Changes in carbohydrate contents in shoot tips,leaves and roots of strawberry (Fragaria × ananassa Duch.) during flower-bud differentiation

Flowering is an important step in crop production. Under flower-inducing conditions, biochemical or physiological changes can be recognized. Changes in carbohydrates have an important role in flower development in plants; however, carbohydrate changes during flower bud differentiation in strawberry have not been thoroughly investigated. In this study, runner plants potted in 18 cm diameter pots and grown under non-inducing conditions (28 ± 3/22 ± 3 °C day/night; 16 h day length). When the plants were established, half of the plants then were put under inducing conditions (23 ± 3/13 ± 3 °C day/night; 8 h day length). After the induction period of 21 short-day cycles, plants were brought to non-inductive conditions again. In order to evaluate the carbohydrate changes during flower differentiation, shoot tips, leaves and roots were sampled from four replicated plants collected weekly for the period of 7 weeks. Sucrose, glucose and fructose contents were determined by HPLC, and starch by the anthrone method. The results obtained indicated that the most abundant soluble sugar in all organs tested was sucrose. Sucrose in the shoot tips of induced plants at 42, 56 and 70 days after the start of the short-day treatment were significantly higher than corresponding time in non-induced plants. However, the glucose, fructose and starch contents in shoot tips, leaves and roots of non-induced plants in most sampling dates were greater than those of induced plants. In other words, the shoot tips (bud) of induced plants acted as strong ‘utilizing sink’ and preferentially metabolized carbohydrates rather than storing them. It seems that non-structural carbohydrate contents in shoot tips, leaves and roots of strawberry may have an important role in flower-bud differentiation.     

Immunogenicity of a Fusion Protein Comprising Coli Surface Antigen 3 and Labile B Subunit of Enterotoxigenic Escherichia coli

Background: Enterotoxigenic Escherichia coli (ETEC) strains are the major causes of diarrheal disease in humans and animals. Colonization factors and enterotoxins are the major virulence factors in ETEC pathogenesis. For the broad-spectrum protection against ETEC, one could focus on colonization factors and non-toxic heat labile as a vaccine candidate. Methods: A fusion protein is composed of a major fimbrial subunit of coli surface antigen 3, and the heat-labile B subunit (LTB) was constructed as a chimeric immunogen. For optimum level expression of protein, the gene was synthesized with codon bias of E. coli. Also, recombinant protein was expressed in E. coli BL21DE3. ELISA and Western tests were carried out for determination of antigen and specificity of antibody raised against recombinant protein in animals. The anti-toxicity and anti-adherence properties of the immune sera against ETEC were also evaluated. Results: Immunological analyses showed the production of high titer of specific antibody in immunized mice. The built-in LTB retains native toxin properties which were approved by GM₁ binding assay. Pre-treatment of the ETEC cells with anti-sera significantly decreased their adhesion to Caco-2 cells. Conclusion: The results indicated the efficacy of the recombinant chimeric protein as an effective immunogen inducing strong humoral response. The designated chimer would be an interesting prototype for a vaccine and worthy of further investigation. Key Words: Recombinant vaccine, Enterotoxigenic Escherichia coli (ETEC), cstH, eltB     

Assessment of growth condition for a candidate probiotic, <Emphasis Type="Italic">Shewanella algae</Emphasis>, isolated from digestive system of a healthy juvenile <Emphasis Type="Italic">Penaeus monodon</Emphasis>

To conquer disease problem in shrimp industries, probiotic biocontrol is a well-known remedy now. The antagonistic ability of separated isolates from different parts of juvenile P. monodon was screened against shrimp Vibrio pathogens, V. parahaemolyticus and V. alginolyticus. The most antagonistic effect was observed for an isolate that primarily identified as Shewanella algae using conventional method followed by Biolog GN and GP microplates. Since adaptability to the host optimum cultural condition of the target organism is of the great importance, response surface methodology, with central composite design, was applied to assess log cell count response of S. algae in different incubation conditions. Therefore, four independent variables were assumed as: temperature (10–50°C), pH (6–10), NaCl concentration (0–50‰) and time (12–60 h). The coefficients of multiple determinations (R ²) for the responses log cell count of S. algae being 0.827. Temperature was the merely significant independent variable that affected the log cell count of the candidate probiotic. The candidate probiotic was revealed a reasonable growth response in quite wide range of temperature, pH and NaCl concentration in which the maximum levels were in same range of optimum shrimp culture.