Detection of Bacillus thuringiensis genes in transgenic maize by the PCR method and FTA paper technology

We optimized the PCR method to detect genetically engineered Bacillus thuringiensis (Bt) maize in open quarantine fields in Kenya. Many factors affect the extraction of the DNA from plants, such as the amount of tissue available, the condition of the plant material, the numbers of steps involved in the extraction procedure, and the required purity needed. We tested the application of the FTA paper technology for field sampling whereby leaf materials are not removed and transported from the site. We also applied the PCR method, a technique that is widely used for detection of genetically modified organism (GMOs). We used primers specific to the Bt genes present in the transgenic maize to screen for the Bt genes Cry 1Ab and Cry 1Ba

Screening tropical maize lines for the production and regeneration of friable and embryogenic type II callus

Twenty two maize lines popularly used by breeders in the Kenyan maize program were screened for their ability to form type II callus. The immature embryos were harvested two weeks after pollination. Two highland lines showed high embryogenic response and formed friable, type II calli. While 16 lines screened showed poor or retarded growth with subsequent death. There was successful plant regeneration from four lines collected from the highland breeding program that are genetically related. The results suggested that genetic factors may be responsible for the differences seen in the regenerability of the tropical lines. The two lines CMB7 and CMB8 are considered suitable for further evaluation using a transformation syste

A new intrinsic thermal parameter for enzymes reveals true temperature optima

Two established thermal properties of enzymes are the Arrhenius activation energy and thermal stability. Arising from anomalies found in the variation of enzyme activity with temperature, a comparison has been made of experimental data for the activity and stability properties of five different enzymes with theoretical models. The results provide evidence for a new and fundamental third thermal parameter of enzymes, Teq, arising from a subsecond timescale-reversible temperature-dependent equilibrium between the active enzyme and an inactive (or less active) form. Thus, at temperatures above its optimum, the decrease in enzyme activity arising from the temperature-dependent shift in this equilibrium is up to two orders of magnitude greater than what occurs through thermal denaturation. This parameter has important implications for our understanding of the connection between catalytic activity and thermostability and of the effect of temperature on enzyme reactions within the cell. Unlike the Arrhenius activation energy, which is unaffected by the source (“evolved”) temperature of the enzyme, and enzyme stability, which is not necessarily related to activity, Teq is central to the physiological adaptation of an enzyme to its environmental temperature and links the molecular, physiological, and environmental aspects of the adaptation of life to temperature in a way that has not been described previously. We may therefore expect the effect of evolution on Teq with respect to enzyme temperature/activity effects to be more important than on thermal stability. Teq is also an important parameter to consider when engineering enzymes to modify their thermal properties by both rational design and by directed enzyme evolution

Application of simple sequence repeats (SSRs) markers to study the resistance of locally adapted maize hybrids to damaging maize streak virus disease

Simple sequence repeat markers were used to study S6 recombinant inbred lines originating from a single cross between two inbred lines OSU 23i and EM12-210, for resistance to maize streak virus disease. A total of 115 recombinant inbred lines belonging to three families previously selected using conventional methods were screened using 52 SSR markers contained between Bin 1.04 and 1.05 of maize chromosome 1. Of these, only three markers were chosen on the basis of their polymorphism content for use in the study. This paper discusses the results of combined selection with both artificial inoculation and the three selected SSR markers. The use of artificial inoculation detected 78 resistant lines and 36 susceptible lines. On the other hand, the SSR markers detected 40 resistant lines, and 74 susceptible lines. But a combination of both the artificial inoculation and SSR marker selection reduced the number of resistant lines to 29 and increased the number of susceptible lines to 85. With these findings it was concluded that, a conventional maize breeder requires the use of molecular markers in order to improve selection intensity and maximize genetic gai

The equilibrium model for the effect of temperature on enzymes: Insights and implications

A new, experimentally-validated “Equilibrium Model” describes the effect of temperature on enzymes, and provides a new mechanism for the reversible loss of enzyme activity with temperature. It incorporates two new, fundamental parameters that allow a complete description of the effect of temperature on enzyme activity: ΔHeq and Teq. ΔHeq emerges as an intrinsic and quantitative measure of enzyme eurythermal adaptation, while Teq, the equilibrium temperature, has fundamental and technological significance for our understanding of the effect of temperature on enzymatic reactions. For biotechnological purposes, these parameters need to be considered when enzymes are applied or engineered for activity at high temperatures

Application of simple sequence repeats (SSRs) markers to study the resistance of locally adapted maize hybrids to damaging maize streak virus disease

Simple sequence repeat markers were used to study S6 recombinant inbred lines originating from a single cross between two inbred lines OSU 23i and EM12-210, for resistance to maize streak virus disease. A total of 115 recombinant inbred lines belonging to three families previously selected using conventional methods were screened using 52 SSR markers contained between Bin 1.04 and 1.05 of maize chromosome 1. Of these, only three markers were chosen on the basis of their polymorphism content for use in the study. This paper discusses the results of combined selection with both artificial inoculation and the three selected SSR markers. The use of artificial inoculation detected 78 resistant lines and 36 susceptible lines. On the other hand, the SSR markers detected 40 resistant lines, and 74 susceptible lines. But a combination of both the artificial inoculation and SSR marker selection reduced the number of resistant lines to 29 and increased the number of susceptible lines to 85. With these findings it was concluded that, a conventional maize breeder requires the use of molecular markers inorder to improve selection intensity and maximize genetic gai

PATENTS, R&D AND LAG EFFECTS: EVIDENCE FROM FLEXIBLE METHODS FOR COUNT PANEL DATA ON MANUFACTURING FIRMS

Hausman, Hall and Griliches (1984) and Hall, Griliches and Hausman (1986) investigated whether there was a lag in the patent-R&D relationship for the U.S. manufacturing sector using 1970¿s data. They found that there was little evidence of anything but contemporaneous movement of patents and R&D. We reexamine this important issue employing new longitudinal patent data at the firm level for the U.S. manufacturing sector from 1982 to 1992. To address unique features of the data, we estimate various distributed lag and dynamic multiplicative panel count data models. The paper also develops a new class of count panel data models based on series expansion of the distribution of individual effects. The empirical analyses show that, although results are somewhat sensitive to different estimation methods, the contemporaneous relationship between patenting and R&D expenditures continues to be rather strong, accounting for over 60% of the total R&D elasticity. Regarding the lag structure of the patents-R&D relationship, we do find a significant lag in all empirical specifications. Moreover, the estimated lag effects are higher than have previously been found, suggesting that the contribution of R&D history to current patenting has increased from the 1970¿s to the 1980¿s.Innovative activity, Patents and R&D, Individual effects, count panel data methods.