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981.
Pollinator Specificity and Convergence in Fly-pollinated Pleurothallis(Orchidaceae) Species: A Multiple Population Approach 总被引:1,自引:0,他引:1
We studied the floral biology of 12 populations of five rupicolousPleurothallis(Orchidaceae) species occurring in campo rupestre vegetationat nine localities in Brazil. All of these species are pollinatedby flies belonging to the families Chloropidae and Phoridae.In the five Pleurothallis species studied, all conspecific populationsattracted the same pollinator species. All pollinators werefemales; they laid eggs in flowers of the two nectarless species,but never in the flowers of nectar-presenting species. The twopairs ofPleurothallis species with similar flower morphologiesand odours attracted the same pollinators: P. johannensis -P. fabiobarrosii, pollinated by Tricimba sp. (Chloropidae) andP. teres - P. ochreata pollinated by Megaselia spp. (Phoridae).There was no overlap in the distribution of thePleurothallisspecies that shared pollinators. Despite similarities in floralmorphology and odour, genetic data show that these species pairsare not each other's closest relatives. We hypothesize thatthese similarities are due to convergence in allopatric speciesthat evolved similar pollination mechanisms. Conversely, thereare reasons to believe that adaptation to different pollinationmechanisms occurred in the closely related species P. johannensisand P. teres.Copyright 2001 Annals of Botany Company Pleurothallis, Orchidaceae, floral biology, fly-pollination, Chloropidae, Phoridae, pollinator specificity, campo rupestre 相似文献
982.
Francesca Salvemini Anne-Marie Marini Anna Riccio Eduardo J. Patriarca Maurizio Chiurazzi 《Gene》2001,270(1-2)
NH4+ is the main product of symbiotic nitrogen fixation and the external concentration of combined nitrogen plays a key regulatory role in all the different step of plant-rhizobia interaction. We report the cloning and characterization of the first member of the ammonium transporter family, LjAMT1;1 from a leguminous plant, Lotus japonicus. Sequence analysis reveals a close relationship to plant transporters of the AMT1 family. The wild type and two mutated versions of LjAMT1;1 were expressed and functionally characterized in yeast. LjAMT1;1 is transcribed in roots, leaves and nodules of L. japonicus plants grown under low nitrogen conditions, consistent with a role in uptake of NH4+ by the plant cells. 相似文献
983.
984.
985.
Tallman Gary; Zhu Jianxin; Mawson Bruce T.; Amodeo Gabriella; Nouhi Zepedeh; Levy Kathleen; Zeiger Eduardo 《Plant & cell physiology》1997,38(3):236-242
Facultative CAM plants such as Mesembryanthemum crystallinum(ice plant) possess C3 metabolism when unstressed but developCAM under water or salt stress. When ice plants shift from C3metabolism to CAM, their stomata remain closed during the dayand open at night. Recent studies have shown that the stomatalresponse of ice plants in the C3 mode depends solely on theguard cell response to blue light. Recent evidence for a possiblerole of the xanthophyll, zeaxanthin in blue light photoreceptionof guard cells led to the question of whether changes in theregulation of the xanthophyll cycle in guard cells parallelthe shift from diurnal to nocturnal stomatal opening associatedwith CAM induction. In the present study, light-dependent stomatalopening and the operation of the xanthophyll cycle were characterizedin guard cells isolated from ice plants shifting from C3 metabolismto CAM. Stomata in epidermis detached from leaves with C3 metabolismopened in response to white light and blue light, but they didnot open in response to red light. Guard cells from these leavesshowed light-dependent conversion of violaxan-thin to zeaxanthin.Induction of CAM by NaCI abolished both white light- and bluelight-stimulated stomatal opening and light-dependent zeaxanthinformation. When guard cells isolated from leaves with CAM weretreated with 100 mM ascorbate, pH 5.0 for 1 h in darkness, guardcell zeaxanthin content increased at rates equal to or higherthan those stimulated by light in guard cells from leaves inthe C3 mode. The ascorbate effect indicates that chloroplastsin guard cells from leaves with CAM retain their competenceto operate the xanthophyll cycle, but that zeaxanthin formationdoes not take place in the light. The data suggest that inhibitionof light-dependent zeaxanthin formation in guard cells mightbe one of the regulatory steps mediating the shift from diurnalto nocturnal stomatal opening typical of plants with CAM. (Received July 5, 1996; Accepted December 12, 1996) 相似文献
986.
Eduardo A. B. Almeida Marcio R. Pie Seán G. Brady Bryan N. Danforth 《Journal of Biogeography》2012,39(3):526-544
Aim The evolutionary history of bees is presumed to extend back in time to the Early Cretaceous. Among all major clades of bees, Colletidae has been a prime example of an ancient group whose Gondwanan origin probably precedes the complete break‐up of Africa, Antarctica, Australia and South America, because modern lineages of this family occur primarily in southern continents. In this paper, we aim to study the temporal and spatial diversification of colletid bees to better understand the processes that have resulted in the present southern disjunctions. Location Southern continents. Methods We assembled a dataset comprising four nuclear genes of a broad sample of Colletidae. We used Bayesian inference analyses to estimate the phylogenetic tree topology and divergence times. Biogeographical relationships were investigated using event‐based analytical methods: a Bayesian approach to dispersal–vicariance analysis, a likelihood‐based dispersal–extinction–cladogenesis model and a Bayesian model. We also used lineage through time analyses to explore the tempo of radiations of Colletidae and their context in the biogeographical history of these bees. Results Initial diversification of Colletidae took place at the Late Cretaceous (≥ 70 Ma). Several (6–14) lineage exchanges between Australia and South America via Antarctica during the Late Cretaceous and Eocene epochs could explain the disjunctions observed between colletid lineages today. All biogeographical methods consistently indicated that there were multiple lineage exchanges between South America and Australia, and these approaches were valuable in exploring the degree of uncertainty inherent in the ancestral reconstructions. Biogeographical and dating results preclude an explanation of Scrapterinae in Africa as a result of vicariance, so one dispersal event is assumed to explain the disjunction in relation to Euryglossinae. The net diversification rate was found to be highest in the recent history of colletid evolution. Main conclusions The biogeography and macroevolutionary history of colletid bees can be explained by a combination of Cenozoic vicariance and palaeoclimatic changes during the Neogene. The austral connection and posterior break‐up of South America, Antarctica and Australia resulted in a pattern of disjunct sister lineages. Increased biome aridification coupled with floristic diversification in the southern continents during the Neogene may have contributed to the high rates of cladogenesis in these bees in the last 25–30 million years. 相似文献
987.
Eduardo Krainer Ruth E. Stark Fred Naider Kumar Alagramam Jeffrey M. Becker 《Biopolymers》1994,34(12):1627-1635
Intact cells of Saccharomyces cerevisiae were examined as an aqueous paste by 13C-nmr spectroscopy with direct polarization and magic-angle spinning. The spectra obtained were highly resolved, showing numerous resonances in the 60-105 ppm range that were assigned to carbons of a liquid-like domain of the cell wall glucan. Assignments were confirmed by running the spectrum of S. cerevisiae in which the cell wall glucans were labeled with [13C] by feeding the cell [13C ] galactose. The spectra indicate that the glucan in the cell wall of intact S. cerevisiae assumes a helical conformation and suggest that strain 17A fed with galactose preferentially incorporates the resulting glucose into β(1 → 3)-linkages. © 1994 John Wiley & Sons, Inc. 相似文献
988.
Mary T. Doan Michael D. Neinast Erika L. Varner Kenneth C. Bedi David Bartee Helen Jiang Sophie Trefely Peining Xu Jay P. Singh Cholsoon Jang J. Eduardo Rame Donita C. Brady Jordan L. Meier Kenneth B. Marguiles Zoltan Arany Nathaniel W. Snyder 《Journal of lipid research》2022,63(6):100224
Anabolic metabolism of carbon in mammals is mediated via the one- and two-carbon carriers S-adenosyl methionine and acetyl-coenzyme A. In contrast, anabolic metabolism of three-carbon units via propionate has not been shown to extensively occur. Mammals are primarily thought to oxidize the three-carbon short chain fatty acid propionate by shunting propionyl-CoA to succinyl-CoA for entry into the TCA cycle. Here, we found that this may not be absolute as, in mammals, one nonoxidative fate of propionyl-CoA is to condense to two three-carbon units into a six-carbon trans-2-methyl-2-pentenoyl-CoA (2M2PE-CoA). We confirmed this reaction pathway using purified protein extracts provided limited substrates and verified the product via LC-MS using a synthetic standard. In whole-body in vivo stable isotope tracing following infusion of 13C-labeled valine at steady state, 2M2PE-CoA was found to form via propionyl-CoA in multiple murine tissues, including heart, kidney, and to a lesser degree, in brown adipose tissue, liver, and tibialis anterior muscle. Using ex vivo isotope tracing, we found that 2M2PE-CoA also formed in human myocardial tissue incubated with propionate to a limited extent. While the complete enzymology of this pathway remains to be elucidated, these results confirm the in vivo existence of at least one anabolic three- to six-carbon reaction conserved in humans and mice that utilizes propionate. 相似文献
989.
Brenda Díaz‐Crdenas Eduardo Ruiz‐Sanchez Hctor Gadsden Jos Manuel García‐Enriquez Patricia Castro‐Felix Gamaliel Castaeda‐Gaytn Anne Santerre 《Journal of Zoological Systematics and Evolutionary Research》2019,57(4):864-876
The biogeographic history of the Chihuahuan Desert is known to be complex, and there is evidence of the effects of physiographic and climatic events in species diversification and demographic population changes in many taxa. Here, using DNA sequence data, we studied the influence of the physiographic and climatic events that occurred in the Chihuahuan Desert during the Pliocene–Pleistocene transition on the speciation and evolutionary history of the sister lizard species Sceloporus cyanostictus and S. gadsdeni. First, based on mtDNA and nDNA sequences, we estimated the divergence times of the sister species. Then, based on mtDNA sequences, we investigated the demographic history of both species within a phylogeographic framework. The divergence time was inferred to be 1.48 Mya, date that corresponds to the existence of a large lake in the Mapimian subprovince, between the current geographic locations of S. cyanostictus and S. gadsdeni. This lake could have acted as a barrier, leading to the speciation of both species. For the demographic history of the two species, we identified two distinct patterns: the population expansion of S. gadsdeni within the Last Glacial Maximum and the potential population decline of S. cyanostictus. Our results can be used as a guide for the study of other aspects that could be critical to developing conservation actions that ensure the survival of not only S. gadsdeni and S. cyanostictus, but also other co‐occurring lizard species. 相似文献
990.
Daniel Pérez-Nú?ez Eduardo García-Urdiales Marta Martínez-Bonet María L. Nogal Susana Barroso Yolanda Revilla Ricardo Madrid 《PloS one》2015,10(4)
African swine fever virus (ASFV) CD2v protein is believed to be involved in virulence enhancement, viral hemadsorption, and pathogenesis, although the molecular mechanisms of the function of this viral protein are still not fully understood. Here we describe that CD2v localized around viral factories during ASFV infection, suggesting a role in the generation and/or dynamics of these viral structures and hence in disturbing cellular traffic. We show that CD2v targeted the regulatory trans-Golgi network (TGN) protein complex AP-1, a key element in cellular traffic. This interaction was disrupted by brefeldin A even though the location of CD2v around the viral factory remained unchanged. CD2v-AP-1 binding was independent of CD2v glycosylation and occurred on the carboxy-terminal part of CD2v, where a canonical di-Leu motif previously reported to mediate AP-1 binding in eukaryotic cells, was identified. This motif was shown to be functionally interchangeable with the di-Leu motif present in HIV-Nef protein in an AP-1 binding assay. However, we demonstrated that it was not involved either in CD2v cellular distribution or in CD2v-AP-1 binding. Taken together, these findings shed light on CD2v function during ASFV infection by identifying AP-1 as a cellular factor targeted by CD2v and hence elucidate the cellular pathways used by the virus to enhance infectivity. 相似文献