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991.
Non-Additive Effects of Water and Nitrogen Addition on Ecosystem Carbon Exchange in a Temperate Steppe 总被引:1,自引:0,他引:1
Shuli Niu Haijun Yang Zhe Zhang Mingyu Wu Qi Lu Linghao Li Xingguo Han Shiqiang Wan 《Ecosystems》2009,12(6):915-926
Changes in precipitation and nitrogen (N) deposition can influence ecosystem carbon (C) cycling and budget in terrestrial
biomes, with consequent feedbacks to climate change. However, little is known about the main and interactive effects of water
and N additions on net ecosystem C exchange (NEE). In a temperate steppe of northern China, a field-manipulated experiment
was conducted to evaluate the responses of NEE and its components to improve N and water availability from 2005 to 2008. The
results showed that both water and N additions stimulated gross ecosystem productivity (GEP), ecosystem respiration (ER),
and NEE. Water addition increased GEP by 17%, ER by 24%, and NEE by 11% during the experimental period, whereas N addition
increased GEP by 17%, ER by 16%, and NEE by 19%. The main effects of both water and N additions changed with time, with the
strongest water stimulation in the dry year and a diminishing N stimulation over time. When water and N were added in combination,
there were non-additive effects of water and N on ecosystem C fluxes, which could be explained by the changes in species composition
and the shifts of limiting resources from belowground (water or N) to aboveground (light). The positive water and N additions
effects indicate that increasing precipitation and N deposition in the future will favor C sequestration in the temperate
steppe. The non-additive effects of water and N on ecosystem C fluxes suggest that multifactor experiments are better able
to capture complex interactive processes, thus improving model simulations and projections. 相似文献
992.
Man Yu Yanfang Wan Yanwei Xi 《Biochemical and biophysical research communications》2009,390(3):447-450
Somatic mutations and polymorphisms in the noncoding displacement (D)-loop of mitochondrial DNA (mtDNA) are present in a variety of human cancers. To investigate whether Ewing’s sarcoma (EWS) harbors genetic alterations within the D-loop region and their potential association with EWS carcinogenesis, we analyzed and compared the complete mtDNA D-loop sequences from 17 pairs of tumor tissues and corresponding peripheral blood samples using the direct DNA sequencing method. Our results revealed that 12 of the 17 EWS tumor specimens (70.6%) carried 19 somatic mutations in the D-loop of mtDNA, including 11 single-base substitutions, 3 insertions and 5 deletions. Among the tested 17 patients, we screened a total of 40 germline polymorphisms including one novel sequence variant in the D-loop fragment. Most of these identified mutations and germline variations were clustered within two hypervariable segments (HVS1 and HVS2) as well as the homopolymeric C stretch between nucleotide position 303 and 309. In addition, there was no significant correlation between mtDNA D-loop mutations and various clinicopathological factors of EWS. In conclusion, our study reports for the first time that mtDNA D-loop mutations occur at a high frequency in EWS. These data provide evidence of mtDNA alterations’ possible involvement in the initiation and/or progression of this rare malignancy. 相似文献
993.
Alessandra Pesce Liesbet Thijs Marco Nardini Lorenza Sisinni Louise Gourlay Massimiliano Coletta Xuehua Wan Paolo Ascenzi Martino Bolognesi 《Journal of molecular biology》2009,386(1):246-35534
Among heme-based sensors, recent phylogenomic and sequence analyses have identified 34 globin coupled sensors (GCS), to which an aerotactic or gene-regulating function has been tentatively ascribed. Here, the structural and biochemical characterization of the globin domain of the GCS from Geobacter sulfurreducens (GsGCS162) is reported. A combination of X-ray crystallography (crystal structure at 1.5 Å resolution), UV-vis and resonance Raman spectroscopy reveals the ferric GsGCS162 as an example of bis-histidyl hexa-coordinated GCS. In contrast to the known hexa-coordinated globins, the distal heme-coordination in ferric GsGCS162 is provided by a His residue unexpectedly located at the E11 topological site. Furthermore, UV-vis and resonance Raman spectroscopy indicated that ferrous deoxygenated GsGCS162 is a penta-/hexa-coordinated mixture, and the heme hexa-to-penta-coordination transition does not represent a rate-limiting step for carbonylation kinetics. Lastly, electron paramagnetic resonance indicates that ferrous nitrosylated GsGCS162 is a penta-coordinated species, where the proximal HisF8-Fe bond is severed. 相似文献
994.
Xuehua Wan Jennifer A. Saito James S. Newhouse Michael Y. Galperin Marie-Alda Gilles-Gonzalez 《Journal of molecular biology》2009,388(2):262-35534
Globin-coupled sensors are heme-binding signal transducers in Bacteria and Archaea in which an N-terminal globin controls the activity of a variable C-terminal domain. Here, we report that BpeGReg, a globin-coupled diguanylate cyclase from the whooping cough pathogen Bordetella pertussis, synthesizes the second messenger bis-(3′-5′)-cyclic diguanosine monophosphate (c-di-GMP) upon oxygen binding. Expression of BpeGReg in Salmonella typhimurium enhances biofilm formation, while knockout of the BpeGReg gene of B. pertussis results in decreased biofilm formation. These results represent the first identification a signal ligand for any diguanylate cyclase and provide definitive experimental evidence that a globin-coupled sensor regulates c-di-GMP synthesis and biofilm formation. We propose that the synthesis of c-di-GMP by globin sensors is a widespread phenomenon in bacteria. 相似文献
995.
996.
997.
上海地区番茄黄化曲叶病毒病的鉴定及嫁接接种法研究 总被引:4,自引:0,他引:4
番茄黄化曲叶病毒(tomato yellow leafcurl virus,TYLCV)是一种由烟粉虱(Bemisia tabaci)和嫁接传播的双生病毒,在热带、亚热带地区给番茄生产造成严重威胁.根据番茄黄化曲叶病毒的保守序列设计一对引物,运用PCR技术从上海地区的感病番茄中扩增出一条575bp的特异带,而健康植株无此带.测序表明该序列与番茄黄化曲叶病毒具有极高的同源性(97%~99%).将健康接穗嫁接到感染番茄黄化曲叶病毒的番茄砧木上,间隔15 d和30 d,分别提取接穗的DNA,并用PCR法检测病毒,发现嫁接15 d后在部分接穗中检测到TYLCV病毒,嫁接30 d后在所有的接穗中均检测到病毒,因此,嫁接法可以作为番茄黄化曲叶病毒病的接种鉴定方法. 相似文献
998.
999.
Amur tiger is the largest subspecies of tiger in the world and his conservation has also received much attention. In this
study, we isolated and characterized twenty-one tri- and tetranucleotide microsatellite markers from this species. The number
of alleles for each locus ranged from two to nine in a group of 60 individuals and the observed and expected heterozygosities
were 0.333–0.917 and 0.302–0.822, respectively. The overall discrimination power and exclusion probabilities in parentage
and paternity testing for these markers were 1.00, 0.9947 and 0.9999, respectively, indicating high-resolution power of microsatellite
markers. 相似文献
1000.
Lili Hao Xiaomeng Ge Haolei Wan Songnian Hu Martin J Lercher Jun Yu Wei-Hua Chen 《BMC evolutionary biology》2010,10(1):316