Changes in biosynthesis of exopolysaccharide in Lactococcus lactis subspecies cremoris treated by moderate pulsed electric field treatment

Metabolome analysis and physicochemical analyses were executed with cell extracts of a Lactococcus lactis subspecies cremoris strain treated by moderate pulsed electric field (PEF) to elucidate the mechanism of enhanced production of exopolysaccharide (EPS) by the treatment. Metabolome analysis by capillary electrophoresis time of flight mass spectrometry annotated 224 metabolites from the cytoplasmic extract of the strain, which, however, showed no significant changes in metabolites related to the EPS production. Electron microscopic observation and chemical analysis of undecaprenoids as carrier of EPS biosynthetic intermediates suggested that PEF treatment dissociated immature EPSs from the intermediates due to the focal electro-condensation of hydrogen ions at the cell surface. Thus, liberated undecaprenyl phosphates were recycled efficiently, which resulted in mass increase of EPS with smaller molecular weight. The study suggested the feasibility of moderate PEF treatment as a food processing technique and revealed the mechanism of enhanced production of EPS by the treatment.     

粳稻龙锦1号/香软米1578杂交组合F_5家系群糙米总花色苷含量变异及相关性分析

随着环境污染加剧和人们对自身健康关注度的提高,功能性食品在全球范围内蓬勃发展。彩色稻米作为稻米家族中的一员,由于富含微量元素、花色苷、生物碱等功能性成分,已成为当前功能性食品研究开发的热点之一。本研究利用粳稻品种龙锦1号/香软米1578杂交组合214个F_5家系,对水稻糙米总花色苷含量、粒色等级和千粒重的变异及其相关性进行了分析。糙米粒色等级变异范围为1~9,平均值为4.98,变异系数为57.87%;糙米总花色苷含量变异范围为0~5459.34 mg/kg,平均值为834.47 mg/kg,变异系数为191.96%;糙米千粒重变异范围为11.96~26.24 g,平均值为17.75 g,变异系数为12.89%。糙米总花色苷含量、粒色等级和千粒重在F5家系中不符合正态分布,表现为右偏态,其中糙米总花色苷含量的偏斜程度最大。糙米总花色苷含量和千粒重的峰度系数为正值,表明为尖顶峰;而糙米粒色等级的峰度系数为负值,表明为平顶峰。糙米总花色苷含量与粒色等级呈极显著正相关,相关系数为0.69;糙米总花色苷含量、粒色等级均与千粒重呈极显著负相关,相关系数分别为-0.20和-0.34。与高亲龙锦1号相比,27个家系的糙米总花色苷含量极显著提高,占214个F_5家系的12.62%,为高花色苷水稻种质创新奠定了基础。     

A second Warburg-like effect in cancer metabolism: The metabolic shift of glutamine-derived nitrogen

Carbon and nitrogen are essential elements for life. Glucose as a carbon source and glutamine as a nitrogen source are important nutrients for cell proliferation. About 100 years ago, it was discovered that cancer cells that have acquired unlimited proliferative capacity and undergone malignant evolution in their host manifest a cancer-specific remodeling of glucose metabolism (the Warburg effect). Only recently, however, was it shown that the metabolism of glutamine-derived nitrogen is substantially shifted from glutaminolysis to nucleotide biosynthesis during malignant progression of cancer—which might be referred to as a “second” Warburg effect. In this review, address the mechanism and relevance of this metabolic shift of glutamine-derived nitrogen in human cancer. We also examine the clinical potential of anticancer therapies that modulate the metabolic pathways of glutamine-derived nitrogen. This shift may be as important as the shift in carbon metabolism, which has long been known as the Warburg effect.     

Regulation of endomembrane biogenesis in arabidopsis by phospatidic acid hydrolase

Coordination of membrane lipid biosynthesis is important for cell function during plant growth and development. Here we summarize our recent work on PHOSPHATIDIC ACID PHOSPHOHYDROLASE (PAH) which suggests that this enzyme is a key regulator of phosphaticylcholine (PC) biosynthesis in Arabidopsis thaliana. Disruption of PAH activity elevates phosphatidic acid (PA) levels and stimulates PC biosynthesis and biogenesis of the endoplasmic reticulum (ER). Furthermore, the activity of PHOSPHOCHOLINE CYTIDYLYLTRANSFERASE (CCT), which is the key enzyme controlling the rate of PC biosynthesis, is directly stimulated by PA and expression of a constitutively active version of CCT replicates the effects of PAH disruption. Hence PAH activity can control the abundance of PA, which in turn can modulate CCT activity to govern the rate of PC biosynthesis. Crucially it is not yet clear how PAH activity is regulated in Arabidopsis but there is evidence that PAH1 and PAH2 are both phosphorylated and further work will be required to investigate whether this is functionally significant.     

Immunogold Labeling of Terminal Cellulose-Synthesizing Complexes

Received 20 September 2001/ Accepted in revised form 10 October 2001     

Biosynthesis of hydroxyphaseollin and related isoflavanoids in disease-resistant soybean hypocotyls

Phenylalanine-U-¹⁴C and isoliquiritigenin-9-¹⁴C were readily incorporated into the antifungal pterocarpan hydroxyphaseollin in soybean hypocotyls that were inoculated with incompatible strains of the phytopathogenic fungus Phytophthora megasperma var. sojae. Hydroxyphaseollin accounted for over half of the phenylalanine and isoliquiritigenin incorporated into ethyl acetate soluble compounds. Daidzein, coumestrol, and sojagol were identified as major compounds which accumulated coordinately with hydroxyphaseollin and contained significant amounts of radioactivity from the labelled isoflavanoid precursors. Hydroxyphaseollin was not present in healthy soybean plants and was not detected until ca. 16 hr after inoculation with the fungus. The pterocarpan then accumulated rapidly between 16 and 48 hr after inoculation, while the greatest accumulations of daidzein, coumestrol, and sojagol occurred between 48 and 72 hr after inoculation, when hydroxyphaseollin accumulation had ceased. Although soybean hypocotyls contained the anthocyanin malvin, neither this compound nor any other flavone pathway product was observed to accumulate after fungus-inoculation. The results therefore indicate that the accumulation of hydroxyphaseollin in fungus-inoculated soybean hypocotyls involves the activation of isoflavanoid biosynthesis with 'direction' of metabolic intermediates to biosynthesis of the pterocarpan.