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991.
High salinity is an environmental factor that inhibits plant growth and development, leading to large losses in crop yields.
We report here that mutations in SIZ1 or PHO2, which cause more accumulation of phosphate compared with the wild type, enhance tolerance to salt stress. The siz1 and pho2 mutations reduce the uptake and accumulation of Na+. These mutations are also able to suppress the Na+ hypersensitivity of the sos3-1 mutant, and genetic analyses suggest that SIZ1 and SOS3 or PHO2 and SOS3 have an additive effect on the response to salt stress. Furthermore, the siz1 mutation cannot suppress the Li+ hypersensitivity of the sos3-1 mutant. These results indicate that the phosphate-accumulating mutants siz1 and pho2 reduce the uptake and accumulation of Na+, leading to enhanced salt tolerance, and that, genetically, SIZ1 and PHO2 are likely independent of SOS3-dependent salt signaling. 相似文献
992.
Phloem loading is the process by which photoassimilates synthesized in the mesophyll cells of leaves enter the sieve elements
and companion cells of minor veins in preparation for long distance transport to sink organs. Three loading strategies have
been described: active loading from the apoplast, passive loading via the symplast, and passive symplastic transfer followed
by polymer trapping of raffinose and stachyose. We studied phloem loading in Amborella trichopoda, a premontane shrub that may be sister to all other flowering plants. The minor veins of A. trichopoda contain intermediary cells, indicative of the polymer trap mechanism, forming an arc on the abaxial side and subtending a
cluster of ordinary companion cells in the interior of the veins. Intermediary cells are linked to bundle sheath cells by
highly abundant plasmodesmata whereas ordinary companion cells have few plasmodesmata, characteristic of phloem that loads
from the apoplast. Intermediary cells, ordinary companion cells, and sieve elements form symplastically connected complexes.
Leaves provided with 14CO2 translocate radiolabeled sucrose, raffinose, and stachyose. Therefore, structural and physiological evidence suggests that
both apoplastic and polymer trapping mechanisms of phloem loading operate in A. trichopoda. The evolution of phloem loading strategies is complex and may be difficult to resolve. 相似文献
993.
Basu A 《Statistics in biosciences》2011,3(1):6-27
Instrumental variables methods (IV) are widely used in the health economics literature to adjust for hidden selection biases
in observational studies when estimating treatment effects. Less attention has been paid in the applied literature to the
proper use of IVs if treatment effects are heterogeneous across subjects. Such a heterogeneity in effects becomes an issue
for IV estimators when individuals’ self-selected choices of treatments are correlated with expected idiosyncratic gains or
losses from treatments. We present an overview of the challenges that arise with IV estimators in the presence of effect heterogeneity
and self-selection and compare conventional IV analysis with alternative approaches that use IVs to directly address these
challenges. Using a Medicare sample of clinically localized breast cancer patients, we study the impact of breast-conserving
surgery and radiation with mastectomy on 3-year survival rates. Our results reveal the traditional IV results may have masked
important heterogeneity in treatment effects. In the context of these results, we discuss the advantages and limitations of
conventional and alternative IV methods in estimating mean treatment-effect parameters, the role of heterogeneity in comparative
effectiveness research and the implications for diffusion of technology. 相似文献
994.
Yifeng Miao Yongming Qiu Yuchang Lin Zengli Miao Jing Zhang Xiaojie Lu 《Molecular biology reports》2011,38(5):3235-3242
Pyruvate, an endogenous metabolite of glycolysis, is an anti-toxicity agent. Recent studies have suggested possible roles
for pyruvate in protecting CNS neurons from excitotoxic and metabolic insults. Utilizing cultures derived from embryonic rat
cortex, the studies presented in this paper indicate that an astroglia-mediated mechanism is involved in the neuroprotective
effects of pyruvate against glutamate toxicity. Glutamate-induced toxicity could be reversed by pyruvate in a mixed culture
of cortex cells. Importantly, in pure neuronal cultures from the same tissue, pyruvate failed to protect against glutamate
toxicity. Addition of astroglia to the pure neuronal cultures restores the ability of pyruvate to protect neurons from glutamate-induced
toxicity. Our results further suggest that pyruvate can induce glia to up-regulate the synthesis of glutathione (GSH), an
antioxidant that protects cells from toxins such as free radicals. Taken together, our data suggest that astroglia in mixed
cultures are essential for mediating the effects of pyruvate, revealing a novel mechanism by which pyruvate, an important
intermediate of tricarboxylic acid cycle in the body, may act to protect neurons from damage during insults such as brain
ischemia. 相似文献
995.
To determine the species of the yeast-like symbionts (YLS) in the brown planthoppers (BPH), Nilaparvata lugens, YLS were first isolated and purified by ultracentrifugation from the fat bodies of BPH, and then 18S rDNA and internal transcribed
spacer (ITS)–5.8S rDNA sequences of YLS were amplified with the different general primers for fungi. The results showed that
the two different 18S and ITS–5.8S rDNA sequences of YLS were obtained. One 2291-bp DNA sequence, which contained 18S and
ITS–5.8S rDNA, showed the high similarity to Cryptococcus and was named Cryp-Like symbiotes. Another 1248-bp DNA sequence, which contained a part of 18S and ITS–5.8S rDNA, showed the high similarity
to Pichia guilliermondii and was named Pichia-Like symbiotes. It was further proved that Cryp- and Pichia-Like symbiotes existed in BPH through nested PCR with specific primers for two symbiotes and in situ hybridization analysis
using digoxigenin-labeled probes. Our results showed that BPH harbored more than one species of eukaryotic YLS, which suggested
that diversity of fungal endosymbiotes may be occurred in planthoppers, just like bacterial endosymbiotes. 相似文献
996.
Ghada Baraket Khaled Chatti Olfa Saddoud Ahmed Ben Abdelkarim Messaoud Mars Mokhtar Trifi Amel Salhi Hannachi 《Plant Molecular Biology Reporter》2011,29(1):171-184
This study characterises the genetic variability of fig, Ficus carica L., using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. It compares the efficiency
and utility of the two techniques in detecting variation and establishing genetic relationships among Tunisian fig cultivars.
Our results show that using both marker systems, the Tunisian fig germ plasm is characterised by having a large genetic diversity
at the deoxyribonucleic acid level, as most of AFLP bands were detected and all SSR markers were polymorphic. In fact, 351
(342 polymorphic) and 57 (57 polymorphic) bands were detected using AFLP and SSR primers, respectively. SSR markers were the
most polymorphic with an average polymorphic information content value of 0.94, while AFLP markers showed the highest effective
multiplex ratio (56.9) and marker index (45.2). The effective marker index was recorded highest (4.19) for AFLP markers and
lowest (0.70) for the SSR ones. Our results demonstrate that (1) independent as well as combined analyses of cluster analyses
of SSR and AFLP fragments showed that cultivars are clustered independently from their geographical origin, horticultural
classifications and tree sex; (2) the analysis of molecular variance allowed the partitioning of genetic variation within
and among fig groups and showed greater variation within groups and (3) AFLP and SSR markers datasets showed positive correlation.
This study suggests the SSR and AFLP markers are suitable for diversity analysis and cultivars fingerprinting. An understanding
of the genetic diversity and population structure of F. carica in Tunisia can also provide insight into the conservation and management of this species. 相似文献
997.
Christopher Liao Yonatan Klausner David Starobinski Eran Simhon Azer Bestavros 《Cluster computing》2018,21(3):1595-1606
Many research institutions are deploying computing clusters based on a shared/buy-in paradigm. Such clusters combine shared computers, which are free to be used by all users, and buy-in computers, which are computers purchased by users for semi-exclusive use. The purpose of this paper is to characterize the typical behavior and performance of a shared/buy-in computing cluster, using data traces from the Shared Computing Cluster (SCC) at Boston University that runs under this paradigm as a case study. Among our main findings, we show that the semi-exclusive policy, which allows any SCC user to use idle buy-in resources for a limited time, increases the utilization of buy-in resources by 17.4%, thus significantly improving the performance of the system as a whole. We find that jobs allowed to run on idle buy-in resources arrive more frequently and run for a shorter time than other jobs. Finally, we identify the run time limit (i.e., the maximum time during which a job is allowed to use resources) and the type of parallel environment as two factors that have a significant impact on the different performance experienced by shared and buy-in jobs. 相似文献
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