Comparing nitrate storage and remobilization in two rice cultivars that differ in their nitrogen use efficiency

Soil nitrogen (N) is available to rice crops as either nitrate or ammonium, but only nitrate can be accrued in cells and so factors that influence its storage and remobilization are important for N use efficiency (NUE). The hypothesis that the ability of rice crops to remobilize N storage pools is an indicator of NUE was tested. When two commonly grown Chinese rice cultivars, Nong Ken (NK) and Yang Dao (YD), were compared in soil and hydroponics, YD had significantly greater NUE for biomass production. The ability of each cultivar to remobilize nitrate storage pools 24 h after N supply withdrawal was compared. Although microelectrode measurements of the epidermal sub-cellular nitrate pools in leaves and roots showed similar patterns of vacuolar remobilization in both cultivars, whole-tissue analysis showed very little depletion of storage pools after 24 h. However, leaf epidermal cell cytosolic nitrate activities were significantly higher in YD when compared with NK. Before N starvation and growing in 10 mM nitrate, the xylem nitrate activity in YD was lower than that of NK. After 24 h of N starvation the xylem nitrate had decreased more in YD than in NK. Tissue analysis of stems showed that YD had accumulated significantly more nitrate than NK, and the remobilization pattern suggested that this store is important for both cultivars. Changes in nitrate reductase activity (NRA) and expression were measured. Growing in 10 mM nitrate, NRA was undetectable in roots of both cultivars, and the leaf total NRA of equivalent leaves was similar in NK and YD. When the N supply was withdrawn, after 24 h NRA in NK was reduced to 80% but no decrease was found in YD. The proportion of NRA in an active form in YD was significantly higher than that in NK under both nitrate supply and deprivation conditions. Checking NR gene expression showed that leaf expression of OsNia1 was faster to respond to nitrate deprivation than OsNia2 in both cultivars. These measurements are discussed in relation to cultivar differences and physiological markers for NUE in rice.     

A MAP4 kinase related to Ste20 is a nutrient-sensitive regulator of mTOR signalling

The mTOR (mammalian target of rapamycin) signalling pathway is a key regulator of cell growth and is controlled by growth factors and nutrients such as amino acids. Although signalling pathways from growth factor receptors to mTOR have been elucidated, the pathways mediating signalling by nutrients are poorly characterized. Through a screen for protein kinases active in the mTOR signalling pathway in Drosophila we have identified a Ste20 family member (MAP4K3) that is required for maximal S6K (S6 kinase)/4E-BP1 [eIF4E (eukaryotic initiation factor 4E)-binding protein 1] phosphorylation and regulates cell growth. Importantly, MAP4K3 activity is regulated by amino acids, but not the growth factor insulin and is not regulated by the mTORC1 inhibitor rapamycin. Our results therefore suggest a model whereby nutrients signal to mTORC1 via activation of MAP4K3.     

Association of PI3K-Akt signaling pathway with digitalis-induced hypertrophy of cardiac myocytes

Our previous studies on cardiac myocytes showed that positive inotropic concentrations of the digitalis drug ouabain activated signaling pathways linked to Na(+)-K(+)-ATPase through Src and epidermal growth factor receptor (EGFR) and led to myocyte hypertrophy. In view of the known involvement of phosphatidylinositol 3-kinase (PI3K)-Akt pathways in cardiac hypertrophy, the aim of the present study was to determine whether these pathways are also linked to cardiac Na(+)-K(+)-ATPase and, if so, to assess their role in ouabain-induced myocyte growth. In a dose- and time-dependent manner, ouabain activated Akt and phosphorylation of its substrates mammalian target of rapamycin and glycogen synthase kinase in neonatal rat cardiac myocytes. Akt activation by ouabain was sensitive to PI3K inhibitors and was also noted in adult myocytes and isolated hearts. Ouabain caused a transient increase of phosphatidylinositol 3,4,5-trisphosphate content of neonatal myocytes, activated class IA, but not class IB, PI3K, and increased coimmunoprecipitation of the alpha-subunit of Na(+)-K(+)-ATPase with the p85 subunit of class IA PI3K. Ouabain-induced activation of ERK1/2 was prevented by Src, EGFR, and MEK inhibitors, but not by PI3K inhibitors. Activation of Akt by ouabain, however, was sensitive to inhibitors of PI3K and Src, but not to inhibitors of EGFR and MEK. Similarly, ouabain-induced myocyte hypertrophy was prevented by PI3K and Src inhibitors, but not by an EGFR inhibitor. These findings 1) establish the linkage of the class IA PI3K-Akt pathway to Na(+)-K(+)-ATPase and the essential role of this linkage to ouabain-induced myocyte hypertrophy and 2) suggest cross talk between these PI3K-Akt pathways and the signaling cascades previously identified to be associated with cardiac Na(+)-K(+)-ATPase.     

Targeted gene disruption by use of a group 11 intron （targetron） vector in Clostridium acetobutylicum

Dear Editor： Clostridium acetobutylicum, a gram-positive, anaerobic, spore-forming bacterium, is capable of using a wide variety of carbon sources to produce acetone, butanol and ethanol. To improve solvent productivity of C. acetobutylicum, metabolic engineering is considered as a useful tool in developing strains with industrially desirable character-istics. However, to date, there are few useful methods for genetic manipulation of C. acetobutylicum, especially for gene disruption. To our knowledge, two types of vectors, including non-replicative and replicative integrative plasmids, have been developed for gene-inactivation in C. acetobutylicum. By using non-replicative integrative plasmids, buk and solR genes of C. acetobutylicum were inactivated [1,2]. However, due to their low frequencies of transformation and recombination, the non-replicative integrative plasmids are usually transformed at less than 1 integrative transformant per mg plasmid DNA. To obtain the integrative mutant, it may require higher transformation frequencies up to 10^5, but the typical transformation fre-quencies were reported at 10^3 [3].[第一段]     

The disulfide loop of gp41 is critical to the furin recognition site of HIV gp160

The importance of the HIV gp41 conserved disulfide loop to envelope function has been examined by mutational and functional analyses. Based on a luciferase-reporter entry assay, mutants gp41-CC/AA (C598A/C604A) and gp41-Delta (deletion of residues 596-606) result in a nonfunctional envelope protein. Western blot analysis shows both mutants to be properly expressed but not processed to form gp120 and gp41, which explains their nonfunctionality. The presence of mutant gp160 on the cell surface, as well as their ability to bind to sCD4, suggests that the mutations have disrupted processing at the furin recognition site encoded within the gp120 conserved domain 5, without resulting in an overall misfolding of the protein. With respect to the furin recognition site, the mutations are sequentially distant, which implies that the gp41 disulfide loop is interacting with gp120 C5 in gp160. In addition, we have modeled the gp120-gp41 interaction in unprocessed precursor gp160 using structural data available for gp120 and gp41 domains in isolation, supplemented by mutagenesis data. We suggest that the mutations have altered the interaction between gp120 C5 and the gp41 disulfide loop, resulting in decreased accessibility of the furin recognition site and implying that the interaction between the gp120 C5 and gp41 loop is a conformational requirement for gp160 processing. The sensitivity of this interaction could be exploited in future antivirals designed to disrupt HIV pathogenesis by disrupting gp160 processing.     

A highly sensitive biosensor with (Con A/HRP)n multilayer films based on layer-by-layer technique for the detection of reduced thiols

The bilayer of Con A/HRP through the biospecific affinity of concanavalin A (Con A) and glycoprotein horseradish peroxidase (HRP) was prepared on the surface of an Au electrode modified by the precursor film consisted of poly(allylamine hydrochloride) poly(sodium-p-styrene-sulfonate). Atomic force microscopy and electrochemical impedance spectroscopy were adopted to monitor the uniform layer-by-layer assembly of the Con A/HRP bilayers. The amperometric measurement was based on the inhibition of reduced thiols and performed in the presence of the electron mediator hydroquinone in 0.2 M phosphate buffer of pH 6.5 at an applied potential of −0.15 V versus Ag/AgCl. Under the optimal conditions, the biosensor presented a linear response for cysteine from 0.1 to 23.5 μM, with a detection limit of 0.02 μM. The biosensor demonstrated high stability and repeatability. A series of reduced thiols were detected by this inhibition biosensor and oxidized thiols showed no effect on the current response of the biosensor.     

Reproduction strategy of Trias verrucosa (Orchidaceae) from China

Trias, an orchid genus, was reported in this paper from China as a newly recorded genus for the first time. The genus and its new species, T. verrucosa Z. J. Liu, L. J. Chen et S. P. Lei, were described and discussed. Trias consists of 19 species ranging from Assam of India to Indonesia and Australia in the southeast via Myanmar to Deccan of India in the southwest. Its occurrence in West Yunnan of China is a further indication of phytogeographical relations between this region and the tropical Asia. This new species grows on shady rocks in forests. By observing of its biological characteristics such as phenology and blooming biology, lots of cloned ramets of generation overlap were found, but there were no fruited plants, and that clonal reproduction could repeat had nothing to do with whether the ramet bloomed or not. The flowering season of this species is from early April to early May. The opening of flowers on plants or inflorescence was irregular and the florescence of single flowers was rather short, only lasting 4–5 d, and no fruited flowers were found. Based on the detection of mating systems, no flowers of artificial self-pollination and artificial cross-pollination have fruited. Since the flowering period is just before the rainy season in this region, the ecological conditions of dryness, strong wind, low temperature and weak light during that period of time are evidently unfavorable to plant blooming, pollinating and fruiting. Apparently, the short duration and sterility of each flower would avoid the invalid energy waste in unfavorable circumstances and save the limited energy for more valid asexual reproduction so that the opportunity of multiplication in an uncertain environment would be increased to ensure the progenitive success. The P/O value of T. verrucosa is 187.4 ± 22.4, which is obviously related with the highly valid usage of its conglutinated and hard tuberous pollinarium during pollination, indicating that this species could hold the characteristic of sexual reproduction. This is an adaptation of this type of plants to the rather atrocious ecological circumstance there by its reproduction strategy of strengthening asexual reproduction and weakening sexual reproduction, and so it enables the plants to survive in this region, long-distanced from the places where its relatives dwell.     

中草药化妆品的研究与开发

对传统中草药在古代化妆品和现代天然日化领域的应用进行了阐述,提出了中草药在现代日化领域应用的思路.     

Neuropeptide Y acts directly in the periphery on fat tissue and mediates stress-induced obesity and metabolic syndrome

The relationship between stress and obesity remains elusive. In response to stress, some people lose weight, whereas others gain. Here we report that stress exaggerates diet-induced obesity through a peripheral mechanism in the abdominal white adipose tissue that is mediated by neuropeptide Y (NPY). Stressors such as exposure to cold or aggression lead to the release of NPY from sympathetic nerves, which in turn upregulates NPY and its Y2 receptors (NPY2R) in a glucocorticoid-dependent manner in the abdominal fat. This positive feedback response by NPY leads to the growth of abdominal fat. Release of NPY and activation of NPY2R stimulates fat angiogenesis, macrophage infiltration, and the proliferation and differentiation of new adipocytes, resulting in abdominal obesity and a metabolic syndrome-like condition. NPY, like stress, stimulates mouse and human fat growth, whereas pharmacological inhibition or fat-targeted knockdown of NPY2R is anti-angiogenic and anti-adipogenic, while reducing abdominal obesity and metabolic abnormalities. Thus, manipulations of NPY2R activity within fat tissue offer new ways to remodel fat and treat obesity and metabolic syndrome.