Regulation of s6 kinase 1 activation by phosphorylation at ser-411

Ribosomal S6 kinase 1 (S6K1), as a key regulator of mRNA translation, plays an important role in cell cycle progression through the G(1) phase of proliferating cells and in the synaptic plasticity of terminally differentiated neurons. Activation of S6K1 involves the phosphorylation of its multiple Ser/Thr residues, including the proline-directed sites (Ser-411, Ser-418, Thr-421, and Ser-424) in the autoinhibitory domain near the C terminus. Phosphorylation at Thr-389 is also a crucial event in S6K1 activation. Here, we report that S6K1 phosphorylation at Ser-411 is required for the rapamycin-sensitive phosphorylation of Thr-389 and the subsequent activation of S6K1. Mutation of Ser-411 to Ala ablated insulin-induced Thr-389 phosphorylation and S6K1 activation, whereas mutation mimicking Ser-411 phosphorylation did not show any effect. Furthermore, phosphomimetic mutation of Thr-389 overcame the inhibitory effect of the mutation S411A. Thus, Ser-411 phosphorylation regulates S6K1 activation via the control of Thr-389 phosphorylation. In nervous system neurons, Cdk5-p35 kinase associates with S6K1 via the direct interaction between p35 and S6K1 and catalyzes S6K1 phosphorylation specifically at Ser-411. Inhibition of the Cdk5 activity or suppression of Cdk5 expression blocked S6K1 phosphorylation at Ser-411 and Thr-389, resulting in S6K1 inactivation. Similar results were obtained by treating asynchronous populations of proliferating cells with the CDK inhibitor compound roscovitine. Altogether, our findings suggest a novel mechanism by which the CDK-mediated phosphorylation regulates the activation of S6K1.     

True phosphorus digestibility and the endogenous phosphorus outputs associated with brown rice for weanling pigs measured by the simple linear regression analysis technique

The objectives of this study were to determine true phosphorus (P) digestibility, degradability of phytate-P complex and the endogenous P outputs associated with brown rice feeding in weanling pigs by using the simple linear regression analysis technique. Six barrows with an average initial body weight of 12.5 kg were fitted with a T-cannula and fed six diets according to a 6 × 6 Latin-square design. Six maize starch-based diets, containing six levels of P at 0.80, 1.36, 1.93, 2.49, 3.04, and 3.61 g/kg per kg dry-matter (DM) intake (DMI), were formulated with brown rice. Each experimental period lasted 10 days. After a 7-day adaptation, all faecal samples were collected on days 8 and 9. Ileal digesta samples were collected for a total of 24 h on day 10. The apparent ileal and faecal P digestibility values of brown rice were affected ( P < 0.01) by the P contents in the assay diets. The apparent ileal and faecal P digestibility values increased from − 48.0 to 36.7% and from − 35.6 to 40.0%, respectively, as P content increased from 0.80 to 3.61 g/kg DMI. Linear relationships ( P < 0.05), expressed as g/kg DMI, between the apparent ileal and faecal digestible P and dietary levels of P, suggested that true P digestibility and the endogenous P outputs associated with brown rice feeding could be determined by using the simple regression analysis technique. There were no differences ( P>0.05) in true P digestibility values (57.7 ± 5.4 v. 58.2 ± 5.9%), phytate P degradability (76.4 ± 6.7 v. 79.0 ± 4.4%) and the endogenous P outputs (0.812 ± 0..096 v. 0.725 ± 0.083 g/kg DMI) between the ileal and the faecal levels. The endogenous faecal P output represented 14 and 25% of the National Research Council (1998) recommended daily total and available P requirements in the weanling pig, respectively. About 58% of the total P in brown rice could be digested and absorbed by the weanling pig. Our results suggest that the large intestine of the weanling pigs does not play a significant role in the digestion of P in brown rice. Diet formulation on the basis of total or apparent P digestibility with brown rice may lead to P overfeeding and excessive P excretion in pigs.     

Higher insulin, triglycerides, and blood pressure with greater trunk fat in Tanner 1 Chinese

Objective: The aims of this study were to investigate the body fat distribution pattern in prepubertal Chinese children and to investigate the relationship between central fat distribution and specific biomarkers of cardiovascular disease. Research Methods and Procedures: The study was conducted in an urban Mainland Chinese (Jinan, Shandong) sample of children using a cross‐sectional design. Pubertal status was determined by Tanner criteria. Measurements included weight, height, waist circumference, DXA measures of total body fat and trunk fat; fasting serum measures of glucose, insulin, triglyceride, cholesterol, high‐density lipoprotein‐cholesterol; and systolic and diastolic blood pressure. Multiple regression models were developed with the biomarkers of cardiovascular risk factor as the dependent variables, and adjustments were made for significant covariates, including sex, age, height, weight, waist circumference, total body fat, trunk fat, and interactions. Results: A total of 247 healthy prepubertal subjects were studied. After co‐varying for age, weight, height, and extremity fat (the sum of arm fat and leg fat), girls had greater trunk fat than boys (p < 0.0001, R² for model = 0.95). Insulin and triglyceride were positively related to central fat measured by DXA‐trunk fat (p < 0.05) but not related to the waist circumference. In the blood pressure model, waist circumference was a significant predictor of both systolic blood pressure and diastolic blood pressure, while DXA‐trunk fat was associated with diastolic blood pressure only. Significant interactions between sex and trunk fat, and sex and total fat, were found in relation to diastolic blood pressure. Discussion: In prepubertal Chinese children, greater trunk fat was significantly associated with higher insulin and triglyceride in boys and girls and was associated with higher diastolic blood pressure in boys only.     

Waist-to-height ratio is an accurate and easier index for evaluating obesity in children and adolescents

Objectives: The present study aims to evaluate the accuracy of the index of waist‐to‐height ratio (WHTR), and proposed the optimal thresholds of WHTR in the definition of childhood overweight and obesity in a bi‐ethnic Chinese school‐aged population. Research Methods and Procedures: Overweight and obese were identified by BMI for age and gender in a random sample including 2055 Han and 2132 Uygur ethnic school‐aged children (8 to 18 years old). WHTR was calculated by waist circumference divided by height on the basis of standard anthropometric measurements. Receiver operating characteristic (ROC) curve analyses were performed to assess the accuracy of WHTR as a diagnostic test for childhood overweight and obesity, compared with waist circumference. The optimal thresholds of WHTR for defining overweight and obesity were recommended respectively by gender. The correlation between WHTR and age was analyzed and compared with BMI. Results: A‐values (area under curve) of WHTR for diagnosing overweight and obesity were both over 0.90 in both genders and better than those of waist circumference. A threshold of 0.445 was identified for overweight in both genders, with the sensitivity and specificity >0.80. The thresholds for defining obesity was 0.485 in boys and 0.475 in girls, both having the sensitivity and specificity >0.90. WHTR showed less association with age than BMI. Conclusions: WHTR is a simple, easy, accurate, and non‐age‐dependent index with high applicability to screening overweight and obesity in children and adolescents. The use of WHTR in the general childhood population has been justified by this study.     

Endless Hide-and-Seek： Dynamic Co-evolution in Plant-Bacterium Warfare

Plants possess innate Immune systems to prevent most potential Infections. The ancient and conserved innate immune responses are triggered by microbe-associated molecular patterns （MAMPs） and play important roles in broad-spectrum defenses. However, successful bacterial pathogens evolved type Ⅲ virulence effectors to suppress MAMP-medlated immunity. To survive, plants further developed highly specific resistance （R） genes to trigger gene-for-gene-mediated immunity and turn the virulent pathogens into avirulent ones. We summarize here the very recent advances in this dynamic coevolution of plantbacterium interaction.     

Astaxanthin Accumulation in the Green Alga Haematococcus pluvialis： Effects of Cultivation Parameters

The green alga, Haematococcus pluvlalis Flotow is used as a source of the ketocarotenoid astaxanthin for application in fish aquaculture, pharmaceutical and cosmetic industries. Ceils of the green alga were induced by the application of different light and starvation conditions to evaluate the effect in astaxanthin accumulate. The conditions used for the Induction were high light intensity （170 μmol·m^-2·s^-1）, iron starvation, sulfur starvation and phosphate starvation. The results show that stresses applied in culture, which interfere with cell division, trigger the accumulation of astaxanthin. Notably, sulfur starvation results in a massive accumulation of this commercially important carotenoid.     

小立碗藓叶绿体分裂相关基因PpMinE的克隆及其功能与进化分析

用RT-PCR技术从小立碗藓中(Physcomitrella patens)克隆了核编码的MinE基因,命名为PpMinE,并克隆了该基因的基因组DNA。序列比对显示该基因编码的蛋白质与真细菌和绿藻叶绿体编码的MinE蛋白具有较高的相似性。pMinE-EGFP融合蛋白在烟草中的瞬时表达证明该蛋白定位于叶绿体内。在大肠杆菌中过量表达PpMinE导致细胞不正常分裂,产生无染色体的小细胞,这表明MinE的功能在进化上是保守的。在系统发育树中,PpMinE和高等陆生植物有较近的亲缘关系。在已知的陆生植物的叶绿体基因组中没有找到MinE的同源蛋白,这暗示在进化过程中MinE从叶绿体到细胞核的水平转移可能发生在陆生植物发生以前。     

植物开花的组蛋白甲基化调控分子机理

开花是指植物从营养生长转变到生殖生长的生理过程, 是植物个体发育和后代繁衍的中心环节, 既受遗传基础决定,同时又受到温度和光周期等多种环境因素的调控。在拟南芥中, 已经分离了大量的与开花相关的基因, 从遗传学上已初步形成了一个开花调控的网络。组蛋白甲基化是植物发育过程的重要调节方式, 近年来关于其参与开花调控的研究有了重要进展。本文综述了具有代表性的组蛋白H3赖氨酸甲基化修饰参与调控植物开花发育的机制, 提出该研究领域的发展方向和前景。