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31.
Here we elucidate a paradox: how a single chemoattractant-receptor system in two individuals is used for communication despite the seeming inevitability of self-excitation. In the filamentous fungus Neurospora crassa, genetically identical cells that produce the same chemoattractant fuse via the homing of individual cell protrusions toward each other. This is achieved via a recently described "ping-pong" pulsatile communication. Using a generic activator-inhibitor model of excitable behavior, we demonstrate that the pulse exchange can be fully understood in terms of two excitable systems locked into a stable oscillatory pattern of mutual excitation. The most puzzling properties of this communication are the sudden onset of oscillations with final amplitude, and the absence of seemingly inevitable self-excitation. We show that these properties result directly from both the excitability threshold and refractory period characteristic of excitable systems. Our model suggests possible molecular mechanisms for the ping-pong communication.  相似文献   
32.
The CCN family of proteins includes six members presently known as CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6. These proteins were originally designated CYR61, CTGF, NOV, and WISP-1, WISP-2, WISP-3. Although these proteins share a significant amount of structural features and a partial identity with other large families of regulatory proteins, they exhibit different biological functions. A critical examination of the progress made over the past two decades, since the first CCN proteins were discovered brings me to the conclusion that most of our present knowledge regarding the functions of these proteins was predicted very early after their discovery. In an effort to point out some of the gaps that prevent us to reach a comprehensive view of the functional interactions between CCN proteins, it is necessary to reconsider carefully data that was already published and put aside, either because the scientific community was not ready to accept them, or because they were not fitting with the « consensus » when they were published. This review article points to avenues that were not attracting the attention that they deserved. However, it is quite obvious that the six members of this unique family of tetra-modular proteins must act in concert, either simultaneously or sequentially, on the same sites or at different times in the life of living organisms. A better understanding of the spatio-temporal regulation of CCN proteins expression requires considering the family as such, not as a set of single proteins related only by their name. As proposed in this review, there is enough convincing pieces of evidence, at the present time, in favor of these proteins playing a role in the coordination of multiple signaling pathways, and constituting a Centralized Communication Network. Deciphering the hierarchy of regulatory circuits involved in this complex system is an important challenge for the near future. In this article, I would like to briefly review the concept of a CCN family of proteins and critically examine the progress made over the past 10 years in the understanding of their biological functions and involvement in both normal and pathological processes.  相似文献   
33.
Cell-to-cell interactions (CCIs) through ligand-receptor (LR) pairs in the tumor microenvironment underlie the poor prognosis of pancreatic ductal adenocarcinoma (PDAC). However, there is scant knowledge of the association of CCIs with PDAC prognosis, which is critical to the identification of potential therapeutic candidates. Here, we sought to identify the LR pairs associated with PDAC patient prognosis by integrating survival analysis and single-cell CCI prediction. Via survival analysis using gene expression from cancer cohorts, we found 199 prognostic LR pairs. CCI prediction based on single-cell RNA-seq data revealed the enriched LR pairs associated with poor prognosis. Notably, the CCIs involved epithelial tumor cells, cancer-associated fibroblasts, and tumor-associated macrophages through integrin-related and ANXA1FPR pairs. Finally, we determined that CCIs involving 33 poor-prognostic LR pairs were associated with tumor grade. Although the clinical implication of the set of LR pairs must be determined, our results may provide potential therapeutic targets in PDAC.  相似文献   
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35.
Electronic telemetry is frequently used to document animal movement through time. Methods that can identify underlying behaviors driving specific movement patterns can help us understand how and why animals use available space, thereby aiding conservation and management efforts. For aquatic animal tracking data with significant measurement error, a Bayesian state‐space model called the first‐Difference Correlated Random Walk with Switching (DCRWS) has often been used for this purpose. However, for aquatic animals, highly accurate tracking data are now becoming more common. We developed a new hidden Markov model (HMM) for identifying behavioral states from animal tracks with negligible error, called the hidden Markov movement model (HMMM). We implemented as the basis for the HMMM the process equation of the DCRWS, but we used the method of maximum likelihood and the R package TMB for rapid model fitting. The HMMM was compared to a modified version of the DCRWS for highly accurate tracks, the DCRWS, and to a common HMM for animal tracks fitted with the R package moveHMM. We show that the HMMM is both accurate and suitable for multiple species by fitting it to real tracks from a grey seal, lake trout, and blue shark, as well as to simulated data. The HMMM is a fast and reliable tool for making meaningful inference from animal movement data that is ideally suited for ecologists who want to use the popular DCRWS implementation and have highly accurate tracking data. It additionally provides a groundwork for development of more complex modeling of animal movement with TMB. To facilitate its uptake, we make it available through the R package swim.  相似文献   
36.
Microbial plant interaction plays a major role in the sustainability of plants. The understanding of phytomicrobiome interactions enables the gene-editing tools for the construction of the microbial consortia. In this interaction, microbes share several common secondary metabolites and terpenoid metabolic pathways with their host plants that ensure a direct connection between the microbiome and associated plant metabolome. In this way, the CRISPR-mediated gene-editing tool provides an attractive approach to accomplish the creation of microbial consortia. On the other hand, the genetic manipulation of the host plant with the help of CRISPR-Cas9 can facilitate the characterization and identification of the genetic determinants. It leads to the enhancement of microbial capacity for more trait improvement. Many plant characteristics like phytovolatilization, phytoextraction, phytodesalination and phytodegradation are targeted by these approaches. Alternatively, chemical communications by PGPB are accomplished by the exchange of different signal molecules. For example, quorum-sensing is the way of the cell to cell communication in bacteria that lead to the detection of metabolites produced by pathogens during adverse conditions and also helpful in devising some tactics towards understanding plant immunity. Along with quorum-sensing, different volatile organic compounds and N-acyl homoserine lactones play a significant role in cell to cell communication by microbe to plant and among the plants respectively. Therefore, it is necessary to get details of all the significant approaches that are useful in exploring cell to cell communications. In this review, we have described gene-editing tools and the cell to cell communication process by quorum-sensing based signaling. These signaling processes via CRISPR- Cas9 mediated gene editing can improve the microbe-plant community in adverse climatic conditions.  相似文献   
37.
Animal communication theory holds that in order to be evolutionarily stable, signals must be honest on average, but significant dishonesty (i.e. deception) by a subset of the population may also evolve. A typical praying mantid mating system involves active mate searching by males, which is guided by airborne sex pheromones in most species for which mate-searching cues have been studied. The Femme Fatale hypothesis suggests that female mantids may be selected to exploit conspecific males as prey if they benefit nutritionally from cannibalism. Such a benefit exists in the false garden mantid Pseudomantis albofimbriata—females use the resources gained from male consumption to significantly increase their body condition and reproductive output. This study aimed to examine the potential for chemical deception among the subset of females most likely to benefit from cannibalism (poorly fed females). Females were placed into one of four feeding treatments (‘Very Poor’, ‘Poor’, ‘Medium’ and ‘Good’), and males were given the opportunity to choose between visually obscured females in each of the treatments. Female body condition and fecundity varied linearly with food quantity; however, female attractiveness did not. That is, Very Poor females attracted significantly more males than any of the other female treatments, even though these females were in significantly poorer condition, less fecund (in this study) and more likely to cannibalise (in a previous study). In addition, there was a positive correlation between fecundity and attractiveness if Very Poor females were removed from the analysis, suggesting an inherently honest signalling system with a subset of dishonest individuals. This is the first empirical study to provide evidence of sexual deception via chemical cues, and the first to provide support for the Femme Fatale hypothesis.  相似文献   
38.
Behavioral barriers to gene flow often evolve faster than intrinsic incompatibilities and can eliminate the opportunity for hybridization between interfertile species. While acoustic signal divergence is a common driver of premating isolation in birds and insects, its contribution to speciation in mammals is less studied. Here we characterize the incidence of, and potential barriers to, hybridization among three closely related species of grasshopper mice (genus Onychomys). All three species use long‐distance acoustic signals to attract and localize mates; Onychomys arenicola and Onychomys torridus are acoustically similar and morphologically cryptic whereas Onychomys leucogaster is larger and acoustically distinct. We used genotyping‐by‐sequencing (GBS) to test for evidence of introgression in 227 mice from allopatric and sympatric localities in the western United States and northern Mexico. We conducted laboratory mating trials for all species pairs to assess reproductive compatibility, and recorded vocalizations from O. arenicola and O. torridus in sympatry and allopatry to test for evidence of acoustic character displacement. Hybridization was rare in nature and, contrary to prior evidence for O. torridus/O. arenicola hybrids, only involved O. leucogaster and O. arenicola. In contrast, laboratory crosses between O. torridus and O. arenicola produced litters whereas O. leucogaster and O. arenicola crosses did not. Call fundamental frequency in O. torridus and O. arenicola was indistinguishable in allopatry but significantly differentiated in sympatry, a pattern consistent with reproductive character displacement. These results suggest that assortative mating based on a long‐distance signal is an important isolating mechanism between O. torridus and O. arenicola and highlight the importance of behavioral barriers in determining the permeability of species boundaries.  相似文献   
39.
Fine structure of plasmodesmata in mature leaves of sugarcane   总被引:1,自引:0,他引:1  
The fine structure of plasmodesmata in vascular bundles and contiguous tissues of mature leaf blades of sugarcane (Saccharum interspecific hybrid L62–96) was studied with the transmission electron microscope. Tissues were fixed in glutaraldehyde, with and without the addition of tannic acid, and postfixed in OsO4. The results indicate that the fine structure of plasmodesmata in sugarcane differs among various cell combinations in a cell-specific manner, but that three basic structural variations can be recognized among plasmodesmata in the mature leaf: 1) Plasmodesmata between mesophyll cells. These plasmodesmata possess amorphous, electron-opaque structures, termed sphincters, that extend from plasma membrane to desmotubule near the orifices of the plasmodesmata. The cytoplasmic sleeve is filled by the sphincters where they occur; elsewhere it is open and entirely free of particulate or spokelike components. The desmotubule is tightly constricted and has no lumen within the sphincters, but between the sphincters it is a convoluted tubule with an open lumen. 2) Plasmodesmata that traverse the walls of chlorenchymatous bundle-sheath cells and mestome-sheath cells. In addition to the presence of sphincters, these plasmodesmata are modified by the presence of suberin lamellae in the walls. Although the plasmodesmata are quite narrow and the lumens of the desmotubules are constricted where they traverse the suberin lamellae, the cytoplasmic sleeves are still discernible and appear to contain substructural components there. 3) Plasmodesmata between parenchymatous cells of the vascular bundles. These plasmodesmata strongly resemble those found in the roots of Azolla, in that their desmotubules are closed for their entire length and their cytoplasmic sleeves appear to contain substructural components for their entire length. The structural variations exhibited by the plasmodesmata of the sugarcane leaf are compared with those proposed for a widely-adopted model of plasmodesmatal structure.Abbreviation ER endoplasmic reticulum This study was supported by National Science Foundation grants DCB 87-01116 and DCB 90-01759 to R.F.E. and a University of Wisconsin-Madison Dean's Fellowship to K. R.-B. We also thank Claudia Lipke and Kandis Elliot for photographic and artistic assistance, respectively.  相似文献   
40.
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