Development of a construct-based risk assessment framework for genetic engineered crops.

Experience gained in the risk assessment (RA) of genetically engineered (GE) crops since their first experimental introductions in the early nineties, has increased the level of familiarity with these breeding methodologies and has motivated several agencies and expert groups worldwide to revisit the scientific criteria underlying the RA process. Along these lines, the need to engage in a scientific discussion for the case of GE crops transformed with similar constructs was recently identified in Argentina. In response to this need, the Argentine branch of the International Life Sciences Institute (ILSI Argentina) convened a tripartite working group to discuss a science-based evaluation approach for transformation events developed with genetic constructs which are identical or similar to those used in previously evaluated or approved GE crops. This discussion considered new transformation events within the same or different species and covered both environmental and food safety aspects. A construct similarity concept was defined, considering the biological function of the introduced genes. Factors like environmental and dietary exposure, familiarity with both the crop and the trait as well as the crop biology, were identified as key to inform a construct-based RA process.

Delay model of the circadian pacemaker.

We present a simple and realistic model of the circadian pacemaker that can be interpreted in molecular terms. The model, which consists of a single time-delay differential equation, simulates the expression of a generic clock protein that inhibits its own expression through a feedback mechanism. Despite its simplicity, this model fulfils most of the necessary characteristics of a realistic representation of natural circadian clocks: robust and stable oscillations with circadian free-running periods, typical phase response curves and entrainment to environmental zeitgebers. The present model reduces the molecular mechanism necessary to sustain stable oscillations to its bare bones, suggesting that the essential factor is the time-delayed negative feedback of the oscillating protein on its own expression.