Characterization of the first tuber mustard calmodulin-like gene, BjAAR1, and its functions in responses to abiotic stress and abscisic acid in Arabidopsis

The first tuber mustard calmodulin-like (CML) gene BjAAR1 (Brassica juncea var. tumida Tsen et Lee Abiotic stress and Abscisic acid (ABA) Responsive gene 1) was cloned and characterized. The protein encoded by BjAAR1 contains four predicted Ca²⁺ binding sites (EF-hand motif) and its recombinant protein can bind Ca²⁺ in vitro. qRT-PCR showed that the expression level of BjAAR1 was rather high in non-swollen stem of tuber mustard and largely reduced in swollen stem. Expression of BjAAR1 enhanced ABA- and stress-induced gene expression in Arabidopsis (Arabidopsis thaliana). Transgenic plants also exhibited hypersensitivity to NaCl, mannitol, and ABA during the seed germination and post-germination stages. ABA biosynthesis inhibitor, norflurazon (NF), rescued hypersensitivity phenotype of transgenic plants to NaCl and mannitol, indicating that BjAAR1 functions in multiple abiotic stresses response through ABA-dependent process.     

A new strategy for structure determination of large proteins in solution without deuteration

So far high-resolution structure determination by nuclear magnetic resonance (NMR) spectroscopy has been limited to proteins <30 kDa, although global fold determination is possible for substantially larger proteins. Here we present a strategy for assigning backbone and side-chain resonances of large proteins without deuteration, with which one can obtain high-resolution structures from (1)H-(1)H distance restraints. The strategy uses information from through-bond correlation experiments to filter intraresidue and sequential correlations from through-space correlation experiments, and then matches the filtered correlations to obtain sequential assignment. We demonstrate this strategy on three proteins ranging from 24 to 65 kDa for resonance assignment and on maltose binding protein (42 kDa) and hemoglobin (65 kDa) for high-resolution structure determination. The strategy extends the size limit for structure determination by NMR spectroscopy to 42 kDa for monomeric proteins and to 65 kDa for differentially labeled multimeric proteins without the need for deuteration or selective labeling.     

Solution structures of the adhesion molecule DdCAD-1 reveal new insights into Ca(2+)-dependent cell-cell adhesion

DdCAD-1 is a novel Ca(2+)-dependent cell adhesion molecule that lacks a hydrophobic signal peptide and a transmembrane domain. DdCAD-1 is expressed by the social amoeba Dictyostelium discoideum at the onset of development. It is synthesized as a soluble protein and then transported to the plasma membrane by contractile vacuoles. Here we describe the novel features of the solution structures of Ca(2+)-free and Ca(2+)-bound monomeric DdCAD-1. DdCAD-1 contains two beta-sandwich domains, belonging to the betagamma-crystallin and immunoglobulin fold classes, respectively. Whereas the N-terminal domain has a major role in homophilic binding, the C-terminal domain tethers the protein to the cell membrane. From structural and mutational analyses, we propose a model for the Ca(2+)-bound DdCAD-1 dimer as a basis for understanding DdCAD-1-mediated cell-cell adhesion at the molecular level. Our results provide new insights into Ca(2+)-dependent mechanisms for cell-cell adhesion.     

Molecular mechanisms that govern the specificity of Sushi peptides for Gram-negative bacterial membrane lipids

Factor C-derived Sushi peptides (S1 and S3) have been shown to bind lipopolysaccharide (LPS) and inhibit the growth of Gram-negative bacteria but do not affect mammalian cells. On the premise that the composition of membrane phospholipids differs between the microbial and human cells, we studied the modes of interaction between S1 and S3 and the bacterial membrane phospholipids, POPG, in comparison to that with the mammalian cell membrane phospholipids, POPC and POPE. S1 exhibits specificity against POPG, suggesting its preference for bacterial anionic phospholipids, regardless of whether the phospholipids form vesicles in a solution or a monolayer on a solid surface. The specificity of the Sushi peptides for POPG is a consequence of the electrostatic and hydrophobic forces. The unsaturated nature of POPG confers fluidity to the lipid layer, and being in the proximity of LPS in the microenvironmental milieu, POPG probably enhances the insertion of the peptide-LPS complex into the bacterial inner membrane. Furthermore, during its interaction with POPG, the S1 peptide underwent a transition from random to alpha-helical coil, while S3 became a mixture of beta-sheet and alpha-helical structures. This differential structural change in the peptides could be responsible for their different modes of disruption of POPG vesicles. Conceivably, the selectivity for POPG spares the mammalian membranes from undesirable effects of antimicrobial peptides, which could be helpful in designing and developing a new generation of antibiotics and in offering some clues about the specific function of Factor C, a LPS biosensor.     

湖南省南岳种子植物区系的研究

湖南省南岳种子植物属的成分主要是泛热带、北温带和东亚3种分布区类型,分别占总属数的22．6％、18．8％和14．9％,温带和热带2种性质分子比例相当,分别占47．5％和52．5％;其种的区系成分主要由华夏、东亚、中国－日本和华东－华中等4种分布式样构成,分别占总种数的24．47％、16．60％、14．17％和11．65％,若扣除分布范围较广的世界广布、旧世界热带、热带亚洲至热带非洲、热带亚洲至热带澳洲、热带亚洲、南北温带（全温带）、北温带、东亚、中国－喜马拉雅、中国－日本和华夏等11种式样,则“华东－华中”及其邻近分布的式样共计177种,占剩余总种数（287种）的61．67％,说明南岳种子植物区系具有典型的“华东－华中”过渡色彩。数量分析结果表明,南岳植物区系与庐山的关系十分密切,南岳在区系归属归于华东植物地区比较恰当。     

Fungal Wound Healing through Instantaneous Protoplasmic Gelation

1. Download : Download high-res image (189KB)
2. Download : Download full-size image