Cupin: A candidate molecular structure for the Nep1-like protein family

Background  

NEP1-like proteins (NLPs) are a novel family of microbial elicitors of plant necrosis. Some NLPs induce a hypersensitive-like response in dicot plants though the basis for this response remains unclear. In addition, the spatial structure and the role of these highly conserved proteins are not known.     

Protein kinase C prevents oligodendrocyte differentiation: modulation of actin cytoskeleton and cognate polarized membrane traffic.

In a previous study, we showed that activation of protein kinase C (PKC) prevents oligodendrocyte differentiation at the pro-oligodendrocyte stage. The present study was undertaken to identify downstream targets of PKC action in oligodendrocyte progenitor cells. Activation of PKC induced the predominant phosphorylation of an 80-kD protein, identified as myristoylated alanine-rich C-kinase substrate (MARCKS). Upon phosphorylation, MARCKS is translocated from the plasma membrane to the cytosol. Furthermore, PKC activation perturbed the organization of the actin cytoskeleton, causing a redistribution of actin filaments to the submembranous or cortical actin cytoskeleton. As a consequence, transport of a protein traffic marker, the vesicular stomatitis virus glycoprotein, from the trans-Golgi network to the plasma membrane becomes perturbed. The effect of disruption of the actin filament network by cytochalasin D perfectly matched the effect of PKC. These data thus favor the existence of a causal relationship between actin rearrangement and docking and/or fusion of proteins to the plasma membrane. Interestingly, neither in control cells nor in PKC-activated cells did another protein traffic marker, influenza hemagglutinin (HA), reach the cell surface. However, an eminent and specific accumulation of HA just underneath the plasma membrane became apparent upon PKC activation. Yet, this effect could not be simulated by cytochalasin D treatment. Therefore, these observations imply that although MARCKS represents a prominent PKC target site in regulating differentiation, another target involves the differential control of cognate polarized trafficking pathways, which are apparently operating in oligodendrocyte progenitor cells.     

Relationship between synthesis of ribosomes and RNA polymerase in Bacillus subtilis

The relationship between RNA polymerase synthesis and ribosome synthesis has been investigated in Bacillus subtilis growing at different rates. The amount of polymerase was determined by quantitation of polymerase subunits on polyacrylamide gels, while ribosome synthesis was estimated from accumulation of total RNA. The ratio of ribosome to RNA polymerase synthesis was 5:1 at slower growth rates and increased with growth rate. Bacillus subtilis was estimated to contain between 10-and 2-fold excess of RNA polymerase depending on its growth rate.     

Cloning of an exclusion-determining fragment of the IncI plasmid, R144

By cloning a distinct 8 MDa fragment of the IncI plasmid, R144, in the vector pACYC184, two recombinant plasmids were isolated. In these plasmids, pRAH303 and pRAH308, the inserted fragment was in opposite orientations. Both plasmids when present in a recipient strain caused a conjugation-specific exclusion in crosses with donor cells carrying the IncI plasmid R144. Some derivatives of the recombinant plasmids in which parts were deleted, or in which Tn5 transposons were inserted, appeared to be exclusion negative. Analysis in minicells of the gene products of such plasmids together with those of the original recombinant plasmids revealed that the presence of two proteins, with apparent molecular weights of 13,000 and 19,000 Da could be correlated with the exclusion phenomenon.     

The competence to acquire cellular desiccation tolerance is independent of seed morphological development.

Acquisition of desiccation tolerance and the related changes at the cellular level in wheat (Triticum aestivum cv. Priokskaya) kernels during normal development and premature drying on the ear were studied using a spin probe technique and low temperature scanning electron microscopy. During normal development, the ability of embryos to germinate after rapid drying and rehydration was acquired after completion of morphological development, which is a few days before mass maturity. The acquisition of desiccation tolerance, as assessed by germination, was associated with an upsurge in cytoplasmic viscosity, the onset of accumulation of protein and oil bodies, and the retention of membrane integrity upon dehydration/rehydration. These features were also used to assess cellular desiccation tolerance in the cases when germination could not occur. Slow premature drying was used to decouple the acquisition of cellular desiccation tolerance from morphogenesis. Upon premature drying of kernels on the ears of plants cut at 5 d after anthesis, desiccation-tolerant dwarf embryos were formed that were able to germinate. When plants were cut at earlier stages poorly developed embryos were formed that were unable to germinate, but cellular desiccation tolerance was nevertheless acquired. In such prematurely dried kernels, peripheral meristematic endosperm cells had already passed through similar physiological and ultrastructural changes associated with the acquisition of cellular desiccation tolerance. It is concluded that despite the apparent strong integration in seed development, desiccation tolerance can be acquired by the meristematic cells in the developing embryo and cambial layer of endosperm, independently of morphological development.     

Effects of training on maximal working capacity and haemodynamic response during arm and leg-exercise in a group of paddlers.

Maximal oxygen uptake and circulatory adaptation to work with legs and arms were studied in a group of 5 paddlers members of the Belgian national squad and a control-group of 9 trained subjects. The results showed that the specific armtraining of paddlers induced changes in the arm-to-leg ration of physiological parameters at submaximal and maximal work. In the group of paddlers maximal oxygen intake and workload during arm-exercise averaged respectively 88.6% and 80.3% of the scores obtained with leg-exercise. In the control group the arm to leg ratio varied between 81.2% and 65.2%. At a submaximal load of 100 W the difference in heartfrequency was 21 beats/min in the canoe group and 35 beats/min in the control group. Oxygen consumption and ventilation during work with the arms was lower in the group of paddlers. The data of our study suggest that the specific training of paddlers do result in a effect on the haemodynamic adaptations to arm work.