中国耳蕨属高山耳蕨组的分类学研究

高山耳蕨组的成员是中国西部、印度北部和喜马拉雅山区常见的蕨类。其成员为夏绿植物,叶片 薄而柔弱。秋季叶片枯萎后叶柄基部宿存在地面形成一个丛堆以保护幼芽,这显然是对高山严峻环境 的适应。作为高山地带特有类型,1972年日本蕨类学家Sigeru Daigobo将它们作为耳蕨属下的一个组 ——高山耳蕨组Sect．Lasiopolystichum Daigobo,这是合理的。Daigobo建立此组时只包含3个种,经过 对中国大量标本及有关文献的研究,现知在中国约有30种应归人此组,其中有3新种:红鳞耳蕨P．ru- fopaleaceum,石生耳蕨P.saxicola,康定耳蕨P．kangdingense;2新变种．裂叶耳蕨P．sinense var．loba- tum,条裂耳蕨P．mollissimum Var．laciniatum;1新组合,钝裂耳蕨P．integrilobum(Sorolepidium)。据羽片背面的小鳞片类型可将高山耳蕨组划分为2个系:穆坪系Ser．Moupinensia和中华系Ser．Sinensia。     

DHHC protein-dependent palmitoylation protects regulator of G-protein signaling 4 from proteasome degradation

Regulator of G-protein signaling 4 (RGS4), an intracellular modulator of G-protein coupled receptor (GPCR)-mediated signaling, is regulated by multiple processes including palmitoylation and proteasome degradation. We found that co-expression of DHHC acyltransferases (DHHC3 or DHHC7), but not their acyltransferase-inactive mutants, increased expression levels of RGS4 but not its Cys2 to Ser mutant (RGS4C2S). DHHC3 interacts with and palmitoylates RGS4 but not RGS4C2S in vivo. Palmitoylation prolongs the half-life of RGS4 by over 8-fold and palmitoylated RGS4 blocked α_1A-adrenergic receptor-stimulated intracellular Ca²⁺ mobilization. Together, our findings revealed that DHHC proteins could regulate GPCR-mediated signaling by increasing RGS4 stability.

Structured summary

MINT-8049215: Rgs4 (uniprotkb:P49799) physically interacts (MI:0915) with DHHC3 (uniprotkb:Q8R173) by anti-tag coimmunoprecipitation (MI:0007)     

The extended conformation of the 2.9-Å crystal structure of the three-PASTA domain of a Ser/Thr kinase from the human pathogen Staphylococcus aureus

PASTA (penicillin-binding protein and serine/threonine kinase associated) modules are found in penicillin-binding proteins and bacterial serine/threonine kinases mainly from Gram-positive Firmicutes and Actinobacteria. They may act as extracellular sensors by binding peptidoglycan fragments. We report here the first crystal structure of a multiple-PASTA domain from Ser/Thr kinase, that of the protein serine/threonine kinase 1 (Stk1) from the Firmicute Staphylococcus aureus. The extended conformation of the three PASTA subunits differs strongly from the compact conformation observed in the two-PASTA domain of penicillin-binding protein PBP2x, whereas linear conformations were also reported for two-subunit fragments of the four-PASTA domain of the Actinobacteria Mycobacterium tuberculosis studied by liquid NMR. Thus, a stretched organization appears to be the signature of modular PASTA domains in Ser/Thr kinases. Signal transduction to the kinase domain is supposed to occur via dimerization and ligand binding. A conserved X-shaped crystallographic dimer stabilized by intermolecular interactions between the second PASTA subunits of each monomer is observed in the two crystal forms of Stk1 that we managed to crystallize. Extracellular PASTA domains are composed of at least two subunits, and this molecular assembly is a plausible candidate for the biological dimer. We have also performed docking experiments, which predict that the hinge regions of the PASTA domain can accommodate peptidoglycan. Finally, a three-dimensional homology molecular model of full-length Stk1 was generated, suggesting an interaction between the kinase domain and the cytoplasmic face of the plasma membrane via a eukaryotic-like juxtamembrane domain. A comprehensive activation mechanism for bacterial Ser/Thr kinases is proposed with the support of these structural data.     

A novel regulation on developmental gene expression of fruiting body formation in Myxobacteria

Myxobacteria are Gram-negative soil microorganisms that prey on other microorganisms. Myxobacteria have significant potential for applications in biotechnology because of their extraordinary ability to produce natural products such as secondary metabolites. Myxobacteria also stand out as model organisms for the study of cell–cell interactions and multicellular development during their complex life cycle. Cellular morphogenesis during multicellular development in myxobacteria is very similar to that in the eukaryotic soil amoebae. Recent studies have started uncovering molecular mechanisms directing the myxobacterial life cycle. We describe recent studies on signal transduction and gene expression during multicellular development in the myxobacterium Myxococcus xanthus. We provide our current model for signal transduction pathways mediated by a two-component His–Asp phosphorelay system and a Ser/Thr kinase cascade.     

中老年奶粉对肠道菌群、血清免疫球蛋白及钙的影响

目的了解中老年奶粉对中老年人肠道菌群、血清免疫球蛋白及钙的影响。方法用培养方法检测肠道菌群,速率散射浊度法测血清免疫球蛋白,化学法测血清钙。结果服用中老年奶粉后,中老年人肠道内双歧杆菌明显增加（P〈0．01）,血清IgG,IgA、IgM含量及血清钙水平也显著提高（分别为P〈0．001,P〈0．001,P〈0．01和P〈0．001）。结论中老年奶粉对调整中老年人肠道菌群、增加免疫力、预防脱钙等具有一定的作用。     

A complex multilevel attack on Pseudomonas aeruginosa algT/U expression and algT/U activity results in the loss of alginate production

Infection by the opportunistic pathogen Pseudomonas aeruginosa is a leading cause of morbidity and mortality seen in cystic fibrosis (CF) patients. This is mainly due to the genotypic and phenotypic changes of the bacteria that cause conversion from a typical nonmucoid to a mucoid form in the CF lung. Mucoid conversion is indicative of overproduction of a capsule-like polysaccharide called alginate. The alginate-overproducing (Alg(+)) mucoid phenotype seen in the CF isolates is extremely unstable. Low oxygen tension growth of mucoid variants readily selects for nonmucoid variants. The switching off mechanism has been mapped to the algT/U locus, and the molecular basis for this conversion was partially attributed to mutations in the algT/U gene itself. To further characterize molecular changes resulting in the unstable phenotype, an isogenic PAO1 derivative that is constitutively Alg(+) due to the replacement of the mucA with mucA22 (PDO300) was used. The mucA22 allele is common in mucoid CF isolates. Thirty-four spontaneous nonmucoid variants, or sap (suppressor of alginate production) mutants, of PDO300 were isolated under low oxygen tension. About 40% of the sap mutants were rescued by a plasmid carrying algT/U (Group A). The remaining sap mutants were not (Group B). The members of Group B fall into two subsets: one similar to PAO1, and another comparable to PDO300. Sequence analysis of the algT/U and mucA genes in Group A shows that mucA22 is intact, whereas algT/U contains mutations. Genetic complementation and sequencing of one Group B sap mutant, sap22, revealed that the nonmucoid phenotype was due to the presence of a mutation in PA3257. PA3257 encodes a putative periplasmic protease. Mutation of PA3257 resulted in decreased algT/U expression. Thus, inhibition of algT/U is a primary mechanism for alginate synthesis suppression.