SummaryThe carboxy-terminus of the γ chain of fibrinogen contains a sequence which is believed to be one of the domains that interacts with glycoprotein (GP) IIb/IIIa to support platelet aggregation. A normal variant of fibrinogen exists in which the four carboxy-terminal amino acids are replaced by 20 amino acids. This variant, known as γ’, has been reported to bind less effectively to platelets. The purpose of the present study was to engineer novel proteins to determine what differences in amino acid sequence between the γ and γ’ chains influence the interaction of the carboxyterminus with GPIIb/IIIa. In this regard, the γ chain cDNA in a bacterial plasmid expression vector was modified by oligonucleotide-directed mutagenesis to produce recombinant γ chains with amino acid changes in the carboxy-terminus which reflect the differences between γ and γ’. The recombinant γ chain with an unmodified carboxy-terminus supported adenosine diphosphate (ADP)-induced platelet aggregation to the same extent as intact fibrinogen. In contrast, the ability of γ’ 427 (the recombinant γ’ variant) and γ 427 (where the 16 amino acid γ’ extension [412–427] was added to the carboxy-terminus of γ) to support platelet aggregation was markedly reduced. In addition, the extent of ADP-induced platelet aggregation was decreased in the presence of γ’ 411 (where amino acids 408–411 in γ were replaced with amino acids 408–411 in γ’), while γ 407 (where the four carboxy-terminal amino acids were deleted) was not capable of supporting aggregation. These findings demonstrate that the four residues AGDV are not only required but must be carboxy-terminal to support platelet aggregation.

Transgenic creeping bentgrass (Agrostis palustris Huds., cv. Pencross; Poaceae) plants have been obtained by microprojectile bombardment of and regeneration from embryogenic calli with a vector designed to deliver the β-glucuronidase (GUS) gene under the control of rice actin 1 5' regulatory sequences. Southern analysis of polymerase chain reaction (PCR)-amplified and restriction-digested genomic DNA of four transgenic plants regenerated from these cultures showed the unscrambled integration of the gus fragment. Northern blot analysis confirmed the expression of gus mRNA in one of the transgenic plants. Western blot analysis revealed a high level of accumulation of gus protein. Histochemical assays showed enzymatic activity of β-glucuronidase in all parts of the transgenic turfgrass plant. The order of gus expression level in different tissues of the transgenic plant is as follows: stem node > first young leaf > root tip > second / third / fourth young leaf > stem internode > root hair-zone.

No abstract

No abstract

Cet article de synthèse présente une revue des recherches concernant les interactions moléculaires et cellulaires de la maladie hollandaise de l'orme. Cette maladie, causée par le champignon Ophiostoma ulmi, provoque un flétrissement vasculaire et elle est transmise d'ormes infectés à des ormes sains par des scolytes. Des toxines fongiques sont décrites en relation avec la pathogénèse, l'une d'elles, la cérato-ulmine, étant sous investigation au niveau moléculaire, plus particulièrement en ce qui concerne son mode d 'action et sa localisation. Le champignon a aussi été examiné au niveau moléculaire pour différencier des isolats agressifs et non agressifs sur la base de profils protéiques et d'acides nucléiques. Des cartes de lien génétique sont en développement afin de corréler la perturbation de certains gènes avec la perte du pouvoir pathogène. Des antagonistes viraux et bactériens du champignon, qui peuvent être utilisés comme mécanisme de lutte biologique contre la maladie hollandaise de l'orme, ont été caractérisés ainsi que plusieurs des molécules actives intervenant dans cette lutte. Les réponses de l'hôte sont discutées aux niveaux moléculaire et biochimique, incluant les phy toalexines et les éliciteurs des mécanismes de défense. Plusieurs avenues de recherche sont discutées afin de fournir une revue des approches moléculaires visant à comprendre et à manipuler les organismes impliqués en vue du but ultime de lutter contre la maladie hollandaise de l'orme.The folio wing review gives an overview of current research in the area of molecular and cellular interactions in Dutch elm disease. This vascular wilt disease is caused by the fungus Ophiostoma ulmi and is transmitted from diseased to healthy trees by the elm bark beetles. Fungal toxins are described which are associated with pathogenesis, one of which, ceratoulmin, is under investigation at the molecular level, particularly regarding its mode of action and localization. The fungus has also been examined at the molecular level to differentiate between aggressive and non-aggressive isolates on the basis of protein and nucleic acid profiles. Genetic linkage maps are being developed to correlate disruption of certain genes with the loss of pathogenicity. Viral and bacterial antagonists of the fungus, which may serve as biological control mechanisms for Dutch elm disease, have been characterized, as have several of the active molecules responsible for control. Host responses are also discussed at the molecular and biochemical level, including phytoalexins and defense mechanism elicitors. Several Unes of investigation are discussed to provide an overview of molecular approaches to understanding and manipulating the organisms involved with the ultimate goal of controlling Dutch elm disease