Metabolic priming by a secreted fungal effector

Maize smut caused by the fungus Ustilago maydis is a widespread disease characterized by the development of large plant tumours. U. maydis is a biotrophic pathogen that requires living plant tissue for its development and establishes an intimate interaction zone between fungal hyphae and the plant plasma membrane. U. maydis actively suppresses plant defence responses by secreted protein effectors. Its effector repertoire comprises at least 386 genes mostly encoding proteins of unknown function and expressed exclusively during the biotrophic stage. The U. maydis secretome also contains about 150 proteins with probable roles in fungal nutrition, fungal cell wall modification and host penetration as well as proteins unlikely to act in the fungal-host interface like a chorismate mutase. Chorismate mutases are key enzymes of the shikimate pathway and catalyse the conversion of chorismate to prephenate, the precursor for tyrosine and phenylalanine synthesis. Root-knot nematodes inject a secreted chorismate mutase into plant cells likely to affect development. Here we show that the chorismate mutase Cmu1 secreted by U. maydis is a virulence factor. The enzyme is taken up by plant cells, can spread to neighbouring cells and changes the metabolic status of these cells through metabolic priming. Secreted chorismate mutases are found in many plant-associated microbes and might serve as general tools for host manipulation.     

Mutations in SEC63 cause autosomal dominant polycystic liver disease

Mutations in PRKCSH, encoding the beta-subunit of glucosidase II, an N-linked glycan-processing enzyme in the endoplasmic reticulum (ER), cause autosomal dominant polycystic liver disease. We found that mutations in SEC63, encoding a component of the protein translocation machinery in the ER, also cause this disease. These findings are suggestive of a role for cotranslational protein-processing pathways in maintaining epithelial luminal structure and implicate noncilial ER proteins in human polycystic disease.     

Apoptosis induced by vitamin A signaling is crucial for connecting the ureters to the bladder

Removal of toxic substances from the blood depends on patent connections between the kidney, ureters and bladder that are established when the ureter is transposed from its original insertion site in the male genital tract to the bladder. This transposition is thought to occur as the trigone forms from the common nephric duct and incorporates into the bladder. Here we re-examine this model in the context of normal and abnormal development. We show that the common nephric duct does not differentiate into the trigone but instead undergoes apoptosis, a crucial step for ureter transposition controlled by vitamin A-induced signals from the primitive bladder. Ureter abnormalities occur in 1-2% of the human population and can cause obstruction and end-stage renal disease. These studies provide an explanation for ureter defects underlying some forms of obstruction in humans and redefine the current model of ureter maturation.     

基于设计结构矩阵(DSM)的复杂研发项目建模与优化研究进展

研发项目是由流程架构、组织架构和产品架构组成的复杂系统.本文首先分析了研发项目复杂性的特征、分类和产生原因,指出设计结构矩阵(DSM)方法是量化分析复杂研发项目的有效工具.进一步,本文从流程架构中迭代和重叠的建模,到流程DSM的排序优化与仿真;从组织架构中团队之间依赖度的测度,到组织DSM聚类准则的确定;从产品架构中部件之间依赖度的测度,到产品DSM的模块化设计以及聚类算法的演变和发展;从单一领域的DSM扩展到多领域矩阵(MDM)的建模与应用,清晰地展示了基于DSM的复杂研发项目建模与优化的几条研究脉络和最新研究进展.最后,本文提出"系统架构的复杂性研究-DSM中元素间依赖关系的测度-DSM优化/聚类"相集成的理论分析框架,并指出了有待进一步研究的关键问题.     

A Survey of the Representations of Rational Ruled Surfaces

The rational ruled surface is a typical modeling surface in computer aided geometric design. A rational ruled surface may have different representations with respective advantages and disadvantages. In this paper, the authors revisit the representations of ruled surfaces including the parametric form, algebraic form, homogenous form and Plücker form. Moreover, the transformations between these representations are proposed such as parametrization for an algebraic form, implicitization for a parametric form, proper reparametrization of an improper one and standardized reparametrization for a general parametrization. Based on these transformation algorithms, one can give a complete interchange graph for the different representations of a rational ruled surface. For rational surfaces given in algebraic form or parametric form not in the standard form of ruled surfaces, the characterization methods are recalled to identify the ruled surfaces from them.