Social behaviour of juvenile red sea urchins, Strongylocentrotus franciscanus (Agassiz)

This study examined social behaviour of juvenile red sea urchins, Strongylocentrotus franciscanus (Agassiz). At four coastal locations in British Columbia, Canada, distributions of juvenile sea urchins were examined in relation to adults. One-third of all juveniles were found underneath an adult “spine canopy”, another third outside the spine canopy but close to an adult, and the remainder were found apart from adults. Juveniles associated with adults were contagiously distributed with each other. In the laboratory, juveniles chose adults over other target locations. They selected adults in particular locations over others, and in one case showed selection among adults; but they did not select between fed and non-fed adults, nor between adults that had been “protective” and “non-protective” of juveniles in the field. In time-lapse film studies, starved juveniles showed little change in social behaviour when food was introduced, but showed a dramatic change in behaviour when predators were active. We suggest that juvenile red sea urchins are found under the spine canopies of adults as a result of juvenile behaviour; and that this interaction functions to protect juveniles from predation. The strong gregarious nature of juveniles among themselves may have evolved in a different selective situation as a defence against predation and to ensure reproductive success.     

Wheat PR‐1 proteins are targeted by necrotrophic pathogen effector proteins

Recent studies have identified that proteinaceous effectors secreted by Parastagonospora nodorum are required to cause disease on wheat. These effectors interact in a gene‐for‐gene manner with host‐dominant susceptibilty loci, resulting in disease. However, whilst the requirement of these effectors for infection is clear, their mechanisms of action remain poorly understood. A yeast‐two‐hybrid library approach was used to search for wheat proteins that interacted with the necrotrophic effector SnTox3. Using this strategy we indentified an interaction between SnTox3 and the wheat pathogenicity‐related protein TaPR‐1‐1, and confirmed it by in‐planta co‐immunprecipitation. PR‐1 proteins represent a large family (23 in wheat) of proteins that are upregulated early in the defence response; however, their function remains ellusive. Interestingly, the P. nodorum effector SnToxA has recently been shown to interact specifically with TaPR‐1‐5. Our analysis of the SnTox3–TaPR‐1 interaction demonstrated that SnTox3 can interact with a broader range of TaPR‐1 proteins. Based on these data we utilised homology modeling to predict, and validate, regions on TaPR‐1 proteins that are likely to be involved in the SnTox3 interaction. Precipitating from this work, we identified that a PR‐1‐derived defence signalling peptide from the C‐terminus of TaPR‐1‐1, known as CAPE1, enhanced the infection of wheat by P. nodorum in an SnTox3‐dependent manner, but played no role in ToxA‐mediated disease. Collectively, our data suggest that P. nodorum has evolved unique effectors that target a common host‐protein involved in host defence, albeit with different mechanisms and potentially outcomes.     

Monitoring genetically engineered microorganisms in freshwater microcosms

Summary The effectiveness of gene probe methods for tracking genetically engineered microorganisms (GEMs) in the environment was tested by inoculating nutrient-supplemented freshwater microcosms withAlcaligenes A5 (a naturally occurring 4-chlorobiphenyl degrader) orPseudomonas cepacia AC1100 (a genetically engineered 2, 4, 5 T-degrader) and following the fates of the introduced bacterial populations. Colony hybridization of the viable heterotrophic bacterial populations and dot blot hybridization of DNA recovered from the total microcosm microbial communities showed persistence of bothAlcaligenes A5 andP. cepacia AC1100 in the microcosms in the presence and absence of the xenobiotic substrates that these organisms biodegrade. Although there was a gradual decline in the added populations, both of the bacterial populatins were still detected in the microcosms two months after their introduction into the microcosms. Addition of 2, 4, 5-T enhanced the survival ofP. cepacia AC1100 — and 4-chlorobiphenyl addition resulted in increased levels ofAlcaligenes A5. The results indicate that both organisms may persist for very long periods in freshwater habitats.     

Glucocorticoid-induced glycogen increases in extensor digitorum longus and soleus grafts in the rat

The purpose of the present study was to compare dexamethasone-induced glycogen increases in normal EDL and SOL muscles with that in free muscle grafts. Glycogen in mature EDL and SOL grafts in the rat equalled control concentrations irrespective of whether the graft was a nerve-intact (NI), nerve-crushed (NC), reimplanted, or cross-transplanted graft. The grafts also possessed the glycogen-regulatory mechanisms to respond to the glucocorticoid dexamethasone (DEX), which increases muscle glycogen. The increase in glycogen induced by DEX in the EDL and SOL grafts resembled that of the EDL and SOL muscles, respectively, whether the grafted muscle was originally an EDL or SOL. DEX induced an approximate twofold increase in glycogen concentration in control muscles and nerve-intact SOL grafts, and a smaller but significant increase in all other free grafts. Nerve crushing prior to grafting resulted in no significant change in muscle weight, glycogen concentration, or DEX-induced glycogen increase in these grafts. The data suggest that skeletal muscle grafts are qualitatively similar to normal muscles in terms of metabolic responsiveness to hormones. Leaving the nerve intact during grafting quantitatively enhances the graft's hormonal sensitivity but the technique of nerve crushing prior to grafting has no such effect.     

Synaptosomal Sialyltransferase Glycosylates Surface Proteins that Are Inaccessible to the Action of Membrane-Bound Sialidase

Sialyltransferase has been characterized in P2 pellets derived from animals of increasing age. The enzyme was found to be associated with the plasma membrane and to be developmentally regulated at times coincident with cell migration and fibre outgrowth. This regulation appeared to be due, in part, to an endogenous competitive inhibitor in the P2 pellet but not in the synaptosome. Optimal transfer of [14C]N-acetylneuraminic acid to endogenous synaptosomal acceptors was achieved only in the absence of detergent. Furthermore, the transferred sialic acid was found to be inaccessible to the action of membrane-bound sialidase. The significance of these findings is discussed.