己酸菌LⅡ己酸发酵过程中生理及代谢特点

在了解了产己酸细菌ＬＩＩ的发酵最适条件的基础上,进一步对己酸发酵过程中的生理及代谢特性作了较详细的分析。结果表明,在己酸发酵过程中除产生正常代谢产物己酸外,还产生丁酸、乙酸、戊酸等其它酸类和甲烷,氢气和ＣＯ_２等气体。用１—^１３Ｃ－乙酸钠和未标记的乙醇作为底物发酵,用色质联用仪（ＧＣ／ＭＳ）分析,结果表明：在己酸合成中碳的来源为乙醇和乙酸,中间代谢产物为丁酸。     

菜用大豆产量相关性状的遗传分析

对 19个菜用大豆品种与产量有关的10个农艺性状进行遗传分析的结果表明,生育期和主茎节数遗传力偏高;单株荚数、分枝数遗传力偏低;单株产量、单株荚数的遗传变异系数很大,其遗传进度的值也较大;生育期的遗传变异系数小, 遗传进度也小,遗传相关分析结果表明,产量与生育期、单株结荚数相关关系密切。菜用大豆遗传参数分析结果与前人对食用大豆的研究结果趋势一致。     

Charactererization of novel non-toxic Bacillus thuringiensis isoloates from Korea

J.Y. ROH, H.W. PARK, B.R. JIN, H.S. KIM, Y.M. YU AND S.K. KANG. 1996. Four Bacillus thuringiensis isolates from soil samples produced parasporal inclusions which were non-toxic to insects. The isolates were named B. thuringiensis NTB-1, NTB-2, NTB-3 and NTB-4. The parasporal inclusions were shown to be ovoid by phase contrast and scanning electron microscopy. The serotypes of the four isolates were determined by agglutination using 33 antisera; NTB-1 and NTB-4 seemed to be subsp. isruelensis ,and NTB-2 seemed to be subsp. pondzcheriensis . NTB-3 did not react with the 33 antisera. However, comparison of parasporal protein and plasmid DNA patterns of the four isolates with those of 15 known non-toxic B. thuringiensis strains demonstrated that the four isolates are novel.     

Ras induces anchorage-independent growth by subverting multiple adhesion-regulated cell cycle events.

Anchorage-independent growth is a hallmark of transformed cells, but little is known of the molecular mechanisms that underlie this phenomenon. We describe here studies of cell cycle control of anchorage-independent growth induced by the ras oncogene, with the use of a somatic cell mutant fibroblast line (ER-1-2) that is specifically defective in oncogene-mediated, anchorage-independent growth. Control, nontransformed PKC3-F4 cells and ER-1-2 cells cannot proliferate in semisolid medium. Three important cell cycle events are dependent on adhesion of these cells to a substratum: phosphorylation of the retinoblastoma protein, pRB; cyclin E-dependent kinase activity; and cyclin A expression. PKC3-F4 cells that express ras (PKC3-F4/ras cells) proliferate in nonadherent cultures, and each of these three events occurs in the absence of adhesion in PKC3-F4/ras cells. Thus, ras can override the adhesion requirement of cellular functions that are necessary for cell cycle progression. ER-1-2 cells that express ras (ER-1-2/ras cells) possess hyperphosphorylated forms of pRB and cyclin E-dependent kinase activity in the absence of adhesion but remain adhesion dependent for expression of cyclin A. The adhesion dependence of pRB phosphorylation and cyclin E-dependent kinase activity is therefore dissociable from the adhesion dependence of cyclin A expression. Furthermore, ectopic expression of cyclin A is sufficient to rescue anchorage-independent growth of ER-1-2/ras cells but does not induce anchorage-independent growth of PKC3-F4 or ER-1-2 cells. However, like pRB phosphorylation and cyclin E-dependent kinase activity, the kinase activity associated with ectopically expressed cyclin A is dependent on cell adhesion, and this dependence is overcome by ras. Thus, the induction of anchorage-independent growth by ras may involve multiple signals that lead to both expression of cyclin A and activation of G1 cyclin-dependent kinase activities in the absence of cell adhesion.     

Metabolism of glucose-6-phosphate and utilization of multiple metabolites for fatty acid synthesis by plastids from developing oilseed rape embryos

The aim of this work was to investigate the partitioning of imported glucose 6-phosphate (Glc6P) to starch and fatty acids, and to CO₂ via the oxidative pentose phosphate pathway (OPPP) in plastids isolated from developing embryos of oilseed rape (Brassica napus L.). The ability of the isolated plastids to utilize concurrently supplied substrates and the effects of these substrate combinations on the Glc6P partitioning were also assessed. The relative fluxes of carbon from Glc6P to starch, fatty acids, and to CO₂ via the OPPP were close to 2∶1∶1 when Glc6P was supplied alone. Under these conditions NADPH generated via the OPPP was greater than that required by the concurrent rate of fatty acid synthesis. Fatty acid synthesis was unaffected by the presence or absence of exogenous NADH and/or NADPH and the requirement of fatty acid synthesis for reducing power is therefore met entirely by intraplastidial metabolism. When Glc6P was supplied in the presence of either pyruvate or pyruvate and acetate, the total flux from these metabolites to fatty acids was up to threefold greater than that from either Glc6P or pyruvate when they were supplied singly. In these experiments there was little competition between Glc6P and pyruvate in fatty acid synthesis and the flux to starch was unchanged. This implies that the starch and fatty acid biosynthesis pathways did not compete for the exogenously supplied ATP on which they were strongly dependent. When Glc6P and pyruvate were provided together, the NADPH generated by the OPPP pathway was less than that required by the concurrent rate of fatty acid synthesis. This suggests that the metabolism of exogenous Glc6P via the OPPP can contribute to the NADPH demand created during fatty acid synthesis but it also indicates that other intraplastidial sources of reducing power must be available under the in-vitro conditions used.     

RFLP mapping of QTLs for yield and related characters in rice (Oryza sativa L.)

Quantitative triat loci (QTLs) for yield and related traits in rice were mapped based on RFLP maps from two indica/indica F₂ populations, Tesanai 2/CB and Waiyin 2/CB. In Tesanai 2/CB, 14 intervals carrying QTLs for eight traits were detected, including 3 for grain weight per plant (GWT), 2 for number of panicles per plant (NP), 2 for number of grains per panicle (NG), 1 for total number of spikelets per panicle (TNS), 1 for spikelet fertility (SF), 3 for 1000-grain weight (TGWT), 1 for spikelet density (SD), and 1 for number of first branches per main panicle. The 3 QTLs for GWT were located on chromosomes 1, 2, and 4, with 1 in each chromosome. The additive effect of the single locus ranged from 2.0 g to 9.1 g. A major gene (np4) for NP was detected on chromosome 4 within the interval of RG143–RG214, about 4cM for RG143, and this locus explained 26.1% of the observed phenotypic variance for NP. The paternal allele of this locus was responsible for reduced panicles per plant (3 panicles per plant). In another population, Waiyin 2/CB, 12 intervals containing QTLs for six of the above-mentioned traits were detected, including 3 for GWT, 2 for each of NP, TNS, TGWT and SD, 1 for SF. Three QTLs for GWT were located on chromosome 1, 4, and 5, respectively. The additive effect of the single locus for GWT ranged from 6.7 g to 8.8 g, while the dominance effect was 1.7–11.5 g. QTL mapping in two populations with a common male parent is compared and discussed.     

Inhibition of gap junctional intercellular communication in heptachlor- and heptachlor epoxide-treated normal human breast epithelial cells

Based on the concern of organochlorides in the environment and in human tissue, this study was designed to determine whether various noncytotoxic levels of heptachlor and heptachlor epoxide could inhibit, reversibly, gap junctional intercellular communication in human breast epithelial cells (HBEC). Cytotoxicity and gap junctional intercellular communication (GJIC) were evaluated by lactate dehydrogenase assay and fluorescence redistribution after photobleaching analysis, respectively. Both heptachlor and heptachlor epoxide were noncytotoxic up to 10 μg/ml. At this concentration, heptachlor and heptachlor epoxide inhibited GJIC of normal human breast epithelial cells after 1 h treatment. Within a 24 h treatment with heptachlor and heptachlor epoxide at 10 μg/ml, recovery of GJIC had not returned. GJIC completely recovered after a 12 h treatment of 1 μg/ml heptachlor epoxide, but it did not recover after a 24 h treatment of 1 μg/ml heptachlor. RT-PCR and Western blots were analyzed to determine whether the heptachlor or heptachlor epoxide might have altered the steady-state levels of gap junction mRNA and/or connexin protein levels or phosphorylation state. No significant difference in the level of connexin 43 (Cx43) message between control and heptachlor-treated cells was observed. Western blot analyses showed hypophosphorylation patterns in cells treated with 10 μg/ml heptachlor and heptachlor epoxide for 1 h with no recovery within 24 h. Immunostaining of Cx43 protein in normal HBEC indicated that heptachlor and heptachlor epoxide caused a loss of Cx43 from the cell membranes at noncytotoxic dose levels. Taken together, these results suggest that heptachlor and heptachlor epoxide can alter GJIC at the post-translational level, and that, under the conditions of exceeding a threshold concentration in the breast tissue containing ‘initiated’ cells for a long time and not being counteracted by anti-tumor-promoting chemicals, they could act as breast tumor promoters.     

Genetic and clonal diversity in Korean populations ofVitex rotundifolia (Verbenaceae)

Vitex rotundifolia L.f. is a woody perennial and has sexual and asexual modes of reproduction. Allozyme study was conducted on 550 plants in 13 Korean populations. The levels of genetic variability and divergence within and among populations, respectively, are considerably lower and higher than the mean values for woody plants with similar life history tralts. Mean percentage of polymorphic loci (P _P), mean number of alleles per locus (A _P), and mean genetic diversity (He _P) within populations ofV. rotundifolia were: 16.7%, 1.21, and 0.047. On average, about 79% of the total variation inV. rotundifolia was common to all populations (meanG _ST=0.208). In addition, significant differences in allele frequencies among populations were found in all polymorphic loci examined (P<0.001). On the other hand, levels of genotypic diversity within and among populations were moderate. About 44% (18/41) of multilocus genotypes were “local genotypes” (genotypes occurring in only one population), whereas only one “widespread genotype” (genotypes occurring in more than 75% of the populations) were detected. The mean number of multilocus genotypes per population (G) and mean genotypic diversity index (D _G) were 8.4 and 0.74, respectively. Most common multilocus genotypes found in populations were homozygous for five polymorphic loci. The abundance of ramets of these genets is responsible for the low levels of expected heterozygosity within populations. The results indicate that clonal reproduction may act as an enhancer of genetic drift by reducing effective size of local populations ofV. rotundifolia.