Effects of Alternaria alternata f.sp. lycopersici toxins on pollen

Summary Effects of the phytotoxic compounds (AAL-toxins) isolated from cell-free culture filtrates of Alternaria alternata f.sp. lycopersici on in vitro pollen development were studied. AAL-toxins inhibited both germination and tube growth of pollen from several Lycopersicon genotypes. Pollen from susceptible genotypes, however, was more sensitive for AAL-toxins than pollen from resistant plants, while pollen of species not belonging to the host range of the fungus was not significantly affected by the tested toxin concentrations. AAL-toxins elicit symptoms in detached leaf bioassays indistinguishable from those observed on leaves of fungal infected tomato plants, and toxins play a major role in the pathogenesis. Apparently, pathogenesis-related processes and mechanisms involved in disease resistance are expressed in both vegetative and generative tissues. This overlap in gene expression between the sporophytic and gametophytic level of a plant may be advantageously utilized in plant breeding programmes. Pollen may be used to distinguish susceptible and resistant plants and to select for resistances and tolerances against phytotoxins and other selective agents.     

三个与agropine合成相关的基因在大肠杆菌微细胞中的表达

pTiAch 5 TR区与在植物中积累agropine相关的三个基因片段已导入pINIIA或pACYC184,在大肠杆菌微细胞中表达出杂合蛋白。三个基因片段的pINIIA重组质粒的表达得到稳定蛋白、不稳定蛋白和在两个相表达出相似蛋白的三种结果。基因2'HindⅢ片段上的UGAA序列是在两个相表达相似蛋白的原因。从产生的杂合蛋白分子量和读码方式看,pTiAch 5中基因2'和基因1'的结构与pTi 15955近似,但由基因0'片段产生的杂合蛋白分子量比根据pTi15955 DNA序列数据推测的稍大。从表达强度和微细胞操作看,这个系统还不适应从大肠杆菌中方便地纯化杂合蛋白的需要。     

Relationship of cellular oncogene expression to inhibition of growth and induction of differentiation of Daudi cells by interferons or TPA

Human alpha or beta interferons inhibit the proliferation of Daudi Burkitt lymphoma cells and induce the differentiation of these cells towards a mature plasma cell phenotype. Similar responses are seen when Daudi cells are treated with the phorbol ester, TPA. Both interferons and TPA down-regulate expression of the c-myc oncogene in these cells. Although TPA can mimic the effect of interferon on cell differentiation, it does not induce 2'5' oligoadenylate synthetase or the interferon-sensitive mRNAs, 6-16 or 9-27. Thus chronic stimulation of protein kinase C by TPA cannot mimic all of the effects of interferon treatment on gene expression. Inhibition of ADP-ribosyl transferase activity by 3-methoxybenzamide impairs interferon- or TPA-induced differentiation of Daudi cells. This agent induces a higher level of c-myc mRNA in the cells and stimulates the incorporation of [3H]thymidine into DNA; although these effects are partially counteracted by interferon or TPA treatment, the elevated expression of the c-myc gene may be sufficient to prevent terminal differentiation and allow cell proliferation to continue.     

Molecular cloning,nucleotide sequence and expression of a cDNA encoding an intracellular protein tyrosine phosphatase,PTPase-2, from mouse testis and T-cells

The PTP-2 cDNA encoding an intracellular protein tyrosine phosphatase (PTPase-2) was isolated and sequenced from mouse testis and T-cell cDNA libraries. This PTP-2 cDNA was found to be homologous to human PTP-TC and rat PTP-S, and contained 1,551 nucleotides, including 1,146 nucleotides encoding 382 amino acids as well as 5 (61 nucleotides) and 3 (344 nucleotides) non-coding regions. Northern blot analysis indicated that PTP-2 mRNA of 1.9 Kb was most abundant in testis and kidney, although it was also present in spleen, muscle, liver, heart and brain.Abbreviations PTPase Protein Tyrosine Phosphatase (EC3.1.3.48) - PTKase Protein Tyrosine Kinase (EC2.7.1.112)     

Synthesis of the biologically active β-subunit of human nerve growth factor in Escherichia coli

The gene(NGFB) encoding the β subunit of mature human nerve growth factor (hNGFB) was subcloned into the pJLA503 expression vector under the control of bacteriophage promoters p_R and p_L, and expressed in Escherichia coli. The recombinant protein represented approximately 3% of the total cellular protein. Biologically active hNGFB was solubilized (0.2% total NGFB) and purified by cation-exchange chromatography and it yielded two bands on polyacrylamide-gel electrophoresis under nonreducing conditions, corresponding to the monomeric (14 kDa) and homodimeric (26.5 kDa) forms of the molecule. Both hNGFB forms were immunopositive on Western blots with rabbit anti-NGFB antibodies; however, following additional purification, only the species corresponding to the hNGFB homodimer was biologically active on cultured chicken dorsal root ganglion neurons. These results demonstrate the feasibility of synthesizing the biologically active form of hNGFB in E. coli.