ISSN:0265-9247    

DOI:10.1002/bies.950180602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe formation of segments in theDrosophilaearly embryo is understood in greater detail than any other complex developmental process. Now, by studying other types of insect embryo, we can hope to deduce something of the ancestral mechanism of segmentation and the ways in which it has been modified in evolution. The parasitic wasp,Copidosoma floridanum, is spectacularly atypical of insects in that the small egg cell divides extensively, with no initial syncytial phase, and forms eventually some 2000 embryos(1). This process raises intriguing questions about the control of embryonic polarity and segmentation.

ISSN:0265-9247    

DOI:10.1002/bies.950180603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractMembers of the astacin family of metalloproteinases such as human bone morphogenetic protein 1 (BMP‐1) have previously been linked to cell differentiation and pattern formation during development through a proposed role in the activation of latent growth factors of the TGF‐β superfamily. Recent finding(1)indicate that BMP‐1 is identical to pro‐collagen C‐proteinase, which is a metalloproteinase involved in extracellular matrix (ECM) formation. This observation suggests that a functional link may exist between astacin metalloproteinases, growth factors and cell differentiation and pattern formation during development. Taken together, current studies indicate that BMP‐1 and possibly other astacin metalloproteinases are multifunctional enzymes that act directly on growth factors and the ECM. In combination, these dual actions would have profound effects on development

ISSN:0265-9247    

DOI:10.1002/bies.950180604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractConceptual developments have defined concrete questions about the timing and precise location of cellular pattern formation. Plants in general, and the trichomes of Arabidopsis in particular, are remarkably suited for research on these problems. Genetic analysis requires the quantitative characterizations of the developmental processes by which patterning occurs. Larkinet al.(1)have provided measures of the non‐random distances between trichomes. They have also obtained evidence about the cell lineages leading to trichome development, and this evidence constrains the possible role of intracellular programs. Continued genetic analysis may call for the identification of mutations that are expressed only during development and whose effects are corrected before the phenotype mature

ISSN:0265-9247    

DOI:10.1002/bies.950180605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractChromosome ends have been implicated in the meiotic processes of the nematodeCaenorhabditis elegans. Cytological observations have shown that chromosome ends attach to the nuclear membrane and adopt kinetochore functions. In this organism, centromeric activity is highly regulated, switching from multiple spindle attachments all along the chromosome during mitotic division to a single attachment during meiosis.C. eleganschromosomes are functionally monocentric during meiosis. Earlier genetic studies demonstrated that the terminal regions of the chromosomes are not equivalent in their meiotic potentials. There are asymmetries in the abilities of the ends to recombine when duplicated or deleted. In addition, mutations in single genes have been identified that mimic the meiotic effects of a terminal truncation of the X chromosome. The recent cloning and characterization of theC. eleganstelomeres has provided a starting point for the study of chromosomal elements mediating the meiotic process.

ISSN:0265-9247    

DOI:10.1002/bies.950180606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractSerine proteinase cleavage of proteins is essential to a wide variety of biological processes and is primarily regulated by protein inhibitors. Many inhibitors are conformationally rigid simulations of optimal serine proteinase substrates, which makes them highly efficient competitive inhibitors of target proteinases. In contrast, members of the serpin family of serine proteinase inhibitors display extensive flexibility and polymorphism, particularly in their reactive site segments and in β‐sheet secondary structure, which can take up and expel strands. Reactive site and β‐sheet polymorphism appear to be coupled in the serpins and may account for the extreme stability of serpinproteinase complexes through the insertion of the reactive site strand into a β‐sheet. These unusual properties may have opened an adaptive pathway of proteinase regulation that was unavailable to the conformationally rigid proteinase in

ISSN:0265-9247    

DOI:10.1002/bies.950180607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractChloroplasts and other plastids are plant cell organelles that account for major biochemical functions. They contain their own gene expression system but are integrated into the signaling network of the entire cell. Both nuclear and plastid genes are involved in chloroplast biogenesis, and the gene expression pathways both inside and outside the organelle are subject to developmental and environmental control. The plastid transcription apparatus reflects this general scheme, with a basic organelle‐encoded enzymatic machinery surrounded by factors that may be encoded by nuclear genes. Among the transcription regulatory mechanisms thought to play a role during plastid development are: (1) differential usage of promoter elements; (2) phosphorylation of transcription factors by a protein kinase, which is itself subject to phosphorylation and redox control; (3) dynamic changes in the composition of the transcription apparatus. In etioplasts, the dominating polymerase ‘B’ is a bacterial‐type enzyme, whereas the major chloroplast polymerase ‘A’ is a much larger enzyme reminiscent of those in the nucleus. These two enzyme forms may share common components and recruit others during

ISSN:0265-9247    

DOI:10.1002/bies.950180608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractVulval development in the Caenorhabditis elegans hermaphrodite represents a simple, genetically tractable system for studying how cell signaling events control cell fata decisions. Current models suggest that proper specification of vulval cell fates relies on the integration of multiple signaling systems, including one that involves a receptor tyrosine kinase (RTK)→Ras→mitogen activated protein kinase (MAPK) cascade and one that involves a LIN‐12/Notch family receptor. In this review, we first discuss how genetic strategies are being used to identify and analyze components that control vulval cell fate decisions. We then describe the different signaling systems that have been elucidated and how they relate to one another. Finally, we highlight several recently characterized genes that encode positive regulators, negative regulators or potential targets of the RTK→Ras→MAPK cascade involved in vulval

ISSN:0265-9247    

DOI:10.1002/bies.950180609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractSite‐specific phosphorylation of intermediate filament (IF) proteins on serine and threonine residues leads to alteration of the filament structure,in vitroandin vivo. Protein kinases involved in cell signaling and those activated in mitosis dynamically control spatial and temporal organization of intracellular IF phosphorylation. Thus, IF phosphorylation appears to be one of the most predominant strategies in coordinating intracellular organization of the IF networ

ISSN:0265-9247    

DOI:10.1002/bies.950180610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe concept of homology arose from classical studies of comprative morphology, and took on a new signficance with the advent of evolutionary theory. It is currentlyl undergoing antoher metamorphosis: many developmental geneticists now dfine homology as shared patterns of gene expression. However, this ne usage conflaes difinition with criteri, and fails to recognize the meaninful asignments of homology must speify a biologcal level. We argue the although developmental genetic data can help identify homologus structures. they are niether necessary nor sufficient, and do not in any case jutify a new definition of homology.

ISSN:0265-9247    

DOI:10.1002/bies.950180611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY