Molecular cloning, characterization and expression of a jasmonate biosynthetic pathway gene encoding allene oxide cyclase from Camptotheca acuminata

AOC (allene oxide cyclase; EC 5.3.99.6), an essential enzyme in jasmonic acid and its methyl ester biosynthesis, was cloned from Camptotheca acuminata (named as CaAOC), a native medicinal plant species in China. CaAOC had significant similarity at the amino-acid level with AOCs from other plant species. Comparison between the sequences of the full-length cDNA and genomic DNA of CaAOC revealed that the genomic DNA of CaAOC contained an 89-bp intron and a 240-bp intron. Southern-blot analysis indicated that CaAOC was a multiple-copy gene, and real-time quantitative PCR analysis showed that CaAOC was expressed constitutively in all organs tested, with the highest expression level in leaves. The results from treatment experiments using different signalling components, including methyl jasmonate, abscisic acid, salicylic acid and H(2)O(2), revealed that expression of CaAOC had a prominent diversity. Heavy metal (copper) significantly enhanced CaAOC expression, whereas wounding (induced by UV-B) was not so effective.     

4-(1,1-Dioxo-1,4-dihydro-1lambda6-benzo[1,4]thiazin-3-yl)-5-hydroxy-2H-pyridazin-3-ones as potent inhibitors of HCV NS5B polymerase

4-(1,1-Dioxo-1,4-dihydro-1lambda(6)-benzo[1,4]thiazin-3-yl)-5-hydroxy-2H-pyridazin-3-one analogs were discovered as a novel class of inhibitors of HCV NS5B polymerase. Structure-based design led to the identification of compound 3a that displayed potent inhibitory activities in biochemical and replicon assays (1b IC(50)<10 nM; 1b EC(50)=1.1 nM) as well as good stability toward human liver microsomes (HLM t(1/2)>60 min).     

乳酸菌细菌素的研究进展

简要介绍了乳酸菌细菌素的概念和分类,并以nisin为例对其分子结构、理化性质、抑菌范围及机制、遗传控制作了较为详尽的介绍,简要概括了乳酸菌细菌素的应用和今后的研究方向。     

Structure-activity relationships of novel antibacterial translation inhibitors: 3,5-diamino-piperidinyl triazines

Structure-activity relationships of the 3,5-diamino-piperidinyl triazine series, a novel class of bacterial translation inhibitors, are described. Optimization was focused on the triazine C-4 position in which aromatic substituents that contained electron-withdrawing groups led to potent inhibitors. The initial lack of antibacterial activity was correlated with poor cellular penetration. Whole cell antibacterial activity was achieved by linking additional aromatic moieties at the triazine C-4 position.     

兔胃肠道中双歧杆菌的初步研究

双歧杆菌(Bifidobacterium)是兔体及其它某些哺乳动物的重要生理细菌,在微生态学上属于原籍菌群(autochthonous flora)。它是一属革兰氏阳性、无芽胞、无荚膜、无鞭毛、多形性厌氧杆菌。该菌对人、     

Factors affecting anther culturability of recalcitrant barley genotypes

One major problem encountered with cereal anther culture is that some genotypes are low or non-responders to the technique. The objective of this study was to improve anther culture efficiency of recalcitrant barley (Hordeum vulgare L.) genotypes. Reciprocal F₁s between the two low responsive cultivars, Morex and Steptoe, were used. These were chosen because doubled haploids (DH) were required from these genotypes for the North American Barley Genome Mapping project. Ficoll 400 at 200 g l^–1 in the induction medium significantly increased green plant production compared to four other media formations containing different gelling/viscosity modifying agents. Cold pretreatment of donor spikes of 28 vs 14 d resulted in an increase in embryoid, total plant and green plant production. Anther culture response in these experiments was little influenced by donor plant growth conditions. Indole-3-acetic acid (1 mg l^–1) or 1-naphthaleneacetic acid (2 mg l^–1) in the induction medium did not affect anther culturability or plant regeneration. Based on this research, the negative genotypic effect for doubled haploid production could be diminished, which is desirable for practical application.Abbreviations BAP 6-benzylaminopurine - IAA Indole-3-acetic acid - LS Linsmaier & Skoog - NAA 1-naphthaleneacetic acid - DH doubled haploid     

Molecular cloning of BPL1, a pectate lyase-like gene in Brassica napus

Pectate lyase (EC 4.2.2.2) is an enzyme involved in the maceration and soft rotting of plant tissue via degradation of cell wall in organisms. Plants as well as bacteria and fungi are capable of producing pectate lyases. Here we report the cloning of a novel full-length cDNA of pectate lyase gene, designated BPL1, from Brassica napus by rapid amplification of cDNA ends. BPL1 cDNA is 1787 bp containing a 1503 bp ORF encoding a 500 amino acid protein precursor. The protein precursor has a potential signal peptide with 22 amino acids. Alignment of sequences shows that there are some extremely conserved amino acids among pectate lyase-like proteins from different plant species, and novel C-terminal domains are found in Arabidopsis and Brassica. Phylogenetic analysis of 50 pectate lyase-like proteins from various species demonstrates the obvious distinction among pectate lyase-like proteins from plants, bacteria and fungi, which are subsequently clustered into three groups. The cloning of BPL1 enables us to explore its diverse roles in higher plants and potential application in crop improvement.     

Molecular cloning, characterization and functional analysis of a 2C-methyl- D-erythritol 2, 4-cyclodiphosphate synthase gene from ginkgo biloba

2C-methyl-D-erythritol 2, 4-cyclodiphosphate synthase (MECPS, EC: 4.6.1.12) is the fifth enzyme of the non-mevalonate terpenoid pathway for isopentenyl diphosphate biosynthesis and is involved in the methylerythritol phosphate (MEP) pathway for ginkgolide biosynthesis. The full-length mecps cDNA sequence (designated as Gbmecps) was cloned and characterized for the first time from gymnosperm plant species, Ginkgo biloba, using RACE (rapid amplification of cDNA ends) technique. The full-length cDNA of Gbmecps was 874 bp containing a 720 bp open reading frame (ORF) encoding a peptide of 239 amino acids with a calculated molecular mass of 26.03 kDa and an isoelectric point of 8.83. Comparative and bioinformatic analyses revealed that GbMECPS showed extensive homology with MECPSs from other species and contained conserved residues owned by the MECPS protein family.Phylogenetic analysis indicated that GbMECPS was more ancient than other plant MECPSs. Tissue expression pattern analysis indicated that GbMECPS expressed the highest in roots, followed by in leaves, and the lowest in seeds. The color complementation assay indicated that GbMECPS could accelerate the accumulation of beta-carotene. The cloning, characterization and functional analysis of GbMECPS will be helpful to understand more about the role of MECPS involved in the ginkgolides biosynthesis at the molecular level.