Organization of the MAL loci of Saccharomyces. Physical identification and functional characterization of three genes at the MAL6 locus

Summary We have physically and functionally identified three genes at the MAL6 locus of Saccharomyces carlsbergensis. Using multicopy yeast plasmid vectors, we have subcloned various segments of the entire MAL6 locus. The functional characterization of the MAL6 subcloned regions was determined by (1) analyzing biochemically the levels of MAL-encoded proteins (maltase [-D-glucosidase, E.C. 3.2.1.20] and maltose transport protein) in cells transformed with various MAL6 subclones, and (2) testing the ability of the subclones to complement the maltose fermentation defects of well characterized Mal^– mutants in the highly homologous MAL1 locus. The physical homology between MAL6 and MAL1 is in part demonstrated by the gene disruption of MAL1 using subcloned MAL6 DNA sequences. The results demonstrate that the MAL6 locus is a complex of at least three genes: MAL6R, MAL6T and MAL6S. These genes specify, respectively, a regulatory function, a maltose transport activity (presumably the maltose permease) and the structural gene for maltase. The functional organization of the MAL6 locus is thus identical to that which we had previously determined by mutational analysis for the MAL1 locus.     

The modulation of growth of normal rat liver epithelial cells in calcium-poor medium by epidermal growth factor,phenobarbital, phorbol ester,and retinoic acid

Summary The ability of a normal rat liver epithelial cell line with phenotypic characteristics of “oval” cells to grow in calcium-poor medium has been investigated. The growth of these cells could be arrested in medium containing 0.03 mM Ca²⁺, a concentration below which cell necrosis began to occur 24 h postexposure. With increasing calcium concentration, progressive cell proliferation was observed. Epithelial growth factor (EGF) (10 ng/ml) increased the survival and proliferation of cells in calcium-poor medium and the response was inversely correlated with the extracellular calcium concentration. In contrast, phenobarbital (0.2 to 2 mM), 12-0-tetradecanoylphorbol-13-acetate (0.01 to 1 μg/ml), or retinoic acid (0.001 to 0.1 μg/ml) depressed growth of cells in calcium-poor medium. The results confirm the ability of EGF to lower the calcium requirement for proliferation of normal cells, but such an effect does not seem to be a universal property of tumor promoters. This research was supported by National Institutes of Health Grant CA 29323.     

Enzyme layers on glass as a new model for the quantitative study of capture reactions in cytochemistry,with special attention to acid phosphatase

Summary A model system is described for the study of capture reactions for diffusable compounds in enzyme cytochemistry. The model, which allows the investigation of the influence of the composition of the cytochemical medium, the enzymatic activity, and the dimensions of the enzymatic site on the capture reaction, consists of very thin homogeneous layers of enzyme (0.01–0.1 m thick) on glass, which are incubated in the cytochemical medium. The fraction of the total amount of liberated product precipitated in the enzyme layer is dependent not only on the trapping efficiency of the cytochemical medium but also on the concentration of the primary reaction product that can be built up in the enzyme layer. Calculations were performed to determine the steady-state concentration of the primary reaction product that can be built up in the enzyme layer. Acid phosphatase was used as enzyme. The problems associated with the model and its applicability to other types of cytochemical reactions are discussed.     

Differing effects of isoleucine deficiency on the toxicity of MNNG for 10T1/2 and CHO cells

Summary Isoleucine deficiency sensitizes C3H 10T1/2 cells to the cytotoxic effects of MNNG. Synchrony of proliferation is not required for this effect since it occurs prior to full growth arrest and subsequent establishment of synchronous proliferation after refeeding in complete medium. Furthermore, confluence arrest of proliferation of 10T1/2 cells does not affect their cytotoxic response to MNNG, although they proliferate synchronously after replating at low density. In contrast, the toxicity of MNNG for CHO cells is not altered by isoleucine deficiency, even though these cells are readily synchronized by refeeding in complete medium after transient isoleucine deficiency. This research was supported by Grant BC-142 from the American Cancer Society and Grants CA-16086 and CA-17973 from the National Cancer Institute.     

In situ feeding as a new management tool to conserve orphaned Eurasian lynx (lynx lynx)

High human‐caused mortality due to wildlife‐vehicle‐collisions and illegal killing leads to frequent cases of orphaned Eurasian lynx juveniles. Under natural conditions, this would result in starvation of the young. To avoid this, wildlife managers conventionally rear animals in captivity and release them later. However, this measure is an undesirable outcome for species conservation, managers, and animals alike. Increased awareness of Eurasian lynx orphaned by human‐caused mortality means managers must often intervene in endangered populations. In this study, we report for the first time a successful case of in situ feeding designed to avoid captivity of two orphaned Eurasian lynx. We exposed 13 roe deer and 7 red deer carcasses in the field to successfully support two orphans to the age of independence and confirm dispersal from the natal range. We present this management approach as a feasible and complimentary tool that can be considered in small or isolated large carnivore populations where every individual counts toward population viability.     

Vertical farming systems bring new considerations for pest and disease management

Vertical farming is an emerging area of food production that aims to provide sustainable intensification of agriculture by maximising the obtainable yield per unit area of land. This approach commonly utilises stacked horizontal levels of crop growth in glasshouse or controlled environment (CE) facilities. Vertical farming has, however, received relatively little scientific investigation to date. Consequently, important factors such as economic feasibility, system design and optimisation of production methods are still being evaluated. Vertical farming methods bring additional considerations for the effective management of pests and diseases compared with conventional protected horticulture, such as movement of both pest and beneficial insects between growth levels. This article aims to provide a perspective on the positive and negative issues facing pest and disease control in Vertical farming systems. We highlight important considerations for system optimisation and areas for future investigation.     

Functional analysis of RXLR effectors from the New Zealand kauri dieback pathogen Phytophthora agathidicida

New Zealand kauri is an ancient, iconic, gymnosperm tree species that is under threat from a lethal dieback disease caused by the oomycete Phytophthora agathidicida. To gain insight into this pathogen, we determined whether proteinaceous effectors of P. agathidicida interact with the immune system of a model angiosperm, Nicotiana, as previously shown for Phytophthora pathogens of angiosperms. From the P. agathidicida genome, we defined and analysed a set of RXLR effectors, a class of proteins that typically have important roles in suppressing or activating the plant immune system. RXLRs were screened for their ability to activate or suppress the Nicotiana plant immune system using Agrobacterium tumefaciens transient transformation assays. Nine P. agathidicida RXLRs triggered cell death or suppressed plant immunity in Nicotiana, of which three were expressed in kauri. For the most highly expressed, P. agathidicida (Pa) RXLR24, candidate cognate immune receptors associated with cell death were identified in Nicotiana benthamiana using RNA silencing-based approaches. Our results show that RXLRs of a pathogen of gymnosperms can interact with the immune system of an angiosperm species. This study provides an important foundation for studying the molecular basis of plant–pathogen interactions in gymnosperm forest trees, including kauri.