Fungal proteinase expression in the interaction of the plant pathogen Magnaporthe poae with its host.

Infection by pathogenic fungi involves breaching the outer layer of the host by either mechanical or enzymatic means. Subtilisin-like proteinases are considered to be important in the infection process of entomopathogenic, nematophagous, and mycoparasitic fungi. Little is known regarding the expression of such proteinases by plant pathogenic fungi. Magnaporthe poae, a fungal pathogen of Kentucky bluegrass, expressed a subtilisin-like proteinase, proteinase Mp1, in the infected roots. Antibody was produced against the purified enzyme. From immunoblot analysis, expression of the proteinase in infected roots correlated with increasing severity of disease symptoms. Sequence analysis of a genomic clone indicated proteinase Mp1 was homologous to other fungal subtilisin-like proteinases. DNA gel blot analysis indicated proteinase Mp1 was encoded by a small gene family.     

Identification of UDP-linked murein precursors as contaminants in recombinant proteins of low molecular weight.

The A(280)/A(260) ratio of a purified protein is frequently used as an indication of the purity of the preparation with respect to nucleic acids. We show here that for low-molecular-weight recombinant proteins purified from Escherichia coli, a low A(280)/A(260) ratio can also result from contamination with UDP-linked murein precursors derived from bacterial cell wall metabolism. Although these precursors are small molecules of molecular weight 1000-1200, they comigrate in gel filtration with recombinant human FKBP (MW 11,820). This gel filtration behavior, which is distinct from that of unmodified mononucleotides, does not reflect binding interactions with FKBP, but is an intrinsic property of these precursors. Therefore, these molecules would be expected to copurify with other low-molecular-weight proteins, especially in the abbreviated purification protocols made possible by freeze-thaw release of recombinant proteins from E. coli (Johnson, B. H., and Hecht, M. H. (1994) BioTechnology 12, 1357-1360). Several alternative strategies are discussed for integrating these findings into the design of improved purification procedures for low-molecular-weight recombinant proteins.     

Somatic growth processes: how are they altered in captivity?

The cellular growth mechanisms of captive cephalopods were examined to determine whether the growth processes in aquaria are the same as those of wild individuals. Mantle muscle tissue growth in cephalopods is a function of both the production of muscle fibres and the growth of existing fibres. After seven days, captive animals had thicker mantles, a greater proportion of mitochondria-rich tissue, muscle fibres with smaller mitochondrial cores and fewer small muscle fibres. This suggests a reduced rate of new fibre generation, indicating an alteration to the cellular growth mechanisms and not simply a change in the physiological rate of growth. Smaller individuals were affected to a greater extent. Such modifications to the actual mechanisms of growth may have the potential to alter the shape of an individual''s growth curve and can also affect final body size. Alterations to the proportion and structure of mantle components may impact upon many critical aspects of an individual''s biology, as the muscular mantle is central to locomotion, ventilation of gills, energy storage and possibly subcutaneous oxygen extraction.     

The natural history, thermal physiology, and ecological impacts of intertidal mesopredators, Oedoparena spp. (Diptera: Dryomyzidae)

Abstract. The ecological roles of small (1–1000 mg) predators in benthic marine systems are poorly understood. We investigated the natural history and predatory impact of one group of such mesopredators—larvae of dipteran flies in the genus Oedoparena —which prey on intertidal barnacles. We 1) quantified patterns of larval Oedoparena distribution and abundance in the Northwest Straits of Washington State, USA, 2) determined larval physiological tolerance limits in the laboratory, and 3) conducted a manipulative field experiment to assess the role of microhabitat temperature on predation rates in Oedoparena . Members of Oedoparena in Washington are univoltine, with peak larval abundance in late spring and early summer. Infestation frequencies in the barnacles Balanus glandula and Chthamalus dalli were as high as 22% and 35%, respectively. In laboratory studies, larvae of O . glauca were able to tolerate temperatures up to 37°C; however, this temperature is often exceeded in high intertidal habitats. In a field manipulation using experimental shades, we demonstrate that the alleviation of physiological stress greatly increased the abundance of larvae of Oedoparena spp. As a result of increased larval densities under shades, adult B. glandula mortality increased from 5% to nearly 30%, and C. dalli mortality increased from less than 20% to over 60%. Because high intertidal barnacles serve as food and habitat for a diverse array of species, Oedoparena spp. have the potential to play a major role in structuring high intertidal communities, particularly in cooler microhabitats.