日本大萝卜引种栽培研究

本文报道日本大萝卜引种栽培的试验结果,并为推广这一蔬菜新品种提供了有效的栽培技术措施。     

Immunolocalization of the G protein alpha subunit encoded by the GPA1 gene in Arabidopsis.

Heterotrimeric GTP binding proteins (G proteins) are important signal transducers in lower eukaryotes and in animal cells. In plants, the occurrence of GTP binding proteins has been reported, but their biological function remains unclear. Two genes coding for G protein alpha subunits have been cloned: GPA1 in Arabidopsis and TGA1 in tomato. To gain some insights into the function of GPA1, we describe an extensive immunolocalization of GPalpha1, the gene product of GPA1, during Arabidopsis development. Our results show that the GPalpha1 is present through all stages of development and in all organs examined, with the exception of mature seeds. It is expressed in roots, floral stem, rosette leaves, cauline leaves, flowers, and seed pods. Interestingly, the level of GPalpha1 protein is higher in immature organs than in mature organs. GPalpha1 is present at a high level in the root meristem and elongation zone, in the shoot and floral meristems, and in the leaf primordium and floral organ (sepal, petal, stamen, and gynoecium) primordia. During flower development, dividing microspores, but not mature pollen, show high levels of GPalpha1. During pollination, GPalpha1 is present in the growing pollen tubes. The protein is also present in nectaries and developing ovules and, after fertilization, in developing embryos. In mature tissue, GPalpha1 is preferentially found in the vascular system but is also present in other cell types. The complexity of the GPalpha1 localization pattern suggests that GPalpha1 might be involved in different signaling pathways depending on the developmental stage.     

Effects of hypothalamic microinjection of PGE2 on body temperature and sympathetic nervous activities in the rabbit

The febrile response and sympathetic nervous response to hypothalamic microinjections of prostaglandin E₂ (PGE₂) were investigated in anesthetized rabbits. Microninjection of PGE₂ (500–1000 ng) caused an increase in rectal temperature of more than 0.3°C in 13 of 50 loci in the preoptic and anterior hypothalamic area (PO/AH). At 8 of these 13 loci, PGE₂ elicited response patterns in the sympathetic nervous system, such as an increase in cutaneous sympathetic nervous activity and decrease in renal sympathetic nervous activity. This pattern of sympathetic nervous responses was induced with a simultaneous increase in rectal temperature of more than 0.5°C. The 8 loci were distributed in the preoptic area, especially in the vicinity of the supraoptic nucleus. Electrolytic lesions of this region were made bilaterally, and intracerebroventricular injection of PGE₂ (8 µg/kg) was found to inhibit fever and sympathetic activity. The results demonstrate that the action of PGE₂ is responsible for the response patterns of sympathetic twigs during fever. The preoptic area, especially in the vicinity of the supraoptic nucleus, is most sensitive to PGE₂ for the patternized response of sympathetic neurons and fever.     

Plasmid retention and gene expression in suspended and biofilm cultures of recombinant Escherichia coli DH5alpha(pMJR1750)

Differences in plasmid retention and expression are studied in both suspended and biofilm cultures of Escherichia coli DH5alpha(PMJR1750). An alternative mathematical model is proposed which allows the determination of plasmid loss probability in both suspended batch and continuously fed biofilm cultures. In our experiments, the average probability of plasmid loss of E. coli DH5alpha(pMJR1750) is 0.0022 in batch culture in the absence of antibiotic selection pressure and inducer. Under the induction of 0.17 MM IPTG, the maximum growth rate of plasmid-bearing cells in suspended batch culture dropped from 0.45 h(-1) to 0.35 h(-1) and the beta-galactosidase concentration reached an experimental maximum of 0.32. pg/cell 4 hours after the initiation of induction. At both 0.34 and 0.51 mM IPTG, growth rates in batch cultures decreased to 0.16 h(-1), about 36% of that without IPTG, and the beta-galactosidase concentration reached an experimental maximum of 0.47 pg/cell 3 hours after induction.In biofilm cultures, both plasmid-bearing and plasmid-free cells in increase with time reaching a plateau after 96 hours n the absence of both the inducer and any antibiotic selection pressure. Average probability of plasmid loss for biofilm-bound E. coli DH5beta(pMJR1750) population was 0.017 without antibiotic selection. Once the inducer IPTG was added, the concentration of plasmid-bearing cells in biofilm dropped dramatically while plasmid-free cell numbers maintained unaffected. The beta-galactosidase concentration reached a maximum in all biofilm experiments 24 hours after induction; they were 0.08, 0.1, and 0.12 pg/cel under 0.17, 0.34, and 0.51 mM IPTG, respectively. (c) 1993 John Wiley & Sons, Inc.     

Mutagenesis analysis of a hepatitis delta virus genomic ribozyme.

We conducted extensive mutagenesis analysis on a hepatitis delta virus (HDV) genomic ribozyme to study the sequence specificity of certain region and to derive the secondary structure associated with the catalytic core. The results confirmed that the autocatalytic domain of HDV genomic RNA contained four base-pairing regions as predicted in the 'pseudo-knot' model [Perrotta & Been (1990) Nature 350, 434-436]. The size and sequence of one of the base-pairing regions, i. e. stem-and-loop, could be flexible. Helix 3 and the first basepair of helix 1 required specific sequence to retain self-cleavage activity. The structural requirement of helix 2 was less stringent than the other base-pairing regions. Moreover, the size of helix 1 affected self-cleavage whereas the length of hinge could be variable even though the first three residues of hinge had stringent sequence requirement.     

Foliar Application of Fungal Biocontrol Agents for the Control of White Mold of Dry Bean Caused by Sclerotinia sclerotiorum

Field experiments were conducted during 1992–1994 to evaluate the effectiveness of five indigenous fungi for control of white mold (Sclerotinia sclerotiorum) of dry bean (Phaseolus vulgaris). The five fungi consisted of one antagonist, Epicoccum purpurascens, and four mycoparasites, Coniothyrium minitans, Talaromyces flavus, Trichothecium roseum, and Trichoderma virens. Spore suspensions of each fungus were sprayed onto bean plants two or three times during the early bloom to midbloom period. Incidence of white mold of dry bean was significantly reduced by all biocontrol agents. C. minitans and E. purpurascens, the most effective agents, reduced the proportion of plants infected by an average of 56 and 43%, respectively (P < 0.001). C. minitans was the only biocontrol agent recovered consistently from sclerotia and diseased seed present in harvested samples. It was recovered at similar frequencies in samples from all treatments. Of the sclerotia of S. sclerotiorum collected from harvested seed, 59% were infected by C. minitans in 1993 and 20% were infected by C. minitans in 1994. In three additional trials in 1994, comparing C. minitans with the fungicide benomyl, the fungus was not effective in any of the experiments, whereas benomyl reduced disease incidence relative to the control in one trial. The study suggests that, among the five indigenous fungi, C. minitans is the most promising agent for control of white mold of dry bean under Canadian prairie conditions.     

Effects of Boron Deficiency on Anther Development and Floret Fertility in Wheat (Triticum aestivum L. 'Wilgoyne')

Boron (B) deficiency limits reproductive growth more than vegetativegrowth in cereals such as wheat. The purpose of the presentstudy was to identify the critical stages of anther developmentof wheat (‘Wilgoyne’) during which B deficiencycauses a significant and irreversible decrease of floret fertilityin order to formulate timely measures for correcting or preventingthis problem. Withdrawing B from the rooting medium for 3 dbetween premeiotic interphase through meiosis to late tetrad,limited anther elongation and resulted in the loss of pollenviability. The negative effects of B withdrawal on anther lengthsuggest that the role of B in reproductive cell walls is similarto that in vegetative ones. The results indicated that as moreflorets reached meiosis within the period of B withdrawal, thelower was floret fertility and the number of grains set in awhole ear. For the whole ear, the critical period during whichB deficiency causes maximal and irreversible damage to floretfertility was about 7 d, extending from the early emergenceof the flag leaf to 2–3 d after its full emergence. Theresults suggest that there are two phases of pollen developmentsensitive to boron deficiency: the period from premeiotic interphasethrough meiosis to late tetrad was the most sensitive stageof microsporogenesis in wheat while the period from mitosis-Ito II during which starch accumulation occurred in pollen grainswas less sensitive. Copyright 2000 Annals of Botany Company Anther, boron (B) deficiency, floret fertility, Grain Set Index (GSI), pollen, wheat (‘Wilgoyne’)     

Water ingestion provides an early signal inhibiting osmotically stimulated vasopressin secretion in rats

Dehydrated dogs are known to inhibit secretion of vasopressin (VP) within minutes after drinking water, before plasma osmolality (P(osmol)) diminishes. The present studies determined whether water ingestion causes a similar rapid inhibition of neurohypophyseal hormone secretion in rats. Adult rats were infused with 1 M NaCl (2 ml/h iv) for 240 min to stimulate VP and oxytocin (OT) secretion. After 220 min of infusion, rats were given water to drink for 5 min, and blood samples were taken 5 and 15 min later for RIA. Plasma VP (pVP) was much lower when rats ingested water than when they drank nothing even though P(osmol) was not significantly altered. Plasma OT (pOT) was affected similarly. In contrast, no effects on pVP or pOT occurred when rats drank isotonic NaCl solution for 5 min in amounts comparable to the water intakes (approximately 5.5 ml). These results suggest that neurohypophyseal secretion of VP and OT in rats is inhibited rapidly by water drinking, and that this inhibition is mediated by a visceral signal of osmotic dilution rather than by the act of drinking per se.     

柔嫩艾美耳球虫第二代裂殖子表面抗原基因（λMZ5—7）在大肠杆菌中的表达

将重组克隆质粒（PGEM－λMZ）用EooRⅠ酶切后,电泳回收目的的片段,克隆到经EooRⅠ酶切、CIAP处理的表达载体pET－28a中,转化大肠杆菌JM109感受态细胞,得到的转子化经PCR鉴定和酶切分析,筛选出符合正确阅读框的重组子,构建成重组表达质粒（PET－λMZ）,并在大肠杆菌BL21（DE3）表达菌中成功地表达了含目的蛋白的融合蛋白,融合蛋白的分子量的34KDa,加入IPIG诱导6h后,蛋白表达接近最高 水平。表达产物经Ni-NTA亲和层析柱纯化,SDS－PAGE检测为要带。经Western-blotting杂交实验,纯化出的目的蛋白能与兔抗E．tenella第二代裂殖子抗血清发生反应,说明MZP蛋白是E．tenella第二代裂殖子抗原蛋白,具有一定的免疫原性,为进一步研究重组疫苗创造了一定的条件。