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941.
Laura Tatjer Almudena Sacristán-Reviriego Carlos Casado Asier González Boris Rodríguez-Porrata Lorena Palacios David Canadell Albert Serra-Cardona Humberto Martín María Molina Joaquín Ari?o 《Genetics》2016,202(1):141-156
The Saccharomyces cerevisiae type 2C protein phosphatase Ptc1 is required for a wide variety of cellular functions, although only a few cellular targets have been identified. A genetic screen in search of mutations in protein kinase–encoding genes able to suppress multiple phenotypic traits caused by the ptc1 deletion yielded a single gene, MKK1, coding for a MAPK kinase (MAPKK) known to activate the cell-wall integrity (CWI) Slt2 MAPK. In contrast, mutation of the MKK1 paralog, MKK2, had a less significant effect. Deletion of MKK1 abolished the increased phosphorylation of Slt2 induced by the absence of Ptc1 both under basal and CWI pathway stimulatory conditions. We demonstrate that Ptc1 acts at the level of the MAPKKs of the CWI pathway, but only the Mkk1 kinase activity is essential for ptc1 mutants to display high Slt2 activation. We also show that Ptc1 is able to dephosphorylate Mkk1
in vitro. Our results reveal the preeminent role of Mkk1 in signaling through the CWI pathway and strongly suggest that hyperactivation of Slt2 caused by upregulation of Mkk1 is at the basis of most of the phenotypic defects associated with lack of Ptc1 function. 相似文献
942.
Temperate migrants and resident bird species in Afro‐tropical savannahs show similar levels of ecological generalism 下载免费PDF全文
The specificity of an animal's habitat requirements will determine its ability to deal with anthropogenic climate and habitat change. Migratory birds are thought to be particularly vulnerable to such change, but theory predicts that they should be largely generalists. This prediction was tested with the aim of assessing whether migratory Palaearctic‐breeding birds wintering in the savannah biome of Africa are more or less generalist in their habitat use compared with taxonomically and ecologically similar Afro‐tropical resident species. The degree of specialization of these species groups to certain habitat characteristics was assessed and compared by calculating the relative occurrence of the species along habitat gradients, where wide occurrence indicates generalism and narrow occurrence indicates specialism. Palaearctic migrants as a group could not clearly be distinguished as generalists relative to Afro‐tropical residents with respect to habitat attributes. The only indication of greater flexibility in Palaearctic migrants was a significant tendency to use habitats over a wider latitudinal range. The results suggest that migrants are generalists, but not necessarily more generalist than taxonomically similar resident species that also occur over a wide range of habitat types within the savannah biome. The availability of specific habitat requirements on the wintering grounds in Africa is therefore unlikely to be a primary limiting factor for many Afro‐Palaearctic migratory bird species. 相似文献
943.
James J. H. St Clair Barbara C. Klump Jessica E. M. van der Wal Shoko Sugasawa Christian Rutz 《Biological journal of the Linnean Society. Linnean Society of London》2016,118(2):226-232
Functional tool use requires the selection of appropriate raw materials. New Caledonian crows Corvus moneduloides are known for their extraordinary tool‐making behaviour, including the crafting of hooked stick tools from branched vegetation. We describe a surprisingly strong between‐site difference in the plant materials used by wild crows to manufacture these tools: crows at one study site use branches of the non‐native shrub Desmanthus virgatus, whereas only approximately 7 km away, birds apparently ignore this material in favour of the terminal twigs of an as‐yet‐unidentified tree species. Although it is likely that differences in local plant communities drive this striking pattern, it remains to be determined how and why crows develop such strong site‐specific preferences for certain raw materials. 相似文献
944.
H. Sepahvand 《Chemical Speciation and Bioavailability》2016,28(1-4):182-188
Concentrations of Natural stable and unstable carbon in ecosystems have been used extensively to help to understand a wide range of soil processes and functions. This study was conducted to explore the effects of land use changes on different carbon fractions (F1, F2, F3 and F4), permanganate oxidizable carbon (POXC), soil organic carbon (SOC) and total organic carbon (TOC) associated with soils in calcareous soils of western Iran. Four popular land uses in the selected site including natural forest, range land, dryland farming and irrigated farming systems were employed as the basis of soil sampling. The results showed a strong relationship between land use conversion and SOC stocks changes. The greatest mean values for carbon content and the least mean values of CaCO3 in bulk topsoil (0–15 cm) in the forest land were observed. Dryland farming had the least both active and passive pools of C in comparison with the other land uses. The positive and significant correlations was observed between SOC, Total C and POXC contents and different C fractions. Taking C and POXC pools into account, a more definitive picture of the soil C is obtained than when only total C is measured. The influence of land use changes on overall soil carbon stocks could be helpful for making management decision for farmers and policy makers in the future, for enhancing the potential of C sequestration in western Iran. 相似文献
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Microhabitat selection and seasonal activity of the snake-eyed skink, Ablephaus kitaibelii fitzingeri, are compared to the two lacertid lizards (Lacerta viridis and Podarcis muralis) that co-occur in many of its habitats. The food composition of A. k. fitzingeri is also described. Significant differences in microhabitat selection and seasonal activity among the three species were found.
The snake-eyed skink was associated with open grasslands, and with a low level of scrub, bare soil and rock cover. The microhabitat
preference of L. viridis was quite similar to that of the skink, but with a higher preference for scrub. P. muralis occurred in places with greater rock and bare soil cover, and more scrub than A. k. fitzingeri. Activity of the snake-eyed skink decreased dramatically in summer, probably because of the reduced thermal inertia originating
from the extremely small size of this species, but its seasonal activity overlapped with those of the lacertids. Stomach content
analysis of the snake-eyed skink suggests that it is a generalist predator of small, mainly flightless arthropod prey. Competition
with juvenile lacertids and predation by adult L. viridis are conceivable for the snake-eyed skink. 相似文献
949.
The Granier-system, a relatively simple and continuous method for measuring sap flux density, has been adapted and evaluated
for its use in older, mature grapevines. The original calibration of Granier (1985, Annales Sciences Forestieres, 42, 193-200)
could be extended to a sap flux density of up to 400 10-6 m3 m-2 s-1 with only little error at high flux densities. A time lag of around 20 min was apparent between transpiration and calculated
sap flow which was attributed to the thermal mass of the sensors themselves. The time lag and the consequently dampened response
of the system caused a very low accuracy over short time periods thus reducing the value for detailed plant physiological
investigations. However, when integrating over longer time intervals, much of the error cancelled out. For daily values the
maximum error was within ±10% and after a period of 89 days only 1.5% error remained. This method is thus best suited for
long term measurements of total water use.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
950.
Since the middle of the 19th century, the area covered by forests in France has doubled. These new forests grow on previous
agricultural lands. We have studied the influence of this agricultural history on the 15N abundance of present-day forests planted on farmlands in the Vosges mountains (north-eastern France) between 1898 and 1930.
Different types of land use were identified from old cadastres (1814–1836) of 16 farms. Ancient forests adjacent to farmlands
were used as controls. Former pastures, meadows, croplands, gardens and ancient forests were compared for soil δ15N (fraction <50 μm and total soil), C/N, P and N content and fern (Dryopteris carthusiana) δ15N. The mean δ15N of soil increased in the order ancient forests (+0.0‰)<pastures (+1.4‰)<croplands (+1.6‰)<meadows (+2.5‰)<gardens (+3.8‰).
This increase in soil δ15N with the intensity of former land use was related to the former input of 15N-enriched manure, and to an activation of soil nitrification leading to 15N-depleted nitrate export on previously manured parcels. Fern δ15N increased in the same order as soil δ15N in relation to past land use. The mean δ15N of fern in ancient forests (–4.4‰) and former pastures (–3.4‰) was 5‰ lower than soil δ15N and the two variables were strongly correlated. The δ15N of fern in formerly manured parcels varied little (cropland: –2.7‰, meadows: –2.6‰ and gardens: –2.2‰) and independently
of soil δ15N, suggesting that the soil sources of fern N differed between unmanured and manured parcels. Understorey plant δ15N and soil δ15N appear to be excellent tracers of previous land use in forests, and could be used in historical studies. The persistence
of high isotopic ratios in previously manured parcels, almost a century after afforestation, suggests a long-term influence
of former land use on the N cycle in forest soils.
Received: 22 January 1999 / Accepted: 22 July 1999 相似文献