A Study on Glutamate Oxaloacetate Transaminase Isozymes of Citrus Germplasm Resources

The glutamate oxaloacetate transaminase isozymes (GOT) extracted from 125 biotypes of Citrus and its relatives, Fortunella, Poncirus and Microcitrus were analyzed using polyacrylamide gel electrophoresis to investigate the taxonomic relationships among citrus plants. Besides all the isozymes reported before, two new bands were detected and designated their putative alleles B and C in GOT-l. Among pummelo cultivars wide variations were found. Most of the mandarins were identical, having SS for GOI-1 and MM for GOT-2 except for Zou-Pi-Gan and Yao-Gan, which both had FS at GOT-1 and might be hybrids. This finding suggests that all of the mandarins may have originated from a common ancestor. Sour orange biotypes showed a considerable variation in GOT isozymes. Most of the sour oranges in China were assumed to be hybrids between pummelo and mandarin based on GOT isozyme patterns, but two biotypes, Xiao-Hong-Cheng and Zhu-lan, had FS at GOT-1 and MB at GOT-2, which strongly suggests that they be hybrids of pummelo and Ichang papeda because B allele of GOT-2 occurs only in Ichang papeda and its close relatives Yuzu and Ichang lemon. From this study Yuzu is assumed to be derived from hybridizationof Ichan, papeda and mandarin.     

Studies on Taxonomy and Evolution of Citrus and Its Related Genera by Isozyme Analysis

The leaf or bark tissue extracts of 108 biotypes of Citrus and its five related genera were analyzed by polyacrylamide gel electrophoresis for isozymes of peroxidase, glutamate oxaloacetate transaminase, phosphoglucose isomerase, phosphoglucose mutase, superoxide dismutase, tetrazolium oxidase, NADP+- dependent malate dehydrogenase and esterase. The inter-or intra-generic differences of isozymograms were compared. Dissimilarities of the isozyme patterns among the samples were calculated by computer based on the UPGMA method to demonstrate the phylogenetic relationship of the biotypes. There are remarkable isozymogramatic differences among the six genera. Generally speaking, each genus possesses its own unique bands. Based on the cluster analysis, the total Citrus biotypes are classified into seven groups, i.e. Honghe papeda, Mauritius papeda, Pummelo, Ichang papeda, Citron, Lemon-lime and Mandarin-orange. Ichang papeda is suggested to be the third subgenus of the genus Citrus. The Fuming trifoliata orange is accepted as a new species of Poncirus-P. polyandra S. Q. Ding. It might be the evolutionary bridge between Poncirus and Citrus, and one of the “missing links” as suggested by W. T. Swingle. Microacrumen (small- fruited mandarin) is the primitive form of the mandarins. It seems better to consid er“ Horse-nose mandarin ”or “Xipigoushigan mandarin” as the typic mandarin originated in China. Euacrumen (large-fruited mandarin) might have arised through two ways. One is hybridization of Microacrumen and C. sinensis, and the other is just the variation of Microacrumen. Ancestors of some biotypes are inferred based on isozyme data. Fortunella obovata Tan. may be a hybrid of Fortunella and Citrus. C. unshiu Marc. arose from the nucellar mutation of“Huangyanbendiguangju mandarin”( C. nobilis Lour.) in Huangyan of Zhejiang Province. C. junos Sieb. came from hybridization of Ichang papeda and mandarin. C. grandis Osbeck and mandarin may have been involved in the origin of C. aurantium L.. C. limonia Osbeck may be a hybrid between C. medica L. and mandarin. The evolutionary trend of citrus fruit trees is proposed, anda tentative phylogenetic diagram is drawn.     

湖北西部下二叠纪介虫类化石

The Upper Cambrian fossils were not known in South and SouthwesternChina before 1938,though a thick limestone series ranging from not less than100m to over one thousand meters known as the Ichang Limestone of the Gorgedistrict of the Yangtze and the Loushankwan Limestone of North Kueichou hasbeen partially referred by various authors to represent some part of the Upper     

柑橘体细胞杂种有性后代的创造及杂种鉴定

110 plantlets were obtained from the cross between citrus allotetraploid somatic hybrid [Hamlin sweet orange (Citrus sinensis Osback) + Rough Lemon (C. jambhiri Luss)] (as the pollen parent) and mono-embryonic diploid type Iben No.4 [Huanongbendizao tangerine (C. reticulata Blanco) x Ichang papeda (C. ichangensis Swingle)] by the means of young embryo culture in vitro, and there were 93 triploids and 17 diploids through chromosome counting and the ploidy analyser identification. RAPD analyses showed that all sexual progenies were hybrid.     

Molecular phylogeography and population evolution analysis of <Emphasis Type="Italic">Citrus ichangensis</Emphasis> (Rutaceae)

Ichang papeda (Citrus ichangensis), a wild and endemic perennial plant in Rutaceae, is characterized by the existence of wild and natural populations in southwestern and middle-west China. We analyzed a total of 231 individuals across 16 natural populations using chloroplast SSR markers, nuclear SSR markers, and single-copy nuclear genes. Standard population genetic analyses as well as Bayesian and maximum likelihood models were used to clarify the genetic diversity, population differentiation, barriers to gene flow, bottleneck events, isolation by distance, history migration, demographic history among populations, and phylogeny evolution. The chloroplast and nuclear genome analyses revealed a low level of genetic diversity in C. ichangensis. Clear signals of recent bottlenecks and strong patterns of isolation by distance were detected among different subpopulations, indicating a low extent of historical gene flow for this species and that genetic drift would occur after population differentiation. Bayesian clustering analyses revealed a clear pattern of genetic structure, with one cluster spanning the potential refugia in Wuling Mountains and Ta-pa Mountains, and other two clusters covering a more limited distribution range. The demographic history also supported the scenario that two isolated clusters originated in parallel from the genetic diversity center. Taxonomically, Ichang papeda may be a member of subgenus Citrus. Owing to the complicated topography, the mountainous regions and the Yangtze River have provided long-term stable habitats for C. ichangensis and acted as main barriers for its expansion, which might facilitate the process of speciation. Statistical population models and genetic data indicated strong genetic structure in C. ichangensis, which might result from the restricted gene flow, genetic drift, and population bottlenecks.     

湖北西陵峡地区珍稀特有植物分析

湖北西陵峡地区位于湖北西南山地的北部,为了区城上的完整性,作者将临界的巫峡东段也考虑在内,其范围包括宜昌、兴山、秭归、巴东等县的分水岭区域。本文提出峡区存在中国真特有属36属,国家保护植物36种,其它珍贵稀有植物50种,并分析了区系特点,为西陵峡地区植物资源的合理利用和建立峡区自然保护区提供依据。     

柑桔矮化砧木的生理生化预选指标研究

以７４－１积、紫花宜昌橙、Ｒｕｓｋ枳橙、Ｔｒｏｙｅｒ枳橙、江南柑、９２号红桔和蟹橙为标准系列砧木,研究了它们的生理生化特征,从中筛选出了茎还原性糖含量、叶片还原性糖含量、叶片氨基酸含量、茎蛋白质含量、叶片过氧化物酶活性５个柑桔矮化预选指标和叶片可溶性糖含量、叶片蛋白质含量２个辅助预选指标。     

Studies on the initiation of adventitious roots on mung bean hypocotyl

During the early stages of root induction in hypocotyls of mungbean cuttings, four new peroxidase isoenzymes are formed inthat part of the cutting that produces roots. These isoenzymesare in addition to and different from the three already presentin the hypocotyl. Forty-eight hr is required for the changeto take place from the original three to seven isoenzymes. Thechange in isoenzyme pattern and root initiation itself are retardedwhen streptomycin is applied during the very early stages ofroot induction. However, during the latter part of the first24-hr period after the cutting is made and when some of thenew isoenzymes have already been formed, the rooting processbecomes insensitive to this antibiotic. Cytologically, the occurrenceof cell division is paralleled by the formation of the fournew peroxidase isoenzymes. The delay in the occurrence of celldivision caused by the presence of streptomycin is paralleledby a similar delay in the formation of the four new isoenzymes. (Received November 27, 1970; )     

And the segmentation clock keeps ticking

The vertebrate body is organized in segments, easily visible in the consecutive vertebrae of the skeleton. These are first defined in the embryo by the formation of somites. Somites are generated at regular intervals from the presomitic mesoderm by a combination of oscillating signals, known as the segmentation clock, which establish the pace at which new somites are formed, and signaling gradients that set the location of new intersomitic borders. Using a microarray approach, Dequéant et al. have now shown that the segmentation clock is more complex than previously thought and includes oscillating expression of genes from at least three signaling pathways organized in coordinated networks.     

A Screen for Nonconditional Dauer-Constitutive Mutations in Caenorhabditis Elegans

In Caenorhabditis elegans, formation of the developmentally arrested dauer larva is induced by high levels of a constitutively secreted pheromone. Synergy between two groups of incompletely penetrant dauer-constitutive (Daf-c) mutations has recently led to a proposal that these two groups of genes are partially redundant and function in two parallel pathways that regulate dauer formation. A possible weakness in this reasoning is that the mutations used to identify the synergy were specifically obtained as incompletely penetrant mutations. Here we use screens to identify new Daf-c alleles without any requirement for partial penetrance. Nevertheless, 22 of the 25 new mutations are incompletely penetrant mutations in 6 previously identified genes. Among these are mutations in daf-8 and daf-19, genes for which only one mutation had been previously identified. Also included in this group are three daf-1 alleles that do not exhibit the maternal rescue characteristic of other daf-1 alleles. Two of the 25 new mutations are fully penetrant and are alleles of daf-2, the one gene in which a fully penetrant mutation had been found earlier. Finally, one of the 25 new mutations is semidominant, temperature-sensitive, and identifies a new gene, daf-28. The results demonstrate that an incompletely penetrant Daf-c phenotype is characteristic of mutations in most Daf-c genes other than daf-2. This finding strengthens the hypothesis that a branched genetic pathway controls dauer formation.     

Determination of aldosterone in human serum by isotope dilution gas chromatography/mass spectrometry using a new heptafluorobutyryl derivative.

The formation of a new derivative of aldosterone with heptafluorobutyric anhydride for gas chromatography/mass spectrometry (GC/MS) is presented. The highest and also the most prominent ion of this derivative is observed at m/z 734. The new derivative is, under the described conditions, reproducibly formed, is stable and has good gas chromatographic properties. These characteristics make the new derivative extremely suitable for selective, sensitive, precise and accurate analysis of aldosterone in serum by GC/MS in association with isotope dilution. This is proven by the agreement between the measurement results obtained by two laboratories for samples of three batches of lyophilized control serum. The sample pretreatment procedures used in each laboratory are described.     

Palaeodiversity and formation counts: redundancy or bias?

A key question in palaeontology is whether the fossil record taken at face value is adequate to represent true patterns of diversity through time. Some methods of assessing data quality have depended on the commonly observed covariation of palaeodiversity and fossiliferous formation counts through time, based on the assumption that the count of formations containing fossils, to a greater or lesser extent, drives diversity; but what if diversity drives formations? Close study of two fossil records, early tetrapods (Devonian–Jurassic) and dinosaurs, shows how the relationship between new taxa and new fossiliferous formations varies through research time. Initially, each new find represents a new fossiliferous formation and discovery follows the ‘bonanza’ model (fossils drive formations). In unexplored parts of the world, new taxa are identified frequently in new regions/formations. Only after time, in well‐explored continents such as Europe and North America, does collecting style switch to a mix of exploration for new formations and re‐sampling of known fossiliferous formations. Data are most striking for dinosaurs, where the Triassic–Jurassic record largely comprises finds from Europe and North America, where new formation discoveries reached their half‐life in 1914. This contrasts with the Cretaceous, which is dominated by rapidly rising discoveries from regions outside Europe and North America and the formation half‐life for these ‘new’ lands is 1986, showing that 50% of new Cretaceous dinosaur‐bearing formations were identified only in the past 30 years. The relationship between dinosaur‐bearing formations and palaeodiversity then combines three signals in variable amounts, reflecting the original diversity (relative abundances of particular taxa in different formations), redundancy (new fossiliferous formations accruing because of new fossil finds) and sampling (intensity of exploration for new fossiliferous formations, and of search within already‐sampled formations). For fossil vertebrates at least, formation counts of various kinds are poor predictors of sampling, missing, for example, the bonanza samples of Lagerstätten such as the Yixian Formation in China: thousands of specimens, dozens of species, but counted as one formation. These observations suggest that formation count cannot be regarded as an unbiased metric of sampling.     

Setogenesis and molting in planktonic crustaceans

The formation of new setae, termed setogenesis, is describedfor two taxa of planktonic crustaceans: euphausiids, Euphausiapacifica and Thysanoessa spinifera, and a calanoid copepod,Calanus marshallae. Characteristics of setal formation and eversionat ecdysis are described from two time-series of animals preservedat known intervals in their molt cycle. Results from these laboratoryreference series indicate that previous interpretations of setogenesisin the literature can by synthesized to describe a dynamic processof setal formation which is common to all crustacean taxa. The morphological characteristics of developing setae are usedto designate three specific phases in the molt cycle of planktoniccrustaceans (premolt, postmolt, and intermolt). This stagingtechnique may be used to study field-oriented problems relatedto molting in small planktonic crustaceans.     

植物SABATH甲基转移酶研究进展

近年来对植物甲基转移酶（methyltransferases,MTs）的研究发现了新一类成员,并用最初发现的3个酶将其命名为SA-BATH甲基转移酶（SABATHMTs）,这3个酶分别是水杨酸羧基甲基转移酶（salicylic acid carboxyl methyltransferases,SAMT）、苯甲酸羧基甲基转移酶（benzoic acid carboxyl methyltransferases,BAMT）和可可碱合酶（theobromine synthase）。SABATHMTs能对植物激素和其他一些小分子物质进行N位或O位甲基化形成相应的甲基化产物,在植物次生代谢、发育及防御中起重要作用。本文从SABATHMTs潜在底物、进化及调控等方面综述了近年来对该家族的研究。     

环二鸟苷酸信号分子抑制剂的研究进展

环二鸟苷酸(Bis-(3′-5′)cyclic diguanylic acid,c-di-GMP)是细菌所特有的一类核酸类第二信使,参与并调节细菌多种生理功能,包括细胞分化、生物被膜的形成以及致病因子的产生等。阻断c-di-GMP信号的传导对于发展新型抗菌药物具有重要的意义。现有研究结果表明,基于c-di-GMP调控的信号通路开发新型抗菌药物具有3类潜在的靶点,分别是c-di-GMP合成酶(DGCs)、c-di-GMP降解酶(PDEs)以及c-di-GMP受体。文中根据上述3类关键靶点,介绍了相关小分子抑制剂的研究进展,并展望了c-di-GMP信号分子抑制剂的发展方向。     

Efficient nitroso group transfer from N-nitrosoindoles to nucleotides and 2'-deoxyguanosine at physiological pH. A new pathway for N-nitrosocompounds to exert genotoxicity.

The endogenous formation of N-nitrosoindoles is of concern since humans are exposed to a variety of naturally occurring and synthetic indolic compounds. As part of a study to evaluate the genotoxicity of N-nitrosoindoles, the reactions of three model compounds with purine nucleotides and 2'-deoxyguanosine at physiological pH were investigated. The profiles of reaction products were identical for each of the N-nitrosoindoles and three distinct pathways of reaction could be discerned. These pathways were: (i) depurination to the corresponding purine bases, (ii) deamination, coupled with depurination, to give hypoxanthine and xanthine, and (iii) formation of the novel nucleotide 2'-deoxyoxanosine monophosphate and its corresponding depurination product oxanine in reactions with 2'-deoxyguanosine monophosphate. 2'-Deoxyoxanosine and oxanine were observed in reactions with 2'-deoxyguanosine. Further studies showed that formation of all of these products could be rationalized by an initial transnitrosation step. These results suggest that, in contrast to many other genotoxic N-nitrosocompounds which are known to alkylate DNA, the genotoxicity of N-nitrosoindoles is likely to arise through transfer of the nitroso group to nucleophilic sites on the purine bases. All of the products resulting from transnitrosation by N-nitrosoindoles are potentially mutagenic. These findings reveal a new pathway for N-nitrosocompounds to exert genotoxicity.     

多孔钛合金不同孔径大小对新骨长入的影响

目的:评价不同孔径多孔钛合金植入物在骨缺损区对新骨长入的影响。方法:采用电子束熔融(EBM)技术制备三种不同孔径(孔径分别为1.0 mm,2.0 mm,3.0 mm)的多孔钛合金材料,其孔隙率依次为73%,79%,86%。将18只家犬随机分为1.0 mm孔径材料组,2.0 mm孔径材料组,3.0 mm孔径材料组,每组6只。制备家犬双侧股骨外侧髁缺损模型,然后植入各孔径组材料,于术后4周,8周,12周分别行大体标本观察,X线片观察,组织形态学观察三组不同孔径材料与周围骨的整合情况及孔隙中的新骨长入情况。结果:通过大体标本观察和X线片观察显示,12周后三组材料均与周围紧密骨连接。其中1.0 mm孔径组材料中心明显成骨,2.0 mm孔径组和3.0 mm孔径组中心仍为较多白色组织填充。组织学观察显示,12周时2.0 mm孔径组和3.0 mm孔径组材料周围有骨质包绕,但中心空洞,基本无骨质形成。1.0 mm孔径组材料周围骨质包绕紧密,孔中新生骨形成较多,且有大量纤维母细胞和软骨细胞形成。各时间点1.0 mm孔径组新生骨面积百分比明显高于2.0 mm孔径组和3.0 mm孔径组,P<0.01,差异具有统计学意义。2.0 mm孔径组和3.0 mm孔径组相比,P>0.05,无显著差异。结论:孔径大小影响多孔钛合金材料的骨长入,适当孔径的设计将更有利于材料的传导成骨。