Plant development: regulation by protein degradation

Many aspects of eukaryotic development depend on regulated protein degradation by the ubiquitin-proteasome pathway. This highly conserved pathway promotes covalent attachment of ubiquitin to protein substrates through the sequential action of three enzymes called a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin-protein ligase (E3). Most ubiquitinated proteins are then targeted for degradation by the 26S proteasome. Recent studies have also shown that the ubiquitin-related protein RUB/Nedd8 and the proteasome-related COP9 signalosome complex cooperate with the ubiquitin-proteasome pathway to promote protein degradation. Most of these components are conserved in all three eukaryotic kingdoms. However, the known targets of the pathway in plants, and the developmental processes they regulate, are specific to the plant kingdom.     

Farming systems development: Synthesizing indigenous and scientific knowledge systems

Agricultural development strategies to date were chiefly based on Western technological solutions, with mixed success rates. Farming Systems Research (FSR) was advanced as a way to increase the use of indigenous knowledge of farming to make new technologies more adaptable and appropriate to farming conditions. FSR has enabled researchers to focus attention on people and their knowledge by increasing people's participation in problem identification and new technology validation. In practice, though, FSR continues to be a top-down approach: technologies continue to be developed (in most cases) in the exogenous, Western knowledge system. Little has been done to develop indigenous technology generating and diffusing capacities already present in the rural areas. In this paper, a model adapted from Bell (1979) will be advanced that is based on cooperation and collaboration between the exogenous and indigenous knowledge systems leading to a synthesis of the two. The underlying principle of the model is that the ultimate solution for rural development is not the dumping of more scientists upon rural people (of whatever discipline) to make exogenously-generated technologies more adaptable and in-line with people's problems, but to strengthen, empower, and legitimize indigenous capacities for identifying problems and developing solutions for these problems. The “empowerment” of the indigenous knowledge/technology system (however difficult that may be politically) so that it has equal footing with Western knowledge may well be the most important step in a strategy of enabling the people in the developing countries themselves to alleviate their poverty.     

家蚕核型多角体病毒orf79克隆及原核表达

家蚕核型多角体病毒orf79是苜蓿银纹夜蛾核型多角体病毒口服感染因子4的同源基因,为了研究orf79蛋白在家蚕核型多角体病毒感染过程中与宿主的互作关系,利用PCR技术克隆orf79基因并构建了原核表达载体,并进行表达条件的优化.结果表明,SDS-PAGE检测结果发现0.2 mmol· L-1的IPTG诱导2h后,orf...     

Scent organ development in creatonotos moths: regulation by pyrrolizidine alkaloids

7-Hydroxy-6,7-dihydro-5H-pyrolizine-1-carboxaldehyde is the major volatile component of the scent organs in males of two species of Creatonotos (Lepidoptera, Arctiidae). The biosynthesis of this presumed pheromone depends on the presence of pyrrolizidine alkaloids in plants that are ingested by the larvae. In addition, these secondary plant substances control the morphogenesis of the scent organs. This morphogenetic effect of an alkaloid has not been observed previously.     

苏云金芽孢杆菌cry1Ac28基因的克隆及原核表达

研究旨在克隆苏云金芽胞杆菌(Bacillus thuringiensis,Bt)Q-12的cry1Ac28基因并在原核载体中表达。应用PCR-RFLP法鉴定出Bt Q-12中含有cry1Ac基因,根据已知的cry1Ac全长基因序列设计特异引物,以Bt Q-12基因组DNA为模板扩增cry1Ac全长基因,与大肠杆菌(Escherichia coli)表达载体pEB相连接获得含有cry1Ac全长基因的重组质粒pEB-cry1Ac,经过序列分析表明,该基因编码区为3 537 bp,编码1 178个氨基酸,分子质量为133.3176 ku,pI为4.885,为弱酸性蛋白质,亮氨酸(Leu)、丝氨酸(Ser)、谷氨酸(Glu)三种氨基酸含量最高,分别为8.06%、7.80%、7.72%,该基因在大肠杆菌BL21(DE3)菌株能够正常表达133.3176 ku蛋白。该基因核苷酸序列已在GenBank中登录,登录号为FJ610439,并由Btδ-内毒素基因国际命名委员会正式命名为cry1Ac28。为进一步研究cry1Ac28蛋白功能和活性打下了良好的基础。     

Indigenous ecological knowledge systems and development

This paper reviews a selection of the literature that focuses on indigenous ecological knowledge systems and the accompanying cosmology and myth. Traditional ecological knowledge may not be obvious to the western trained scientist or the development worker since it may be disguised in the form of cosmology and ritual. The paper argues that the development process must be based on an understanding of traditional ecological knowledge if projects are to be sustainable both environmentally and sociologically.     

Fragmentation and flow regulation of the world's large river systems

A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments experience higher irrigation pressure and about 25 times more economic activity per unit of water than do unaffected catchments. In view of projected changes in climate and water resource use, these findings can be used to identify ecological risks associated with further impacts on large river systems.     

厚皮甜瓜腔内种子的生长发育规律

[目的]分析厚皮甜瓜腔内种子的生长发育规律,为提高厚皮甜瓜制种产量和质量提供参考依据.[方法]以具有腔内种子发芽特性的厚皮甜瓜自交系05-6为试验材料,分析授粉后果实腔内种子的生长发育规律、腔内种子发芽的发生时期和变化趋势,比较不同授粉天数果实腔内种子的饱满程度、数量、发芽率、成苗率和幼苗健壮程度差异.[结果]厚皮甜瓜腔内种子成熟时间比果实成熟时间早,授粉后第26 d种子已充分饱满.其中,未发芽种子的饱满度、数量、发芽和成苗能力及成苗的健壮程度与授粉后第35 d(即果实完全成熟时)相比差异不显著(P>0.05);已发芽种子数量显著少于授粉后第35 d腔内发芽种子数量(P<0.05).[结论]提前摘瓜采种是降低厚皮甜瓜腔内种子发芽率的有效措施,厚皮甜瓜材料05-6的适宜采种时间为授粉后第26 d.     

不同腐殖酸菌肥及其对高粱种子生长发育的影响

利用已筛选的放线菌菌株AG7与风化煤作用,提高风化煤中游离腐殖酸含量,制备一种腐殖酸菌肥.以腐殖酸的提高率确定其最佳培养条件：培养温度为28℃、培养混合液的初始pH值为6、培养转速为160r/min.在最佳培养条件下,风化煤和菌液以不同的比例混合,初步确定其腐殖酸提高率较高的比例为250g∶500mL（风化煤∶菌液）.对初步得到的腐殖酸菌肥、市场上销售的化学法腐殖酸肥和风化煤进行了植物生长的对比试验,研究其对植物生长的刺激作用.考察了不同腐殖酸肥对高粱种子的发芽率、株高及鲜重的影响.初步得到腐殖酸菌肥在适宜浓度下,对高粱种子的发芽及生长有一定的促进作用.     

Bacterial flagella: polarity of elongation

Newly synthesized regions of Bacillus subtilis flagella were labeled with fluorophenylalanine or [(3)H]leucine. The flagella were then examined for altered gross morphology or by radioautography. Results of both experiments indicate that flagella elongate in vivo by polymerization of flagellin subunits onto the distal end of the filament.     

Bacterial stromatolites: origin of laminations

Laminated mats composed of motile filamentous photosynthetic bacteria and nonmotile unicellular blue-green algae occur in a large number of Yellowstone hot springs at temperatures between 55 degrees and 70 degrees C. Field studies indicate that the bacteria are the predominant mat-forming component. Under low light intensities, mats composed exclusively of bacteria can be formed. The bacteria undergo a diurnal migration, moving on top of the algae dnring the night and becolming mixed again with the algae during the day of differential migration of the bacteria in daily response to reduced light intensities. This response to light is exactly opposite to that previously reported for filamentous stromatolite-forming, blue-green algae, but the net result is the same-formation of a laminated mat.     

变温条件下铃木氏果蝇的生长发育规律

[目的]明确变温对铃木氏果蝇(Drosophila suzukii)生长发育的影响,为铃木氏果蝇发生的预测预报及综合防治提供科学依据.[方法]以铃木氏果蝇为材料,在室内人工气候箱内设14~20、19~25、24~30、26~32和29~35℃5组变温饲养处理,测定铃木氏果蝇各发育阶段的发育历期,并用表现型(Performance)模型对铃木氏果蝇各阶段发育速率数据进行拟合分析.[结果]14~20、19~25、24~30和26~32℃变温条件下铃木氏果蝇均能完成整个世代生长发育,且各阶段的发育历期均随温度的升高而缩短,全代发育历期分别为33.81±0.64、16.64±0.34、13.16±0.37和12.26±0.69 d,29~35℃变温条件下铃木氏果蝇化蛹后蛹不能正常发育.在变温条件下,铃木氏果蝇世代的生长发育符合Perfor-mance非线性模型,该模型对其卵期、幼虫期和蛹期拟合的R2均在0.9000以上,预测得出卵、幼虫和蛹的发育起点温度分别为9.1、10.5和12.3℃,发育终止温度分别为32.2、32.5和29.5℃.[结论]在14~20、19~25、24~30和26~32℃变温条件下铃木氏果蝇均能完成整个世代生长发育,在29~35℃变温条件下不能完成世代生长发育.可运用Performance模型描述变温对铃木氏果蝇生长发育的影响.     

Bacterial domestication: underlying assumptions

On the basis of well-established principles of evolutionary biology and microbiology, I conclude that (i) the deliberate introduction of a novel bacterial strain to the environment is not substantially more dangerous than the accidental release of a smaller number of cells; (ii) distant organisms are less (rather than more) likely to yield dangerous hybrids than more closely related ones; and (iii) the complex attribute of pathogenicity is not likely to emerge from genetic alterations in nonpathogens. If these conclusions are correct, most engineered bacteria need not be regulated more strictly than the bacterial strains that have been tested in the field in the past. The only exceptions would be strains derived from cells, or appropriate genes, of microbes pathogenic for plants or animals. Microbiologists not only recognize the need to handle pathogens with caution: they have long accepted regulations, such as those governing transportation, that reinforce that recognition. It is remarkable that we can still be arguing, on the basis of analogies rather than firm scientific principles or evidence, about hypothetical disasters from kinds of organisms that are being produced in hundreds or thousands of laboratories without a trace of demonstrable harm. RAC required 6 years to adjust its initially conservative guidelines to the emerging understanding of the scientific realities, while maintaining public confidence. Since the level of public concern is not nearly as great today, EPA should be able to relax its excessive restrictions much more quickly. Even better would be a return to having RAC, or a single successor group, evaluate the problems of danger for all classes of engineered bacteria, since the applicable shared principles outweigh any specialized differences in the nature or use of the specific strains. But the regulations are unlikely to be unified in this way, or to be divested of unproductive restrictions, without broad encouragement from the scientific community-including, hopefully, many ecologists. The agenda has been set for too long by apocalyptic activists. To protect this promising field of research and technological application the scientific community must take initiative in helping the public and decision-makers to distinguish reasonable probabilities from remote fantasies.     

Redox regulation of germline and vulval development in Caenorhabditis elegans

In vitro studies have indicated that reactive oxygen species (ROS) and the oxidation of signaling molecules are important mediators of signal transduction. We have identified two pathways by which the altered redox chemistry of the clk-1 mutants of Caenorhabditis elegans acts in vivo on germline development. One pathway depends on the oxidation of an analog of vertebrate low density lipoprotein (LDL) and acts on the germline through the Ack-related tyrosine kinase (ARK-1) kinase and inositol trisphosphate (IP3) signaling. The other pathway is the oncogenic ras signaling pathway, whose action on germline as well as vulval development appears to be modulated by cytoplasmic ROS.     

卵泡生长发育及其调控的研究进展

综述了卵泡生长发育的动态模式,即卵泡经原始卵泡、初级卵泡、次级卵泡和窦腔卵泡发育至排卵卵泡的过程,着重阐述了卵泡生长发育过程中的调控机制,为进一步研究卵泡的生长、发育和排卵机制提供了理论基础。     

MADS-box基因家族调控植物花器官发育研究进展

花器官的发生发育与形态构造是一个高度复杂的项目,涉及众多因素及其相互作用,MADS-box基因作为其中的关键转录因子可以改变整个发育过程,因而成为花器官研究最广泛的基因家族.通过梳理目前MADS-box基因对花器官发生、分化和形态建成方面的调控作用,为了解花发育程序和该基因家族的一般转录调控机制提供新见解,也为进一步深...