多头绒泡菌核仁及其骨架中原肌球蛋白的免疫细胞化学鉴定

分离多头绒泡菌(physarum polycephalum)细胞的核仁,先用Dnase I消化,去除核仁内的DNA;然后用025mol/L (NH4)2ＳＯ４和2mol/L NaCl相继抽提去掉大部分蛋白质,制备成核仁骨架。SDSPAGE分析结果表明,核仁骨架中含有约20种多肽,其中包括37kD左右与原肌球蛋白分子量相当的多肽。以兔抗原肌球蛋白抗体为一抗,FITC标记的羊抗兔IgG抗体为二抗的间接免疫荧光检测结果表明,核仁和核仁骨架样品都能发出明亮的荧光,而对照样品未见明亮的荧光。间接免疫斑点印迹检测结果进一步证明,在核仁骨架的蛋白质成分中存在原肌球蛋白。胶体金免疫电镜检测结果显示,标记原肌球蛋白抗体的标本上有较多的金颗粒,而对照组标本上只有极少的金颗粒。金颗粒在核仁中主要呈散在分布。     

Fitness comparison of Plutella xylostella on original and marginal hosts using age‐stage,two‐sex life tables

The diamondback moth, Plutella xylostella, is an important agricultural pest that severely damages cruciferous vegetables. Although previously considered a threat only to Brassica species, P. xylostella has been observed to feed on noncruciferous vegetables. Here, we established a population of P. xylostella on the pea Pisum sativum (PxP population). We compared this PxP population''s performance on the pea host plant to a population (PxR) reared on the original host plant radish (Raphanus sativus) for several generations using an age‐stage, two‐sex life table and analyzed the correlations between different fitness parameters. In the 1st generation of the PxP population, survival rate of immature stage was 17%, while the survival rate of PxR was 68%; the duration of the 4th larval instar (5.30 d) and mortality (25%) of this generation were significantly longer (2.8 d) and higher (1%) than that of PxR, respectively (both p < .001). Upon long‐term acclimation, the PxP fitness improved significantly, especially that the survival rate of immature stages increased to approximately 60% in the 15th, 30th, and 45th generations. However, PxP feeding on pea exhibited poorer fitness with longer larval developmental time, shorter total life span, lighter pupa, and lower fecundity in different generations compared with PxP feeding on radish. PxP feeding on pea also showed a significantly lower intrinsic rate of increase (r), net reproduction rate (R ₀), finite increase rate (λ), and longer mean generation time (T) than PxP feeding on radish in all generations tested. Significant positive correlations were observed between pupal weight and female fecundity in pea‐fed populations, and between female longevity and female fecundity in pea‐fed and radish‐fed populations. Our findings suggest that P. xylostella adaptation to pea does not improve overall fitness compared with the original host radish, making pea a marginal host for P. xylostella.     

滦河流域河岸带入侵植物分布特征及其与环境的关系

根据滦河流域河岸带56个样点的植被调查,研究入侵植物种类,其组成特征、空间分布,及其与环境因子的关系.结果表明: 滦河流域河岸带共记录入侵植物26种,属12科19属,其中菊科和苋科植物为优势科,占入侵植物总数的50%,一年生植物占总数的73.1%,反枝苋、大狼杷草、小藜是出现频数最高的3种植物;样点的入侵种数、入侵强度与海拔呈显著负相关;人类活动强度对入侵植物分布有显著影响,人口密集、交通便利、人类活动频繁的平原区,水库众多的浅山区,以及中游段旅游业发达的承德市周边山区是入侵植物集中分布的区域;人口分布较稀的高原地区只出现几种宽生态幅的入侵物种.总体上,滦河流域河岸带入侵等级高的植物主要分布在400 m以下的中低海拔地区,除反枝苋外,其他高等级入侵物种尚未扩散进入高海拔地区.     

Complete genome sequence of an H10N8 avian influenza virus isolated from a live bird market in Southern China

An H10N8 avian influenza virus (AIV), designated A/Duck/Guangdong/E1/2012 (H10N8), was isolated from a duck in January 2012. This is first report that this subtype of AIV was isolated from a live bird market (LBM) in Guangdong Province in southern China. Furthermore, the complete genome of this strain was analyzed. The availability of genome sequences is helpful to further investigations of epidemiology and molecular characteristics of AIV in southern China.     

TaTPP-7A positively feedback regulates grain filling and wheat grain yield through T6P-SnRK1 signalling pathway and sugar–ABA interaction

Grain size and filling are two key determinants of grain thousand-kernel weight (TKW) and crop yield, therefore they have undergone strong selection since cereal was domesticated. Genetic dissection of the two traits will improve yield potential in crops. A quantitative trait locus significantly associated with wheat grain TKW was detected on chromosome 7AS flanked by a simple sequence repeat marker of Wmc17 in Chinese wheat 262 mini-core collection by genome-wide association study. Combined with the bulked segregant RNA-sequencing (BSR-seq) analysis of an F₂ genetic segregation population with extremely different TKW traits, a candidate trehalose-6-phosphate phosphatase gene located at 135.0 Mb (CS V1.0), designated as TaTPP-7A, was identified. This gene was specifically expressed in developing grains and strongly influenced grain filling and size. Overexpression (OE) of TaTPP-7A in wheat enhanced grain TKW and wheat yield greatly. Detailed analysis revealed that OE of TaTPP-7A significantly increased the expression levels of starch synthesis- and senescence-related genes involved in abscisic acid (ABA) and ethylene pathways. Moreover, most of the sucrose metabolism and starch regulation-related genes were potentially regulated by SnRK1. In addition, TaTPP-7A is a crucial domestication- and breeding-targeted gene and it feedback regulates sucrose lysis, flux, and utilization in the grain endosperm mainly through the T6P-SnRK1 pathway and sugar–ABA interaction. Thus, we confirmed the T6P signalling pathway as the central regulatory system for sucrose allocation and source–sink interactions in wheat grains and propose that the trehalose pathway components have great potential to increase yields in cereal crops.     

Evaluation of BACTEC MGIT 960 System for Testing Susceptibility of Mycobacterium tuberculosis to First-Line Drugs in China

Background

The purpose of this study was to evaluate the performance of the BACTEC MGIT 960 (M960) system compared with the proportion method (PM) on Löwenstein-Jensen (L-J) medium in a peripheral laboratory in China for the testing of Mycobacterium tuberculosis (MTB) susceptibility to streptomycin (SM), isoniazid (INH) rifampicin (RIF) and ethambutol (EMB) a combination known as SIRE.

Methods

The susceptibility of 205 clinical isolates of MTB to SM, INH, RIF and EMB was performed with the M960 system. The drugs were tested at the following concentrations: 1.0 µg/ml for SM, 0.1 µg/ml for INH, 1.0 µg/ml for RIF, and 5.0 µg/ml for EMB. The results were compared with those obtained by the L-J PM. The L-J PM at an arbiter site was used to resolve any discordant results.

Results

The overall consistency was 96.6% and concordance values were 95.6% for SM, 97.6% for INH, 98.0% for RIF and 95.1% for EMB. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the M960 system for PM (the standard method) was 95.6%, 97.3%, 96.2% and 96.9% respectively, and the sensitivity were 93.3% for SM, 96.9% for INH, 97.4% for RIF and 94.6% for EMB, the specificity were 96.9% for SM, 98.2% for INH, 98.4% for RIF and 95.5% for EMB, the PPV were 94.6% for SM, 97.9% for INH, 97.4% for RIF and 94.6% for EMB, the NPV were 96.2% for SM, 97.3% for INH, 98.4% for RIF and 95.5% for EMB. The turnaround time with the M960 system (median 8.0 days, ranged from 5 to 14 days) was significantly shorter than that with the PM (28 days or 42 days).

Conclusion

There was a substantial degree of agreement between the two methods. The M960 system was a reliable and rapid method for SIRE susceptibility testing of tuberculosis in China.     

Brassica rapa plants adapted to microgravity with reduced photosystem I and its photochemical activity

The photosynthetic apparatus contains several protein complexes, many of which are regulated by environmental conditions. In this study, the influences of microgravity on PSI and PSII in Brassica rapa plants grown aboard the space shuttle were examined. We found that Brassica plants grown in space had a normal level of growth relative to controls under similar conditions on Earth. Upon return to Earth, cotyledons were harvested and thylakoid membranes were isolated. Analysis of chlorophyll contents showed that the Chl a/b ratio (3.5) in flight cotyledons was much higher than a ratio of 2.42 in the ground controls. The flight samples also had a reduction of PSI complexes and a corresponding 30% decrease of PSI photochemical activity. Immunoblotting showed that the reaction centre polypeptides of PSI were more apparently decreased (e.g. by 24-33% for PsaA and PsaB, and 57% for PsaC) than the light-harvesting complexes. In comparison, the accumulation of PSII complex was less affected in microgravity, thus only a slight reduction in D1, D2 and LHCII was observed in protein blots. However, there was a 32% decrease of OEC1 in the flight samples, indicating a defective OEC subcomplex. In addition, an average 54% increase of the 54 kDa CF1-beta isoform was found in the flight samples, suggesting that space-grown plants suffered from certain stresses, consistent with implications of the increased Chl a/b ratio. Taken together, the results demonstrated that Brassica plants can adapt to spaceflight microgravity, but with significant alterations in chloroplast structures and photosynthetic complexes, and especially reduction of PSI and its activity.     

Slit2 Inactivates GSK3β to Signal Neurite Outgrowth Inhibition

Slit molecules comprise one of the four canonical families of axon guidance cues that steer the growth cone in the developing nervous system. Apart from their role in axon pathfinding, emerging lines of evidence suggest that a wide range of cellular processes are regulated by Slit, ranging from branch formation and fasciculation during neurite outgrowth to tumor progression and to angiogenesis. However, the molecular and cellular mechanisms downstream of Slit remain largely unknown, in part, because of a lack of a readily manipulatable system that produces easily identifiable traits in response to Slit. The present study demonstrates the feasibility of using the cell line CAD as an assay system to dissect the signaling pathways triggered by Slit. Here, we show that CAD cells express receptors for Slit (Robo1 and Robo2) and that CAD cells respond to nanomolar concentrations of Slit2 by markedly decelerating the rate of process extension. Using this system, we reveal that Slit2 inactivates GSK3β and that inhibition of GSK3β is required for Slit2 to inhibit process outgrowth. Furthermore, we show that Slit2 induces GSK3β phosphorylation and inhibits neurite outgrowth in adult dorsal root ganglion neurons, validating Slit2 signaling in primary neurons. Given that CAD cells can be conveniently manipulated using standard molecular biological methods and that the process extension phenotype regulated by Slit2 can be readily traced and quantified, the use of a cell line CAD will facilitate the identification of downstream effectors and elucidation of signaling cascade triggered by Slit.     

Epidermal restriction confers robustness to organ shapes

The shape of comparable tissues and organs is consistent among individuals of a given species, but how this consistency or robustness is achieved remains an open question. The interaction between morphogenetic factors determines organ formation and subsequent shaping, which is ultimately a mechanical process. Using a computational approach, we show that the epidermal layer is essential for the robustness of organ geometry control. Specifically, proper epidermal restriction allows organ asymmetry maintenance, and the tensile epidermal layer is sufficient to suppress local variability in growth, leading to shape robustness. The model explains the enhanced organ shape variations in epidermal mutant plants. In addition, differences in the patterns of epidermal restriction may underlie the initial establishment of organ asymmetry. Our results show that epidermal restriction can answer the longstanding question of how cellular growth noise is averaged to produce precise organ shapes, and the findings also shed light on organ asymmetry establishment.