Are tissue cultures of Peganum harmala a useful model system for studying how to manipulate the formation of secondary metabolites?

This article reviews our present knowledge on the formation of tryptophan derived secondary metabolites in tissue cultures of Peganum harmala. With the presence of -carboline alkaloids and serotonin, P. harmala contains two rather simple, interrelated biosynthetic pathways. The long term disadvantage of low and unstable productivity of P. harmala suspension culture has recently been overcome by establishing highly productive hairy root cultures. The first -carboline alkaloid biosynthetic enzymes, specific for the O-methylation of harmalol and harmol as well as for the oxidation of harmaline to harmine, have been detected in these cultures, and they should thus provide a suitable source for studying the yet unknown initial two enzymatic steps of -carboline alkaloid biosynthesis. Seedlings of P. harmala have also been successfully transformed with constructed strains of Agrobacterium, as demonstrated by the overexpression of a tryptophan decarboxylase gene from Catharanthus roseus in cultures of P. harmala. In such transgenic cultures a large overproduction of serotonin was observed. The relative simplicity of these pathways and the rather easy handling of the cultures could make P. harmala a useful and attractive model system for studying the interaction, regulation and manipulation of secondary pathways in cultured cells.Abbreviations TDC tryptophan decarboxylase - tdc gene of tryptophan decarboxylase     

Improved metabolic action of a bacterial lysine decarboxylase gene in tobacco hairy root cultures by its fusion to arbcS transit peptide coding sequence

The gene of a bacterial lysine decarboxylase (ldc) fused to arbcS transit peptide coding sequence (tp), and under the control of the CaMV 35S promoter, was expressed in hairy root cultures ofNicotiana tabacum. The fusion of theldc to the targeting signal sequence improved the performance of the bacterial gene in the plant cells in many respects. Nearly all transgenic hairy root cultures harbouring the35S-tp-ldc gene contained distinctly higher lysine decarboxylase activity (from 1.5 to 30 pkat LDC per mg protein) than those which had been transformed with constructs in which the gene had been directly cloned behind the CaMV 35S promoter. The higher enzyme activity led to the accumulation of up to 0.7% cadaverine on a dry mass basis. In addition, part of the cadaverine pool was used for increased biosynthesis of anabasine, an alkaloid which was hardly detectable in control cultures. The best line contained anabasine levels of 0.5% dry mass, which could further be enhanced by feeding of lysine.     

Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

Isocitrate dehydrogenase 1 R132C mutation occurs exclusively in microsatellite stable colorectal cancers with the CpG island methylator phenotype

The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features.     

奥美拉唑联合法莫替丁治疗反流性食管炎的临床效果分析

目的：观察并分析奥关拉唑联合法莫替丁治疗反流性食管炎的临床效果。方法：选取2008年5月至2012年5月在本院确诊并治疗的反流性食管炎患者45例,随机平均分为三组。联合用药组（15例）：每日早餐前口服20mg奥关拉唑,睡前口服20mg法莫替丁;奥关拉唑组（15例）：每日口服两次奥美拉唑,每次20mg;法莫替丁组（15例）：每日口服两次法莫替丁,每次20mg。每组的治疗时间均为8周。在内镜指导下观察并比较三组患者的胸痛、反酸和烧心等主要病征的改善情况,综合评价三种治疗方法的临床疗效。结果：联合用药组较其他两组获得的疗效更明显,患者的症状得到较好的改善,差异有统计学意义（P〈0．05）。结论：奥美拉唑联合法莫替丁能够有效地抑制胃酸的分泌,对于反流性食管炎的,临床治疗具有良好的效果。