Sporophore production ofAgaricus bisporus in aseptic environments

Production of mature sporophores ofAgaricus bisporus was achieved for the first time in amended, autoclaved soil, gamma-sterilized soil, and soil-extract agar medium. The initiation of sporophores was triggered by metabolites of soil-inhabiting bacteria, particularly nodule forming isolates. Whether a single metabolite or several metabolites of these bacteria caused formation of sporophores could not be established; however, biotin alone when added to soil extract medium produced comparable results. The potentiality of different bacteria to induce sporophore formation varied considerably within species and isolates.Amino acids favored vegetative growth ofA. bisporus, but failed to induce formation of sporophores. Organic acids supported luxuriant growth and poor sporophore formation. Among several growth-promoting substances and vitamins, biotin induced abundant formation of mature sporophores.The authors are thankful to Dr. C. Corke, Department of Soil Microbiology, University of Guelph, Ontario, for providing some bacterial cultures used in this study.     

The essential role of hypusine in eukaryotic translation initiation factor 4D (eIF-4D). Purification of eIF-4D and its precursors and comparison of their activities

Eukaryotic translation initiation factor 4D (eIF-4D) is the only protein known to contain the amino acid, hypusine [N epsilon-(4-amino-2-hydroxybutyl)lysine]. This unusual amino acid is formed post-translationally by modification of a single specific lysine residue in an eIF-4D precursor protein. Two separate eIF-4D precursors, each of which contains a lysine residue in place of the hypusine residue and each of which thereby serves as a protein substrate for the hypusine modification, were purified from DL-2-difluoromethylornithine-treated Chinese hamster ovary cells by means of a five-step procedure. These two precursors termed PI and PII both have apparent molecular masses of approximately 17 kDa, indistinguishable from that of eIF-4D, but exhibit more acidic isoelectric points (5.1 and 5.25 for PI and PII, respectively, compared with 5.37 for eIF-4D). These physical characteristics, together with other properties, indicate that eIF-4D differs from PII only in possessing the hypusine residue in place of a lysine residue, whereas an additional structural difference exists between PI and eIF-4D. eIF-4D from CHO cells provides a significant enhancement of methionyl-puromycin synthesis, a model assay for translation initiation. Neither PI nor PII stimulates this in vitro system. These findings are the first direct evidence that hypusine is essential for the biological activity of eIF-4D.     

Immobilization ofColeus blumei cells in a column reactor using a spray feeding system

Summary Coleus blumei cells were immobilized in a column reactor packed withLuffa cylindrica pieces. Medium was fed from the top of the column using a spray system and cells maintained high viability for 52 days. Cell growth was slower but rosmarinic acid production was better compared to immobilized cells in the shake flasks.     

Enhancement of CO2 tolerance of Chlorella vulgaris by gradual increase of CO2 concentration

Summary Chlorella vulgaris UTEX259 was cultivated using two different methods of gas supply. In one method the CO₂ concentration in bubbled gas was held constant and in the other method it was increased gradually. Algal growth was almost linear after a short period of lag phase in both methods. With the constant CO₂ concentration, the CO₂ fixation rate in the linear growth phase decreased over 10%(v/v) CO₂, while the rate increased up to 6% CO₂. However, the rate was enhanced by using the latter incremental increase method, especially under a higher concentration of CO₂. The maximum rate of CO₂ fixation was 52 mg CO₂/l·h at 20% CO₂ during the gradual increase of CO₂ concentration.     

Characterization of quantitative trait loci (QTLs) in cultivated rice contributing to field resistance to sheath blight (Rhizoctonia solani)

Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases of rice. Despite extensive searches of the rice germ plasm, the major gene(s) which give complete resistance to the fungus have not been identified. However, there is much variation in quantitatively inherited resistance to R. solani, and this type of resistance can offer adequate protection against the pathogen under field conditions. Using 255 F₄ bulked populations from a cross between the susceptible variety Lemont and the resistant variety Teqing, 2 years of field disease evaluation and 113 well-distributed RFLP markers, we identified six quantitative trait loci (QTLs) contributing to resistance to R. solani. These QTLs are located on 6 of the 12 rice chromosomes and collectively explain approximately 60% of the genotypic variation or 47% of the phenotypic variation in the LemontxTeqing cross. One of these resistance QTLs (QSbr4a), which accounted for 6% of the genotypic variation in resistance to R. solani, appeared to be independent of associated morphological traits. The remaining five putative resistance loci (QSbr2a, QSbr3a, QSbr8a, QSbr9a and QSbr12a) all mapped to chromosomal regions also associated with increased plant height, three of which were also associated with QTLs causing later heading. This was consistent with the observation that heading date and plant height accounted for 47% of the genotypic variation in resistance to R. solani in this population. There were also weak associations between resistance to R. solani and leaf width, which were likely due to linkage with a QTL for this trait rather than to a physiological relationship.