Autophagy in plants: Physiological roles and post‐translational regulation

In eukaryotes, autophagy helps maintain cellular homeostasis by degrading and recycling cytoplasmic materials via a tightly regulated pathway.Over the past few decades, significant progress has been made towards understanding the physiological functions and molecular regulation of autophagy in plant cells. Increasing evidence indicates that autophagy is essential for plant responses to several developmental and environmental cues, functioning in diverse processes such as senescence, male fertility, root meristem maintenance, responses to nutrient starvation,and biotic and abiotic stress. Recent studies have demonstrated that, similar to nonplant systems,the modulation of core proteins in the plant autophagy machinery by posttranslational modifications such as phosphorylation, ubiquitination,lipidation, S-sulfhydration, S-nitrosylation, and acetylation is widely involved in the initiation and progression of autophagy. Here, we provide an overview of the physiological roles and posttranslational regulation of autophagy in plants.     

Nuclear volume estimation using different sampling, measurement and calculation methods

OBJECTIVE: To study the reliability of volume parameter measured on tissue sections through different sampling, measurement and calculation methods. STUDY DESIGN: The largest nuclear profile image under a 100x, NA 1.30 oil immersion objective of primary spermatocytes and spherical spermatoblasts on 11-micron-thick seminiferous tubule sections and tissue images, under a 20x objective, on 4-micron sections were captured. Their volumes were measured and calculated by the five methods provided by the Technology for Image and Graphics Engineering Research cell image analysis system. RESULTS: The nuclear volumes obtained by nucleator and area equivalent diameter on the largest nuclear profile image were almost the same, including binary images by automated and manual interactive nucleator and grey scale images only by the latter. Nuclear volumes, calculated by random Feret diameter and equivalent diameter of the perimeter, the minimal circumference of the largest nuclear profile binary image, were obviously larger than those of the nucleator and area equivalent diameter. Due to different-sized nuclear slices entrapped in the same section, those nuclear volumes from the seminiferous tubule tissue images were strikingly lower than that of the largest nuclei profile image. The shape factors of primary spermatocytes and spherical spermatoblast nuclei under 100x and 20x objectives were approximately the same. CONCLUSION: The sample preparation, sampling methods and calculation formulas suitable to nuclear form are necessary to obtain reproducible volume parameters.     

TDZ对植物体细胞胚胎发生的作用

介绍了TDZ在植物体细胞胚胎发生中的作用及其可能的作用机制的研究进展。     

Apelin activates L-arginine/nitric oxide synthase/nitric oxide pathway in rat aortas

Apelin was recently found to be an inotropic polypeptide in isolated rat hearts, and intravenous injection of apelin can induce a transient decrease in blood pressure. To illustrate the mechanism of apelin-induced vasodilation, we observed the in vitro effects of apelin on the L-arginine (L-Arg)/nitric oxide (NO) pathway in the incubated, isolated rat aorta. Apelin stimulated vascular NO(2)(-) product and NOS activation in a concentration- and time-dependent manner. Compared with no apelin treatment, incubation with apelin (10(-9), 10(-8), and 10(-7)mol/L) increased NO(2)(-) product by 33%, 46%, and 69% (all p<0.01), respectively, and Ca(2+)-dependent constitutive NOS (cNOS) activity by 200%, 460%, and 550% (all p<0.01), respectively. However, Ca(2+)-independent NOS (iNOS) activity was not significantly altered (p>0.05). Apelin incubation (10(-9), 10(-8), and 10(-7)mol/L) increased L-Arg uptake by 130%, 180%, and 240% (all p<0.01), respectively. The mRNA level of cationic amino acid transporters, CAT-1 and CAT-2B, in rat aortic tissues treated with 10(-7)mol/L apelin was increased by 110% and 128%, respectively (both p<0.01). Incubation with 10(-7)mol/L apelin elevated eNOS mRNA and protein levels, by 53% (p<0.05) and 319% (p<0.01), respectively. Collectively, these results demonstrate that apelin directly activated the vascular L-Arg/NOS/NO pathway, which could be one of the important mechanisms of apelin-regulated vascular function.     

Cultured subventricular zone progenitor cells transduced with neurogenin-2 become mature glutamatergic neurons and integrate into the dentate gyrus

We have previously shown that transplantation of immature DCX+/NeuN+/Prox1+ neurons (found in the neonatal DG), but not undifferentiated neuronal progenitor cells (NPCs) from ventral subventricular zone (SVZ), results in neuronal maturation in vivo within the dentate niche. Here we investigated whether we could enhance the integration of SVZ NPCs by forced expression of the proneural gene Neurogenin 2 (NEUROG2). NPCs cultured from neonatal GFP-transgenic rat SVZ for 7 days in a non-differentiating medium were transduced with a retrovirus encoding NEUROG2 and DsRed or the DsRed reporter gene alone (control). By 3 days post-transduction, the NEUROG2-transduced cells maintained in culture contained mostly immature neurons (91% DCX+; 76% NeuN+), whereas the control virus-transduced cells remained largely undifferentiated (30% DCX+; <1% NeuN+). At 6 weeks following transplantation into the DG of adult male rats, there were no neurons among the transplanted cells treated with the control virus but the majority of the NEUROG2-transduced DsRed+ SVZ cells became mature neurons (92% NeuN+; DCX-negative). Although the NEUROG2-transduced SVZ cells did not express the dentate granule neuron marker Prox1, most of the NEUROG2-transduced SVZ cells (78%) expressed the glutamatergic marker Tbr1, suggesting the acquisition of a glutamatergic phenotype. Moreover, some neurons extended dendrites into the molecular layer, grew axons containing Ankyrin G+ axonal initial segments, and projected into the CA3 region, thus resembling mature DG granule neurons. A proportion of NEUROG2 transduced cells also expressed c-Fos and P-CREB, two markers of neuronal activation. We conclude that NEUROG2-transduction is sufficient to promote neuronal maturation and integration of transplanted NPCs from SVZ into the DG.     

Multiple antibiotic resistance of Vibrio cholerae serogroup O139 in China from 1993 to 2009

Regarded as an emerging diarrheal micropathogen, Vibrio cholerae serogroup O139 was first identified in 1992 and has become an important cause of cholera epidemics over the last two decades. O139 strains have been continually isolated since O139 cholera appeared in China in 1993, from sporadic cases and dispersed foodborne outbreaks, which are the common epidemic types of O139 cholera in China. Antibiotic resistance profiles of these epidemic strains are required for development of clinical treatments, epidemiological studies and disease control. In this study, a comprehensive investigation of the antibiotic resistance of V. cholerae O139 strains isolated in China from 1993 to 2009 was conducted. The initial O139 isolates were resistant to streptomycin, trimethoprim-sulfamethoxazole and polymyxin B only, while multidrug resistance increased suddenly and became common in strains isolated after 1998. Different resistance profiles were observed in the isolates from different years. In contrast, most V. cholerae O1 strains isolated in the same period were much less resistant to these antibiotics and no obvious multidrug resistance patterns were detected. Most of the non-toxigenic strains isolated from the environment and seafood were resistant to four antibiotics or fewer, although a few multidrug resistant strains were also identified. These toxigenic O139 strains exhibited a high prevalence of the class I integron and the SXT element, which were rare in the non-toxigenic strains. Molecular subtyping of O139 strains showed highly diverse pulsed-field gel electrophoresis patterns, which may correspond to the epidemic state of sporadic cases and small-scale outbreaks and complex resistance patterns. Severe multidrug resistance, even resistance transfers based on mobile antibiotic resistance elements, increases the probability of O139 cholera as a threat to public health. Therefore, continual epidemiological and antibiotic sensitivity surveillance should focus on the occurrence of multidrug resistance and frequent microbial population shifts in O139 strains.     

中国(竹思)簩竹属(Schizostachyum Nees)的研究及其它

对国产(竹思)(竹劳)竹属(Schizostachyum Nees)进行了系统整理。对属的范围进行了修订,认为本属应包括乔草竹属(Dendrochloa Parkinson),薄竹属(Leptocanna Chia et H.L.Fung),长穗竹属(Teinostachyum Munro)和李海竹属(Neohouzeaua A.Camus),并首次建立了本属的属下分类系统。此外,对二种竹子起了新名:甲竹(Bambusa austro-sinensis Xia)和毛环单竹(B.yunnanensis Xia);作了4个新组合,即Schizostachyum coradatum(Wen et Dai)Xia, S.dumetorum(Hance)Munro var.xinwuense(Wen et J. Y Chin)Xia, Bambusa glaucescens glaucescens(Willd)Sieb. ex Munro var.annulata(W.T.Lin et Z.J.Feng)Xia和B.glaucescens (Willd)Sieb.ex Munro var.pubivagina(W.T....     

Mapping of the Glycoprotein 330 (Gp330) Gene to Mouse Chromosome 2

Glycoprotein 330 (Gp330) is a member of the low-density lipoprotein receptor gene family that is expressed in the kidney. We have mapped the Gp330 gene to mouse chromosome 2, 4.5 cM proximal to Acra, in an interspecific backcross of (C57BL/6J × Mus spretus) F1 × C57BL/6J.     

硝化抑制剂DCD、 DMPP对褐土氮总矿化速率和硝化速率的影响

采用15N库稀释-原位培养法研究了硝化抑制剂DCD、DMPP对华北盐碱性褐土氮总矿化速率和硝化速率的影响.试验在山西省运城市种植玉米的盐碱性土壤上进行,设单施尿素、尿素+DCD、尿素+DMPP 3个处理.结果表明:施肥后2周,DCD、DMPP分别使氮总矿化速率和氮总硝化速率减少了25.5％、7.3％和60.3％、59.1％,DCD对氮总矿化速率的影响显著高于DMPP,两者对氮总硝化速率的影响无显著差异;而在施肥后7周,不同硝化抑制剂对氮总硝化速率的影响存在差异.施肥后2周,3个处理的土壤氮总矿化速率和硝化速率分别是施肥前的7.2 ～10.0倍和5.5 ～21.5倍;NH4+和NO3-消耗速率分别是施肥前的9.1 ～12.2倍和5.1 ～8.4倍,这是由氮肥对土壤的激发效应所致.硝化抑制剂使氮肥更多地以NH4+形式保持在土壤中,减少了NO3-的积累.土壤氮总矿化速率和总硝化速率受硝化抑制剂的抑制是N2O减排的主要原因.     

Diversity of telomere palindromic sequences and replication genes among Streptomyces linear plasmids

Streptomyces sp. linear plasmids and linear chromosomes usually contain conserved terminal palindromic sequences bound by the conserved telomeric proteins Tap and Tp, encoded by the tap and tpg genes, respectively, as well as plasmid loci required for DNA replication in circular mode when the telomeres are deleted. These consist of iterons and an adjacent rep gene. By using PCR, we found that 8 of 17 newly detected linear plasmids in Streptomyces strains lack typical telomeric tap and tpg sequences. Instead, two novel telomeres in plasmids pRL1 and pRL2 from the eight strains and one conserved telomere in pFRL1 from the other strains were identified, while multiple short palindromes were also found in the plasmids. The complete nucleotide sequence of pRL2 revealed a gene encoding a protein containing two domains, resembling Tap of Streptomyces and a helicase of Thiobacillus, and an adjacent gene encoding a protein similar to Tpg of Streptomyces and a portion of the telomere terminal protein pTP of adenoviruses. No typical iterons-rep loci were found in the three plasmids. These results indicate an unexpected diversity of telomere palindromic sequences and replication genes among Streptomyces linear plasmids.