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991.
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Gabriel E Hoffman M Virginia Sanchez Puerta Charles F Delwiche 《BMC evolutionary biology》2011,11(1):101
Background
Light harvesting complex (LHC) proteins function in photosynthesis by binding chlorophyll (Chl) and carotenoid molecules that absorb light and transfer the energy to the reaction center Chl of the photosystem. Most research has focused on LHCs of plants and chlorophytes that bind Chl a and b and extensive work on these proteins has uncovered a diversity of biochemical functions, expression patterns and amino acid sequences. We focus here on a less-studied family of LHCs that typically bind Chl a and c, and that are widely distributed in Chl c-containing and other algae. Previous phylogenetic analyses of these proteins suggested that individual algal lineages possess proteins from one or two subfamilies, and that most subfamilies are characteristic of a particular algal lineage, but genome-scale datasets had revealed that some species have multiple different forms of the gene. Such observations also suggested that there might have been an important influence of endosymbiosis in the evolution of LHCs. 相似文献994.
Background
Stomatal guard cells are the regulators of gas exchange between plants and the atmosphere. Ca2+-dependent and Ca2+-independent mechanisms function in these responses. Key stomatal regulation mechanisms, including plasma membrane and vacuolar ion channels have been identified and are regulated by the free cytosolic Ca2+ concentration ([Ca2+]cyt).Scope
Here we show that CO2-induced stomatal closing is strongly impaired under conditions that prevent intracellular Ca2+ elevations. Moreover, Ca2+ oscillation-induced stomatal closing is partially impaired in knock-out mutations in several guard cell-expressed Ca2+-dependent protein kinases (CDPKs) here, including the cpk4cpk11 double and cpk10 mutants; however, abscisic acid-regulated stomatal movements remain relatively intact in the cpk4cpk11 and cpk10 mutants. We further discuss diverse studies of Ca2+ signalling in guard cells, discuss apparent peculiarities, and pose novel open questions. The recently proposed Ca2+ sensitivity priming model could account for many of the findings in the field. Recent research shows that the stomatal closing stimuli abscisic acid and CO2 enhance the sensitivity of stomatal closing mechanisms to intracellular Ca2+, which has been termed ‘calcium sensitivity priming’. The genome of the reference plant Arabidopsis thaliana encodes for over 250 Ca2+-sensing proteins, giving rise to the question, how can specificity in Ca2+ responses be achieved? Calcium sensitivity priming could provide a key mechanism contributing to specificity in eukaryotic Ca2+ signal transduction, a topic of central interest in cell signalling research. In this article we further propose an individual stomatal tracking method for improved analyses of stimulus-regulated stomatal movements in Arabidopsis guard cells that reduces noise and increases fidelity in stimulus-regulated stomatal aperture responses ( Box 1). This method is recommended for stomatal response research, in parallel to previously adopted blind analyses, due to the relatively small and diverse sizes of stomatal apertures in the reference plant Arabidopsis thaliana.Box 1. Improved resolution of stimulus-induced stomatal movements in guard cells by tracking of individual stomatal apertures
Arabidopsis guard cells have become a prime model system for analysing signal transduction, since early research combining genetic and ion channel analyses in this system (Ichida et al., 1997; Pei et al., 1997, 1998; Roelfsema and Prins, 1997). Arabidopsis stomata are small relative to other stomatal model systems and stomatal apertures of various plant types including Arabidopsis are known to show variability in the size of individual stomatal complexes and also variability in the opening apertures of stomata of similar size in a given leaf (Gorton et al., 1988; Mott and Buckley, 2000; Mott and Peak, 2007). Thus stomatal aperture measurements are expected to show a clear degree of statistical variation. Use of blind experiments, in which the genotype and, when possible, the stimulus being applied to guard cells is unknown to the experimenter (Murata et al., 2001) has been employed by several laboratories, has become a standard in the field and has aided in addressing the above limitations of the range of stomatal aperture sizes found under any given condition.Research in our laboratory has shown that a major additional improvement in experiments can be made, by adding imaging of the same individual stomatal apertures over time (Allen et al., 2001; Mori et al., 2006; Vahisalu et al., 2008; Siegel et al., 2009), while performing blind experiments. In such ‘stomatal tracking’ experiments the lower side of a leaf is attached to a glass coverslip in an extracellular incubation medium (Webb et al., 2001; Young et al., 2006). The mesophyll and upper leaf epidermis are removed surgically for better optical resolution of stomatal apertures in the intact lower leaf epidermis (Young et al., 2006). For stimulus-induced stomatal closing analyses, a field of well-opened stomata is located and images are captured (e.g. using Scion Image software) for later analyses and data storage. The bottom (dry side) of coverslips can be marked with colour marker pens to label grids in the regions where apertures where imaged, for finding these same stomata subsequently if needed. Images of the same stomatal apertures are taken over time and can be stored for later analyses of individual stomatal apertures and for deposition of image files. While this approach has been used as a standard for imposed Ca2+ oscillation studies (Allen et al., 2001; Mori et al., 2006; Vahisalu et al., 2008; Fig. 4), we have found that this method also substantially improves stomatal movement response analyses to any given stimulus (Siegel et al., 2009; see Figs 1 and 4 and, Box Fig. 1). For example, while individual stomata are known to have diverse apertures (e.g. Box Fig. 1C), the relative responses of wide open stomata and smaller stomatal apertures to ABA or to CO2 were comparable (Fig. 1 and Box Fig. 1; Siegel et al., 2009). Note that this method has previously been proposed and used in Vicia faba (Gorton et al., 1988), for which stomata exhibit relatively weak ABA and CO2 responses, compared with, for example, Arabidopsis. We propose that this simple image-capturing approach, together with blind analyses, be used as a standard for stomatal response research in arabidopsis. Our research experience with this method shows that this approach will aid in greatly improving resolution and robustness and in defining the functions of individual Ca2+-independent and Ca2+-dependent components and mechanisms in stomatal response analyses. Open in a separate windowBox Fig. 1.ABA-induced stomatal closing of individually tracked stomatal apertures. (A) Average individually tracked stomatal apertures in the presence of 50 µm Ca2+ (open triangles) and in the presence of 200 nm free Ca2+ (open squares) in the bath solution from three experiments are shown and were normalized to the stomatal apertures at time = 0. (B, C) ABA-induced stomatal closing in the presence of 50 µm Ca2+ in five individually tracked stomatal apertures. In (A; open triangles) normalized stomatal apertures of the same stomata depicted in (B) and (C) are shown. Methods used in these experiments tracking individual stomatal apertures are described in Siegel et al. (2009). ABA-induced stomatal closing experiments are reproduced from Siegel et al. (2009) with permission of the publisher. 相似文献995.
Manuo-ocular coordination in target tracking. II. Comparing the model with human behavior 总被引:2,自引:0,他引:2
Several studies have shown that humans track a moving visual target with their eyes better if the movement of this target
is directly controlled by the observer's hand. The improvement in performance has been attributed to coordination control
between the arm motor system and the smooth pursuit (SP) system. In such a task, the SP system shows characteristics that
differ from those observed during eye-alone tracking: latency (between the target-arm and the eye motion onsets) is shorter,
maximum SP velocity is higher and the maximum target motion frequency at which the SP can function effectively is also higher.
The aim of this article is to qualitatively evaluate the behavior of a dynamical model simulating the oculomotor system and
the arm motor system when both are involved in tracking visual targets. The evaluation is essentially based on a comparison
of the behavior of the model with the behavior of human subjects tracking visual targets under different conditions. The model
has been introduced and quantitatively evaluated in a companion paper. The model is based on an exchange of internal information
between the two sensorimotor systems, mediated by sensory signals (vision, arm muscle proprioception) and motor signals (arm
motor command copy). The exchange is achieved by a specialized structure of the central nervous system, previously identified
as a part of the cerebellum. Computer simulation of the model yielded results that fit the behavior of human subjects observed
during previously reported experiments, both qualitatively and quantitatively. The parallelism between physiology and human
behavior on the one hand, and structure and simulation of the model on the other hand, is discussed.
Received: 6 March 1997 / Accepted in revised form: 15 July 1997 相似文献
996.
997.
998.
Gabriel Vargas-Asensio Adrian Pinto-Tomas Beatriz Rivera Myriam Hernandez Carlos Hernandez Silvia Soto-Montero Catalina Murillo David H. Sherman Giselle Tamayo-Castillo 《PloS one》2014,9(11)
Coleopterans are the most diverse insect order described to date. These organisms have acquired an array of survival mechanisms through their evolution, including highly efficient digestive systems. Therefore, the coleopteran intestinal microbiota constitutes an important source of novel plant cell wall-degrading enzymes with potential biotechnological applications. We isolated and described the cultivable fungi, actinomycetes and aerobic eubacteria associated with the gut of larvae and adults from six different beetle families colonizing decomposing logs in protected Costa Rican ecosystems. We obtained 611 isolates and performed phylogenetic analyses using the ITS region (fungi) and 16S rDNA (bacteria). The majority of fungal isolates belonged to the order Hypocreales (26% of 169 total), while the majority of actinomycetes belonged to the genus Streptomyces (86% of 241 total). Finally, we isolated 201 bacteria spanning 19 different families belonging into four phyla: Firmicutes, α, β and γ-proteobacteria. Subsequently, we focused on microbes isolated from Passalid beetles to test their ability to degrade plant cell wall polymers. Highest scores in these assays were achieved by a fungal isolate (Anthostomella sp.), two Streptomyces and one Bacillus bacterial isolates. Our study demonstrates that Costa Rican beetles harbor several types of cultivable microbes, some of which may be involved in symbiotic relationships that enable the insect to digest complex polymers such as lignocellulose. 相似文献
999.
Juan José Soler Juan Gabriel Martínez Manuel Soler &Anders Pape Møller 《Ecology letters》2001,4(5):470-476
Interactions between parasitic cuckoos and their hosts represent a classic example of coevolution, where adaptations in the parasite to exploit the host select for defences, which in turn select for new parasite adaptations. Current interactions between the two parties may be at an evolutionary equilibrium or, alternatively, a coevolutionary arms race may be taking place. By taking into account the effect of gene flow in 15 European magpie ( Pica pica ) populations, we studied the coevolutionary interactions with its brood parasite, the great spotted cuckoo ( Clamator glandarius ). Our results suggest that, in Europe, magpies and cuckoos are engaged in an ongoing coevolutionary process because, despite controlling for the large amounts of gene flow among different magpie populations, we still found a positive relationship between host defence (i.e. foreign egg recognition and rejection) and parasite selection pressure. 相似文献
1000.
Gabriel Sergio Costa Alves Luana Ferreira Torres Sinara Oliveira de Aquino Tharyn Reichel Luciana Perreira Freire Natalia Gomes Vieira Felipe Vinecky Dominique This David Pot Hervé Etienne Luciano Vilela Paiva Pierre Marraccini Alan Carvalho Andrade 《Tropical plant biology》2018,11(1-2):31-48
Climate change is posing a major challenge to coffee production worldwide leading to a need for the development of coffee cultivars with increased drought tolerance. In several plant species, the use of DREB genes in crop improvement has achieved promising results to desiccation tolerance engineering. Recent studies reported CcDREB1D specific patterns of expression in Coffea canephora and functional evidence of this gene involvement in drought stress responses. However, knowledge on natural diversity of this gene is largely unknown. In this context, this study aimed at evaluating the sequence variability of the DREB1D gene in several Coffea genotypes. Nucleotide variation in promoters and coding regions of this gene were evaluated in a population consisting of 38 genotypes of C. canephora, C. arabica and C. eugenioides, most of them characterized by different phenotypes (tolerance vs. susceptibility) in relation to drought. The genetic diversity of the loci revealed different haplotypes for the promoter and coding regions. In particular, our findings suggest association between drought tolerance and the genetic variations on DREB1D promoter regions, but not with those from its corresponding coding regions. Gene expression studies revealed up-regulated expression of DREB1D gene upon drought mainly in leaves of drought-tolerant clones of C. canephora, and in response to drought, high, and low temperatures in leaves of C. arabica, suggesting a key role of this gene in coffee responses to abiotic stress. 相似文献