Biosynthesis of the enediyne antitumor antibiotic C-1027     

Liu W  Christenson SD  Standage S  Shen B 《Science (New York, N.Y.)》2002,297(5584):1170-1173

C-1027 is a potent antitumor agent with a previously undescribed molecular architecture and mode of action. Cloning and characterization of the 85-kilobase C-1027 biosynthesis gene cluster from Streptomyces globisporus revealed (i) an iterative type I polyketide synthase that is distinct from any bacterial polyketide synthases known to date, (ii) a general polyketide pathway for the biosynthesis of both the 9- and 10-membered enediyne antibiotics, and (iii) a convergent biosynthetic strategy for the C-1027 chromophore from four building blocks. Manipulation of genes governing C-1027 biosynthesis allowed us to produce an enediyne compound in a predicted manner.  相似文献   

云南香料烟害虫种类及发生规律研究   总被引：2，自引：0，他引：2  

李光西  杜绍明  杨本立  李正兰  宋玉川  兰应海  屈生彬  殷端 《西南大学学报(自然科学版)》2005,27(6):868-872

通过6a系统调查,在云南省香料烟主产区烟田内共发现7目31科88种昆虫和野蛞蝓、灰巴蜗牛2种软体动物危害云南冬春香料烟。其中重要害虫是烟蚜（Myzus persicae Suizer）、棉铃虫（Heliothis arrnigera Hubner）、烟草夜蛾（Heliothis assuha Guenee）、烟草盲蝽[Cyrtopeltis tenuis（Reuter）]、野蛞蝓（Agriolimax agresfis Linnaeus）、小地老虎（Agrotis ypsilon Rottemberg）、东方蛄蝼（G．orlentalis Burmeister）、小长蝽（Nysius ericae（Schilling）]等7种。烟蚜、野蛞蝓、小地老虎均为香料烟和烤烟上的重要害虫,在发生危害时期上较一致。棉铃虫、烟草夜蛾在香料烟上危害损失较大．而在烤烟上危害较轻。东方蝼蛄和小长蝽是香料烟上的主要害虫,在烤烟上发生较少,烟草盲蝽和金龟子在香料烟上发生较少．却又是烤烟的主要害虫。  相似文献   

桑园小长蝽发生危害规律及防治技术研究     

史淑琼  杨本立  梁明生  俞红美 《云南农业大学学报(自然科学版)》2002,17(3):261-263

 1998年在云南陆良县首次发现小长蝽［(Nysius ercae(schilling)］危害桑树,有的桑园暴发成灾。经1998～2000年调查研究,小长蝽1年发生1代,以成虫在桑园内外杂草丛中越冬,4月下旬至6月中旬是若虫大量发生时期,此时正值桑树发芽抽条,若虫以刺吸式口器吸食桑芽养份和水份,造成桑芽生长不良,不易展叶,以致枯萎脱落。小长蝽发生危害与气候条件、耕作栽培水平有关清洁田园,冬季提早翻耕桑园,翻耕前喷洒化学农药、深施腐施厩肥,桑芽萌发期(4月上旬)喷药防治等综合措施,能有效的控制其危害。  相似文献   

Geochemistry. Diamond window into the lower mantle     

Harte B 《Science (New York, N.Y.)》2011,334(6052):51-52

  相似文献   

Ecology. Conflict over cooperation     

Shouse B 《Science (New York, N.Y.)》2003,299(5607):644-646

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Computer science. Science 2.0     

Shneiderman B 《Science (New York, N.Y.)》2008,319(5868):1349-1350

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Lhx2 selector activity specifies cortical identity and suppresses hippocampal organizer fate     

Mangale VS  Hirokawa KE  Satyaki PR  Gokulchandran N  Chikbire S  Subramanian L  Shetty AS  Martynoga B  Paul J  Mai MV  Li Y  Flanagan LA  Tole S  Monuki ES 《Science (New York, N.Y.)》2008,319(5861):304-309

The earliest step in creating the cerebral cortex is the specification of neuroepithelium to a cortical fate. Using mouse genetic mosaics and timed inactivations, we demonstrated that Lhx2 acts as a classic selector gene and essential intrinsic determinant of cortical identity. Lhx2 selector activity is restricted to an early critical period when stem cells comprise the cortical neuroepithelium, where it acts cell-autonomously to specify cortical identity and suppress alternative fates in a spatially dependent manner. Laterally, Lhx2 null cells adopt antihem identity, whereas medially they become cortical hem cells, which can induce and organize ectopic hippocampal fields. In addition to providing functional evidence for Lhx2 selector activity, these findings show that the cortical hem is a hippocampal organizer.  相似文献   

An evolutionarily conserved mechanism delimiting SHR movement defines a single layer of endodermis in plants   总被引：2，自引：0，他引：2  

Cui H  Levesque MP  Vernoux T  Jung JW  Paquette AJ  Gallagher KL  Wang JY  Blilou I  Scheres B  Benfey PN 《Science (New York, N.Y.)》2007,316(5823):421-425

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关于我国发展适于深加工优质专用玉米的思考   总被引：2，自引：0，他引：2  

李本逊  吴渝生 《云南农业大学学报(自然科学版)》2002,17(3):291-293

 介绍了我国玉米生产的现状、存在问题以及世界玉米生产和加工情况,提出我国玉米生产发展的方向为稳定普通玉米生产,迅速扩大专用玉米生产,从粉、糖、酒、酸、油5个方面研究、开发相应的加工技术,从而发挥我国玉米资源优势,解决玉米相对过剩的问题,为玉米深加工的长远发展打下基础。  相似文献   

Long-term trends in the abundance of Mediterranean wetland vertebrates: From global recovery to localized declines     

Thomas Galewski  Ben Collen  Louise McRae  Jonathan Loh  Patrick Grillas  Michel Gauthier-Clerc  Vincent Devictor 《Biological conservation》2011,(5):1392-1399

Biodiversity loss is unevenly distributed in space and time. Species have reached critically low population sizes in some areas, and remain abundant in others. Similarly, some species may benefit from successful conservation plans, while others still experience severe population depletions driven by negative impacts of human activities. Although several indicators have been proposed to measure the fate of biodiversity, they are generally only implemented globally so their relevance for regional assessment is still unclear. Here, we calculated the first regional trend in the Living Planet Index for the Mediterranean wetlands (Med LPI), an indicator that summarizes the fate of global biological diversity based on the temporal trends in abundance of vertebrate populations. The Med LPI was based on 1641 vertebrate populations of 311 species recorded in Mediterranean wetlands from 1970–2008, in 27 different countries. We investigated whether trends in the Med LPI differed between eastern and western Mediterranean countries, which have different socio-economic contexts. Finally, we assessed whether and how the trend in the Med LPI was robust to changes in the number and identity of species considered. We found that, at the Mediterranean scale, the Med LPI increased steeply, which could be taken at first sight, as a general recovery of wetland biodiversity in this biogeographical region. However, we found highly contrasting spatial trends within the Mediterranean region: the average trend was positive for western and negative for eastern countries. Moreover, we showed that depending on the method used to estimate the trend in Med LPI, it can be sensitive to the number and identity of the species considered. We suggest that understanding the regional discrepancies of the trend in biodiversity indicators as well as their robustness to the species represented in the index will enhance progress assessment towards global and regional conservation strategies.  相似文献