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Donatella Zona Peter M. Lafleur Koen Hufkens Beniamino Gioli Barbara Bailey George Burba Eugénie S. Euskirchen Jennifer D. Watts Kyle A. Arndt Mary Farina John S. Kimball Martin Heimann Mathias Göckede Martijn Pallandt Torben R. Christensen Mikhail Mastepanov Efrén López-Blanco Albertus J. Dolman Roisin Commane Charles E. Miller Josh Hashemi Lars Kutzbach David Holl Julia Boike Christian Wille Torsten Sachs Aram Kalhori Elyn R. Humphreys Oliver Sonnentag Gesa Meyer Gabriel H. Gosselin Philip Marsh Walter C. Oechel 《Global Change Biology》2023,29(5):1267-1281
Long-term atmospheric CO2 concentration records have suggested a reduction in the positive effect of warming on high-latitude carbon uptake since the 1990s. A variety of mechanisms have been proposed to explain the reduced net carbon sink of northern ecosystems with increased air temperature, including water stress on vegetation and increased respiration over recent decades. However, the lack of consistent long-term carbon flux and in situ soil moisture data has severely limited our ability to identify the mechanisms responsible for the recent reduced carbon sink strength. In this study, we used a record of nearly 100 site-years of eddy covariance data from 11 continuous permafrost tundra sites distributed across the circumpolar Arctic to test the temperature (expressed as growing degree days, GDD) responses of gross primary production (GPP), net ecosystem exchange (NEE), and ecosystem respiration (ER) at different periods of the summer (early, peak, and late summer) including dominant tundra vegetation classes (graminoids and mosses, and shrubs). We further tested GPP, NEE, and ER relationships with soil moisture and vapor pressure deficit to identify potential moisture limitations on plant productivity and net carbon exchange. Our results show a decrease in GPP with rising GDD during the peak summer (July) for both vegetation classes, and a significant relationship between the peak summer GPP and soil moisture after statistically controlling for GDD in a partial correlation analysis. These results suggest that tundra ecosystems might not benefit from increased temperature as much as suggested by several terrestrial biosphere models, if decreased soil moisture limits the peak summer plant productivity, reducing the ability of these ecosystems to sequester carbon during the summer. 相似文献
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Mariana D. Carrillo-Del Valle Jorge A. De la Garza-García Efrén Díaz-Aparicio Arturo G. Valdivia-Flores Luis F. Cisneros-Guzmán Cecilia Rosario Ángel H. Manjarrez-Hernández Armando Navarro Juan Xicohtencatl-Cortes Pablo Maravilla Rigoberto Hernández-Castro 《European Journal of Wildlife Research》2016,62(4):415-421
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Four types of tanycytes can be distinguished in the rat hypothalamus: 1 and 2 tanycytes establish an anatomical link between the ventricular cerebrospinal fluid (CSF) and the arcuate nucleus, whereas 1 and 2 tanycytes establish a link between CSF and portal blood. Endocytosis and transcytosis in these cells have been investigated by (1) immunocytochemistry with antibodies against molecular markers of the endocytotic and transcytotic pathways; (2) the administration of wheat germ agglutinin (WGA) into the ventricular or subarachnoidal CSF and following its internalisation by and its routing through tanycytes. The four populations of tanycytes show marked differences concerning the expression and subcellular location of proteins involved in endocytosis and transcytosis, such as clathrin, caveolin-1, Rab4 and ARF6. Thus, 1,2 tanycytes express caveolin-1 at the ventricular cell pole and at their terminals contacting the portal capillaries, whereas 1,2 tanycytes do not, suggesting that caveolae-dependant endocytosis does not occur in the latter and that, in 1,2 tanycytes, it may occur at both cell poles. In 1,2 tanycytes, clathrin is only expressed at the ventricular cell pole indicating that clathrin-dependant endocytosis operates for compounds present in the ventricular CSF and not for those exposed to the terminals. This agrees with the property of 1,2 tanycytes of internalising WGA through the ventricular cell pole but not through the terminals. The subcellular distribution in 1,2 tanycytes of WGA and of the proteins clathrin and Rab4 indicates that part of the internalised WGA follows the degradative pathway and part is sorted to a transcytotic pathway and that the transcytotic and the secretory pathways might intersect. Financial support was provided by grants 01/1050, from FIS, Spain (to J.L.B.) and 1030265, from FONDECYT, Chile (to E.M.R.) 相似文献
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Girardinichthys multiradiatus, locally known as "mexcalpique", is a small endemic fish of the Lerma river basin. Its presence in lakes (Zempoala) suggests a long-standing connection between these lakes and the river basin. The current range of this species in the Mexico and Toluca valley appears to have been reduced, making this park a refuge for the species. Nevertheless, little is known about its biology. We studied its diet and feeding habits in Acoyotongo Lake, Lagunas de Zempoala National Park (19 degrees 01'30"-19 degrees 06' N, 99 degrees 16'20"-99 degrees 21' W) where seasonal collections were carried out. The gut contents of 97 specimens were identified to the most specific taxonomic category possible and analyzed with numeric and frequency of occurrence methods. The general diet of this species consists of twelve dietary components, eleven of which are of animal origin. Hymenopterans, springtails and chironomids represented the highest percentage of ingestion and preference. G. multiradiatus is as a carnivorous species with entomophagous tendencies. 相似文献
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Efrén Santos Serge Remy Els Thiry Saskia Windelinckx Rony Swennen László Sági 《BMC plant biology》2009,9(1):77
Background
Next-generation transgenic plants will require a more precise regulation of transgene expression, preferably under the control of native promoters. A genome-wide T-DNA tagging strategy was therefore performed for the identification and characterization of novel banana promoters. Embryogenic cell suspensions of a plantain-type banana were transformed with a promoterless, codon-optimized luciferase (luc +) gene and low temperature-responsive luciferase activation was monitored in real time. 相似文献7.
Rogelio de J. Treviño-Rangel Byron A. Bodden-Mendoza Alexandra M. Montoya Hiram Villanueva-Lozano Mariana Elizondo-Zertuche Efrén Robledo-Leal Gloria M. González 《Revista iberoamericana de micología》2018,35(1):17-21
Background
Candida tropicalis is an increasingly important human pathogen which usually affects neutropenic oncology patients with common hematogenous seeding to peripheral organs and high mortality rates. Candida pathogenicity is facilitated by several virulence attributes, including secretion of hydrolytic enzymes; however, little is known regarding the C. tropicalis ability to secrete them and their role in the disease.Aims
To confirm by molecular means the identification of 187 clinical isolates (127 from blood, 52 from urine, and 8 from diverse clinical origins) phenotypically identified as C. tropicalis, and to investigate their in vitro aspartyl proteinase, phospholipase, esterase, hemolysin, DNase and coagulase activities.Methods
The molecular confirmation was performed by ITS sequencing, and the enzymatic determinations were conducted using plate assays with specific substrates, with the exception of coagulase, which was determined by the classical tube test.Results
The majority of the strains exhibited a very strong or strong activity of aspartyl proteinase, phospholipase and esterase. A 4.7% of the bloodstream isolates were hemolysin producers, and all were negative for the coagulase and DNase assays.Conclusions
Very strong activities of aspartyl proteinase, phospholipase and esterase profiles were detected, and a statistical association between phospholipase production and blood and urine isolates was found. 相似文献8.
Mendoza M Diaz E Alvarado P Romero E Bastardo de Albornoz MC 《Revista iberoamericana de micología》2007,24(4):317-319
The dimorphic fungus Sporothrix schenckii is the etiological agent of sporotrichosis, a subcutaneous mycosis frequently found in Latin America. The isolation of this fungus from the environment and other sources has been widely reported. Nevertheless, to our knowledge this fungus has not been isolated from the endemic areas of Venezuela. In studies related to a clinical case of sporotrichosis in "Colonia Tovar", produced by traumatism after manipulating soil samples, the fungus was isolated from the soil of that particular area. This is the first report of the isolation of S. schenckii from environmental sources in an endemic area of Venezuela. 相似文献
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Analysis of genes involved in arsenic resistance in Corynebacterium glutamicum ATCC 13032 总被引:2,自引:0,他引:2
Ordóñez E Letek M Valbuena N Gil JA Mateos LM 《Applied and environmental microbiology》2005,71(10):6206-6215