cooperation that is the only hope for the preservation of the planet. 相似文献
995.
Krause J James R Croft DP 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1560):4099-4106
There is great interest in environmental effects on the development and evolution of animal personality traits. An important component of an individual's environment is its social environment. However, few studies look beyond dyadic relationships and try to place the personality of individuals in the context of a social network. Social network analysis provides us with many new metrics to characterize the social fine-structure of populations and, therefore, with an opportunity to gain an understanding of the role that different personalities play in groups, communities and populations regarding information or disease transmission or in terms of cooperation and policing of social conflicts. The network position of an individual is largely a consequence of its interactive strategies. However, the network position can also shape an individual's experiences (especially in the case of juveniles) and therefore can influence the way in which it interacts with others in future. Finally, over evolutionary time, the social fine-structure of animal populations (as quantified by social network analysis) can have important consequences for the evolution of personalities-an approach that goes beyond the conventional game-theoretic analyses that assumed random mixing of individuals in populations. 相似文献
996.
Uri Grodzinski Nicola S. Clayton 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1542):977-987
The scatter hoarding of food, or caching, is a widespread and well-studied behaviour. Recent experiments with caching corvids have provided evidence for episodic-like memory, future planning and possibly mental attribution, all cognitive abilities that were thought to be unique to humans. In addition to the complexity of making flexible, informed decisions about caching and recovering, this behaviour is underpinned by a motivationally controlled compulsion to cache. In this review, we shall first discuss the compulsive side of caching both during ontogeny and in the caching behaviour of adult corvids. We then consider some of the problems that these birds face and review the evidence for the cognitive abilities they use to solve them. Thus, the emergence of episodic-like memory is viewed as a solution for coping with food perishability, while the various cache-protection and pilfering strategies may be sophisticated tools to deprive competitors of information, either by reducing the quality of information they can gather, or invalidating the information they already have. Finally, we shall examine whether such future-oriented behaviour involves future planning and ask why this and other cognitive abilities might have evolved in corvids. 相似文献
997.
Alex Thornton Jamie Samson Tim Clutton-Brock 《Proceedings. Biological sciences / The Royal Society》2010,277(1700):3623-3629
Reports of socially transmitted traditions based on behavioural differences between geographically separated groups of conspecifics are contentious because they cannot exclude genetic or environmental causes. Here, we report persistent differences between neighbouring groups of meerkats (Suricata suricatta) where extensive gene flow precludes genetic differentiation. Over 11 years, some groups consistently emerged later from their sleeping burrows in the morning than others, despite complete turnovers in group membership and the influx of immigrants. Group territories overlapped and, in many cases, the same sleeping burrows were used by different groups. Differences persisted even after accounting for effects of group size, weather and burrow characteristics, and were unrelated to food availability within territories. These results provide compelling evidence that the emergence times of meerkat groups represent conservative traditions. 相似文献
998.
999.
Among parasitic platyhelminths with complex life cycles, it has been well documented that transmission opportunities are the main forces shaping the diversity of life‐history traits and parasite developmental strategies. While deviations in the development pathway usually involve shortening of life cycles, their extension may also occur following perception of remaining time by parasites. Polystoma gallieni, the monogenean parasite of Hyla meridionalis, is able to trigger two alternative developmental strategies depending on the physiological stage of the tadpoles upon which larvae attach. The distribution and reproductive outputs of both resulting phenotypes were surveyed to address questions about the dynamics of transmission in natural environments. Because modifications in the completion of life cycles can have drawbacks which may perturb the dynamic equilibrium of the resulting host–parasite systems, experimental infestations were also performed to assess parasite–parasite interactions. Our results suggest that the bladder adult phenotype, which involves transmission between frogs and tadpoles, is supplied secondarily by the branchial phenotype which involves transmission between tadpoles and metamorphs. They also support the occurrence of finely tuned trade‐offs between hosts and parasites and highlight positive trends behind the extension of direct life cycles, in which host‐derived signals account for the remaining time to achieve parasitic transmission. 相似文献
1000.
Social insect colonies represent distinct units of selection. Most individuals evolve by kin selection and forgo individual reproduction. Instead, they display altruistic food sharing, nest maintenance and self‐sacrificial colony defence. Recently, altruistic self‐removal of diseased worker ants from their colony was described as another important kin‐selected behaviour. Here, we report corroborating experimental evidence from honey bee foragers and theoretical analyses. We challenged honey bee foragers with prolonged CO2 narcosis or by feeding with the cytostatic drug hydroxyurea. Both treatments resulted in increased mortality but also caused the surviving foragers to abandon their social function and remove themselves from their colony, resulting in altruistic suicide. A simple model suggests that altruistic self‐removal by sick social insect workers to prevent disease transmission is expected under most biologically plausible conditions. The combined theoretical and empirical support for altruistic self‐removal suggests that it may be another important kin‐selected behaviour and a potentially widespread mechanism of social immunity. 相似文献