长白山某些树种叶子的分解动态研究

 在长白山针阔叶混交林下,红松、蒙古栎、春榆、白桦、山杨、色木及紫椴叶分解至300天时,其重量损失百分数分别为24.2,37.6,30.8,44.47,50.6及55.6。在分解过程中,每种叶子的重量损失同该叶子的木质素、水溶性物质、全碳及全氮的变化成线性相关(R=0.99**)。在叶子分解前期,木质素、N素的绝对量有所增加,而水溶性物质则急剧减少。除紫椴叶外,其它几种叶子在分解过程中氮的含量有一定增加。但是,当红松、蒙古栎、春榆、白桦、山杨及色木叶中N素浓度分别为0.96%,1.41%,2.38%,1.67%,1.32%及1.32%时,则开始了N素的矿化释放。     

羊草种群年龄结构及无性繁殖对策的分析

天然割草场羊草 ( Aneurolepidium chinense( Trin.) Kitag.)种群的生殖枝中有 87%为冬性植株。羊草分蘖节最老为 4龄 ,其生活时间可达 5个年度。在分蘖节成株的年龄结构中 ,1、2龄株占绝对优势 ,其所占比重达 92 .5 %。 1龄株生产力最高 ,至 3龄株生活力已明显衰弱。割草场羊草种群为增长型与稳定型混合的年龄结构类型。综合分析了羊草以根茎顶端成株调节种群年龄结构的无性繁殖对策 ,以及羊草草地自然持续更新的生物生态学机制     

A new set of chemotaxis homologues is essential for Myxococcus xanthus social motility

Myxococcus xanthus cells aggregate and develop into multicellular fruiting bodies in response to starvation. A new M. xanthus locus, designated dif for defective in fruiting, was identified by the characterization of a mutant defective in fruiting body formation. Molecular cloning, DNA sequencing and sequence analysis indicate that the dif locus encodes a new set of chemotaxis homologues of the bacterial chemotaxis proteins MCPs (methyl-accepting chemotaxis proteins), CheW, CheY and CheA. The dif genes are distinct genetically and functionally from the previously identified M. xanthus frz chemotaxis genes, suggesting that multiple chemotaxis-like systems are required for the developmental process of M. xanthus fruiting body formation. Genetic analysis and phenotypical characterization indicate that the M. xanthus dif locus is required for social (S) motility. This is the first report of a M. xanthus chemotaxis-like signal transduction pathway that could regulate or co-ordinate the movement of M. xanthus cells to bring about S motility.     

中国木薯栽培种通过器官发生再生植株研究

本文研究了中国木薯栽培种四种外植体通过器官发生再生植株的条件。结果表明:在MS附加0.05mg/L TIBA,1mg/L BA的培养基上“NZ 188”初步的萌发胚状体“切头”后切口处可直接产生丛芽,出芽率为43%。“SC201”胚状体子叶块在MS附加0.5 mg/L NAA,0.5mg/L BA的培养基上可直接出芽,出芽率为42%,在MS附加0.5mg/L IBA,1.5mg/L BA培养基上·出芽率为31%,AgNO_3和ABA单独使用或配合使用均不利于芽的再生。“NZ188”胚状体下胚轴在MS附加0.5mg/LNAA,0.5mg/L BA的培养基上形成的愈伤组织转入MS附加1mg/L NAA,2mg/L BA的培养基上,3周后大多数愈伤组织有绿点出现、仅4.4%外植体分化出芽。“HZ188”无菌苗茎段接种在MS附加0.05mg/L TIBA,2mg/LBA的固体培养基上,2周后形成大量愈伤组织,4周后仅见一块愈伤组织分化出芽。     

Retina-specific expression from the IRBP promoter in transgenic mice is conferred by 212 bp of the 5'-flanking region

IRBP is a photoreceptor-specific glycoprotein that has been suggested as a retinoid carrier in the visual process. Previous research has shown that 1.3 kb of 5'-flanking sequence from the human IRBP gene is sufficient to promote photoreceptor-specific expression of reporter genes in transgenic mice. To define more narrowly the sequences that promote tissue-specific expression, chimeric constructs with shorter promoters were used to generate transgenic mice. The bacterial CAT gene was fused to fragments of 706 bp or 212 bp from the 5' end of the human IRBP gene. Analysis of the three transgenic families bearing the 706 bp IRBP promoter revealed that CAT expression was confined to the neuro-retina and the pineal gland. Analysis of the four transgenic families bearing the 212 bp IRBP promoter revealed the same tissue-specific CAT expression in three families. These results establish that tissue-specific expression of IRBP can be regulated by a short 212 bp promoter which has been conserved between humans and mice.     

多个数量性状的拓广遗传参数

运用多元分析方法定义了拓广表型方差(?)(generalized phenotypic variance),拓广遗传方差(?)(generalized genetic variance),拓广遗传力(?)(generalized heritability)和拓广遗传相关系数(?)(generalized genetic correlation coefficient): 这些参数可用来对多个数量性状总体的变异、协变异及不同组向量之间的相关性进行轮廓分析(profile analysis)。用棉花和紫花苜蓿的两个实例说明了这些参数的估算和应用。     

PATHOGENICITY OF METARHIZIUM ANISOPLIAE VAR. ACRIDU TO THE DEVEOLPMENTAL STAGES OF BROWN PLANTHOPPER NILAPARVATA LUGENS STÅL AND SOGATELLA FURCIFERA (HORVATH)

Abstract  The susceptibility and virulence of entomopathogenic fungus Metarhizium anisopliae var. acridum to the stages of brown planthopper (BPH), Nilaparvata lugens (Stål) and whitebacked planthopper (WBPH), Sogatella furcifera (Horvath) were investigated under laboratory conditions. Three dosages of M. anisopliae var. acridum ranging from 10.5, 116.3 and 1027.1 conidial/mm² were used in the experiment. The tested stages of host included three developmental stages, young nymphs (1–2 instars), old nymphs (3–5 instars) and adults. It was found that all tested stages of the planthoppers were susceptible to the fungal infection. The degree of virulence LT₅₀ of M. anisopliae var. acridum against young nymphs of N. lugens are >21, 20.82 and 16.55, respectively with the 3 dosages, the LT₅₀ of the fungus against the old nymphs are 17.68, 15.49 and 13.98, respectively with the 3 dosages; the LT₅₀ of the fungus against the adults are 17.10, 12.57 and 9.14 respectively with the 3 dosages. The degree of virulence LT₅₀ of M. anisopliae var. acridum on young nymphs of S. furcifera are >21, 17.29 and 13.13, respectively with the 3 dosages _; the LT₅₀ of the fungus against the old nymphs are 16.94, 15.02 and 13.03, respectively with the 3 dosages; the LT₅₀ of the fungus against the adults are 12.78, 10.16 and 7.64, respectively with the 3 dosages. Adults were more susceptible to M. anisopliae var. acridum infection than their nymphs and the young nymphs were most resistant to the fungal infection. The cumulative mortality of each stage was dosage-dependent. Of all the developmental stages, WBPH was more susceptible than BPH to M. anisopliae var. acridum infection with the same dosages.     

A DnaK Homolog in Myxococcus xanthus Is Involved in Social Motility and Fruiting Body Formation

Myxococcus xanthus is a gram-negative soil bacterium which exhibits a complex life cycle and social behavior. In this study, two developmental mutants of M. xanthus were isolated through Tn5 transposon mutagenesis. The mutants were found to be defective in cellular aggregation as well as in sporulation. Further phenotypic characterization indicated that the mutants were defective in social motility but normal in directed cell movements. Both mutations were cloned by a transposon-tagging method. Sequence analysis indicated that both insertions occurred in the same gene, which encodes a homolog of DnaK. Unlike the dnaK genes in other bacteria, this M. xanthus homolog appears not to be regulated by temperature or heat shock and is constitutively expressed during vegetative growth and under starvation. The defects of the mutants indicate that this DnaK homolog is important for the social motility and development of M. xanthus.     

Identification and characterization of a human herpesvirus 6 gene segment that trans activates the human immunodeficiency virus type 1 promoter.

Human herpesvirus 6 (HHV-6) is a lymphotropic herpesvirus, and in vitro, HHV-6 can productively infect many of the same cell types as can human immunodeficiency virus (HIV). Coinfection by both viruses in vitro can lead to both activation of the HIV promoter and acceleration of cytopathic effects. We have previously demonstrated that a large, 22.25-kb cloned HHV-6 fragment, pZVB70, can trans activate HIV promoter expression in vitro. In this study, we show that the pZVB70 fragment can trans activate the HIV promoter in human T-cell lines as well as in the monkey kidney cell line CV-1. The pZVB70 insert was digested with various restriction enzymes, and individual fragments were transfected into cells to test for their ability to trans activate the HIV promoter. By this method, we have identified a 1.8-kb subfragment, B701, that is involved in trans activation. Sequence analyses show that B701 potentially encodes a 143-amino-acid protein. This protein shares no homology with other herpesvirus proteins, such as ICP0 and ICP4, that have been shown to trans activate the HIV promoter. However, it shows weak sequence homology with the gene products encoded by the cytomegalovirus early US22 gene family, suggesting that the putative B701 protein may be an HHV-6 early regulatory protein. The 143-amino-acid coding sequence of B701 was cloned by polymerase chain reaction, and transfection of this construct into cells activated HIV promoter expression. The target site on the HIV promoter for the putative B701 protein is mapped to the NF-kappa B binding site. Our results suggest that the putative B701 protein may function by directly binding to the NF-kappa B site or may involve cellular factors, such as NF-kappa B, either directly or indirectly.     

Pathways of energy flow through the light-harvesting antenna of the photosynthetic purple bacterium rhodobacter sphaeroides

Using low intensity picosecond absorption spectroscopy with independently tunable excitation and probing infrared pulses, we have studied the pathways of energy transport through the light-harvesting antenna pigments of the photosynthetic purple bacterium Rhodobacter sphaeroides. From the observed excited-state rise time of the red-most pigment B896 as a function of excitation wavelength it is concluded that the B850 pigment of LH2 is spectrally heterogeneous. For excitations originating in the B850 pigment this results in a fast channel (9 ps) that is mainly excited in the peak of the B850 absorption band, and a slow channel (35 ps) that is predominantly excited at ~840 nm. Upon excitation of B800, more than 90% of the excitations follow the fast path. From the observed kinetics it is concluded that the majority of the LH2 → LH1 energy transfer takes place within at most a few picoseconds. The rate-limiting step in the whole energy transfer sequence appears to be the B896 → reaction center transfer. The origin of the B850 heterogeneity and the slow 35-ps component is at the moment unclear. Possibly it represents a highly extended form of LH2 in which transfer to LH1 takes a relatively long time, due to a large number of transfer steps.